P L A N ING A ND

M I L L ING

A TREATISE ON THE USE OF PLANERS,

SHAPERS, SLOTTERS, AND VARIOUS

TYPES OF HORI Z ONTAL AND VERTI

CAL MILLING MACHINES AND THEIR

ATTACHMENTS

BY FRANKL IN D. "ONESASSOCIATE EDITOR or MACHINERY

Amen or TunmmAND Bounce”

FI RS T EDI TI ON

SECOND pR INTING

NEW YORK

THE . INDUSTR IAL PRESS

LONDON : THE MACHINERY PUBLISHING CO LTD.

Con fluent , 1914

BY

THE INDUSTRIAL PRESSNEW YORK

THI S book deals with the practical problems connec ted withthe adjustment and use of planets, shapers, slotters andmillingmachines of standard and special designs. Each subject istreated fromthe standpoint of the man in the shop, and a

special efiort has beenmade to present needed information pertaining to problems which the practicalman often finds difi cult

to solve . Many operations fromactual practice are illustratedand described to show the adaptability of different machinesfor certain classes of work

,and the relation between various

designs and types. Examples and operations have been selectedthat would not only show how a spec ific result is obtained,b utillustrate fundamental principles and serve as a general guide.

Descriptions of methods involving mathematical calculationscontain the necessary rules or formulas and are accompaniedby examples illustrating the problems which arise in actualpractice.

While some of thematerial is rather elementary,many of the

more advanced and difli cult operations are explained,so that

the book is not only a general treatise but containsmuch usefulinformation of value even to experiencedmachinists . Detaileddescriptionsof differen t c lasses of plan ing andmillingmachinesare given to show, in a general way, howmodernmachine toolsare constructed and controlled, but, as far as possible, the praetical application or use of the machine has been emphasizedrather than its constructional details. Themachines illustratedwere selected as designs typical of difierent types, and not nec

essarily because they were considered superior to othermachinesof the same class.

Readers of mechanical literature are familiar with MACHIN

BRY’

S 25-cent Reference Books

,of which one hundred and

twenty-nve difierent titles have been published during the pastV

vi PREFACE

six years. Asmany subjects cannot be covered adequately inall their phases in books of this size, and in response to a demandfor more comprehensive and detailed treatments of the moreimportantmechanical subjects , it has been deemed advisable topublish a number of larger volumes, of which this Is one. Thiswork includes MACHINERY’

5 Reference Books Nos. 93 96 and

97 , together with a large amoun t of additional information on

modern planing and milling practice . In the preparation ofthe subjec t matter, many practical methods and interestingOperations were obtained fromthe columns of MACHINERY and

represent approvedmachine-shOp practice.

As the illustrations in a book of this kind constitu te a veryimportant feature , they have received particular atten tion .

P ractically all of the drawings are original andmost of themare

simple diagrams which can easily be understood , even by thosenot accustomed to “ reading ” drawings. Care was taken also

to sec ure photographs which would c learly illustrate the difierent

subjects presented. The cooperation of themachine toolmanufac turers who generously supplied many of these views isgreatly appreciated.

F. D. ".

NEw You , " uly, 1914.

CONTENTS

CHAPTER I

PLANING MACHINES

Des c ription of P laner Examples Of P lanerWork Use ofTwo-head P laner P laning Vertical and Angular SurfacesMethods of Holding Work on P laner Use of MagneticChucks Holding Cylindrical Parts for P laning Causes Of

Distorted Work Points on Setting up P laner WorkVarious Forms of P laner Tools Points on Grinding P lanerTools Multiple or Gang P laning Use of Planer IndexCenters Attachments for P laning Curved Surfaces At

tachments for P laning Spiral Flutes Rack Cutting on the

P laner P laner Extension Head and Independent HousingOpen

-side P laners P laning Locomotive Frames and Cylin

ders P laning Speeds and Feeds Determining Net or

Actual Cutting Speed of P laner Variable Speed and Elec

tric P laner Drives Double—cutting P laners

CHAPTER I I

SHAPER AND SLOTTER

Des c ription Of a Crank Shaper Examples of ShaperWork Shaper Attachments Morton Draw-cut Shaper

Pratt Whitney Vertical Shaper Cochrane—Bly UniversalShaper Shaper Attachment for Machining Clutches The

SlottingMachine Examples of Straight and Circular Slotting

CHAPTER II I

PLAIN MILLING MACHINE

Des c ription of P lain Milling Machine Method Of Ad;

justing and Operating Methods of Holding Work on Mil"vii

PAGES

viii CONTENTSPm

ing Machine Difierent Forms of Milling Cutters FormMilling Straddle and Gang M illing with Examples of WorkEnd and Face Milling Keyseat Milling Speeds and

Feeds for M illing Lubricants forM illing 106- 142

CHAPTER IV

UNIVERSAL MILLING MACHINE

Des cription of Universal Milling Machine Constructionand Application of Spiral Head Simple, Compound, Difierential, and Angular Indexing Helical or Spiral MillingCalculating Change Gears for Spiral Milling Attachmentfor Vertical M illing Slotting Attachment for Milling Ma

chine Milling Taper Flutes M illing Clutch TeethMilling P late Cams in the Universal Machine CuttingTeeth in End and Side Mills M illing Angular Cutters . 143

-195

CHAPTER V

GEAR CUTTING IN MILLING MACHINE

Method of Cutting a Spur Gear in M illing Machine— Testing Chordal Tooth Thickness of Spur Gear Teeth Attachment for Cutting Large Gears Rack Cutting in the MillingMachine Index Table for Rack Cutting Gashing and

Hobbing a Worm-wheel in Milling Machine How to SelectCutter and Adjust Machine for M illing a Spiral GearMilling Teeth in Bevel Gears Milling Teeth in ChainSprockets Formulas for Determining Roller and B lock

chain Sprocket Diameters 196—227

CHAPTER VI

MISCELLANEOUS MILLING MACHINES

Des cription of Vertical M illing Machine Examples ofVertical Milling Operations Continuous Circular M illingSingle and Double SpindleDie-sinking Machines Under

cutting Diemilling Machine Combined Horizontal and

Vertical M illing Machine Pratt Whitney P rofiling Ma

CONTENTS ix

PmExamples of P rofiling Different Types of Profiling

Fixtures and Formers Semi-automatic P rofiler Lincoln

Type Milling Machine Horizontal or P laner-type M illingMachine Examples of Horizontal Milling Planing vs.

M illing Multiple-head Milling Machine Open-side Hori

zontal M illing Machine Duplex Milling Machine HandMilling Machine Camor FormM illing Machine M illingFace and Cylinder Cams Thread Milling Machines 228- 298

PLAN ING AND M ILL ING

CHAPTER I

PLANING MACHINES AND THEIR APPLICATION

THE planer is used prin cipally for producing flat surfaces.

The construction or design of planers of differentmakes variessomewhat , and spec ial types are built for doing certain kinds ofwork. There is

,however

,what might be called a standard

type which is found in allmachine shops and is adapted to general work . A typical planer of small size is illustrated in Fig. I .

The prin cipal parts are the bed B ,the housings H which are

bolted to the bed, the table or platen P to which the work is

attached , the cross-rail C, and the tool-head Twhich ismountedon the cross-rail. When the planer is in operation ,

the platenslides back and forth on the bed in V-shaped grooves G whichcause it

'

to move in a straight line . While this reciprocatingmovement takes place

, the work , which is clamped to the platen ,

is planed by a tool held in position by clamps A This tool temains stationary while cu tting, and when the platen is near

the end of the return stroke, the tool-head and tool feed slightlyfor taking a new c ut. The amount of feed for each stroke canbe varied to su it the conditions, as will be explained later. Themovement of the table or of the length of its stroke is governedby the position of the dogs D and D1. These dogsmay be ad

justed along the groove shown and they serve to reverse thetable movement by engaging tappet I . Before explaining justhow themovement of tappet I controls the point of reversal,the arrangement of the driving mechanism,

a plan view ofwhich is shown inFig. 2

, will be explained.

Planer Driving and Reversing Mechanism.— The shaft on

which the belt pulleysf , f ;and r, 7 1 aremounted carries a pinion a

THE PLANER

thatmesheswith a gear on shaft b . This shaft drives, through thegears c and d

,a second shaft which carries a pinion e

,meshingwith a large gear g. This large gear, which is called the

“ bullwheel

,engages a rack attached to the under side of the table,

and, as the gear revolves, the table moves along the ways ofthe bed. There are two pairs of driving pulleys and also twodriving belts connecting with an overhead countershaft. One

pulley of each set is keyed to the shaft and the other is loose and

Fig . 1 . S ingle-head Planing Machine

revolves freely . The belt operating on the large pulleys j and

f l is crossed , whereas the belt for the smaller pulleys r and r;

is open ,which gives a reversemotion . The position of both

belts is controlled by guides I (one of which is seen in Fig. I )which are operated by tappet I . Now when the crossed belt

is running on the tight pulley f , the reverse belt is on the loose

pulley n ,and the tablemoves as shown by the arrow as

,which

is in the direction for the cu tting stroke. When the table is

advanced far enough to bring dog D (Fig. 1) into engagement

CONSTRUCTION OF A PLANER

with tappet I , the latter is pushed over, which shifts the crossedbelt on loose pulley f l and the open belt on the tight pulley r.

The pulley shaft and the entire train of driving gears is thenrotated in the opposite direction by the open belt and the tablemovement is reversed . This is the return stroke, during whichthe planing tool glides back over the work to the starting poin tfor a new c ut.

To change the length of the stroke, it is simply necessary to

shift dogs D and D; as their position determines the poin t of

Pig. 3 . Driving Mechanismof a Spur-geared Planer

reversal. When the workman desires to reverse the table byhand or stop it temporarily, this can be done by operating handlever K . I t will be noted that there is considerable diff erence

in the diameter of the two sets Of belt pulleys, those for the forward or cutting stroke being much larger than those for thereturn movement. As the size of the countershaft pulleys is

in the reverse order, the speed Of the table ismuch less whenthe tool is cu tting than when

'

the table is on the returnmovement. The table is returned quickly after the cutting stroke

4 THE PLANER

in order to reduce the idle time that elapses between the end

of one c ut and the beginning of the next.The Feeding Mechanism. As previously mentioned the

feedingmovement of the tool takes place on the return strokeand before the tool begins to cut. I f a horizontal surface isbeing planed, the tool has a crosswisemovement parallel to theplaten , b ut if the surface is vertical

,the tool is fed downward

at right angles to the platen . In the first case the entire toolhead Tmoves along the cross-rail C

,but for vertical planing

,

slide S moves downward . Su rfaces which are at an anglewith the table can also beplaned by loosening nu ts Nand swiveling slide S to therequired angle as shown bygraduations on the circularbase. The horizontal and

vertical movements of thetool can be efi

'

ec ted by handor automatically. The handfeed is used principally foradjusting the tool to the

proper position for starting

a cut. The tool can be setPig. 3 . Planer Friction Feed Disk to the right height by a

crank at the top of the tool-head , and the cross-wise position

of the tool and head can be varied by tu rning horizontal feedscrew E .

The au tomatic feedingmovement is derived froma feed diskF

,which tu rns part of a revolution at each end of the stroke

and is connected to a rack R . This rack slides up and downwith each movement of the crank and imparts its motion to

gear M whichmeshes with a gear 0 placed on the feed-screw.

The feedingmovement is engaged, disengaged or reversed by a

pawl attached to gear M (on this particular planer) and theamount of feed per stroke is varied by adjusting the crankpinof the disk F

,to or fromthe center. The vertical feed is Oper

ated by a splined shaft L which transmits its motion to the

CONSTRUCTION OF A PLANER 5

tool-head feed-screw through gearing. This shaft is also drivenby gear 0 which is removable and is placed on shaft L when an

automatic vertical feed is desired .

The friction disk F is turned by pinion shaft 6 (Fig. 2) Of the

driving mechanism. The number of revolutions made by thispinion shaft for each stroke depends

,of course

,on the length of

the stroke, but the feed disk is so arranged that it only rotates partof a revolution at each end of the stroke

,so that

,

the feedingmovement is not governed by the length Of the stroke. In otherwords the feed disk is disengaged fromthe driving shaft afterbeing turned part of a revolution . One type of feed disk is shownin the sectional view

,Fig. 3 . The c up-shaped part A having an

inner tapering surface is attached to the main pinion shaft.Crank-disk B has a tapering hub C which fits into part A as

shown . I f the hub is engaged with cupA when the planer isstarted

,the crank-disk is tu rned until a tapered projection D

strikes a stationary taper boss on the bed which disengages hub Cfromthe drivingmember bymoving it outward against the tension of spring E . The disk then stops turning and remainsstationary until the drivingmember A reverses at the end of thestroke. The hub then springs back into engagement and the diskturns in the opposite direction until another taper projection D1,on the opposite side

,strikes a second boss on the bed which

again arrests the feedingmovement . I t will be seen that thissimplemechanismcauses the disk to oscillate through the samearc whether the stroke is long or short .

Spiral-geared P laner.

— There are two general methods of

driving a planer table. Themost common formof drive is thatin which themotion is transmitted fromthe belt pulleys throughspur gearing to a bull-wheel or spur gear

,whichmeshes with

a rack attached to the under side of the planer table, as described

in connection with Figs. 1 and 2 . A planer driven in this wayis known as a

“Spur-geared ” type to distinguish it fromthe

spiral-geared planer . With a spiral-gear drive (sometimesknown as the Sellers drive) themotion is transmitted fromthe

belt pulleys through bevel gears to a shaft which extends under

the bed diagonally and carries a spiral pinion or wormwhich

6 THE PLANER

meshes with the table rack . The belt pulleys aremounted on a

shaft that is parallel to the table, instead of being at right anglesas with a spur gear drive. Smoothness of action is the principaladvantage claimed for the spiral gear drive .

Example of Planer Work. A simple example of planing isillustrated in Fig. 4. The work W is a base casting , the topsurface of which is to be planed true . The casting is first fas

ll‘ig. 4. Side View of Planer with Work in Position

tened to the table by bolts and clamps C and C1, and it is furtherheld fromshifting by stop-pins S . The platens of all planersare provided with a number of slots and holes for the receptionof clamping bolts and stop-pins. When the casting is secu relyattached to the platen ,

a planing tool T is clamped in the toolpost

, and cross-rail R is set a little above the top surface of thework. The dogs D and D1 are then placed opposite the casting

EXAMPLE OF PLANING

and are set far enough apart to give the platen a stroke slightlygreater than the length of the surface to be planed . Themovement of the work during a stroke is illustrated in Fig. 5 , the fulllines showing its position wi th relation to the tool at the beginning of the cutting stroke

,and the dotted lines the end of the

stroke or the point of reversal . The dogs should be adjustedso that the distance x is notmore than I } to 2 inches and the

tool should just clear the work at the other end. I f the strokeismuch longer than the length of the surface being planed, obviouslymore time is required for planing than when the stroke isproperly adjusted.

Taking the Cut — The tool is moved over to the work by

handle A and is fed down to the right depth for a cut by handle

Fig. 5 . Movement of Work with Relation to Planing Tool

B . The planer is started by shifting an overhand belt (assuming that it is belt and notmotor-driven) and the power feed isengaged by throwing the feed pawl into mesh. On this par

ticular planer, the feed pawl is inside the gear and it is engagedor disengaged by a small handle E . The tool planes the surfaceof the casting by feeding horizontally across it and removing a

chip during each forward stroke. I f there is notmuch metalto be planed off , one roughing and one finishing cut would prob

ably be all that is necessary. For the finishing cut a broad toolhaving a flat edge is often used

,especially for cast iron ,

as it

enables wide feeds to be taken , which reduces the time requiredfor the finishing cut. The different types of tools ordinarily

used on a planer will be referred to later.

THE PLANER

Position of the Tool and Cross-rail. The tool should be set

abou t square with the surfac e to be planed , as shown at A ,

Fig. 6, when planing horizontal surfaces. I f it is clamped in thetool-block at an angle, as shown at B , and the lateral thrust orpressure of the cut is sufi c ient tomove the tool sidewise , thecutting edge will sink deeper in to themetal, as indicated by thedotted line

,whereas a tool that is set square will swing upward .

Of course , any shifting of the tool downwardmay result in planingbelow the level of the finished surface which would spoil the work.

The tool shou ld also be clamped with the cu tting end quite closeto the tool-block ,

so that it will be rigidly supported .

Fig. 6. Correct and Incorrec t Positions for Tool when Planing a

Horizontal Surface

As previously mentioned, the cross-rail should be lowereduntil it is quite Close to the top surface of the work. I f it is set

much higher than the work, the tool-slide has to be loweredconsiderably to bring the tool in position for planing; cousequently , both the slide and the tool extend below the rail andthey are not backed up and supported against the thrust of thecut as solidly as when the rail ismore directly in the rear. The

vertical adjustment of the cross-rail on the face of the housingsis effected by two screws which are connected through bevelgearing with the horizontal shaft U (Fig. I ) at the top . On smallplaners this shaft is turned by hand, but on larger ones it isdriven by a belt. Beforemaking the adjustment

,bolts at the

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10 THE PLANER

of which is shown at A in Fig. 8,has one fixed jaw J and one

movable jaw J1 and the work is clamped between the jaws bythe screws shown . The work is “

bedded ” by hammering itlightly

,until the sound indicates that it rests solidly on the

bottomof the chuck .

After a cut has been taken over the upper side a (Fig. the

casting is turned to bring its finished face against the stationary

jaw J as shown atA,Fig. 8. A finished or planed surface should

always be located against the fixed or stationary jaw of the vise ,

Fig. 7 . Planing Work held in a Chuck

because themovable jaw ismore liable to be out of alignment .If the fixed jaw is square with the planer table

,and face a is

held flat against it, evidently face b, when planed, will be at

right angles to face 0. Unless care is taken,however

,the work

may be tilted slightly as the movable jaw is set up, especiallyif the latter bears against a rough side of the casting . The waythis occurs is indicated at B . Suppose

,for example , that the

rough side 6 is tapering (as shown somewhat exaggerated) andthe jaw " ; only touched the upper corner as shown . Thefinished face will then tend to move away at x (sketch C) as

PLANER CHUCK I I

jaw 11 is tightened, so that face b, when planed , would not be

square with the side a.

Onemethod of overcoming this difi culty is to insert narrowstrips of tin (or strips of paper when the irregularity is small)in the space S (sketch B ) to give the clamping jaw amore evenbearing. This tilting can also be prevented by placing a wire

or cylindrical rod 10 along the center of the work as shown atD;the pressure of clamping is then concentrated at the center and

Fig. 8. Plans: Chuck Diagrams showing how Work is

and Methods of Holding it S quare

the opposite side is held firmly against the fixed jaw. Sometimesa special packing strip p, having a rounded face, is inserted be

tween the jaw and the work to prevent tilting, as at E . This

strip acts on the same principle as the wire, and it ismore convenient to use.

When the sides 0 and b are fin ished and the casting is being set

for planing side 0 it is necessary not only to have a good bearing

against the fixed jaw,b ut as the sides are to be parallel, the lower

side amust‘, at this setting, bear evenly on the bottomof the

12 THE PLANER

chuck . A simple method of determining when work is firmlybedded is as follows: P lace strips of thin paper beneath each

end of the work, and after tightening the chuck and hammeringthe casting lightly to give it a good bearing, try to withdraw the

paper strips. I f both are held tightly, evidently the casting

rests on the chuck and the upper side will be planed parallel,provided the chuck itself is true.

The foregoingmethod of planing a block square and parallel,by holding it in a chuck, is not given as one conducive to accu

racy, but rather to illustrate some of the points which should be

observed when clamping work in a planer chuck. I f consider

able acc uracy were required, the block could be held to better

advantage by fastening it directly to the table with spec ial

P ig . 9. Holding Block directly against Platen by Finger-clamps

clamps, as indicated in Fig. 9. The particular clamps illustratedhave round ends which are inserted in holes drilled in the work.

Of course , such clamps can only be.used when the holes are not

objectionable . As will be seen ,these clamps are not in the way

of the planing tool,and the block is held directly against the

true surface of the platen .

This block could be planed acc urately as follows: A roughingcut is first taken over all the sides to remove the hard ou ter surface, and then one side is finished. This finished surface is nextclamped to the platen

,thus permitting the opposite side to be

planed . These two surfaces will then be parallel,provided the

planer itself is in good condition . The finished sides are nextset at right angles to the platen by using an accurate square

,and

the third side is planed. The fourth and last side is then fin

DOUBLE-HEAD PLANER 13

ished with the third side clamped against the platen . By thismethod of holding the work, itwould be easier to secure accurateres ults than by using a chuck; a chuck

,however

,is often very

convenient for holding small parts .

Doub le-head Planers Use of Side-heads. Modern planers,

with the exception of comparatively small sizes, are ordinarily

equipped with two tool-heads on the cross-rail, as shown in Fig.

10, so that two tools can be used at the same time. Some

planers also have side-heads S moun ted on the housings belowthe cross-rail for planing vertical surfaces or for doing other work

Fig . 10. Cincinnati Four-head Planer

on the sides Of a casting. These side-heads have an automati cvertical feed and can Often be used while the other tools are

planing the top surface,the method being to start first the

regular tools (which usually have the largest surfaces to plane)and then the side-heads . I f the planing on the side requires handmanipulation

,as when forming narrow grooves, etc .

,the planing

would be done first on one side, and then on the other,assuming

that both sides requiredmachining, but when the surfaces are

broad the au tomatic feed enables both side-heads to be used at

thesame time, on some classes of work. These side-heads Often

14 THE PLANER

greatly reduce the time required for planing and they alsomakeit possible to finish some parts at one setting, whereas the workwould have to be set up in one or two diflerent positions if aplaner withou t side-heads were used.

Application of Two-head Planer. Two ormore tools c an beused at the same time in connection with many planing operations. Fig. I I shows a cross-sec tion of an engine bed and

illustrates how a double-head planer would be used on this par

ticular job . The tool to the left is started first because it is

Fig. 1r. Planing Two Surfaces Simultaneously with Two-head Planer

the leading too", as determined by the direction of the feed. Thisis a good rule to follow , especially when the tool-heads are quite

Close to each other on the cross-rail, as it prevents one head fromfeeding against the other, which might occur if the followingtool were started first. The tools illustrated cut principally

on the side and are in tended for deep roughing cu ts in cast iron .

The surfaces should be finished with a broad tool with a widefeed. I f the planer were heavy and rigid

,a feed of i or inch

for each stroke,or even more , could be used for the finishing

cut, but if the planer were rather light or in poor condition , it

USE OF SIDE—HEAD 15

might be neces sary to reduce the feed to 1; inch or less to avoidchatter . It is impossible to give any fixed rule for the amountof feed as this is governed not only by the planer itself

,but also

by the rigidity of the work when set up for planing, the hardnessof themetal, etc. Thefinal cut should be taken by a single toolto insure finishing both sides to the same height. This tool

should be fed by power froma to b,and then rapidly by hand

fromb to c for finishing the opposite side . The use of two tools

for rough planing greatly reduces the time required formachining work of this kind .

Fig. rz. Planing Top Edge and S ide of Casting — Illustratinguse of S ide-head

Application of Side-head. A typical example of the Class ofplaner work on which a side-head can be used to advantage is

shown in Fig. 12 . The operation is that of planing the edge andface of a large casting. The tool in the side-head is rough plan

ing the vertical surface, while the other tool planes the edge .

As the side-tool has the broadest surface to plane,it is started

first. On some work two side-tools can be used simu ltaneously.

The use of both cross- rail tool-heads at the same time is verycommon in connection withmodern planer practice .

Whether it is feasible to use one tool or four, simultaneously,

16 THE PLANER

depends altogether on the shape of the work and the locationOf the surfaces to bemachined . Very often only one tool canbe used

,and

,occasionally

,four tools can be operated at the

same time,provided

,of course

,the planer is equ ipped with four

heads. There are few fixed rules which can be applied generallyto planer work , because the best way to set up and plane a certain part depends on its shape

,the relative location of the sur

faces to be finished,the degree of accu racy necessary and other

Fig. 13 . Positions of Tool and Head for Planing Vertical and

Angular Surfaces

things which vary for difierent kinds of work. Before beginningto plane any part, it is well to consider carefully just what therequirements are and then keep theminmind as the work pro

gresses.

P laning Vertical Surfaces. When vertical surfaces or thosewhich are at right angles to the platen are to be planed , a tool

having a bent end as shown at A in Fig. 13 is ordinarily used ,unless the planer has side-heads

,in which case a straight tool

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18 THE PLANER

the slide shmld be at right angls to the platm. I ts position ,

however, can be determinedmore aomratc ly by holding the b ladeof a square which rcsts on thé platen against one side of the

tool-slide, as it is difi c ult to set graduation lines to exac tly coin

Fig. I 4. Tool-heads set for Planing Angu lar Surfaces

Planing Angular Surfaces. The planing of an angular sur

face is illustrated at B ,Fig. 13 . The tool-head is first set to the

proper angle by loosening bolts F and tu rning the base D untilthe graduations Show that it ismoved the required number ofdegrees. For example, if surface s were to be planed to an angle

of 60 degrees with the base, as shown , the head should be set

over 30 degrees fromthe vertical or the difference between goand 60 degrees. The tool would then be fed downward , as in

dicated by the arrow. The tool-block is also set at an angle

CLAMPING METHODS 19

with slide S ,when planing angular surfaces, so that the tool will

swing clear on the return stroke . The top of the block shouldalways be turned awayf romthe surface to beplaned, which appliesto the planing of either vertical or angular surfac es when usingthe cross-rail head.

An example of angular work is illustrated in Fig. 14, whichshows a planer arranged for planing the V—shaped ways or guideson the bottomof a planer platen . Both tool slides are set tothe required angle for planing one side Of each vee . As thereare two tool-heads, both vees can ,

of course,be planed simu lta

neously . The sides of the platen are also planed at the samesetting by tools held in the side-heads.

Holding Work on the P laner. A great deal of the work doneon a planer is very simple as far as the actual planing is con

cerned,but often considerable skill and ingenuity are required

in setting parts on a planer and clamping themin the bestmanner. There are three important points that should be considered when doing work of this kind . First

,the casting or

forgingmust be held securely to prevent its being shifted by thethrust of the cut; second, the work should not be sprung out ofshape by the clamps; and third , the workmust be held in sucha position that it will be possible to finish all the surfaces thatrequire planing

,in the right relation with one another. Pre

quently a little planning before the setting-up” operation will

avoid considerable worry afterwards,to say nothing of spoiled

work.

Difierent Forms of P laner Clamps and Bolts. Mu ch of thework done on a planer is clamped directly to the platen although

inmany cases special fixtures are used . A formof clamp thatis often used is shown at A in Fig. I 5 , 0 being the Clamp proper,b the bolt, and d the packing block on which the ou ter end of theclamp rests. Obviously, when the bolt is tightened, the Clamppresses the work downward against the platen

,and as this

pressure is greatest when the bolt is close to the work, it should ,if possible

,be placed in that position . I f the bolt were located

near the packing block , the latter would be held tightly insteadof the work. Another point to be Observed is the height of the

20 THE PLANER

packing block. This height as should equal the height y of thepart being clamped , provided a straight clampis used. The end

of the clamp will then have an even bearing on the work whichwill be held more securely than it would be if the clamp wereinclined so that all the hearing was on the end of the clamp orat the edge of the casting. Packing blocks aremade Of eitherhard wood or cast iron .

An excellent formof clamp,known as the U-clamp , is shown

at B . This type ismade by simply bending a square or rec tangu lar bar of steel around , as shown , SO as to forma slot in which

Fig. rs. Clamps for Attaching Work to Planer Platen

the bolts can be placed . This continuous slot enables a bolt tobe located in the best position

,which is not always the case

with clamps having holes.

Bent or off -set clamps are preferable to the straight type for

holding certain kinds of work. Fig . I 6 shows an off -set Clampapplied to a casting which, we will assume, is to be planed on

the top . I f, in this case , a straight Clamp were used

,the clamp

ing nutmight be high enough to interfere with the plan er tool,

but the ofl-set clamp enables a shorter bolt to be used.

Frequently the “finger ” Clamps illustrated at A and B in

Fig. 17 are convenient if not absolutely necessary. This type is

CLAMPING METHODS 2 I

used for holding work which cannot be held by ordinarymeanswithout interfering with the planer tool. The style to the left

has a round end which enters a hole drilled in the work,whereas

the clamp to the right has a flat end which engages amilled slot.

Fig. 16. 03 -3“ Clamp

An illustration of the use of finger clamps is given in connectionwith Fig. 9. As previously stated

,they are only adapted to

work in which holes or slots are not Ob jec tionab le. Sometimesthese clamps can be inserted in cored pockets or holes that are

Fig. 17 . Methods of ClamOrmy

wort which cannot be held by

needed for other purposes. Sketch C illustrates amethod thatis sometimes resorted to when there are no projections for clampsand when holes or slots are not desirable . The clamps are

placed in an angular position between the work and stop-pins Sor strips clamped to the platen

,and when the bolts are tightened

the work is forced downward. The bolt holes are elongated to

2 2 THE PLANER

permit the angular position of the clamps to be varied somewhat,and the nu ts bear on the cu rved ends .

Three styles of bolts that are generally used for planer workare shown at A

,Fig. 18. Bolt a has a square head so that it

must be inserted at the end of a platen slot and then bemovedto the required position . Occasionally it is desirable to place abolt through some opening in a casting, in which case the bolt bcan be used . The head is narrow enough to be inserted in theT-slot fromabove

,and when the bolt is given a quarter turn

,

it is held the same as the square-headed type . Another style

Fig. 18. Planer Clamping Bolts— Stop-fins — Use of Stop-fins

is shown at c which can be inserted fromabove. The lower endor head of this bolt is in the formof a nut planed to fit the T-slot.

When the bolt is to be inserted fromabove , this nut ismovedalong theT-slot to the proper position and then the bolt is screwedinto it after which the upper clamping nut is tightened .

Stop-pins and Brac es. I t would be very difficult to hold

work securely by using only clamps and bolts,because the pres

sure of the clamp is in a vertical direction,whereas the thrust of

the cut is in a horizontal direction,which tends to shift the work

along the platen . To prevent such amovement,practically all

work that is clamped to the platen is further secured by one or

CLAMPING METHODS 3

more stop-pins S , which are placed at one end of the part beingplaned as indicated at D

, Fig. 18. These pins are generallymade in two styles, one of which has a shank that fits the holesin the planer platen as shown at B

, and the other an end whichenters the T-slot as at C. By having one type for holes and

another for T-slots, the stop-pins can be located in practicallyany position . After the pins are inserted in the platen

,the

screws shown are adjusted against the work. Stop-pins are

ordinarily placed at one end of the work to take the thrust ofthe cut, and sometimes they are needed along the sides to pre

vent lateralmovement. The screws of some stop-pins are in

Fig. rp. High Casting supported by Brace which takes Thrust of Cut

clined, as shown at C

,in order to force the work down against

the platen . Stop-pins are alsomade withou t adjusting screws.

Some castings have surfaces to be planed that are a considerable distance above the platen

,as shown in Fig. 19, which

illustrates a large pillow-block set up for planing the base. AS

will be seen,the end restin g on the platen is comparatively small,

and if the casting were simply clamped at the lower end,itwould

tend to topple over when being planed , because the thrust ofthe tool is so far above the point of support . To prevent anysuchmovement, braces B are used . These braces serve practically the same purpose as stop-pins. The style of brace shown

24 THE PLANER

has a hinged pin in its lower end which enters a hole in theplaten

, and the body of the brace 15 a piece of heavy pipe. At

the‘

upper end there is an adjustable fork-shaped piece whichengages the work, and the hinged joint at the lower end enablesthe brace to be placed at any angle. In some Shops woodenblocks are used as braces. The arrangement of these braces and

the number employed for any given case depend of course on theShape and size of the casting, and this also applies to the use of

stop-pins and clamps. The location of all braces and clampingappliances should be determined by considering the strains towhich the part will be subjected during the planing operation .

Pig. so. Work held b etween Stop-pins and Strip Bolted to Platen

Use of Stop-pins and P laner Strip Parallel Strips. An

arrangement which can often be used to advantage in place of achuck is shown in Fig. 20. The part to be planed is held between ordinary stop-pins S and a

“planer strip ” P that is boltedto the platen . This strip has a tongue piece t, which fits into theT-slot and locates the side a parallel to the travel of the platen .

A stop-pin should be placed against the end b of the work toprevent longitudinalmovement.Parallel strips are placed beneath parts to be planed usually

for the purpose of raising themto a suitable height,or to align

a finished surface on the under side with the platen,when such

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26 THE PLANER

Fig. 22 . The angle-plate A has two faces a and b which are

square with each other, and the work W is bolted or clampedto the vertical face, as shown . The arrangement of the clampsor bolts depends, of course , on the shape of the work. Theparticular part illustrated , which is to be planed at f , is held bybolts inserted through previously drilled holes, and the left end

is supported by a clamp C,set against the under Side to act as a

brace and take the downward thrust of the cut. Angle-plates

are generally used for holding pieces, which, because of their Odd

shape, cannot very well be c lamped directly to the platen .

Occasionally an angle-plate can be used in conjunction withclamps for holding castings, as illustrated in Fig. 23 . In this

Fig. 3 3 . Use of Angle-plate in Conjunction with Clamps for Holding Work

example the angle-plate A is placed across the platen and servesas a stop for taking the thrust of the cut. The flange on theopposite end is supported by a block B against which the casting is clamped .

Some castings are so shaped that a great deal of time wouldbe required for Clamping themwith ordinarymeans and

,for such

work,special fixtures are Often used . These fixtures are de

signed to support the casting in the right position for planingand they often have clamps for holding it in place. Some workwhich could be clamped to the platen In the usual way is heldin a fixtu re because less time is required for setting it up. Thisis the practice where a large number of pieces have to be

planed.

CLAMPING METHODS 2 7

Holding Thin P lates for Planing. When it is nec essary toplane thin plates or similar work which cannot be clamped inthe usual way, either wedge-shaped or pointed pieces similarto those shown atA and B

,Fig. 24, are used . These are known

as spuds or toe-dogs, and one way in which they are

applied is indicated at C. Stop-pins S are inserted in the platen

on each side of the work,and the dogs are forced against the

work by tightening the screws. Owing to the angular position

of the dogs, the work is pressed down against the platen.

The

inclination should not be too great, as the outer end of the dogwillmove upward when the screws are tightened , withou t trans

Pig. 34. Method of Holding Thin Flat Plates while Planing

mitting any pressure to the work. One or more stop-pins 1:

should be placed in front of the part being planed to take the

thrust, and at least two dogs will be required on each side unless

the work is comparatively short.

Use of Magneti c Chucks on P laner. Magnetic chucks, such

as are used on su rface grindingmac hines, can also be applied toplaning andmilling operations, especially for holding thin parallelparts that are difficult to hold by othermeans. Fig. 25 showshow amagneti c Chu ck of rectangular shape is used for holdingthree castings while the upper surfaces are being planed. Thecurren t (whichmust be direct and not alternating) is suppliedby a cable A which passes under the cross-rail to a plug abovethe machine. The chuck is magnetized by closing switch B

28 THE PLANER

which is a duplex type . In order to demagnetize the chuckface

,open the switch andmove the handle un til the switch bars

nearly come into con tact with the posts on the opposite end;then quicklymove the switch bars in and out of contact with

the posts . Thismovement, if timed correctly, will remove themagnetismleft by the previousmagneti c charge. I f the contact

should be too long, the chuck will simply become oppositely

Fig. 3 5 . Walker Magnetic Chuck applied to Planing Operation

charged and in such a case , it can be discharged again bymovingthe switch in and out Of contact with the opposite posts .

The castings are held against end-wisemovement by the stripC which takes the thrust Of the cut. Slotted clamps D are also

used to stay the work laterally. When a number Of pieces are

held on the Chuck at one time, it is advisable to separate themwith strips of non-magnetic material. I ron or steel parts can

be held on magnetic chucks, and the gripping power dependsupon the amount Of surface in contact with the Chuck face.

CLAMPING METHODS 29

Imbedding Work in P laster of Paris or Wax. Sometimes itis necessary to plane thin parts which cannot be held onmagneticchucks because they aremade of some non-magnetic material,such as bronze , or because they are so irregular in Shape thatthere is not sufficient surface in contact with the Chuck face tohold the work securely. In such cases, itmay be advisable toimbed the work in plaster of Paris, especial ly if the parts are

flexible and liable to be sprung out of shape and it is impossibleto use ordinary clamps. A mixture of melted bees-wax and

‘

rosin in about equal proportions is also used for this purpose.

One ormore pieces are placed in a box-shaped enclosure and

Fig. 26. V-b lock for Holding Cylindrical Parts in AlignmentMachine Tab le

plaster of Paris or wax is poured around themand allowed toset

,thus holding the parts for planing and supporting themin

every direction . Thismethod Of clamping work is rarely neces

Holding Cylindrical Parts for Planing. The planer is sometimes used for cutting keyways or splines in shafts, and , occa

sionally, other cylindrical work requires a planing operation . In

order to hold and at the same time align round work with theplaten ,V-blocks (Fig. 26) are used . These blocks have a tonguepiece t at the bottomwhich fits into a T-slot in the platen

,and

the upper part of the block is V-shaped as shown in the end

view. This angular groove is central with the tongue piece so

that it holds a round shaft in alignment with the T-slot, which is

30 THE PLANER

parallel with the travel of the platen . The diameter of a shaftheld in one of these blocks c an vary considerably, as indicated bythe two circles

,withou t affecting the alignment. In other words,

the centers c and 6; of the large and small circles, respectively,coincide with the vertical center-line.

Fig. 27 illustrates how V-blocks are used in loc omotive shopsfor holding a piston-rod while the cross-head, which ismountedon the end, is being planed. The bearing surfaces of the crossheadmust be in line with the rod which fits a tapering hole in

Fig. 2 7 . Piston-rod and Attached Cross-head Mounted in V-b locksfor Planing

one end of the cross-head. By assembling the cross-head and

rod and thenmounting the latter in V-blocks,the bearing

faces are planed in alignment with the rod .

A spec ial planer strip which is used in conjunction with screwstops for holding round parts is illustrated in Fig. 28. Thestrip has an angular face f so that pressure fromthe screws S

tends to force the shaft down against the platen as well as againstthe strip itself. This angular face is aligned with the platen bythe tongue piece t.Method of P laning Accurate V-b locks. A good method of

making a pair of accurate V-blocks is as follows : First plane the

CLAMPING METHODS I

bottomof each block and formthe tongue piece t, Fig. 26

,to

fit closely the platen T-slots . Then bolt both blocks in line onthe platen and plane themat the same time so that they will beexact duplicates . A square slot or groove is first planed at thebottomof the vee, as shown

,to forma clearance space for the

tool. The head is then set to an angle of 45 degrees and one

side of the vee is rough planed . The blocks are then reversed

or turned end for end and the opposite side is rough planedwithout disturbing the angular setting of the head. Theseoperations are then repeated for the finishing cuts . Thismethodof reversing the work , instead of setting the head to the opposite

Fig. 38. Method of Holding Shaft for Splining or I eyseating

angle,insures equal angles for both sides and a vee that is exactly

central with the tongue piece .

Distortion of Work by Clamping. When cas tings or forgingsare set up on the planer for taking the first cut, usually the sidethat is clamped against the platen is rough and uneven , so thatthe work bears on a few high Spots. This condition is shownillustrated on an exaggerated scale in Fig. 29, which shows a

casting that bears at a and b,but does not touch the platen at

the ends where the c lamping is to be done. I f the c lamps weretightened with

‘out supporting the work at the end,the entire

casting would probably be sprung out of shape more or less,depending on its rigidity, with the result that the planed surface

3 2 THE PLANER

would not be true after the clamps were released,because the

casting would then resume its natural shape. To prevent inaccurate work fromthis cause , there should always be a goodbearing just beneath the clamps, which can be obtained by inserting pieces of sheetmetal, or even paper when the unevenness

is slight. Thin COpper or iron wedges are also used for packing under the clamps. I t is good practice when accuracy isrequired and the work is not very rigid to release the clampsslightly before taking the finishing cu t. This allows the part to

spring back to its normal shape andthe finished surface remains trueafter the clamps are removed.

Very long castings or those whichare rather frail but quite large andheavy sometimes bend by theirown weight or are sprung out of

shape by the pressu re of the planing tool, unless supported at theweak points. When setting suchcastings on the planer, jacks, suchas the one illustrated in Fig. 30,

forma very convenient means of

Fig. 30. PM “ "acksupport . This particular jack hasa ball joint at the top which allows

the end to bear evenly on the work, and the screw can be lockedafter adjustment to prevent it fromjarring loose . These jacks

,

which aremade in different heights, can also be used in various

ways for supporting work being planed . Fig. 2 7 shows a praetical application of planer jacks, two being inserted beneath thecross-head to prevent any downward spring. Hard-wood blockscut to the right length are also used as supports .

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34

then finished, they would tend to remain true , though slight

changes might occur even then . Because of this tendency todistortion as the result of internal stresses, all work, especially if

not rigid, should be rough-planed before any finishing cu ts are

taken . Of course, such a change of shape does not alwaysoc cur, because the stressesmay be comparatively slight and theplaned surface so small in proportion to the size of the castingthat distortion is impossible. When great accuracy is required ,it is the practice in some shops to rough plane the casting and

then allow it to season for several weeks before taking the

finishing c uts. This seasoning period is to allow the stresses

Fig. 3a. DiagramIllustrating Points Relating to Position of Work

to become adjusted so that little or no Change will occu r after

all the surfaces are finished.

Locating Work with Relation to Surfaces to be Planed.

Another important point in setting work is to locate it so that

all surfaces to be planed can be finished to the required dimensions. On some work it is also desirable to have a planed partfairly true with a surface which remains rough

,either to secure

a neater finish or formore important reasons. Therefore,when

either a casting or forging is being set up on the planer,it should

be located according to the requirements for that particu lar part.As an illustration ,

suppose a flange a, the boss b and the surface

0 of a cast-iron cover plate, Fig. 32 , is to be planed so that the

THE SURFACE GAGE 35

distance between these surfaces corresponds to the dimensionsgiven on a drawing. The first operation wou ld be to plane theside 6

,the work being set up in the position indicated at A

The casting is first set abou t parallel with the platen, but it

should be remembered that the surface which is set level orparallel is not necessarily the one to be planed . In this case theside d is to remain rough, and it is desirable to have a uniformthickness at when the cover is finished; therefore the casting isset by side (1 rather than by the

upper surface c , or, in other words,is located so that the finished surface will be true with the rough

side of the cas ting.

The amount ofmetal to removewhen planing side 6must be determined by considering the relationoi this side to the other parts that

are to be finished when the cast

ing is turned over . For examme,it shou ld be possible to plane flange

a to a height h (as given on the

drawing) without removing too

much or too littlemetal fromtheflange. Suppose a light cut weretaken fromside c just deep enough to true it and then the castingwere turned over, as indicated at B ,

for finishing the opposite

side. When planing the flange itmight be necessary tomake thethickness l considerably less than it Should be, in order to secure

the proper height h. This, however, would not occ ur if whenplaning side 6 the thickness of the flange as well as the height

h were considered . Therefore,the relation between the difier

ent surfaces shou ld be kept inmind. Sometimes it is necessaryto set a casting very carefully and to plane ofl

'

just the right

amoun t, in order to finish the'

other surfaces to the required di

mensions .

The Surface Gage and its Use. The surface gage is usedvery extensively in connection with planer work for scribing

Fig. 33 . Surface Gage

36 THE PLANER

lines to Show the location of finished surfaces, and also for settingparts parallel with the platen . This tool, which is shown in

Fig. 33 , has a rather heavy base on which ismounted a rod R

carrying a pointer or scriber S . The latter can be adjusted in or

out and it also can be moved to any position along the rod.

Af ter the scriber or pointer has been set to abou t the right height,it can be set accurately to the position desired by turning screw

A which gives a fine adjustment. There are two pins B in thebase which can be pushed down when it is necessary to keep

the gage in line with the edge of a plate or the side of aT-slot.

Themethod of using a surface gage for setting a surface parallelto the platen is indicated in Fig. 34. The scriber S is first set

Fig. 34. Testing Alignment by Using Surface Gage

to just touch the work at some point; the gage is then movedaround to the opposite side, as shown by the dotted lines , and in

this way the heights at various points are compared .

The surface gage is also used extensively for laying out work.

As a simple illustration ,suppose the sides b and c (Fig. 34) were

to be planed and it were necessary to have the thicknesses x and

y of the flanges and the height 2 all conformto given dimensions.

I f lines I and ll representing the finished su rfaces were first

scribed on theflanges, these would serve as a guide when planing,and such lines could easily be drawn by using a surface gage ,even though the sides did not lie in the same vertical plane.

The surface gage is also used for setting lines which have been

PLANER TOOLS 37

scribed on the work and represent the location of finished sur

faces , parallel with the planer platen .

Various Forms of P laner Tools . The number and varietyOf cu tting tools used on a planer depend upon the character of thework which is done on that particu lar machine . I f the workvaries considerably, espec ially in its form,

quite a number of toolsOf diflerent shapes will be needed , whereas , planers that are usedprincipally formaking duplicate parts do not need a large tool

equipment. In Figs. 35 and 36 , two sets of tools intended for

general work are shown . Occasionally, tools of special formare

required,but the various types in the sets illustrated will take

care of practically all ordinary planing operations. Fig . 35

also shows some typical examples of the kind of planing forwhich the diflerent tools are adapted .

The tool shown at A is a roughing tool. This formis particularly adapted for taking deep “ roughing cu ts in cast iron

,

when it is necessary to remove considerablemetal. This styleof tool is alsomade to the opposite hand , as at B ,

because it issometimes desirable to feed the tool toward the operating sideof the planer; ordinarily, however , horizontal surfaces are planedby feeding the tool away fromthe operator

,the tool moving

fromright to left,as viewed fromthe front of the machine .

This enables the workman to see just what depth of cut is beingtaken at the beginn ing of the cu t.

The tool C with a broad cu tting edge is used for taking finishing cu ts in cast iron . The cutting edge is set parallel with theplaner platen ,

and the feed for each cu tting stroke is a little lessthan the width of the edge . Notwithstanding the coarse feed

,

a smooth surface is left on the work, provided the tool is properlyground and set

,and does not chatter when in use. Tools of

this type aremade in various widths, and when planing verylarge and rigid castings, wide cu tting edges and coarse feeds areused . (See

“ Feeds for P laning”

) Wide finishing tools for castiron are sometimes ground so that the cu tting edge

,instead of

being parallel with the front side of the tool,slopes back at an

angle to give a shearing cu t. A plain round-nose tool is shownatD. This style is often

"

used for rough planing steel or wrought

Fig. 35 . Planer Tools of Diflerent Formand Operations for whichThey are Adapted

PLANER TOOLS 39

iron . I t can also be made into a finishing tool for the samemetals by grinding the nose or tip end flat. The width of theflat cu tting edge ismuch less, however, than for cast-iron finishing tools, because if very broad edges and feeds were used when

planing steel, there would be danger of the tool gouging into thework. Steel ofiers a greater resistance to cu tting than cast ironand that is why broad tools tend to gouge in ,

espec ially if thetool is not held rigidly to prevent its springing downward. ToolE

, which is known as a diamond point, is also used for roughplaning steel or iron and for taking light cu ts .

The bent tools F and G are used for planing either verticalsurfaces or those which are at a considerable angle with theplaten . These are right and left-side roughing tools

,and they

are adapted to either cast iron or steel. They can also be usedfor finishing steel. Finishing tools for vertical or angular castiron surfaces are shown at H and I . These have wide cuttingedges to permit coarse finishing feeds. Vertical surfaces can

often be planed to better advantage by using a straight tool inthe side-head, when the planer is so equipped. Right and leftangle tools are shown at J and K . This style of tool is for plan

ing angular surfaces which, by reason of their relation to hori

zontal or other surfaces , can only be finished by a tool having a

formsimilar to that illustrated . A typical example of the kindof angular planing requiring the use of an angle tool is indicated

in the illustration . Af ter finishing side a,the horizontal surface

b (fromwhich a roughing cu t should have been taken previously)could be planed by feeding the same tool horizontally.

A square-nose tool is shown at L . This is used for cu tting

slots and squaring corners, and the same style of tool ismade indiflerent widths. A narrow square nose or

“parting ” tool is

shown at M . I t is adapted to cu tting narrow grooves, and can

also be used for cu tting a part in two ,provided the depth does

not exceed the length of the narrow cu tting end. Right and

left side-tools are shown at N and 0. These can frequently be

used to advantage on vertical or angular surfaces. A tool forplaning brass is shown at P . I t has a narrow rounded cu ttingedge and is verymuch like a brass tu rning tool. For finishing

40 THE PLANER

cuts in brass,tools having narrow flat ends are often used .

Right and left,bent

,square-nose tools are shown at " and R .

Such tools are used for cu tting grooves or slots in vertical sur

faces and for similar operations .

The peculiarly-shaped tool, shown by front and Side views at

S ,is especially adapted to finishing cast-iron surfaces . This

type is known as the goose-neck ” because of its Shape, and it isintended to eliminate chattering and the tendency which a reg

ular finishing tool has of gouging into the work . By referring

to the side view it will be seen that the cutting edge is on a line

Fig. 36. Set of Planer Tools Ground on Sellers Tool-grinurngMachine

with the back of the tool shank,so that any backward spring

of the tool while taking a cu t wou ld cause the cu tting edge to

move along an arc c or away fromthe work . When the cu ttingedge is in advance at some point x

,as with a regular tool, it will

move along an arc d,if the strain Of the cu t causes any springing

action , and the cu tting edge will gouge in below the finished

surface. Ordinarily,the tool and the parts of the planer which

support it are rigid enough to prevent such a movement,so

that the goose-neck tool is not always necessary .

All of the tools shown in Fig. 35 are forged froma solid bar of

steel, the cu tting end being forged to abou t the right shape,

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42 THE PLANER

shank by a bolt as shown . This style of tool is used for finishinground surfaces, the cutter beingmade to the required diameter.I t is also used for finishing the upper sides of T-slots as illus

trated at A in Fig. 38, the diameter d of the c utter being equal

to the width of slot required . When the cu tter bec omes dull,its retaining bolt is loosened and the c utter is turned around farenough to bring a new edge in the working position . Formtools are sometimes used on planers for finishing surfaces of

irregular form the c utter beingmade to correspond In shape to

the formrequi red .

Fig. 38. (A) Sirin . T-slot with Circular Tool. (8 ) Adjustab le Tool.(C) nderc utting Tool with Lifting Latch

A tool having two cu tters is shown at C,Fig. 37 . This style

is sometimes used for planing duplicate work, having two sur

faces S and $1, a given distance apart. By having two cutters,both sides arefinished at the same time . As the cutters are ground

away, they aremoved ou t to the requ ired width by drawing in

the taper bolt 1against which the inner ends of the cu tters rest.This is an example of the special tools sometimes used in planerwork . The tool shown atD is a solid forged type , that is adaptedfor finishing steel. The way this tool operates is shown by theplan view. The c utting edge e is at an angle with the shank,

PLANER TOOLS 43

and as the workmoves in the direction shown by the arrow, the

comer or edge e removes a light shaving and leaves a smoothsurface . The edge is cu rved slightly, as shown by the side view,

so that the cutting is done at the center. By using soda water,

or even plain water, while planing, a bright su rface is Obtained.

Only very light cuts are taken with this tool.Another formof tool for finishing the sides of T-slots is illus

trated at B in Fig. 38. The cu tting end is slotted through thecenter

'and a small conical headed screw S is used to spread the

two sections when the width of the end has been reduced byrepeated grinding.

Sketches C and D show how a latch is sometimes applied to anunder-cu tting tool such as is used on planers formachining the

Fig. 39. Roughing and Finishing Tools for Planingbottoms of T-slots . The stroke of the planer is adjusted so thatthe hinged latch l which drags over the upper surface on thecutting stroke drops down and , when the tool returns, prevents

it fromentering the slot. The position of the tool on the return

stroke is illustrated at D. When a lifting latch is not u sed , it isneces sary to block the tool so that it cannot rise against theupper part of the slot. B locking the tool is objectionable, be

cause the cu tting edge drags back over the planed su rface and is

dulled quickly.

Points on Grinding Planer Tools. While the action of a

planer is entirely difl'

erent fromthat of a lathe ,many of the principles which govern the shape of turning tools also apply in thegrinding of tools for planing. Front and side views of a planerroughing tool are shown atA Fig. 39. As the cu tting is done by

44 THE PLANER

the curved edge e, the front su rface b is ground to slope backwardfromthis edge, to give the tool keenness, the slope being awayfromthe working part of the cu tting edge . The end or flank ofthe tool is also ground to slope inwards to provide c learance.

The angle 6 of clearance is about 4 or 5 degrees for plan er tools,which ismuch less than for lathe tools. This small clearance isallowable because a planer tool is held abou t square with the

platen,whereas a lathe tool, the height of whichmay be varied ,

is not always clamped in the same position . A lathe tool alsorequiresmore clearance because it has a continuous feedingmoveinent, whereas a planer tool is stationary du ring the cut, the

Fig. 40. Diflerent Types of Planing Tools

feed taking place just before the cu t begins . This point-

Should

be considered when grinding planer tools, because the clearanceOf any tool shou ld not be greater than is necessary to permitthe tool to cut freely

,as excessive Clearance weakens a tool.

The slope Of the top surface b depends on the hardness of the

metal to b e planed , the slope angle being less for hardmaterial,tomake the cu tting edgemore blunt and stronger. When toolsare ground by hand , the angles Of slope and clearance are not

ordinarilymeasured , the workman being guided by experience.

By grinding a flat spot on the nose or lower end , this tool can beused for taking finishing cu ts in steel. Finishing cuts are alsotaken with a round nose tool by u sing a fine feed .

PLANER TOOLS 43

The edge e of the cast-iron finishing tool B should be groundstraight by testing it with a small straight edge or scale . Thecomers should also be rounded Slightly

, as shown ,as a square

corner on the leading side will dull quickly . The illustrationshows clearly the shape of the tool. Tool A Fig. 40 ,

is shapedsomewhat like a side tool except that cutting edge e is cu rved .

The face b slopes away fromedge e and the end is given a slightclearance c . The square-nose tool, seen atB ,

cuts along its loweredge e, and is given Clearance c on the end and sides, as shown inthe two views. The lower edge is the widest part Of the cu ttingend

,the sides sloping inward in both a vertical and horizontal

direction,which prevents the tool frombinding as it moves

through a narrow slot.The side-tool C c uts along edge e

,which

,as the side view

shows, Slopes backward . P laner side-tools are not alwaysmadein this way, but it is a good form,

as the sloping edge starts a

cut gradually, whereas a vertical edge takes the full width Ofthe c ut suddenly

, thus producing a greater shock. As too"D isused for vertical planing

,the cu tting is done by edge e; hence

face b should slope back fromedge e. The diamond point E isground with a narrow rounded poin t; this type of tool is usefulwhen a light c ut is necessary

,either because the work cannot b e

held secu rely for planing or for some other reason . The formtool F is used for rounding edges . Tools of this type are sharpened by grinding on the front face only

,in order to retain the

curved edge. When sharpening other than formed tools, thegrinding is done both on the face and end, because a sharp edgecan be secu redmore quickly by this method.

Reference has beenmade to the grinding of these few types oftoolsmerely to point out some of the principles connected withthe grinding of planing tools. When the principle of tool grinding is understood, the various tools required, whether regular orspecial in form, can be ground withou t difli culty . One thingthat should be remembered when grinding a tool is that it doesnot pay to force the tool too hard against the grinding wheel

,

as is Often done in attempting to sharpen the tool quickly. Thetool Shou ld be ground with amoderate pressure, and it Shou ld

46 THE PLANER

be withdrawn frequently when forming a flat surface to preventexcessive heating and burning Of the tool. The grinding wheelshould always be supplied with plenty of cooling water.Multiple or Gang Planing. When a number Of duplicate

parts have to be planed,much time can Often be saved by arrang

ing the castings in a straight row along the platen so that theycan all be planed at the same time . This method enables a

number Of parts to be finishedmore quickly than would be possi

Fig. 41. An Example of Gang Planing

b le bymachining themseparately, and it also insures duplicate

work. An example Of mu ltiple or gang planing is shown in

Fig. 41 . The particular castings illustrated are the “ saddles ” Ofplaner tool-heads and eight are being planed at the same time.

Both tool-heads are in use,and the top surfaces and sides of the

castings are finished at this setting .

This method of planing cannot always b e employed to ad

vantage as the shape of the work or location of the surfaces to be

GANG PLANING 47

machined sometimesmakes gang planing impracticable and evenimpossible. I f the castings are so shaped that there will beconsiderable space between the surfaces to be planed

,when they

are placed in a row,somuch timemight be wasted while the tool

was passin g between the differen t surfaces that it would bebetter to plane each part separately . Some castings al so havelugs or other projections whichmake it impossible for the toolto pass fromone to the other withou t being raised to clear the

Fig. 42 . Twenty Connecting-rods b eing Planed Simultaneously

obstruction . On the other hand, when castings are qu ite symmetrical in formand the surfaces are so located that the planingtool can pass fromone to the other with a continuous stroke,the gangmethod of planing insu res a uniformproduct and greatlyreduces the time required formachining.

Another example of gang planing is shown in Fig. 42 . Twentyengine c onnecting-rods are clamped to the platen and the twoheads of the planer are working on the bosses at each end Of the

rod, the operation being that of planing the sides. The rods

48 THE PLANER

are placed against one another,with every alternate rod reversed ,

to bring a large and small end together, in order tomake a straightline Of castings . The entire string of castings is prevented fromshifting along the table by two stop-pins at the end

,and they

are held down on the platen by a series Of straps or clamps alongthe center. These connecting-rods are steel castings; the planerhas a cu tting speed of 40 feet perminu te with a 3 inch depth Ofc ut and a transverse feed Of 3

32

“ inch per stroke .

Castings that are finished by gang planing are often held inSpecial fixtures

,especially if they are of irregular shape and not

readily clamped directly to the planer table.

Fig. 43 . Illustrating Use of Index Centers as Applied to Planer Work

Use of Planer Index Centers. Centers are sometimes used

on the planer to support work thatmust be indexed or rotatedpart of a revolu tion between successive operations. Fig. 43

shows a set of planer centers and illustrates their application .

The centers are bolted to the table and are aligned with eachother by tongues on the base which fit into one Of the T-slots.

The example of work shown has been turned in a lathe,and the

operation is that of planing the enlarged part square . The

sides of the square section must be parallel with the cylindricalends. The piece is held by the same c enter-holes that were

used for turning it, and a dog is attached to one end . This dogengages the slotted armof the headstock center, all play between

the dog and armbeing eliminated by adjusting a set-screw pro

vided for this purpose.

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so THE PLANER

first make a cast-iron or sheet-steel templet corresponding tothe cu rvature required . This templet is then clamped against

one end of the work (usually the end at the beginning Of thecutting stroke) and the planing is done by manipulating thehorizontal and cross-feeds so that the tool follows the ou tlineOf the templet. If the hand feeding is done carefully and thefinishing tool is ground to correspond in a general way with thecurvature to be planed , fairly accurate results can be obtainedby this method . Special attachments are commonly used forplaning curved surfaces

,especially when duplicate parts are

required . Some of the attachments that have been used forc ircular planing are described in the following

Fig . 45 . Templet Type of Curve Planing Att'

achment

Attachment for Circular P laning. A very simple formOf

radial planing attachment is shown in Fig. 44 . A bracket A isbolted across the housing and carries a pin B upon which theradial armC swings. The lower end of armC is pivoted to thetool-slide

,the feed-screw of which is removed

,thus allowing it

to move freely. The casting shown in the illustration is the

steamdome of a boiler and the operation is that Of planing itto the radius Of the boiler shell. Af ter the tool is properly set,

the planing is done by simply feeding the saddle along the crossrail. This horizontalmovement causes the tool point to followan are equal to the radius Of armC which ismade to suit thecurvature required .

CIRCULAR PLANING ATTACHMENTS 31

Templet Type of Curve P laning Attachment. An attachment for planing work of a convex or concave shape is shownin Fig. 45 . This attachment consists principally of four parts;namely

,the two side brackets A a templet B which conforms

to the curvature to be planed,and the double-armed leader C

which is attached to the tool-slide. The side brackets are pro

vided with bosses at the top in order to hold the templet so thatit will clear the planer head (see end view) , thus allowing the

Fig. 46. Miner-Boswell Radius Plan ing Attachment for Machining Links, etc.

saddle to bemoved along the cross-rail . The templet, which ismachined to the required formon a profile or slotter

,is attached

to the brackets A by bolts. The double-armed leader C has a

roller at the topwhich engages a slot in the templet, thus irnparting a verticalmovement to the tool-slide when the saddle is fedhorizontally along the cross-rail.

When using this attachment, the power feedmay be engaged,and as the tool is automatically raised or lowered , Obviously it

will plane a surface corresponding to the cu rvature Of the slot

in the templet. As will be seen by referring to the end view,

5 2 THE PLANER

the brackets A fit over the top gu ide on the cross-rail and are

fastened in position by set-screws at the rear. Separate retain

ing pieces are fitted to the bottomof each bracket, these beingbolted in place after the fixture is mounted on the rail . This

attachment, or somemodification of it, is especially adapted for

planing a number Of duplicate parts .

Radius P laning Attachment. In locomotive shops where thecurved links for the valvemechanisms have to be machined , aplaner is Often used

,and various attachments have been designed

Fig. 47 . Elevation and Plan of Radius Planing Attachment

for this purpose. One Of these, known as the Aliner-Boswellradius planing attachment

,is illustrated in Figs. 46 and 47 .

This attachment has a plateA which is fixed to the planer tableand on this plate there is a square projecting block B . Thisblock fits into a cross slot in the ring C

,which has an annular

bearing in the top plate D. The latter forms the work table,and it is attached to a radial bar that passes through a doubletrunnioned bearing mounted in an adjustable stand E . Thering C is kept down by a central plate

,as shown

,and the work

table is provided with a retaining ring F .

SPIRAL PLANING ATTACHMENTS 53

Themovement of the planer table is transmitted by the squareblock B to ring C

,which , in turn , imparts a Circularmovement

to the work table; this is accompanied by a lateralmovementOf ring C with relation to the square driving block. With this

arrangement the driving power is transmitted to the work tablein the direction of the reciprocatingmovement Of the planer, andthe thrust of the tool’s cut is also along parallel lines . Owingto the small amount of stress imposed on the radial bar, thelatter is made of tubing and is comparatively light . The at

tachment is adjusted for planing diflerent radii by shifting standE and its bearing along the bar at right-angles to the planertable . The link to be planed can quickly be located in the fixture by a center-linemarked upon the chuck.

P rior to planing the curved slot,the sides of the link areplaned ,

the edgesmilled , and the clearances for the planing tools drilledand slotted . The work is then placed on the attachment andthe slot is rough planed by using two parting tools simultaneously. These tools cut narrow slots on each Side , and the centralpart of the slot is removed in the formof a solid block. Afterthe link is roughed out in thismanner

, the slot is finished by side

tools. This attachment can also be u sed for planing quadrants,dies

,etc.

Attachments for P laning Spiral Flutes. The spirally-flutedor corrugated rolls

,such as are used in flourmills

,rubbermills,

etc.,are often machined on the planer by the use Of special

attachments such as are illustrated in Figs. 48, 49 and 50 . Theattachment shown in Fig. 48 is a simple design that is often used

,

the construction beingmodified somewhat in diflerent shops tosuit the nature of the work. The journals of the roll to be flu tedaremounted in special V-blocks held in a T-Slot Of the planertable. Straps or clamps are bolted across the topOf each journal,tightly enough to eliminate all play b ut still permit the roll torevolve . Attached to the end of the roll shaft there is an index

plate B containing asmany equally-spaced notches as there areflutes to be cut. At the side of the index plate there is an armCthat is connec ted to the index plate by plunger D. An exten

sion of this armrests upon the inclined bar E which is attached

54 THE PLANER

to a bracket bolted to the planer base . The armis held in con

tact with bar E by a weight F suspended at the end .

When cutting a spiral flute, the armascends the inclined bar,

thus rotating the work part of a revolu tion ,the amount of rota

tion and the angle of the spiral generated depending upon theinclination Of bar E . Af ter one flu te is cut

, plunger D is with

drawn ,the work is rotated one tooth and the next groove is cut.

By repeating this Operation , the entire roll is corrugated or flu ted.

Fig. 48. Attachment for Planing Helical or Spiral Flutes

The flutes generated in this way are not true helices, but whenthe helix angle is small the inaccuracy is negligible formost work.

Angle of Guide Bar for Spiral P laning. The angle at whichbar E should be set for planing a given spiral can be determinedapproximately by the following formula in which 6 angle towhich bar E should be set; I one-half length of work; angle

x 360; L lead of spiral;R horizontal distance fromL

center of work to center Of bar E .

SPIRAL PLANING ATTACHMENTS 55

Example. Grooves or flutes are to be planed in a roll,the

diameter of which is 5 inches and the length 20 inches. Thespiral angle a between the flu tes and the axis i s to be 4 degrees.

The first step is to find the lead of the spiral flu tes or the distance they would advance in one complete revolution . The

lead L equals the circumference C of the work divided by the

Fig. 49. Spiral Planing Attaclément Operated by Chain Drumandcaring

tangent of the spiral angle a,or L

1 I OInches. Angle 0

LX

tangent Of 16 degreesAssuming that the horizontal distance R fromcenter of

to cen ter of bar E is 6 inches, then,

which is the tangent Of 9% degrees, approximately . The bar,therefore, would be set to an angle of 9% degrees fromthe hori

56 THE PLANER

zontal. The angular position cou ld be gaged quite accuratelyeither by using an ordinary protractor placed on parallels ex

tending fromthe planer table , or by using a graduated protractorhead and level such as are provided with combination squares.

Spiral P laning Attachments of the Geared Type . The at

tachment shown in Fig. 49 is given a rotarymovemen t for spiralplaning bymeans Of a drumA around which chains are wound.

One of these chains is fastened to a support at the left and theother to a support at the right

,and as the table reciprocates

,

Fig. 50. Planing Spiral Corrugations in Flour M ill Roll by Use ofGeared Attachment

the drumis rotated part Of a revolution,first in one direction

and then in the other . This rotary movement is transmittedto the roll R ,

through the bevel and spur gearing shown in theplan view . The journals of the roll to be fluted are held in Vblocks fitted with straps or clamps adjusted to eliminate playb ut allow a free rotarymovement . The spur gear C attachedto the end of the work arbor or journal

,as the casemay be , has

concentric rows of holes drilled in the side and the work isindexed after each successive groove is cut, by withdrawingplunger D and engaging it with the next succeeding hole . The

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58 THE PLANER

width of the point or end of the rack tool (before the comers arerounded) equals the linear pitchmultiplied byExpres sing these rules as formulas ,

d h

w p t p

The radius r of the comers Of the tool equals one-seventh thewidth x of the space between the rack teeth at the top or alongthe addendumline.

Indexing the Tool when Planing Racks. When planing theteeth

,the tool is indexed a distance equal to the linear pitch 1)

Fig. 5 1. Diagrams showing Rack Planing Tools and Formation ofRack Teeth

either by means of amicrometer dial and the cross- feed screw

or by the use Of a positive locating device attached to the crossrail. Some planets havemicrometer dials on the feed-screw foradjusting the tool by direct measu rement, and if the planer isin good condition ,

quite accu rate results can be Obtained by thismethod of spacing the tool when cutting rack teeth

, althoughcare should be taken to avoid errors due to lostmotion betweenthe sc rew and feed-nut, bymoving the tool continuously in one

direction whenmaking an adjustment. When using themicrometer dial;it is well to set it to zero beforemaking each adjust

ment. The distance that the tool is indexed can then be read

direct fromthe zero mark,which tends to prevent mistakes

thatmight otherwise bemade. When a planer is not equipped

PLANING RACKS 59

with feed dials, special dials are sometimes applied for rackcutting.

To avoid the possibility Of error whenmeasuring the indexingmovement of the tool by using the cross-feed screw

,a special

indexing bar is sometimes attached to the cross-rail,especially

when a number of duplicate racks are to be planed . This barhas notches or teeth of the same pitch as the rack teeth to becut, and the planer tool-head is located positively by a pin or

plunger on the saddle which engages the notches in the fixedindexing bar.

Fig. 5 2 . Planing Teeth in Steel Racks for Frog and Switch Planers

Another very simple but positivemethod of indexing the tool

is to clamp a stop on the cross- rail in such a position that when

the saddle is against the stop the tool will be set for planing the

first tooth space; when the first space is cut, the stop is set ahead

of the saddle a distance equal to the pitch of the rack,by using

a gage. The saddle is then moved up to this stop for planingthe next tooth space , and this operation of adjusting the stopby the gage and locating the saddle against it is repeated for

each successive tooth.

60 THE PLANER

It is advisable when cutting rack teeth on the planer to have

an adjustable screw stop for down feed; then when the stop is

set correctly , all of the teeth can easily be planed to a uniformdepth. If the automatic down feed is used , it should be dis

engaged before the full depth is reached so that the tool-slide can

be fed against the stop by hand.

To avoidmaking a formtool for finishing rack teeth, a cir

cular cu tter, such as is used when milling racks 15 sometimesemployed when planing the teeth. The cutter Is bolted to a

shank held in the tool-holder, with one of the teeth in the lowestposition to ac t as a planer tool. Of course , this cutter must

Fig. 53 . Suc c essive Tools Used in Cutting S teel Rack Teeth

correspond to the pitch of the rack teeth , and , according to theB . S . systemfor involu te cutters, it should be a No. 1 form

,

as this number is adapted for cutting gearing varying froma

r35-tooth gear to a rack.

P laning Steel Racks. A practical example of rack cuttingon a planer is shown in Fig. 52 . These racks are used on the

Cincinnati frog-and-switch planets, and aremade of steel forgings instead of cast iron, because of the heavy class of work doneon a planer of this type . The rack ismade in sections and whenthe teeth are being cut, these sections are clamped to the planertable as shown in the illustration . The racks aremade from

ATTACHMENTS 61

per cent carbon steel forgings and the linear pitch of theteeth is about 2 inches.

The successive tools used are shown in Fig. 53 . The firstroughing tool, which is similar in Shape to a wide parting tool,is Shown at A . This tool is used to rough out the teeth and it

takes a cut inch deep per stroke, at a cu tting speed of

40 feet perminu te . After all the teeth have been roughed out

to within about 3 inch of the proper depth , tool B having a

stepped face is used to rough out the angular sides of the teeth .

Tool C is then put in the tool-holder and all of the teeth are

Fig. 54. Extension Head Used for Planing Parts which are too Wideto Pass b etween Housings

finished to within abou t 31; inch of the proper depth . The

final shape is given to the teeth by the formed cutter D. Thisis held by a strap, bolts and nuts in a slot in the special blockG

,the latter fitting snugly into the clapper box . The finishn

tool is held in thismanner to insure accurately formed teeth of

the proper angle. The spacing or indexing of the tools is doneby means of the micrometer dial or collar on the cross-feed

screw.

While the planer is Often used for this work,most rack cutting

is done either on amillingmachine by the use of an attachmentor on special rack-cu tting machines. These machines vary

62 THE PLANER

greatly as to size and design al though most of themformthe

teeth by amilling proces s .

Extension Tool-head. When a great variety of work is done

on aplaner , spec ial attachments are occasionally needed. Fig. 54

shows how a planer can be arranged formachining a casting Athat is too wide to pass between the housings when placed lengthwise across the table, for planing the end. The tool is held in an

extension head to locate it far enough forward to prevent thework fromstriking the housings when at the extreme end of

Fig. 5 5 . Floor Stand or Independent Housing for Special PlaningOperations

the cutting stroke. This extension is fastened to the saddle inplace of the swiveling base, and the regular tool-slide is attachedto its outer end .

E xtension tools that are long enough to reach across the workare also used for planing parts that will not pass between the

housings,but themore rigid extension head

, shown in the illustration ,

is preferable .

Floor Stand 01 Independent Housing. Another method of

planing a casting that is too large to pass between the housingsis illustrated in Fig. 55 . The su rface to be planed is too wideto use an extension head, and the tool is held on a special floor

OPEN-SIDE PLANER 63

stand that is bolted to a T-slotted base-plate secured to the

foundation . The stroke Of the planer (as far as its position is

concerned) is adjusted with reference to the tool of this auxiliaryfloor stand , the latter being set far enough forward to provideroomfor the work between the tool and planer housing. Thefloor stand or

“independent housing

,shown in the illustration ,

has an automatic feed operated fromthe planer feedmechanism.

Auxiliary equipment of this kindmakes it possible to handle a

large range Of work on one or two planers, which is especiallydesirable in some shops.

Open-side Planers. The open-side type of planer has a

massive column on only one Side Of the table so that the oppositeside is open and unobstructed

,which greatly increases the range

Of the machine. The cross-rail or beamupon which the toolheads aremounted is Of very rigid design and has a broad bearing su rface on the column to prevent deflection due to the thrustOf the cut. The Chief advantage of an Open-side planer is thatit can be used formachining large castings which could not be

handled on a two-housing planer of ordinary size, as well as forgeneral planing Operations.

Fig. 56 shows a typical example of open-side planer work.

The large casting being planed is the vertical column for anotheropen-side planer . The operation is that ofmachining a pad on

top for the motor bracket, and planing the end . The pad is

finished by a tool held in one Of the cross-rail tool-heads A and

the end su rface is planed by a tool held in side-head B . I f a

casting of this size were machined on a two-housing type of

planer,the distance between the housings would have to be

8 feet 8 inches, but with the open-Side design, the end of thework Simply projects beyond the table as the illustration shows.

When an exceptionally long casting must be held at right

angles to the table, the ou ter or overhanging end is generally

supported on an auxiliary rolling table which is supplied with

some open-side planers. This table is set parallel with the

planer and consists Of a series of rollers upon which ismountedan I -beamthat supports the work and travels to and fro with

the planer table.

64 THE PLANER

The driving and feedingmechanismof an open-side planer issimilar to that used on other types and the stroke is also con

trolled by the position Of dogs or tappets attached to the side ofthe platen . The particu lar planer shown in Fig. 56 is driven by

amotor C,which is connected by belts with countershaft D.

The latter transmi ts themotion by open and cross-belts to theplaner driving shaft at the base Of the column . The cross-rail

Fig. 56. Cleveland Open-side Planer and Examis of Work for whichthis Type of Planer is Adapted

p

can be adjusted vertically by power to suit the height Of the partbeing planed .

P laning Cast-steel Loc omotive Frames. The machining of

a locomotive frame is a good example of the application Of theplaner to large heavy parts requi ring rapid machining ratherthan skillfu l and accurate work. Fig. 5 7 shows how two caststeel frames are planed at the same time

,in the "uniata shops Of

the P ennsylvania Railroad . These shops have,under normal

conditions, a capacity for building a complete locomotive every

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66 THE PLANER

day, and this rate is sometimes exceeded , so that themachiningof frames is

.

an everyday occurrence . Practically all of thelocomotives built in these shops at the present time are equippedwith cast-steel frames instead of wrought-iron frames

,which

were used almost exclusively a few years ago. Frames that arecast aremuch cheaper than the forged type and another advantage of using cast steel is that pads or other projections can be

easily and neatly formed on the frame pattern .

The cast-steel frames are usually warped more or les s as

they come fromthe foundry, owing to unequal cooling,and

it is necessary to straighten themprior to machining. Thisstraightening is done under a large steamhammer . The frameis heated sufi ciently to insure a permanent set

” when straightened, and it is made approximately straight by giving it a fewblows with the hammer . The work is then ready for the first

machining operation which is that of planing the sides and

edges .

Two frames or sections are planed simultaneously on a very

rigid planer having five tool-heads. Fig. 57 shows thismachinetaking a roughing cut over the sides Of two frames . The work

is held on the platen by screw-stops and toe-dogs or “spuds

which are placed in an inclin ed position to force the work down.

Stops are also set against the frames at themost advantageouspositions to take the longitudinal thrust Of the cut. Part Of the

time , all five planing tools are at work , the three tool-heads on

the cross-rai l being used to plane the sides of the two sections,while the right and left side-heads plane the edges. The three

upper tools are started so that each rough planes abou t one-third

of the surface formed by the two castings . In this way theroughing is, Of course , done in much less time than would berequired if an ordinary two-head machine were employed . AS

many of these castings have spongy ,sandy spots

,blow-holes or

similar defec ts on the Cope side, a generous allowance is left forplaning in order to remove all porousmaterial.Owing to the power Of thismachine , very heavy cu ts can be

taken ,as indicated in the illustration . The planer is motor

driven ,andmomentarily asmuch as 90 horsepower is required

PLANING CYLINDERS 67

for driving, owing to the heavy hogging cu ts which are taken

in the tough cast steel. When roughing,‘

the tools frequently

cut to a depth of fromi to inch with a feed of 136 inch. The

average depth of cut for the five tools, however, would be somewhat less than the figures given . After the three heads on thecross-rail are started

,the right and left Side-heads are set. for

planing the edges. The work is set up for rough-planing the

first side, with the top edge of each sec tion outward . This isdone so that the top edges can be finished with reference to padsfor braces or brackets which are. located on the inside Of the topand bottomrails of the frames.

After the roughing cu ts on one side are completed , the finishingcuts are taken with broad flat tools which are given a feed varying fromI inch to 1} inch per stroke. Only two Of the cross-railheads are used for finishing, so that each frame can be planedby a continuous c ut in order to Obtain a smooth surface freefromridges. The frames are next tu rned over for roughing andfinishing the opposite side. The bottomedge of each frame isnow in the outward position

,thus permitting the ends of the

pedestals to be rough-planed. The finishing tools are set forplaning the second side by means Of a post or height gage towhich the cutting edges are adjusted . In this way the properthickness is quickly Obtained, although a fixed caliper gage isused to check this dimension . After the sides and edges havebeen planed, the inside faces Of the jaws are finished in a large

P laning Locomotive Cylinders. The cylinders of locomotivesvary considerably in their general arrangement

,and the exact

method Of planing themdepends, Of course , upon the design.

The various operations referred to represent the practice at the

"uniata shops Of the P ennsylvania Railroad. The style of

cylinder now used almost exclusively on the new locomotivesbuilt by this company is the single-expansion piston-valve type.

The first machining operation on a cylinder casting is that Ofboring the cylinder proper. After the cylinder is bored

,the

various surfaces on the saddle are planed.

By the use of an ingenious set Of fixtures, the castings are

THE PLANER

PLANING CYLINDERS 69

quickly and ac curately set up for the planing Operations. Figs.

58 and 59 show diflerent views Of the work mounted on thefixtures. Three cylinders are placed in a row and planed simultaneously, and the fixtures are so arranged that the bores ofthe various cylinders are aligned with one another and with theplaner platen . These fixtures consist Of heavy brackets or

standards B (see Fig. 60) having flanges as shown . The end

brackets have a single flange, whereas the two which comebetween the cylin ders are double flanged . There is a centralpocket A in each flange face , and the distance fromthese pocketsto the base is exactly the same for each bracket. Each of theconical disks C which engage the counterbores Of the cylindershas a cylindrical boss on the rear side which fits into any Of thecentral pockets AWhen a cylinder is to be set up for planing, one of these conical

disks is clamped in each end of the counterbore by a bolt passingfromone disk to the other. The brackets are also bolted to theplaner platen in the proper position . The distance between thebrackets is governed by the length between the outer faces ofthe disks after the latter are bolted in place, and the centralpockets A are all brought into alignment, laterally, by tonguepieces on the base of each bracket. The cylinder is next picked

up by a crane and lowered until the disks have en tered betweenthe brackets . The temporary holding bolt for the disks is thenremoved and the work is lowered until the cylindrical bosses

on the disks, which slide through the vertical slots D, rest in the

central pockets A Of the fixtures. When three cylindrical cast

ings have been set up in this way, the center line or axis of each

cylinder bore will be in alignment.The valve chamber is next set vertically with relation to the

cen ter Of the cylinder . TO Obtain this setting, a spider F ,

Fig. 59, is placed in the valve chamber and its hub is centeredwith the bore of the valve chamber by using hermaphroditecalipers. The casting is then adjusted vertically by the smallsupporting jacks seen in Fig. 58, until this center is the requireddistance below the center of the cylinder, as shown by an ordinary

su rface gage . The height fromthe platen to the cen ter Of the

70 THE PLANER

cylinder bore is accurately ascertained beforehand and remainsconstant for a given size fixture .

After the three castings are set as described, clamping pieceswhich fit in the slots D

,Fig. 60

,are tightened against the hubs

of the conical disks by clamps E . The cylinders are furthersecured by a long tie-bolt G which extends through the three

castings and holds both the work and fixtures rigidly together.

Fig. 59. Another View of Cylinder Planing Operation Illustratedin Fig. 58

By referring to the illustrations, it will be seen that these fixturesmake it possible to hold the three cylinders with very few Clamps.These fixtures have not only effected a considerable reduction inthe time required for setting the cylinders prior to planing, butthey also insure accurate and uniformwork.

After the cylinders are set as described,the top surface I

(Fig. 59) which forms the joint between the right and left-handcylinders is rough-planed by using the two tool-heads . This

PLANING CYLINDERS 71

surface is then finished with a broad tool which is set to the rightheight for the final cut by a special micrometer gage N . Thecutting edge is adjusted to coincide with the top of this gage,which is graduated with reference to the centers Of the fixtu resso that heights fromthe center of the cylinder bore can be readdirectly. The side I is next roughed ou t and finished by usinga side-head, and while this surface is being planed

,the seats K

and L (Fig. 58) for the steamand exhaust pipes are rough-planedwith the opposite side-head. Side J is finished to a certain distance fromthe planer housing

,the measuremen t being taken

with a special vernier gage. By measuring directly fromthehousing, duplicate work is assured and the liability Ofmistakes

Fig . 60. Fixtures for Holding Locomotive Cylinders while Planing

is lessened. This method Of measuring is made practicableby the improved fixtures

,which are always located in the

same lateral position on the platen and, consequently, hold the

finished cylinder bores in the same vertical and cross-wise

position .

The face M ,against which the frame is bolted when the loco

motive is assembled, is planed at the same time the seats K and L

are finished . The half-seat K for the exhaust pipe is gaged fromthe finished side I and the steampipe seat L is finished withreference to the exhaust seat. The distance between

'

surfaces I

and M ismeasured by a special height gage. This practicallycompletes the planer work. Of course, the order of the operations

is governed entirely by the shape Of the cylinder Casting, and

72 THE PLANER

differs fromthat desc ribed in the foregoing, for other types ofcylinders .

Planing Speeds. The speeds for planing usually vary from30 to 50 feet perminu te on the cu tting stroke

,with a return

speed three or fou r times as great . A general idea of planerspeedsmay be Obtained fromthe following figures given by theCincinnati P laner CO.

,which represent the practice in some of

the bestmachin e shops: Cast iron ,roughing, 40 to 50 feet per

minute; cast iron , fin ishing, 20 to 25 feet per minu te; steel

Ac tual Cutting Speeds of Planers

Return Speed . Feet per Minute

Ac tual Number of Feet Traversed on Cutting Strokes per Minute

Actual Number of Feet Traversed on Cutting Strokes per Hour

castings, roughing, 30 to 35 feet per minute; wrought iron ,roughing

, 30 to 45 feet perminute; steel castings,fin ishing, 20

feet per minu te; wrought iron ,finishing

, 20 feet per minute;bronze and brass, 50 to 60 feet perminu te;machinery steel, 30 to35 feet per minu te. When high-speed steel tools are used , a

speed of 55 feet perminute is given as abou t themaximumthatordinarily c an be used to advantage .

The Net or Actual Cutting Speed. When installing a planer ,the net or actual c utting speed should be considered. For

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74 THE PLANER

driving pulleys because the principal power loss at reversal is

due to the energy stored in the revolving pulleys; hence whenlighter pulleys are used

,there is less kinetic energy for a given

speed and less power is required at the point of reversal.

Fig. 61. Cincinnati Variab le-speed Belt-driven Planer

Feeds for P laning. The feed of a planing tool varies widelyfor difl

'

erent kinds of material and classes of work. I t is alsogoverned by the depth of cut

,the nature Of the cut (whether

roughing or finishing) , and by the rigidity Of the work whenclamped in position for planing. Feeds ordinarily vary from115 to 3 inch when taking deep roughing cu ts in steel, and from3 to 1

36 inch for rough-planing cast iron . When taking light

ELECTRICALLY—DRIVEN PLANER 75

finishing cu ts in cast iron ,a broad tool having a flat edge is

commonly used and the feed ordinarily varies from"} to 3 inchper stroke. When planing large, rigid castings a feed as coarseas or 1 inch per stroke is Often used .

Variab le-speed Drives for P laners. Many planers can onlybe Operated at one cu tting speed

,the driving pulleys being pro

portioned to give a speed that will be abou t right for averageconditions. A change of two ormore speeds

,however

,is very

desirable,because the cu tting speed should be varied to suit

the material being planed or the nature Of the cut. Many

modern planers have a variable-speed drivingmechanism.

A planer Of the variable-speed type is shown in Fig. 61 .

The belt pulley A transmits power to the driving pu lleys B and

C,through gearing enclosed in speed-box D. The speeds are

changed by levers E which control the position Of the slidinggears in the speed-box. This particu larmachine has fou r speedchanges. The speed variator is also u sed on motor-drivenplaners, themotor beingmounted on top Of the housing . Whena variety Of speeds is unnecessary

,a two-speed countershaft is

Often used .

Electri cally-c ontrolled Drive for P laners. The planer illus

trated in Fig. 62 is a variable-speed type driven by a reversing

motor. The speed chan ges are obtained by an electrical controller and a pilot switch. There are twelve cutting speedsranging from2 5 to 50 feet perminute and twelve return speedsranging from50 to 100 feet perminute. These speed changes

are varied by turning two handwheels on the‘

front of the controller case. These handwheels have dials graduated to Show

the various speeds.

In the Operation Of the planer, the point Of reversal is controlledby dogs similar to those on a belt-driven planer. At the instant

of reversal, a pilot switch is thrown by one of the dogs and thecontroller Short Circuits the armature through suitable resistance,causing themotor to ac t as a generator and consequently as a

powerful electric brake on the planer table . When the speed

of themotor has been reduced to a predetermined amount, thearmature current is reversed and the table starts on the next

76 THE PLANER

succeeding stroke. This sequence Of Operations takes place at

the end of each table stroke,whether on the cu tting or return

movement and is entirely au tomatic, being regulated by thecontroller.The pilot switch

,whichmay be operated fromeither side of

the planer, takes the place of the belt-shifting device on beltdriven planers. By manipulating the pilot switch, two speeds

Fig. 62 . Niles-Bement-Pond Planer with Reversing Motor Drive

in either direction are Obtained . One Of these speeds corresponds

to that forwhich the controller is set,and the other is a slow speed

which is useful when setting work or for slowing down whencutting hardmaterial. The planer shown in the illustration isequipped with a pendant switch which is suspended froman

overhead bracket and hangs above the table. This Switch can

bemoved to any convenient position andmay be used to controlthemovement Of the table fromeither side Of themachine.

DOUBLE—CUTTING PLANERS 77

Doub le-cutting P laners. Many attempts have been madeto design a plan er that would cut with equal eflic iency on both

the forward and return strokes. One Objection has been thattwo tools could not be used on some Classes of work , owing tothe lack Of clearance at the end Of the stroke; consequently,when using a planer having an equal speed of the table in bothdirections

,the absence Of a quick return on the idle stroke greatly

discounted,if not entirely Ofl-set

,the advantages gained on

work where double cutting cou ld be employed . In order to overcome this Objeetion ,

a double-cutting planer has been developedby an English concern

,that is equ ipped with a variable-speed

motor drive and a small auxiliary motor for such operationsas feeding and traversing the tools. With this arrangement, theforward and return strokes can be made either at a uniformspeed or the return stroke can be increased when required .

Another design of planer has also been introduced having a

belt drive,by means of which the same flexibility as regards

the rate of speed Of the return stroke c an be obtained. Themethod of holding the double-cutting tools is to fasten themback to back and exactly in line.

Evidently,if planers are to bemade double cu tting, the suc

cessful design must be qu ite difl'erent fromthat of ordinaryplaners in order to secure equal support for the tool when cutting

in both directions . The single-stroke planer is designed to takeamaximumcut in one direction only

,and a radical changemust

bemade in its design before it will be possible to plane eflicientlyin both directions. When the tool-head is clamped to the faceof a cross-rail

,which

,in turn

,is clamped to the face of the hous

ing, Obviously, the stresses produced in these parts when a cut

is taken in one direction are quite diflerent fromthose producedwhen the cut is in the other direction . In one case there is a

tendency to compress all of the parts solidly together, thus

giving a firmsupport to the cutting tool,whereas in the other,

the tendency is to pull all the joints apart, thus depriving the

tool Of the firmness Of its support and increasing the tendency

to chatter.

CHAPTER II

THE SHAPER AND SLOTTER

THE shaper, like the planer, is used principally for producing

flat or plane surfaces, bu t it is intended for smaller work than isordinarily done on a planer . The shaper is preferable to theplaner for work within its capacity because it is less cumbersometo handle and quicker in itsmovement . The action Of a stand

ard shaper,when in use

,is quite diflerent fromthe planer; in

fact,its operation is just the reverse, as the toolmoves back

and forth across the work, which remains stationary,except

for a slight feedingmovement for each stroke.

General Description of a Shaper. A shaper Of typical de

sign is shown ih Fig. 1 . The principal parts are the base andcolumn B and C; the table T which has a vise V for holdingwork; and the ramR which carries a planing tool in tool-post Iand is given a reciprocatingmotion by a crankmechanisminsidethe column . The work-table ismounted on a saddle or crossslide D, and it c an bemoved along the cross-rail A by turningthe lead-screw L with a crank or by an automatic feedingmechanIsm. The cross-rail c an be adjusted vertically on the face of thec olumn to accommodate work Of various heights

,and the tool

slide F with the tool c an be fed downward by handle E .

Shaper Driving Mechanism. The driving mechanismfor

the ramis shown in the sectional views, Fig. 2 . Shaft S on

which the driving pulley ismounted is conn ected through gearing with crank gear C. This gear carries a crank-pin or block Bwhich engages a slot in the armN

,and this arm,

in turn,connects

with the ramR and is pivoted at its lower end . As the crankgear rotates, an oscillatingmotion is given to armN which imparts a reciprocatingmovement to the ram. The amount thatthe armmoves and , consequently, the stroke of the ram

,is

governed by the position Of the crank-block B which can be ad

78

CRANK—SHAPER 79

justed toward or fromthe center of the gear by shaf t 0. Thisshaft connects through spur and bevel gears with a screw thatengages the crank-block

,as shown in the cross-section to the

left. The stroke can be changed while the shaper is inmotion ,

and the pointer G,as it travels along the stationary scale H ,

shows the length of the stroke in inches (see also Fig. I )

Fig. 1. Cincinnati Back-geared Crank-shaper

The position of the stroke can also be varied (while themachine is inmotion) by turning handwheel I which causes screwK to rotate and shifts the position of block L with relation tothe ram. Before making this adjustment

,block L

,which is

ordinarily c lamped to the ram,is loosened by tu rning lever M .

Bymeans Of this adjustment for the position of the stroke,the

tool ismade tomove back and forth over that part of the workthat requires planing, whereas the stroke adjustment serves to

80 THE SHAPER

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82 THE SHAP ER

c utting speed of the tool. This change of speed,however, which

accompan ies a change of stroke , only occurs with a crank shaper,the cutting speed Of a geared or rack shaper being constant for

any length of stroke . The diflerence between these two typeswill be referred to later.

Examples of Shaper Work . Most Of the work done in the

shaper is either held in the vise V (Fig. 1) or is clamped to thetable T,

which is provided with slots for receiving the clamping

Fig. 3. A S imple Example of Shaper Work

bolts . The vise resembles a planer vise,and it can be removed

readily when work is to be attached directly to the table. It

can also be swiveled to any angular position by loosening nutsn , the position being shown by degree graduations . The tableof this particu lar shaper is also removable

,to permit c lamping

parts directly to the face Of the saddle or cross-slide D,which

also has bolt-slots in the front face.

Fig. 3 shows an Example Of the kind of work which is held inthe vise. The operation is that of planing a number of steel

SHAPER OPERATIONS 3

strips which are clamped together between the vise jaws. Afterthese strips are firmly “ bedded ” on parallels which have beenplaced beneath them, the shaper is started and the stroke ad

justed both for length and position,to give the tool amovement

somewhat greater than the total width Of the work. The toolis then fed downward to thework and.the latter ismoved crosswise, by hand , until a cut of the right depth is started; the au to

Fig. 4. Casting of Irregular Shape Fig. 5 . Tab le Removed and CastingBolted to S ide of Tab le Clamped to Cross-slide

matic feed is then engaged by dropping the feed-pawl intomeshwith the ratchet gear on lead-screw

,as previously explained.

The tools used in a shaper are similar in formto planer tools,though smaller. When taking finishing cuts in the shaper

,

broad tools and wide feeds cannot b e used to the same extent asin planer work, because the shaper is less rigid and , consequently,there is a greater tendency for the tool to chatter .

Fig. 4 shows an odd-shaped casting bolted to the side Of the

table for planing the top su rface . The table,in this case, serves

84 THE SHAPER

the same purpose as an angle-plate on the planer , and themethodof holding the casting to it is Clearly shown in the illustration .

Clamp C simply forms a stop for supporting the ou ter end of

the casting,which would otherwise tend to sag down under the

thrust Of the cut. Work that is bolted directly to the table is

held by practically the same kind of clamps that are used in

connection with planer work .

In Fig. 5 the table is shown removed and a casting is clampeddirectly to the face Of the cross-slide for planing the top bearing

Fig. 6. Shaper Equipped with Tilting Tab le and Automatic Vertical Feed

su rface . This is an illustration Of the class Of work that can beheld to advantage in this way. When setting work in the shaper,a surface gage can Often be used efl

'

ec tively the same as in planerwork. The tool itself can also be employed as a gage for setting

the work level, by comparing the distance between the surfacebeing tested and the tool point . When using the tool in this

way , it is placed Close to the work and the latter is shifted so

that its height at various points can be determined .

When vertical or angular surfaces are planed in the shaper,

AD"USTABLE SHAPER TABLES 85

the tool block is swiveled SO that the top Of the block inclinesaway fromthe surface being planed , to avoid any interferencewith the tool on the return stroke, as explained in connectionwith planer work. The entire tool-head can also be set to anyangle for planing angular surfaces, by loosening locking bolt h

(Fig. I ) , and its position is shown by degree graduations. SomeShapers have an automatic vertical feed for the tool as well asan au tomatic horizontal feed for the work

,but most Shapers

are not so equipped,the tool being fed vertically by hand . Both

the horizontal and vertical feed-screws.

Of themachine , shown inFig. 1

,have graduated collars which are used when it is desired

to feed the tool down or crosswise a definite amount. Thesecollars have graduations representing amovement of inch ,and they can Often be used to advantage for adjusting the tools.

Tilting Tab le for Shaper. The detail view,Fig. 6

,shows a

shaper equipped with a tilting table A which is very convenientfor planing tapering parts. The table swings about the bolts orpivots B on each Side

,and it is held at whatever anglemay be

required by the slotted arms C which are bolted to the sides ofthemain table . The workmay be held either in a vise or bebolted directly to the table . When planing tapering parts that

are held between index centers, the tilting table enables the centers to be kept in linewith each other

,which is especially desirable

when indexing is necessary . The cause of the inaccuracy resulting fromindexing with the centers out of line is explained inthe paragraph headed “Milling Taper Flutes

,

”Chapter IV.

The shaper illustrated in Fig. 6 also has an automatic verticalfeed for the tool-slide. The ratchet feed lever Dwhich transmitsmotion to the feed-screw is operated by an adjustable tappet E ,

as the rammoves back and forth. The au tomatic vertical feedis very convenient, especially formachining wide surfaces .

Swiveling Shaper Tab le. The shaper shown in Fig. 7 has a

table which swivels through an arc Of 90 degrees about a hori

zontal axis. The angular position of the table is shown by a

graduated dial D. This swiveling feature is useful especially in

connection with tool and diemaking for planing surfaces at anangle.

86 THE SHAPER

Circular Planing Attachment. The machine illustrated inFig. 7 is also provided with an attachment for circular, concaveplaning. A cu rved su rface is produced as the tool-head and toolare turned about a horizontal axis by the au tomatic feedingmechanismshown . A rotarymovement is derived fromwormgearing A located just back of tool-slide

,thewormbeing turned

intermittently by a ratchet lever B which is connected to itthrough gearing. This ratchet lever is operated by engagementwith the adjustable tappet C.

Fig. 7 . Shaper having Swiveling Tab le and Con cave Attachment

There are also shaper attachments for convex cylindricalplaning

,commonly known as circular or cone mandrels . The

attachment consists Of a base-plate which is bolted to the tableand has two uprights. Between these uprights there is an

arbor which carries two conical bushings for holding parts havingdrilled or bored holes . The arbor and work is given a rotarymovement bymeans of wormgearing at the end , which, in turn,

MOTOR—DRIVEN SHAPER 87

is operated by a feed mechanism. Other attachments are

sometimes used on the shaper in order to adapt it to a widerrange Of work, although the ones referred to are themost common types .

Motor-driven Shaper. Many modern shapers,as well as

other machine tools, are driven by a direct-connected electricmotor instead Of transmitting the power froman overheadcountershaft to a cone pulley on the machine. By having a

Fig. 8. Gould Eb erhardt Shaper having Variab le-speed ElectricM otor Drive

motor drive, the machine can be operated independently,and

overhead belting is eliminated, thus leaving a clear space fortraveling c ranes . An electrically driven shaper is shown in

Fig. 8. Themotor A is a variable-speed type and is connectedto the driving shaft Of the shaper by a silent chain enclosed in

guard B . Variations in speed are obtained electrically bymeansof the combination starting box and field rheostat C.

On some Shapers, a constant-speed motor is used and the

Speed changes are Obtained mechanically by shifting gears in

88 THE SHAPER

a gear box, through which motion is transmitted . The gear

box construction is also found on some belt-driven Shapers,in

which case a single belt pulley is used instead of a cone pulley.

The long curved lever D controls a clutch and brakemechanismfor starting and stopping themachine independently Of themotor. Shifting the lever in one direction starts the shaper,and moving it in the opposite direction stops the ramat any

part Of the stroke.

Fig. 9. M orton Draw-cut Shaper

Morton Draw-c ut Shaper. The shaper illustrated in Fig. 9

differs fromthe ordinary type in that the tool cu ts when it ismoving towards the column of themachine. In other words

,

the tool is pulled or drawn through the metal on the cuttingstroke instead Of being pushed . For this reason the name“ draw-cut

”is applied to a shaper of this type. The planing

tool is,Of course , set with the cutting edge reversed . Themm

of thismachine is driven by a rack and gearing, and the recipro

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90 THE SHAPER

which has an all-geared drive . The driving mechanismof a

rack shaper is similar to that of a spur-gear type of planer. Theramhas a rack on its under side and it is driven by a gear whichmeshes with this rack. Themovement of the ramis reversedeither by open and cross-belts which are alternately shifted on

tight and loose pulleys,or by friction clu tches which alternately

engage the forward and return pulleys. The length of thestroke is controlled by adjustable tappets .

Special Types of Shapers. Shapers Of special types are alsobuilt in a number Of diflerent designs which are varied to suitcertain classes Of work . These differ fromthe standard types

either in the motion of the ramrelative to the work table or

in having a greater range Of adjustment which adapts themtowork which could not be handled in an ordinary shaper.A shaper is shown in Fig. 10

,which is provided with a cross

traverse for the tool-head . The advantage of this feature, for

certain classes Of work,is indicated by the illustration . The

regular table has been removed,and the end Of a 20-ton steel

roll is being planed . The traversing head enables horizontalcu ts to be taken over the work which remains stationary . ThisShaper is a special design built by Gould Eberhardt, and itcan be used to advantage on large

,unwieldy parts such as the

one illustrated .

P ratt Whitney Vertical Shaper. The machine shown inFig. 1 1 resembles a slotter in many respects

,b ut it is known as

a vertical shaper and is adapted for classes Of work that are

done on horizontal Shapers and regu lar slottingmachines. The

work table Of this shaper can be given a transverse , longitudinal,or rotarymovement. The ramwhich carries the planing or slotting toolmoves vertically while the table is fed either by hand or

au tomatically, in whatever direction is required . The transversefeed is eflec ted by Shaft A , the longitudinal feed by screw B ,

and

the rotary feed by Shaft C. Power 18 transmitted to the feed

power being transmitted through a crank at G and shaft H to

the feed pawl and ratchet shown In the illustration .The vari

VERTICAL SHAPER 91

ous power feeds are engaged by sliding pinions I,J and K into

mesh. When these pinions are in the ou tward position ,the

power feed is disengaged and when they are,

pushed inward, thepower feed is operative. The direction of the feed is controlledby pushing in or pulling out the knob L . The feeding action

Fig. 11. Pratt Whitney Vertical Shaper

takes place when the ramis at the upper end Of its travel and thetool is c lear Of the work. Micrometer dials are provided for

making accurate adjustments, and the periphery of the rotary

table is graduated in degrees.

Themechanismfor operating the ramis driven by wormgearing and with this exception it is similar to the drivingmecha

92 THE SHAPER

nismused on the P ratt 81 Whitney horizontal shaper. The ramcan be set perpendicu lar to the table

,or at an angle , as shown

in Fig. 1 2,for slotting dies

,etc . The ramismounted in an inde

pendent bearing, the upper part of which is pivoted on a trunnionthat enables the bearing and the ramto be set in an angularposition , which is indicated by degree graduations. The strokeOf the ramis indicated by the graduated dial M , and the rammay be stopped and started independently Of the countershaftby a friction clu tch controlled through lever P .

Fig. 12 . Angular Adjustment of Fig. 13 . RamHead SwiveledRamon Vertical Shaper through 90 Degrees

The tool is held in a slotted toolpost carried in a clapper whichpermits the tool to clear the work on the return stroke, the sameas on a horizontal shaper. When exceptionally long toolsmustbe used on internal work

,the clapper c an be clamped rigidly to

the head. The tool-head can be swiveled to four diflerent positions

,one of which is shown in Fig. 13 , so that the tool can be

set for planing diflerent sides without changing the position Of

the rotary table and by simply using the transverse or longitudinal feedingmovement, thus insu ring accu racy between the surfaces . Work can Often be completed at one setting on a shaperof this type and itmay be used formachining concave, convexor irregular surfaces.

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94 THE SHAPER

shaper ram, a milling and drilling spindle,and suitable speed

and feed-changingmechanisms . Themilling spindle and shaperramhave universal adjustments so that tools can be presented

to the work at any desired angle. Fig. 15 shows the shaper

ramset in a horizontal position .

The machine is driven froma constant-speed clutch pulley

at the rear, which transmits the power through a double cone

of spur gears to themain head . The latter carries bevel gears

Fig. 15 . Shaper Ramof Cochrane-B ly Universal Shaper Set in a

Horizontal Position

for driving both the shaper ramandmilling spindles . The cones

of spur gears provide means for varying the speeds,and the

speed changes are effected bymeans Of a lever on the right-handside Of the column . The end of this lever swings around a graduated quadrant which shows the number of ramstrokes perminute for any one Of the five positions . The shaper ramhas aquick return and the strokes can b e adjusted from0 to 6 inches.

The ramis equipped with amechanismwhich provides a positiverelief for the tool on the upward or return stroke .

Themilling spindle revolves either to the right or left. It has

UNI VERSAL SHAPER 95

a slidingmovement Of 3§ inches for drilling and boring,which

is controlled by a handwheel Operating through wormgearing.

Amicrometer screw-stop,reading to thousandths Of an inch, is

provided to facilitate accurate adjustments . The main head,including the shaper ramand milling spindle

, can be revolvedabout a horizontal axis (after loosening the clamping bolts) byturning a small crank which is located at the upper end of thegraduated quadrant previously referred to . The shaper and

milling heads each have an independent adjustment abou t anaxis at right angles to themain head, which makes it possibleto locate themat any angle.

Fig. 16. Set of S lotting Tool;for Universal Shaper Illustrated in1g. 14

Power feed is provided for the longitudinal and transverse

movements Of the table. E ither a continuous or intermittentfeed is Obtained froma feed-box at the rear . When themillingspindle is being used, the feed is continuous, whereas an inter

mittent feed, which takes place on the return stroke, is required

for the shaper ram. For a continuous feed , the drive is through

spur gears, and for an intermittent feed , a crank-and-ratchet

mechanism13 brought into action . The circularmilling and slotting attachment, seen On themain table In Fig. 14, is equipped

with power feed and a dividingmechanism.

Tool-holders of various styles for holding Slotting or shaping

96 THE SHAPER

tools can be attac hed to the tool-head. Fig. 16 shows a set ofstandard slotting tools such as are used when shaping out smalldies

,for cutting internal keyways, etc . The shaper toolpost

is used when the machine is working either as a horizontalshaper (as shown in Fig. 15) or as a vertical shaper.The universal features of this machine, in conjunction with

the various tools which can be used,make it possible tomachine

Fig. 17 . Shaper Equipped with Fixture for Generating HelicalClutch Teeth

a large variety of such work as blanking and forging dies,punches, forming tools, such as are used in turret lathes

,auto

matic machines, etc.,jigs

,especially when shaping

,milling and

boring operations are required,and similar classes Of work.

Shaper Attachment for Machining Clutches. The shaper

attachments previously referred to c an be used for diflerent

classes of work, but occasionally a special attachment is designed formachining only one class Of work. An attachment of

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98 THE SLO'ITER

at points corresponding to the faces of the teeth and to a depthrepres ented by the lowest position Of the arbor carrying theclutch . The slotting tool is then replaced by a narrow planingtool which generates helical or spiral teeth as the spindle rotates.

Good results both as to output and accuracy are Obtained withthis simple fixture . The c lu tches are well machined and can

be used withou t fu rther finishing.

The Slotting Machine. The slotting machine or slotter,as it is commonly called, is a verticalmachine used for finishing slots or other enclosed parts which could not be finished bythe tool of a horizontalmachine like the planer or shaper. The

slotter is also used for various other classes of work,requiring

flat or curved surfaces, which can bemachined to better advantage by a tool whichmoves vertically.

The ramR Of the slotter, to which the planing or slotting toolis attached (see Fig. has a vertical reciprocatingmovementat right angles to the work table. This verticalmovement isObtained froma crank disk D which is connected to the slotterramby a link and is driven by a cone pulley P and the largegearing seen at the rear. The tool is fastened to the end of theramby the clamps shown ,

and the work is secured to the platenT. There are two sets Of clamps on the ramso that the tool

c an be held in a vertical Or horizontal position . The tools used

for keyseating or finishing narrow slots are held in a verticalposition ,

whereas larger slots or su rfaces which can readily bereached are planed by a tool held horizontally against the end

of the ram.

The platen T can bemoved crosswise along the saddle S and

the latter c an be traversed at right angles along the bed . In

additi on ,the platen can be rotated about its center for slotting

circular surfaces . These three movements can be effected byhand or power . The lengthwise adjustment on the bed is

eflected by turning squared shaft A with a crank; similarly,squared shaft B is used formoving the platen crosswise . Theplaten is rotated by tu rning shaft C. The au tomati c power feedfor these three movements is derived fromthe camE on theinner side Of the large driving gear . This camis engaged by a

CONSTRUCTION OF A SLOTrER 99 ,

roller on the end of lever F and , whenever the ramor tool is at

the top of its stroke,an irregular place in the camtrack causes

lever F to osc illate . Thismovement is transmitted by connecting link and shaft G at the side of the bed to the Slotted crank

E . This crank tu rns the large gear I slightly for each stroke

of the ram,bymeans of a ratchet disk carrying a double-ended

pawl K which engages the gear . Gear I , in turn ,transmi ts the

Fig. 19. Betta S lotting Machine

movement through the intermediate gears Shown to either of

the three feed shafts . I f a power feed along the bed is wanted,

gear I is placed on the feed-Shaft A as Shown in the illustration .

On the other hand, if a cross-feed is desired, gear I is inserted onshaft B and, similarly, the rotary feed is obtained by placingthis same gear on shaft C. The amount of feed is varied bychanging the position of the crankpin at H

, and the direction of

the feed is reversed by shifting the double-ended pawl K .

The stroke of the ramis varied by adjusting the crankpin of

100 THE SLO’

I‘

TER

disk D to or fromthe center. The vertical position of the ramis changed so that the tool will operate in the right relation tothe work, by loosening nut L and moving the ramup or downby tu rning shaft M with a hand ratchet. The ramis counterbalan ced by a weight W and it has a quick-retu rn movementfor the upward or idle stroke .

Example of Straight and Circular Slotting . A typical example of the kind Of work done on the slotter is shown in Fig. 20

Fig . 20. Example of Straight and Circular Slotting

which illustrates, diagrammatically, the slotting of a locomotive driving-wheel box. The side and top views at A indicatehow the inner sides of the b ox are finished . The work is set onparallel strips S to provide clearance for the tool at the lower endOf the stroke

, and it is secured to the platen by four clamps.

The stroke Of the ramR should be about one inch greater than

the width of the surface to be slotted andmost of the Clearance

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102 THE SLUI‘TER

Slotting an Engine.

Connecting-rod. Fig. 2 1 shows how a

slotter is used formachining the rectangular opening in the endof a connecting-rod

,into which the bearing brasses are af ter

wards fitted . P rior to the Slotting operation, the sides of the

rod are finished by planing ormilling. A row of holes is thendrilled in the solid end of the rod just inside the lines laid out for

Fig. 2 1 . S lotting End of Engine Connecting-10d on a Dill Slotter

the rectangu lar opening, and the interior part is removed in theformof a solid block . The rod is then clamped to the slottertable upon two parallels which provide a clearance space for thetool at the lower end of the stroke . The long sides are slottedby using the longitudinal feed and the short sides bymeans ofthe cross- feed . The tool, Of course , is turned in the toolpost

SLOTTER OPERATIONS 103

to face the difl'

erent surfaces as they are slotted . When using atool-holder of the type shown , on work of this kind , it is necessaryto replace it with another formof tool for finishing the corners.

The style of tool shown at B , Fig. 22 , could be used , becausethe cu tting edge is at an angle Of 45 degrees to the shank .

Ordinarily, when using the slotter tomachine surfaces whichare at right angles to each other

,the table is fed first laterally

and then longitudinally or vice versa,but in this case, owing to

the size and weight of the rod, the lengthwise cu ts are taken by

feeding the tool-head of the slotter, the work remaining stationary except when machining the end surfaces. This feeding ofthe tool is possible with the particularmake of slotter shown as

it has a traveling head, so that the tool can be given a feedingmovement when slotting a part which is large and cumbersome.

When slotting heavy ,overhanging castings Or forgings, such

as the one illustrated , the outer end should be supported, andusually it is advisable to mount the supports on two pairs of

rollers arranged one above the other and at right angles, so thatthe work can easily be fed in a lateral or lengthwise direction.

The supportmay consist simply of blocks with the rollers interposed between them, although special supporting stands equipped

with rollers are often used . Bymeans of roller supports , very

large castings can be machined on the slotter. The support

should be just high enough to hold the part level, thus relieving

the table of the excessive load to which it would be subjected if

no support were used .

The Dill Slotter. The slotter shown in Fig. 2 1 diflers in

several respec ts fromthe one illustrated in Fig. 19. As previ

ouslymentioned , it has a traveling head which permits cu ts tobe taken by feeding the tool instead of the work. The ramand'

tool can also be set close to the column or some distance awayfromit, depending upon the nature of the work. When bothtable feeds are used , the traveling head is clamped in the desiredposition . The machine has a quick traverse for moving thehead or table rapidly in any direction ,

when considerable adjust

ment is required . This quick traverse is operated by a lever

located at the side of themachine. The automatic feedingmove

104 THE SLOTrER

mentmay be either intermittent or continuous, the intermitten tfeed taking place at the top of the stroke and the continuous feedthroughout the cu tting stroke . The intermittent feed is theproper one to use formost work

,but the continuous feed is use

ful, especially for finishing the ends of narrow slots

,which require

a long slender tool. The intermittent feed is used un til the toolreaches the end of the slot; the continuous feed is then engaged,thus causing the feed to take place gradually throughout thelength of the stroke in order to overcome the spring of the tooland square the end Of the slot.

On the crank disk of this slotter there is a stroke indicatorwhich shows the length of stroke for which themachine is set.This is Simply a pointer having a curved end which is held incontact with the crankpin bushing by a spring . As the pin

is adjusted to or fromthe center, the pointer ismoved a propor

tional amount by the curved end and the stroke is indicated by

a suitable scale on the edge of the crank disk. The cu tter bar

or ramis fitted in an adjustable guide which can be raised or

lowered by a crank handle to the position where it will give theramthe best support. The tool is held in a relief apron to prevent the cu tting edge fromdragging over the slotted surface onthe upward stroke .

Slotter Tools. Some of the tools used in the slotter are

illustrated in Fig . 2 2 . Those shown at A,B and C are forged

fromthe solid bar and have cu tting edges formed on the ends,whereas tool D consists of a heavy bar in which a small cutter tis inserted . Tools A and B are used principally for slotting

interior surfaces, where there is little roomfor the tool to operate.

For exterior slotting, or whenever there is plenty of room,tool

D is preferable because it ismore rigid .

The cu tting end of tool B is inclined to the right or left (asindicated by the end view) for working in corners, etc . Theposition of tool D,

which has a round shank k,can be varied by

turning it in clamps at the upper end which hold it to the slotterram. Many tools Of this type have square shanks so that special

Clamps are not required . The cu tter t is held by set-screw c inapivoted

,spring-relief block which allows the tool point to swing

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CHAPTER I I I

CONSTRUCTION AND USE OF PLAIN MILLING MACHINE

MILLINGmachines are used for a great variety of operations ,andmany types have been designed formilling certain classes Ofwork to the best advantage . Themillingmachine was originallydeveloped in armories for manufacturing the small irregularshaped parts used in the construction of fire-arms

,and themill

ing process is still employed very extensively in the productionof similar work, especially when intricate profiles are required

and thepartsmust be interchangeable . M illingmachines arealso

widely used at the present time formilling many large castingsor forgings, which were formerly finished exc lusively by planing;in fact

,it is sometimes difficult to determine whether certain parts

should be planed ormilled in order to secure the best results.

Surfaces aremilled by one or more circular cutters having a

number of teeth or cu tting edges which successivelymill awaythe metal as the cutter rotates. These cutting edges may bestraight and parallel to the axis of the cutter for milling flatsurfaces, or theymay be inclined to it for forming an angular

shaped groove or surface,or theymay have an irregular outline

corresponding to the shape or profile of the parts which are to bemilled by them. An end view of a cylindrical or “plain ” cu tter

is shown in Fig. 1,which illustrates

,diagrammatically

,one

method of producing a flat surface by milling. The cu tter Crotates as Shown by the arrow

,b ut remains in one position,

while the work W,which is held on the table of themillingmachine and is adjusted vertically to give the required depth Ofcut

,slowly feeds to the left in a horizontal direction . Each

tooth on the periphery of the cutter removes a chip every revolution ,

and,as the workmoves along

, a flat surface is formed .

The function of the milling machine is to rotate the cutterand , at the same time, automatically feed the work in the rs

106

PLAIN M ILLING MACHINE 107

quired direction . As it is nec essary to vary the feedingmovemen t and the speed of the cu tter

,in accordance with thematerial

beingmilled and the depth of the cu t,themillingmachinemust

be equipped with feed and speed- changing mechanisms and

other features to facilitate its operation . As the variety of

work that is done bymilling is almost endless,millingmachines

differ widely as to their form,size and general arrangement.

Some are designed for doing a great variety of work, whereasothers are intended for performing

,as emciently as possible

, a

comparatively small number Of operations. Some machinesare arranged for rotating the cu tter horizontally

,whereas with

other types,the cu tter rotates about a vertical axis. In this

Fig. 1. End View of Cylindri cal Cutter M illing Flat Surface

treatise,no attempt will be made to describe all the difl

'

erent

types ofmillingmachines,b ut rather to refer briefly to themore

common designs, and then to illustrate their application and theprinciples of milling by showing typical examples of commonmilling operations.

P lain M illing Machine.— A type ofmillingmachine that is

widely used,especially for milling large numbers of duplicate

parts, is shown In Fig. 2 . This is known as a plain,horizontal

milling machine of the column-and-knee type. The principalparts are the column C and knee K

,the work-table T

,themain

spindle S which drives the cu tter, and the speed and feed-chang

ingmechanisms encased at A and B ,respectively . The spindle

receives itsmotion frombelt-pulley P at the rear. This pu lley

is connected to the driving shaft by a friction clutch Operated

108 M ILLING MACHINES

by lever M which is used for starting and stopping themachine.When the friction clutch is engaged , power is transmitted tothemain spindle S through gearing, and, by varying the combination of this gearing, the required speed changes are obtained .

KneeK is free to slide vertically on the front face.of the column ,

and it carries saddle Z and the table T. The saddle has an ih

Fig. 2 . Cincinnati Plain M illing Machine

and-out or crossmovement on the knee,and the table can be

traversed at right-angles to the axis Of the spindle. Either ofthese threemovements

,that is

,the longitudinal

, c ross, and verticalmovements can be effected by hand or power. The handmovements are used principally for adjusting the table and workto the required position when starting a cut, whereas the automatic power feed is employed whenmilling. The hand-crank D

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MILLING MACHINES

or table , asmay be required . The table feed is engaged or disengaged by lever Y and it is controlled by another lever locatedat " , but not seen in the illustration . The direction in whichlever " is inclined fromthe vertical determines the direction Ofthe table feed . For instance

,if it is Shifted to the right the table

will travel toward the right,and vice versa. This lever " also

controls any feed that happens to be engaged , as well as the table

feed. Lever X engages either the vertical or cross-feeds, andall of the feedingmovements can be controlled by lever R bymeans of which they are reversed .

The rate or amoun t Of feed per revolution Of the cutter canbe varied by the levers and handwheel on case B

,There are

16 changes, and an index-plate shows what the rate of feed isfor any position of the levers. The longitudinal

,cross or ver

tical feeding movements can be au tomatically stopped at any

predetermined point by the trip-plungers l,c and v

,respectively.

These plungers are operated by dogs which can be adjusted sothat the au tomatic trip will operate after the cut is completed.

The dogs H and H1, for the table feed , are clamped to the frontof the table as shown . One Of these dogs trips the feed by lift

ing the plunger and the other by depressing it. Amovementof the plunger in either direction disengages a clu tch at G and

places it in a neutral position . This is the same clutch that isoperated by feed-reverse lever R . The au tomatic trip mechanismis a very convenient feature , as it prevents feeding too far,andmakes themachinemore independent Of the operator.The principal features of a plainmillingmachine, so far as the

operation Of themachine is concerned , have now been described ,but it Should be remembered that while plainmachines of othermakes have the speed and feed-changingmechanisms , au tomatictrips

,etc.

, the arrangement of these parts varies in differentdesigns . When the construction of onemachine is thoroughlyunderstood , however, the changes in other designs in the location Of the speed and feed-control levers

,and the functi ons of

the diflerent parts , can readily be understood.

Adjusting and Operating a Milling Machine. Before amillingmachine can be used , it is necessary

,Of course , to arrange

M ILLING OPERATIONS 111

it for doing the work in hand,which includes moun ting the

cutter in position,and adjusting the driving and feed mecha

nisms for giving the proper speed to the cutter and feed to thework. The part to bemilledmust also be securely attached tothe

'machine, so that it can be fed against the revolving cutterby moving the table in whatever direction may be required.

The way amillingmachine is arranged,and the kind Of cutter

used depends on the nature of themilling operation .

The character of the work, and other considerations which

will be referred to later , also aflect the speed and feed , as well’

as

Fig. 3 . M illing a Small Rectangular Block

themethod of clamping the work to the table; hence , judgmentand experience are needed to properly decide the questions thatarise in connection wi th milling practice

,and no definite rules

ormethods Of procedure can be given . We Shall explain ,how

ever,in a general way, howmillingmachines are arranged and

used under varying conditions, by giving illustrated descriptionscovering typical examples of work representing the variousclasses that aremachined by themilling process .

A~very simple example ofmilling is shown in Fig. 3 , the operation being that ofmilling a flat su rface on top of a steel block

112 MILLING MACHINES

W. Befo'

re referring to this work, itmight be well to explainthat the spindle of the machine, shown in this illustration, isdriven by a stepped or cone pulley P ,

instead Of by a single,constant-speed pulley as in Fig. 2 . Speed changes are obtainedby shifting the driving belt to difl

'

erent steps of the cone,and

the number of changes secured in this way can be doubled bythe engagement of back-gears located at the side of the cone

,the

arrangement being the same as the back-gearing on an engine

lathe.

Method of Holding and Driving the Cutter. The first thing

to be done in connection with milling block W is to selec t the

cutter. As a flat surface is to be milled , a plain cylindrical

Fig. 4. Cutter Arbors for Milling Machine

c utter C would be used (in amachine Of this type) , having awidth somewhat greater than the surface to be milled. Thisc utter ismounted on an arbor D which Is rotated by the spindle

and is supported at its outer end by armB . This is the usual

method ofmounting and driving the cu tter, when a horizontalmillingmachine Of the column-and-knee type is used , although

some cutters ormills aremade with a taper shank which is in

serted directly in the spindle S .

When an arbor is placed in themachine , its ou ter end, in someinstances, is supported by a center (similar to a lathe center) ,which is inserted in the centered end of the arbor as shown atA

in Fig. 4. Another method Of supporting the arbor, which is

very common,is Shown at B . In this case , the arbor passes

through a bearing in the arm. The particularmachine shown in

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MILLING MACHINES

of the cut. Some parts are also sprung out of shape by applyingthe clamps improperly or by omitting to place supports under

some weak or flexible section; as a result , themilled surface is

not true after the clamps are removed and the cas ting springs

back to its natural shape. Generally speaking, work shouldbe clamped more securely formilling than for planing, becausethe pressure Of the cut, when milling, is usually greater thanwhen planing, although this depends altogether upon the depth

of the cu t and the size Of the cutter.

Milling Machine Vises. Three types of milling machinevises which are commonly used are shown In Fig. 5 . The one

Fig. 5 . Milling Machine Vises

illustrated at A is called a plain vise. I t is held to the table bya screw which passes through the vise bed and threads into a

nut inserted into one of the table T-slots. This same style isalso made with flanges so that it can be secured by ordinaryc lamps. The vise Shown at B has a swiveling base and it canbe adjusted to any angle in a horizontal plane, the position beingshown by graduations. This adjustment is used for angularmilling. The vise shown at C is known as the universal type.I t can be swiveled in a horizontal plane and can be set at anyangle up to 90 degrees in a vertical plane, the position ,

in eithercase, being Shown by graduations. The hinged knee whichgives the vertical adjustment can be clamped rigidly by the nuton the end of the bolt forming the hinge, and by bracing levers

MILLING OPERATIONS 115

at the left which are fastened by the bolts shown . This styleof vise is used prin cipally by die and tool-makers, and , owingto its universal adjustment, can Often be utilized in place of ajig or fixture.

When large quan tities of duplicate pieces are to bemilled , theyare usually held in special fixtu res which are so designed thatthe work can quickly be clamped in position formilling. The

arrangement or formof a fixtu re depends, of course, on the shapeof the part for which it is in tended and the nature of themillingoperation . A number of difl

'

erent fixtures are shown in con

nec tion with examples Of'milling referred to later.Direction of Feed and Relative Rotation of Cutter. Af ter

the cu tter ismoun ted on the arbor and the part is clamped tothe table, we are ready to begin milling. Before starting a

c ut, the table is shifted lengthwise and crosswise, if necessary,un til the cu tter is at one end of the work. The knee K (Fig. 2)with the table is then raised sufficiently to give the requireddepth of cut, and the trip-dog at the front of the table is set todisengage the power feed after the cut is completed. The longitudinal power feed for the table is then engaged, and the partWfeeds beneath the revolving cu tter C whichmills a flat surface.By referring to Fig. 6

,it will be seen that the direc tion of the

feedingmovementmight be either to the right or left, as indicated at A and B . When the cu tter rotates as Shown atA

,the

part beingmilled feeds against the direction Of rotation , whereas

at B ,the movement is with the cutter rotation . In the first

case, the cu tter tends to push the work away,but when the

relativemovements are as at:B ,the cu tter tends to draw the part

forward, and if there is any backlash or lostmotion between thetable feed-screw and nut

,this actually occurs when starting a

cut; consequently, the cu tter teeth which happen to be in en

gagement take deeper cu ts than they should, which may resultin breaking the cu tter or damaging the work. Therefore

,the

work should ordinarily feed against the rotation of the cutter.

When milling castings which have a hard sandy scale, thecutting edges of the teeth will also remain sharp for a longerperiod when feeding against the rotation ,

as at A . This is be

116 MILLING MACHINES

cause the teethmove up through themetal and pry 06 the scalefrombeneath

,whereas at B ,

the sharp edges c strike the hardscale each revoluti on

,which dulls themin a comparatively short

time. Occasionally,a part can be milled to better advantage

by feeding it with the cutter. This is especially true when thework is frail and cannot be held very securely, because a cu tter

rotating as at B tends to keep the work down ,whereas the up

wardmovement at A tends to lif t it When the work moveswith the cutter, the table gib -screws should be set up tighterthan usual to prevent a freemovement of the table, because thiswould allow the cu tter teeth to “

dig in”at the beginning Of the

c ut. Somemachines are designed to prevent this, and coun terweights are sometimes used to hold the table back.

Fig . 6. (A) Work feeding against Rotation of Cutter. (B)feeding with Rotation of Cutter

Right and Left-hand Cutters. I t should bementioned thata cu tter does not always rotate in the direction shown at A and

B . If it were turned end for end on the arbor, thus reversingthe position of the teeth

,the rotation would have to be in a

clockwise direction , and the feedingmovement to the right. A

cu tter which rotates to the right (clockwise) , as viewed fromtheSpindle or rear side

,is said to be right-hand

,and

, inversely, aleft-hand cutter is one that turns to the left (counter-clockwise)when milling.

M illing with Nicked Roughing Cutter. Another example ofmilling, which is similar in principle to the one illustrated inFig. 3 , is Shown in Fig. 7 . The Operation is that Ofmilling flatsurfaces on the edges Of cast-iron bearing caps B . Two of these

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1 18 MILLING MACHINES

Difierent Types of M illing Cutters. As the processes ofmilling can be applied to an almost unlimited range of work ,

the cu tters used onmillingmachines aremade in a great varietyof forms. Some Of the di fferent types can be used for generalwork Of a certain class

,whereas other cu tters aremade especi ally

formilling one particular part . Of course,the number Of difl'er

ent types that are used on any onemachine depends altogetheron the variety Of milling operations done on that machine .

When the nature of the work varies widely, the stock of cu ttersmust be comparatively large , and, inversely , when amachine is

Fig. 8. Cylindrical. S ide, and Face M illing Cutters

used for milling only a few parts, a large cutter equipment is

not necessary .

Cylindrical Cutters. A number Of diflerent types Of cuttersin common use are shown in Figs . 8

, 9 and 10. The formillustrated at A

, Fig. 8, is called a cylindrical or plain cutter.

This formis used for producing flat surfaces and it ismade invarious diameters and lengths. Another cutter of the cylindrical type is Shown at B . This difl

'

ers fromcu tter A in that theteeth are nicked at in tervals along the cu tting edges.

The idea

MILLING CUTTERS 1 19

tioned . This enables heavier or deeper cu ts to be taken withthe same expenditure of power; hence, the nicked cu tter isextensively used for roughing cu ts . I t will be noted that theteeth of these two cu tters are not parallel with the axis, but are

helical or spiral. Cu tters having helical teeth are generallyused in preference to the type with straight or parallel teeth ,

especially for milling comparatively wide surfaces,because the

former cutmore smoothly. When teeth are parallel to the axis,each tooth begins to cut along its en tire width at the same time;consequen tly, if a wide surface is beingmilled, a Shock is produced as each tooth engages the metal. This difi culty is not

Fig. 9. End M ills, T-slot Cutter, Shell End M ill , and Angular Cutter

experienced with helical teeth which , being at an angle, begin toc ut at one side and continue across the work with a smoothshaving action . Helical cutters also require less power fordriving and produce smoother surfaces.

Side M illing Cutter. A sidemilling cu tter is Shown at C.

This type has teeth on both Sides , as well as on the periphery, andit is used for cutting grooves or Slots and for other operations,examples Of which will be shown later. The sides of this formOf cutter are recessed between the hub and inner ends of the

teeth, in order that they will clear a surface beingmilled . Two

sidemills are oftenmounted on the same arbor and used in pairs

1 20 M ILLING MACHINES

formilling both sides of a part at the same time. This type Ofcu tter is also employed in conjunction with other forms formilling special Shapes, as will be Shown later .

Cutters of Inserted-tooth Type. Another sidemilling cutteris shown at D. This mill, instead of being made of one solidpiece Of steel, has a cast- iron body into which tool steel teeth are

inserted . These teeth fit in to slots and they are held in placeby flat-sided bushings which are forced against themby the

screws shown . There are many different methods of holding

teeth in cutters Of this type . The inserted- tooth construction is

Fig. 10. Formed Cutters, Angular Cutters, and Slitting Saw

ordinarily used for large cu tters,in preference to the solid form,

because it is cheaper, and the inserted teeth can readily be te

placed when necessary . When solid cu tters aremade in largesizes

, there is danger of their cracking while being hardened,but with the inserted- tooth type , this is eliminated.

A large cylindrical cu tter with inserted teeth is shown at E .

The cu tter illustrated at F also has inserted teeth and is calleda facemilling cutter. This formis especially adapted to end or

facemilling operations . When in use, the cu tter ismounted ona short arbor which is inserted in themillingmachine spindle .

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12 2 MILLING MACHINES

typewriters and other pieces having an irregular and intrieate

shape aremilled with formed cu tters . The teeth Of these cu tters

are“ backed Ofi

'

so that they can be sharpened withou t changing the profile, provided the front faces are ground radial.

The convex and concave c utters , C andD, which are also Of the

formed type , are formilling half-circles, one cutting hal f-round

Fig. 12 . Fly-cutter and Arbor

grooves and the other forming half-round edges . Formed cuttersaremade in a great variety of shapes and they are used formanydifl

'

erent purposes. The diagrams,Fig. 1 1

,illustrate how formed

c utters are used for fluting taps, reamers and four-lipped drills .

Sketch A Shows how the

grooves 01 flu tes are cut

in a tap. As will be seen ,

the groove ismilled to thesame shape as the cu tter.The sketches at B and C

show cu tters of difl'

erent

shapes forflu ting reamers,and D illustrates how thegrooves are c ut in fourlipped twist drills, of thetype used in screw and

chuckingmachines for roughing out holes prior to reaming.

Angular Cutters. The angular cu tters, E and F (Fig.

are u sed extensively for forming teeth on milling cu tters. ThestyleE is employed for cu tting straight teeth

,whereas the double

angle cutter F is especially adapted to milling spiral grooves.

An angular c utter is also shown at F,Fig 9. The teeth are at

an angle Of 60 degrees with the axis . This formof cu tter is used

Fig. 13. Interlocking Side Milling Cutter

M ILLING CUTTERS 123

formilling dovetail slots and for Similar work. The particu larstyle shown has a threaded hole and is screwed onto the arbor.Slitting Saw. The thin c utter illustrated at G (Fig . 10) is

known as a slitting saw,and it is used formilling narrow slots

,

cu tting Ofl stock,and for similar pu rposes.

Fly-cutter. Fig. 12 shows a Simple type Of cu tter that is

often used for operations that will not warrant the expense of

a regular formed cutter. This is called a fly-cu tter. Themill

ing is done by a single tool c which has the required ou tline. Thistool is held in an arbor having a taper shank the same as an end

Fig. 14. M illing Groove with Interlocking Cutter

mill. The advan tage Of the fly-c utter is that a single tool canbe formed to the desired shape , at a comparatively small expense.

Interlocking Side M ill . Themilling cu tter shown in Fig . 13

is similar to a sidemill,but it is composed Of two units instead

of beingmade Of one solid piece of steel. These two sections arejoined as shown by the view to the left, there being projectionson each half which engage corresponding slots in the other half,thus locking both parts together. This type Of cutter is largely

used formilling grooves 01 Slots,because as the side teeth wear

or are ground away,the two sections Of themill can b e spread

apart by washers in order tomaintain a standard width .

An example Of slotmilling with an interlocking c utter is shown

124 M ILLING MACHINE S

in Fig. 14. The cu tter ismounted on an arbor the same as a

regular sidemill, and the part to be grooved is bolted directlyto the table

,one end being supported on parallel strips. When

it is necessary tomill a large number of grooves to a standard

Size, the interlockn cutter is the best type to use, owing to itsadjustment for width .

FormM illing. One Of the great advantages of the millingprocess is that duplicate parts having intricate shapes can

be finished within such Close limits as to be interchangeable.

Fig. 15 . Example of FormMilling

Becau se Of this fact,millingmachines are widely used formanu

fac turing a great variety of smallmachine parts having an irregu lar ou tline . The high-Speed steel cu tters and powerfu lmachinesnow used alsomake it possible to finishmany heavy partsmorerapidly bymilling than in any other way.

When pieces having an irregular outline are to bemilled, it isnecessary to use a cu tter having edges which conformto theprofile of the work . Such a cu tter is called a formor formedcutter . There is a distinction between a formcu tter and a

formed cu tter, which according to the common use of these terms

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126 MILLING MACHINES

Another formmilling Operation is shown in Fig. 15 . The

small levers L are finished on the edges to the required ou tlineby c utter C. These levers aremalleable castings and they are

held in a vise V attached to the table . Whenmilling,the cutter

makes 50 R .P .M . and the feed is inch,giving a table travel

of inches perminute .

Straddle M illing. When it is necessary to mill oppositesides Of duplicate parts so that the surfaces will be parallel,two cu tters can Often be used simultaneously. This is referred

to as straddlemilling. The two cu tters which formthe straddle

mill aremounted on one arbor,as shown at A

, Fig. 17 , and

they are held the right distance apart by one ormore collarsand washers. Sidemills which have teeth on the sides as well

as on the periphery (as shown at C and D,Fig.

‘

8) are used forwork Of this kind . Duplicate pieces can be milled very accu

rately by thismethod , the finished surfaces being parallel and to

a given width within close limits.

I f the proper distance between the cu tters cannot be Obtainedwi th the arbor collars available

,fine adjustments aremade b y

using metal or paper washers. When considerable accuracy is

STRADDLE M ILLING 127

necessary, the final test for width should be made by taking a

trial c ut andmeasu ring the finished surface . When the teeth onone Side of eachmill become dull

,the opposite sides can be used by

placing the right-hand cu tter on the left-hand Side and vice versa;

that is by exchanging the positions of themills on the arbor.Example of Straddle Milling. Figs. 18 and 19 Show how the

rocker-armOf a crank shaper is finished bymilling. This work

requires two operations, one Of which is a good example ofstraddlemilling. A cylindrical cu tter is used tomill both sidesof the central slot, as shown in Fig. 18. The short slot at the

Fig. 19. Finishing End of Rocker-armwith Straddle Mill

left end of the rocker-armis alsomilled by this same cutter, aswell as the raised pads on the top and bottomOf the arm. Thiscu tter is 23 inches in diameter, and whenmilling the long centralSlot, a 1

13 inch cut is taken at the top and bottomwith a feed Of

3 inches perminu te.

The second operation consists inmilling the sides of the slottedend, as shown in Fig. 19. Two 83-inch cu tters of the insertedtooth type are used to forma straddle mill

,which machines

both sides at the same time . The time required formilling eacharmis 23 hou rs. The castn is held in a special two-part fixture

which is bolted to the table. That section of the fixture which

128 M ILLING MACHINES

supports the right-hand end has V-shaped notches,which te

ceive a trunnion as shown,thus setting the casting vertically,

whereas the left-hand end is clamped between set-sc rews that areadjusted to locate the casting horizontally. After this fixture

is once set upand adjusted , very little time is required for settingone of these rocker-arms in position formilling , b ut it would berather difli cult to hold a casting of this shape by the use Of ordi

nary Clamps.

Fig. 20. Example of Gang M illing

Gang M illing. A great deal of the work done in amillingmachine (especially of the plain horizontal type) is machinedby a combination or “ gang ” of two ormore cu ttersmounted onone arbor. This is known as gangmilling. I f a plain cylindrical

cutter were placed between the sidemills Shown atA in Fig. 17 , a

gang cu tter B wou ld be formed formilling the five su rfaces a,b,c,

d and e,Simultaneously . This wou ld not only be a rapidmethod,

b ut one conducive to uniformity whenmilling duplicate parts .

Examples of Gang M illing. An example Of gangmilling isshown in Fig. 20 . Four castings are clamped to a fixture and

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130 M ILLING MACHINES

olutions perminute , a comparatively slow speed being necessaryowing to the large sidemills.

Gang milling is usually employed when duplicate pieces are

milled in large quantities, and the application of thismethod isalmost unlimited . Obviously, the formOf a gang-cu tter and thenumber Of cu tters used depend altogether on the Shape of thepart to be milled. Gang-cu tters are sometimesmade by combining cylindrical and formed cutters , for producing an irregularor intricate profile .

Fig. 2 2 . M illing Two Parts S imultaneously

Fig. 2 2 shows an example of gangmilling in which two castings are placed Side by side and rough-milled simultaneously.

The gang-cu tter is composed of seven units,as the illustration

shows. The large inserted- tooth cu tter a in the center millsthe inner sides Of each casting , while the top su rfaces aremachined by the four cylindrical cutters shown . The cu tters b,placed between the cylindrical cutters

,mill Channels or grooveswhich

,by another operation , are formed into T-slots . All of

these cutters aremade of high-speed steel and the speed~is 36 rev

GANG MILLING 131

Olutions perminute. The work-table feeds 0. I I 2 inch per revolution , thus giving a travel of 4 inches per minute . Two of

thes e castings aremilled in 18minu tes,which includes the time

required for clamping themto themachine.

It should be noted that when more than one spiral-toothedcylindrical cu tter ismounted on one arbor

,for forming a gang

mill,cutters having both right and left-hand spirals are used .

For example, the central part of the cutter shown in Fig. 20 is

composed Of two cu tters having teeth which incline in oppositedirections; that is the teeth of one cutter forma right-hand spiral

Fig. 23 . Another Gang M illing Operation

and the teeth Of the other cutter , a left-hand spiral. The reason

why cutters of opposite hand are used is to equalize the end

thrust, the axial pressure caused by the angular position of the

teeth of one cu tter being coun teracted by a pressure in the

Opposite direction fromthe other cu tter.

Still another gangmilling Operation is shown in Fig. 23 . In

this instance, the top surface of the casting is milled and twotongue-pieces are formed by the central gang of five cutters

,

which are Of the straight-tooth type and vary in diameter togive the required outline . The large angularmills at the ends

M ILLING MACHINES

finish the sloping sides of the casting, as the illustration indicates.

The speed Of rotation is 33 revolu tions perminu te, and the tabletravel, 63 inches perminu te . The feedingmovement is to theleft or against the rotation of the cutters

,which is also true of

Figs. 20,2 1 and 2 2 .

End and Face M illing. All of themilling operations referredto so far have been performed with cu ttersmounted on an arbor

,

the latter being driven by the spindle and supported by an ou t

board bearing. For some classes of work,the cutter

,instead of

being placed on an arbor, is attached directly to the machine

Fig . 24. End Milling Diagrams Illustrating Use of T-slot Cutter

spindle. Endmills,for instance , are driven in this way, as pre

viouslymentioned, and large facemilling cutters are also fastenedto the end of the spindle. Surfaces are frequentlymachined byend mills

,when using a horizontalmilling machine

,because it

would not be feasible to use a cuttermounted on an arbor.

Sketch A ,Fig. 24, illustrates how a pad or raised part on the

side Of a casting would bemachined by an endmill. The sur

face ismilled by the radial teeth Ou the end as well as by the

axial teeth , as the work is traversed at right angles to the cutter.

Occasionally, an endmill is used in this way, after the top sur

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134 M ILLING MACHINES

Fig. 24 . This preliminary Operation is usually done with a side

mill of the proper width, while the work is clamped in a hori

zontal position . The enlarged or T-section is then milled as

shown by sketch D,the casting being clamped in a vertical posi

tion,provided a horizontal milling machine is employed . The

T-slot cutter enlarges the bottomOf the straight groove, as indicated at E

,which shows the finished slot.

M illing P lain S lots. Fig . 25 shows how an endmill is usedfor cu tting an elongated slot in a link L . P rior tomilling, holesare drilled at each end Of the slot. one of which forms a starting

Fig. 26. M illing a Dovetail Groove

place for themilling cutter. The link is held in a vise and themetal between the two holes is c ut away to formthe slot

,by

feeding the table lengthwise . Bymeans of the au tomatic stop,the feed is disengaged when the cu tter has reached the end Of theslot. The shank Of the end mill is not inserted directly intothe spindle Of themachine

,but into a reducing collet C. This

collet fits in to the taper hole of the Spindle and is bored out toreceive the endmill

,the Shank of which is too small to be'placed

directly in the spindle .

M illing aDovetail Groove. Onemethod Ofmachining a clovetail groove for a Slide is shown in Fig. 26, which illustrates another

FACE M ILLING 135

endmilling operation . The cu tter used for this work has radial

teeth on the end , and also angular teeth which in c line 30 degreeswith the axis Of the cu tter. The radial end teethmill the bottomor flat surface of the groove and the angular teeth finish the sides

and formthe dovetail. The way the cas ting is clamped to thetable is plainly Shown by the illustration . The cu tter ismountedon an arbor which is inserted in the spindle.

M illing with a Face Cutter. An end milling operation isshown in Fig. 27 , which difl

'

ers fromthose previously referred to,

Fig. 2 7 . Finishing Vertical Surfaces with Face M ill

in that a large face cu tter is used,which

,in this instance, is

screwed onto the end of the spindle . Large face mills are employed on horizontal machines formilling flat surfaces that liein a vertical plane. Some cutters Of this type

,instead of being

threaded directly to the spindle, aremounted on a short arbor,whereas other designs fit over interchangeable Sleeves threadedto the spindle . The casting illustrated in Fig. 2 7 is clampedagainst an angle-plate to hold it securely , and a strap at the rearprevents it fromshifting backward when a cut is being taken.

136 MILLING MACHINES

The surface ismilled by feeding the table longitudinally,and only

one cut is necessary, as the work is finished afterward by a sur

face grinder . The number of cu ts required,when milling, is

governed by the amount of metal to be removed and also by

the accuracy of the work , as well as the quality of fin ish des ired .

M illing a Keyway in a Shaft. A simple method of holdinga Shaft formilling a keyway is '

illustrated by Sketches A and B,

Fig. 28. The blocks b are aligned with the machine table bytongue-pieces t which fit a T- Slot in the table

,and the work is

held both against the blocks and downward by the Oblique

Fig. 28. Views Illustrating S imple Methods of Holding CylindricalWork and Setting Cutter for Keyseating

pressure fromthe clamps . As the clamps are tightened,they

tend to Shift backward as Shown by the arrow (see view A) . For

this reason Clamps having rather Close-fitting bolt holes should

be used . A special packing block,similar to the one Shown at

B,is sometimes used to keep the clamps in place . This block

has an extension g against which the clamps abu t, and also an

adjustable screw h for varying the height. A tongue-piece whichfits a Slot in the table holds the block in position . By the useof a Clamp bent as indicated by the dotted lines k, any backwardmovement when tightening can also be avoided

,as the end of

this clamp rests against the Side of the T-slot. The clamps

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38 MILLING MACHINES

of the shaft; then set the dial of the elevating screw to zero .

Next sink the cutter to the total depth of the keyway,which

equals the depth d at the side, plus the height a of the arc . Thisheight a can be determined by the following formu la

in which r radius of shaft, and 10 width of keyway.

Example. I f the shaft radius is I i“ inch , thewidth of the keyseat inch

,and the depth at the side 3 inch , what is the total

depth asmeasured fromthe top of the ar c "

r . 25 V r .5 inch .

The total depth then equals or inch .

Therefore the cutter,after being set to graze the top of the shaft,

would be sunk to a depth of inch,the depth beingmeasured

by the graduated dial of the elevating screw .

Speeds for M illing. The proper speed for the cu tter, and thefeedingmovement of the work for each revolu tion of the cutter,are governed bymany different factors. The speed of the cutterdepends largely upon the kind ofmaterial beingmilled. Obvi

ously, tool steel cannot be cu t as fast as soft machine steel orcast iron

,whereas brass c an be cu t at a much higher speed .

The condition of the cutter also afiec ts the speed,it being possible

to operate a sharp cutter faster than a du ll one,because the dull

edges generate an excessive amount of heat . When millingsteel 0r wrought iron

,the application of a lubricant to the cutter

enables higher speeds to be used .

A general idea of the speeds that are feasible when using

carbon-steel cu ttersmay be obtained fromthe following figureswhich represent the velocity (in feet perminute) at the circumference of the cu tter. For taking roughing cu ts in cast iron

,

40 feet perminute; inmachine steel, 60 feet perminute; in toolsteel

,25 feet per minute; and in brass

, 75 feet per minute.

Finishing cuts are taken at speeds varying from50 to 55 feet forcast iron ; 75 to 80 feet formachine steel; 30 to 35 feet for toolsteel; and 95 to 100 feet for brass. These figu res are not givenas representing themaximumspeeds that can be used success

SPEEDS AND FEEDS

Speeds and Feeds forMilling.

PromMACH I NSRY'S Handbook Data represents ac tual practice.

39

140 MILLING MACHINES

Speeds and Feeds for Milling— 2

“illed Surfac e Indicatedb y Heavy Line

Material Milled .Width and Depth of Cut. Feed of Tab le

and Speed of Cutters

Material , c ast iron . Total width of surfac efinished , s inc hes . Depth of out “, inc h . Feedof table, inc hes perminute. Largest c utters

in gang , 535 inc hes; smallest, 2 in ches . Speed ,

53 revolu tions perminu te.

Operation , milling slots in c ast-iron bars 1

inc h thic k , with a single out, u sin a 94-inch ,

3-fluted , high-speed steel end mil . Feed of

table, 3“ inches per minute. Speed of c u tter ,

365 revolutions perminute, giving a surfac e speedof 7 2 feet .

Material , c lose-grained c ast iron . Operation ,

milling both sides of a slot. Diameter of c utter ,294 inches . Width of c ut , 294 inc hes . D

gnb

of c ut at top and bottom, Ho inch . Fee 3inches perminute.

Material , c lose ained c ast iron . ration ,

roughin doveta i bearings . Depth 0 c ut.minch. eed , 754 inches per minu te. Width of

surfac emilled by sidemi ll , 1“ inc h; by angu

lar c utter , 154 inch. Speed . 36 revolutions per

minute. Machine, vertic al type.

Material , steel c astin 3 . First operation ,

roughing out channel an top surfac e. Depthof c ut, inch; 34 inch on the sides of channel .

Feed , 7% inches per minu te. Cutters , hi hspeed steel . (Suc c eeding Operation follows"Sec ond operation , in vertic al mac hine.

Cu tters , 6-inch side mill , 3-inch angu lar mill ,mounted as a gang , b ut used independently.

First c ut, tru ing top surfac e. Feed . 254 in ches

per minute. Dovetailed sides finished in two

ou ts . Feed , me in ch per minute, feed beingslow to insure ac c urac y .

Material , gray iron . Total width of out ,inches . Average depth , an inch. Feed , 654

inches perminute. Diameter of angu lar c uttersfor sloping sides , 7” inches . Diameter of c uttersfor top surfac es , 3“ and inches. Speed , 33revolu tions perminu te.

Operation , underc u tting T-slots in c ast iron .

Cutter , high-speed steel , 1 inch in diameter ,35 inch wide. Speed , 286 revolutions per minute. Feed of table, 15% inc hes perminute.

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142 MILLING MACHINES

fully, even with ordinary carbon c utters,and with high-speed

steel cu tters they can be doubled, owing to the superior cu ttingqualities of high-speed steel.Feeds for M illing . The distance that the work feeds per

revolution of the cuttermust be varied to su it conditions. Whenmilling cu tters were first made, they had fine, closely-spacedteeth between which the chips clogged

,thus preventing any

cu tting action except with fine feeds . Modern cu tters,however

,

have much coarser teeth and, consequently, deeper cuts and

heavier feeds can be used . Aside fromthe question of cu tterdesign

,the feed is affected by the width and depth of the cu t

,

the kind of material being milled, the quality of the finish re

quired,the rigidity of the work and the power of themachine.

As a general rule,a relatively low cu tting speed and a heavy feed

is used for roughing, whereas for finishing, the speed is increased

and the feed diminished. The data given in connection with

some of the examples of milling referred to in this treatise willshow

,in a general way, what speeds and feeds are practicable

when using a well-built machine and modern cu tters. The

tables Speeds and Feeds for M illing ” also contain considerabledata taken fromactual practice.

Lub ricants for M illing . A lubricant that has been exten

sively used for milling is made in the following proportionsI pound of sal soda (carbonate of soda) , I quart of lard oil, I

quart of soft soap , and enough water tomake 10 or I 2 gallons.

Thismixture is boiled for one-half hour, preferably by passinga steamcoil through it. The soap and soda in this solution improve the lubricating quality and also prevent the su rfaces fromrusting. Lard oil and animal or fish oils are also used as a lub ri

cant, and some manu facturers mix mineral oil with lard orfish oil. The soda solu tion or some of the commercial lubricantson themarket aremuch cheaper than o il andmore generally used .

The lubricant is usually applied to the cu tter through a pipe or

spou t which can be adjusted to the proper position . Somemachines have a special pump for supplying the lubricant, andothers are equipped with a can fromwhich the lubricant flowsto the cu tter by gravity . Cast iron and brass aremilled dry.

CHAPTER IV

APPLICATION OF UNIVERSAL MILLING MACHINE AND

SP IRAL HEAD

THE millingmachine illustrated in Fig. I is referred to as a

universal type, because it is adapted to such a wide variety of

milling operations. The general construction is similar to thatof a plainmillingmachine , although the universal type has certain adjustments and attachments which make it possible tomill a greater variety of work . On the other hand , the plain

machine ismore simple,and

,for a given size

,more rigid in con

struction; hence, it is better adapted formilling large numbersof duplicate parts in connection withmanu facturing operations.

The universalmachine has a column C, a knee K which can be

moved vertically on the column ,and a tablewith cross and longi

tudinal adjustmen ts the same as amachine of the plain type.There is a difierence

,however

,in themethod ofmoun ting the

table on the knee. As explained in Chapter I I I , the table of a

plain machine is carried by a saddle which is free tomove in a

crosswise direction,whereas

,the table’s line of motion is at

right angles to the spindle. The table of a universal machinealso has thesemovements, and, in addition

,it can be fed at an

angle to the spindle by swiveling saddle Z on clamp-bed B,which

is interposed between the saddle and knee. The circular baseof the saddle has degree graduations which show the angle at

which the table is set. When the zeromark of these graduations

coincides with the zeromark on the clamp-bed,the table is at

right angles to the spindle . The saddle is held rigidly to theclamp-bed , in whatever position itmay be set

, by bolts which

must be loosened before making an adjustment. The u tility

of this angular adjustment will be explained later in connectionwith examples of universalmilling operations.

The feed motion is derived fromthe main spindle, which is143

x44 MILLING MACHINES

connected with the feed changemechanismenclosed at F by a

chain and Sprockets located inside of the column . The power istransmitted fromF to gear-case A containing the reversemechanismoperated by lever R ,

which serves to start, stop , or reverse

all feeds. Levers T and V control the au tomatic transverse and

Fig. 1 . Brown a Sharpe Universal M illing Machine

vertical feeds, respectively, and the longitudinal feed to thetable is controlled or reversed by lever L . The longitudinalfeed is au tomatically tripped by the adjustable dogs or tappetsD. The vertical feed also has an au tomatic trip mechanismoperated by dogs D, . The table can be traversed by handlesat each end and the cross movement is effec ted by wheel E .

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146 M ILLING MACHINES

The general arrangement of the design used on Brown Sharpe

machines is shown in Fig. 2 . Themain spindle S has attachedto it a worm-gear B (see the cross-sectional view) whichmesheswith the wormA on shaft 0

,and the ou ter end of this shaft

carries a crank I which is used for rotating the spindle when

Fig. 2 . Spiral Head Used for Spiral M illing and Indexing

indexing. Worm-wheel B has forty teeth and a single-threadedwormA is used, so that forty turns of the crank are requiredto turn Spindle S one complete revolu tion ; hence, the requirednumber of turns to index a fractional part of a revolution isfound by Simply dividing forty by the number of divisions desired. (As there are difierentmethods of indexing, this subject

SP IRAL HEAD 47

is referred to separately to avoid confusion .) In order to turn

crank J a definite amount, a plate I is used , having several concentric rows of holes that are spaced equidistant in each separaterow . When indexing , spring-plunger P is withdrawn by pullingout knob I and the crank is rotated asmany holes asmay berequired . The number of holes in each circle of the index platevaries

, and the plunger is set in line with any circle by adjustingthe crank radially. One index plate can be replaced by anotherhaving a difierent series of holes , when this is necessary in orderto obtain a certain division .

Sometimes it is desirable to rotate the spindle S independentlyof crank J and the wormgearing; then wormA is disengagedfromworm-wheel B . This disengagement is efiec ted by tu rningknob E abou t one—quarter of a revolu tion in a reverse directionto that indicated by the arrow stamped on it

,thus loosening nut

G which holds eccentri c bushing H . Both knobs E and F are

then turned at the same time , which rotates bushing H and

throws wormA out ofmesh. The wormis re-engaged by tuming knobs E and F in the direction of the arrow; knob E shou ld

then be tightened with a pin wrench . The wormis disengagedin this way when it is desired to index rapidly by hand , and whenthe number of divisions required can be obtained by using plateC . This plate is attached to the spindle and contains a circle ofholes which are engaged by pin D,

operated by lever D, (seec ross-section) . This direct method of indexing can often beused when milling flu tes in reamers

,taps

,etc .

,but

,as only a

limited number of divisions can be obtained,it is necessary to

use crank J and index plate I formost indexing operations.

When the spiral head is used in connection with themilling ofhelical grooves (which are commonly but erroneously called

spiral grooves) , themain spindle S is rotated slowly by changegears as the work feeds past the c utter. These change gears

(which are not shown in this illustration) transmitmotion fromthe table feed-screw L to shaft W

,which

,in turn

,drives spindle

S through spiral gears,Spur gears and the wormgearing A and

B . For themethod of determining what size gears to use for

milling a helix of given lead see“Helical Milling.

”

148 MILLING MACHINES

There is one other featu re of the spiral head which should bereferred to

,and that is the angular adjustment of the main

spindle. I t is necessary for some classes of taper work to set

the spindle at an angle with the table, and this adjustment ismade by loosening bolts K and turning the circular body T inits base. The angle to which the head is set is Shown by graduations reading to i a degree . The Spindle of this particular headcan be set to any angle between 10 degrees below the horizontaland 5 degrees beyond the perpendicu lar. This adjustment isneeded whenmilling taper work whichmust be set at an anglewith the table.

The footstock M,which is used in connection with the spiral

head when milling parts that are supported between centers, is

also adjustable so that the centers 0 and 61 can be aligned whenmilling flutes in taper reamers, etc. The footstock center is set

in line with center 6,when the latter is in a horizontal position ,

by two taper pins on the rear side. When it is desired to set

the center at an angle,these pins are removed and the nu ts

shown are loosened; the center can then be elevated or depressedby turning a nut at the rear, whichmoves the center through arack and pinion .

Workmounted between the centers is caused to rotate withthe spindle

,either when indexing or when cu tting helical grooves,

by a dog which engages driver plate d. The tail of the dogshould be confined by a set-screw e, to prevent any rockingmovement of the work.

Spiral heads of difierentmakes vary more or less in their

arrangement,which is also true ofmillingmachines , or, in fact,

of any othermachine tools. Machines or attachments of a giventype

,however

, usually have the same general features, and ifone or two typical designs are understood, it is M paratively

easy to become familiar with othermakes. Of course, the operator of anymachine tool should be acquainted with its generalconstruction

, b ut it is more important to have a clear understanding of its application to various kinds of work.

Use of the Spiral Head . The spiral head is ordinarily usedfor such work as milling the teeth in milling cutters, fiuting

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150 MILLING MACHINES

The formof cutter to use is the next thing to consider. As the

grooves which formthe teeth are angular, the cuttermust haveteeth which incline a corresponding amount to the axis. A

cu tter of this type which is largely used for milling straightteeth is Shown at E in Fig. 10, Chapter I I I . The cutting edges

(in this instance) have an inclination of 60 degrees with theside, and the cu tter is known as a 60-degree, single-angle cutter,to distinguish it fromthe double-angle type , the use of whichwill bementioned later.After the cu tter is mounted on an arbor b, as indicated in

Fig. 3 , the straight side or vertical face is set in line with thecenter of the arbor as shown by the detail end-view A . There

are several ways of doing this: A simplemethod is to draw a

horizontal line across the end of the blank with an ordinary sur

face gage (the pointer of which should be set to the height of the

spiral head center) and then rotate the work one-quarter of arevolution to place the line in a vertical position ,

after which theside of the cutter is set to coincide with this line . The side ofthe cu tter can also be set directly by the centers. The tableis first adjusted vertically and horizontally until the cu tter isopposite the spiral head center. A scale or straightedge heldagainst the side of the cu tter is then aligned with the point ofthe center , by shifting the table laterally.

The next step is to set the cu tter to the right depth formillingthe grooves. The depth is regulated according to the widthwhich the toothmust have at the top , this width being knownas the “ land .

” The usualmethod is to raise the knee, table andblank far enough to take a cut, which is known to be somewhatless than the required depth . The blank is then indexed or

tu rned 11; of a revolu tion (as there are to be I 8 teeth) in the

direction Shown by arrow 0,and a second groove is started as at

B . Before taking this cut, the blank is raised until the requiredwidth of land is obtained . The second groove is then milled ,after which the blank is again indexed 1

13 of a revolu tion , thus

locating it as at C. This operation of cu tting a groove and indexing is repeated

,without disturbing the position of the cu tter,

until all the teeth are formed as shown at D.

PLAIN INDEXING 15 1

Plain or Simple Indexing. The dividing of a cylindricalpart into an equal number of divisions by using the spiral head

is called indexing. The work is rotated whatever part of a

revolu tion is required, by turning crank " , Fig. 2 . As previouslyexplained, the shaft carrying this crank has a wormwhichmesheswith a worm-wheel on the spiral-head spindle. As the wormis single-threaded , and as there are 40 teeth in the worm-wheel

,

40 turns of the crank are necessary to rotate the Spindle one

complete revolu tion . I f only a half revolu tion were wanted , the

number of turns would equal 40 2,or 20, and for 1

1, of a

revolu tion ,the turns would equal 40 I 2

,or and so on .

In each case , the number of tu rns the index crankmustmakeis obtain ed by dividing the number of turns required for one revolution of the index-head Spindle by the number of divisionswanted . As the number of turns for one revolu tion is 40, withrare exceptions the rule then is as follows:Divide 40 by the number of divisions into which the periphery of

thework is to be divided to obtain the number of turns for the indexcrank.

By applying this rule to the job illustrated in Fig. 3 , we find

that the crank I must be tu rned 23 times to index the cutterfromone tooth to the next, because there are I 8 teeth

,or divi

sions, and 40 I 8 The next question that naturally

arises is, how is the crank to be rotated exactly § of a turn"This is done bymeans of the index plate I , which has six conc en

tric c ircles of holes. These holes have been omitted in thisillustration owing to its reduced scale , b ut are shown in thedetail view,

Fig. 4. The number of holes in the different circlesof this particular plate are 33 , 3 1 , 29, 27 , 23 and 2 1 .

In order to turn crank J 3 of a revolu tion ,it is first necessary

to adjust the crank radially until the latch-

pin is opposite a

circle having a number of holes exactly divisible by the denominator of the fraction (when reduced to its lowest terms) represen ting the part of a turn required . As the denominator of thefraction in this case is 9, there is only one circle on this platethat can be used

,namely

,the 27

-hole circle . In case none of

the circles have a number which is exactly divisible by the

152 M ILLING MACHINES

denominator of the fractional tu rn required,the index plate is

replaced by another having a difi'

erent series of holes. The number of holes that the latch-pin would have tomove for 3of a tu rnequals 27 X or 6 holes. After the latch-pin is adjusted to the 27hole circle, the indexing of the cutter 1

13 of a revolution is aecom

plished by pulling out the latch-pin and turning the crank 2

complete turns, and then of a turn , or 6 holes in a 2 7-hole Circle.

After each tooth groove ismilled in the cu tter, this indexing opera

Fig. 4. Diagramshowing how Sector is Used when Indexing

tion is repeated,the latch-

pin beingmoved each time 2% of a turnfromthe position it last occupied

,un til the work has been indexed

one complete revolution and all the teeth aremilled.

Use of the Sector. After withdrawing the latch-

pin ,one

might easily forget which hole it occupied , or become confusedwhen counting the number of holes for the fractional turn , and

to avoidmistakes of this kind , as well as tomake it unnecessaryto count

,a device called a sector is used . The sector has two

radial arms A and B (Fig. which have an independent angular

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154 MILLING MACHINE S

The fractional part of a turn is usually given as a fraction havinga denominator which equals the number of holes in the indexcircle to be used , whereas the numerator denotes the number ofholes the latch-

pin should bemoved , in addition to the completerevolutions, if one or more whole tu rns are required . For

example, themovement for indexing 24 divisions would be givenas I §% of a tu rn ,

instead of I ", the denominator 39 represen tingthe number of holes in the index c ircle, and 26 the number ofholes that the crankmust bemoved for obtaining of a revolu

tion,aftermaking one complete tu rn .

Compound Indexing. Ordinarily, the index crank of a

spiral head must be rotated a fractional part of a revolu tion ,

when indexing, even though one ormore complete turns are te

quired . As previously explained , this fractional part of a turn

ismeasured bymoiring the latch-

pin a certain number of holesin one of the index circles; bu t, occasionally , none of the indexplates furnished with themachine has circles of holes containing the necessary number for obtaining a certain division . One

method of indexing for divisions which are beyond the range ofthose secured by the directmethod is to first turn the crank a

definite amount in the regular way, and then the index plateitself

,in order to locate the crank in the proper position . This is

known as compound indexing, because there are two separate

movements which are, in reality , two simple indexing operations.

The index plate is normally kept fromturning, by a stationary

stop-pin at the rear , which engages one of the index holes,the

same as the latch-

pin . When this stop-pin is withdrawn ,the

index plate can be turned.

The Princ iple of Compound Indexing. To illustrate the

principle of the compound method,suppose the latch-

pin is

tu rned one hole in the I 9-hole c ircle and the index plate is also

moved one hole in the 20-hole circle and in the same directionthat the crank is turned . These combined movements willcause the worm(which engages the worm-wheel on the spiralhead spindle) to rotate a distance equal to 115 2

10 3

3395 of a

revolu tion . On the other hand , if the crank ismoved one hole

in the 19-hole circle, as before, and the index plate ismoved one

156 MILLING MACHINES

hole in the 20-hole circle , but in the opposite direction, the rotationof the wormwill equal 115 5

15 7h revolution. By the

simplemethod of indexing, it would be necessary to use a circlehaving 380 holes to obtain these movements , but by rotatingboth the index plate and crank the proper amount, either in thesame or opposite directions, asmay be required , it is possible tosecure divisions beyond the range of the simple or direct system.

Example of Compound Indexing. To illustrate the use of

the compound method,suppose 69 divisions were required .

In order to index the work 315 revolu tion ,it is necessary tomove

the crank of a turu and thiswould require a circle having 69 holes, if the simplemethod ofindexing were employed , but by the compound system

,this

division can be obtained by using the 23 and 33-hole circles

,

which are found on one of the three standard plates furnishedwith Brown Sharpe spiral heads. The method of indexing315 revolu tion by the compound systemis as follows: The crankis firstmoved to the right 2 1 holes in the 23-hole circle, as indicated at A in Fig. 5 and it is left in this position; then the stop

pin at the rear,which engages the 33-hole c ircle of the index

plate,is withdrawn ,

and the plate is turned backward , or to theleft

,I I holes in the 33-hole c ircle. This rotation of the plate

also carries the crank to the left, or fromthe position shown bythe dotted lines atB ,

to that shown by the full lines, so that afterturning the plate backward , the crank ismoved fromits originalposition a distance x which is equal to 3} H; 33 which isthe fractional part of a turn the crankmustmake , in order toindex the work 6

16 of.a revolution .

Indexing by Using Simple and Compound Systems. Sometimes the simplemethod of indexing can be used to advantage

in conjunction with the compound system. For example, ifwe want to cut a 96

-tooth gear, every other tooth can be out

first by using the Simple method and indexing for 48 teeth,which would require amovement of r5 holes in an 18-hole circle.

When half of the tooth spaces have been cut, the work is in

dexed 316of a revolu tion by the compoundmethod , for locating

the cuttermidway between the spaces previouslymilled. The

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158 MILLING MACHINES

44 holes in the 23-hole c ircle , and the index plate is moved

backward 44 holes in the 33-hole c ircle . The movement can

also be forward 44 holes in the 33-hole circle and backward 44holes in the 23

-hole c ircle,withou t afiec ting the res ult. The

movements obtained by the foregoing rule are expressed in

compound indexing tables in the formof fractions, as for example :$3 a. The numerators represent the number of holes

indexed and the denominators the circles used, whereas, theand signs show that themovements of the crank and indexplate are opposite in direction .

These fractions can often be reduced and simplified so that itwill not be necessary tomove somany holes, by adding somenumber to themalgebraically. The number is chosen by trial ,and its sign should be opposite that of the fraction to which it is

added. Suppose , for example , we add a fraction representing

one complete turn , to each of the fractions referred to; we thenhave

— i-t“

Z i't i i

+ 3“ 33

I f the indexing is governed by these simplified fractions, thecrank is moved forward 2 1 holes in the 23

-hole circle and the

plate is turned backward I I holes in the 33-hole circle , insteadofmoving 44 holes , as stated . The resu lt is the same in eachcase bu t the smaller movements are desirable

,especially for

the Index plate,because it is easier to coun t I I holes than 44

holes. For this reason the fractions given in index tables are

Simplified in this way. Ordinarily,the number of circles to

use and the required number ofmovements tomake when indexing is determined by referring to a table, as this eliminates all

calcu lations and lessens the chance of error .Difierential Indexing. One of the improved indexing

systems, which is applied to the universal milling machinesbuilt by the B rown Sharpe M fg. CO.

,is known as the difi

'

er

ential method . This systemis the same in principle as compound indexing , but difiers fromthe latter in that the indexplate is rotated by suitable gearing which connects it to the

DIFFERENTIAL INDEXING 159

spiral-head spindle, as shown in Figs. 6 and 7 . This rotation

or difierentialmotion of the index plate takes place when thecrank is turned

,the platemoving either in the same direction

as the crank or opposite to it, asmay be required . The resultis that the actualmovement of the crank ,

at every indexing, iseither greater or less than its movement with relation to theindex plate.

Thismethod of turning the index plate by gearing instead ofby handmakes it possible to obtain any division liable to arisein practice

,by using

one circle of holes andsimp ly tu rn in g theindex crank in one

direction,the same as

for plain indexing. As

the hand movementof the plate and thecounting of holes ise l imi n a t e d , t h echances of error are

also greatly reduced .

The proper sizedgears to use formov

Fig. 6. Index Head Geared for DiflerentialIng the Index plate

Imam"

the required amoun twould ordinarily be determined by referring to a table which

accompanies the machine . This table (a small part of whichis illustrated in Fig. 8) gives all divisions fromI to 382 and

includes both plain and difierential indexing; that is, it showswhat divisions can be obtained by plain indexing

, and alsowhen it is necessary to use gears and the difierential system.

For example, if I 30 divisions are requ ired , the 39-hole indexcircle is used and the crank ismoved I 2 holes (see fourth columnof table) but no gears are required. For I 3 I divisions a 40-toothgear is placed on the worm-Shaft and a 28- tooth gear ismountedon the spindle . These two gears are connected by the 44-toothidler gear, which serves to rotate the plate in the same direction

160 M ILLING MACHINES

as the crank. To obtain some divisions , it is necessary to rotatethe plate

,and crank in opposite directions, and then two idler

gears are interposed between the spindle and worm-shaft gears.

Principle of the Difierential Indexing System. Fig. 6 shows

a spiral head geared for 2 7 1 divisions . The table calls for a gear

C having 56 teeth; a spindle gear E with 72 teeth and one idlerD. The sector should be set for giving the crank amovementof 7 holes in the 49-hole circle or 3 holes in the 2 1-hole c ircle,either of which equals 3 of a turn . I f an index plate having a

49-hole circle happens

to be on the spindlehead

,this would be

used . Now if the spin

dle and index platewere n ot connectedthrough gearing, 280

divisionswould be obtained by successivelymoving the crank 7holes in the 49

-holec ircle

,b ut the gears

E,D and C cau se the

index plate to turn inFig. 7 .

02333;If”) 1323331333 12131

;Iglo

‘

mpound the same direction as

the crank at such a

rate that when 2 7 1 indexings have beenmade the work is tu rnedone complete revolution;therefore, we have 27 1 divisions insteadof 280

, the number being reduced because the totalmovementof the crank

,for each indexing

,is equal to itsmovemen t relative

to the index plate, plus themovement of the plate itself when

(as in this case) the crank and plate rotate in the same dircetion . I f they were rotated in opposite directions, the crankwould have a total movement equal to the amount it turnedrelative to the plate

,minus themovement of the plate.

Sometimes it is necessary to u se compound gearing, in order tomove the index plate the required amount for each turn of thecrank . Fig. 7 shows a spiral head equipped with compound

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162 MILLING MACHINES

The small gear is placed on the spindle, in this case , becausethe index plate is tomake only of a turn, while the spindlemakes one complete revolution . One idler gear is also in terposed between the gears, because it is necessary for the plate togain of a turn with respect to the crank; therefore, themovements of the index plate and crankmust be in thesame direction.

The difl'

erentialmethod of indexing cannot be used for helicalor Spiralmilling, because the spiral hea d is then geared to thelead-screw of themachine. (See Helical Milling

”

)High-number, Reversib le Index Plates. The dividing heads

furnished with Cincinnati milling machines are equ ipped with

Fig. 9. Index Plates for 0b a Large Number of Divisions b yS imple de

comparatively large index plates. This inc rease in diametergives roomfor more circles and a larger number of holes thanthe smaller plates, and the range is further increased bymakingthe plate reversible, each side having difi

'

erent series of holes.

Therefore, the number of divisions that can be obtained directlyfromone of these plates is greatly increased . The standardplate regularly supplied can be used for indexing all numbers upto 60; all even numbers and those divisible by 5 up to 120, and

many other divisions between 120 and 400. I f it should be

necessary to index high numbers not obtainable with the standard plate, a high-number indexing attachment can be supplied.

This consists of three special plates (see Fig. 9) which have large

ANGULAR INDExING 163

numbers of holes and difierent series on each side. They can

be used for indexing all numbers up to and including 200; all

even numbers and those divisible by 5 up to and including 400.

Owing to the range of the standard plate , the high-number attachment is only needed in rare instances

,for ordinarymilling

machine work.

Angular Indexing. Sometimes it is desirable to index a certain number of degrees instead of a fractional part of a revolu

tion . As there are 360 degrees in a circle and 40 turns of theindex crank are required for one revolu tion of the spiral-head

Spindle, one turn of the crank must equal 3133" 9 degrees.

Therefore,two holes in an 18-hole circle, or three holes in a 27

hole c ircle, is equivalent to a one-degree movement, as this isi of a turn . If we wan t to index 35 degrees, the number of turnsthe c rank must make equals 35 9

é or three completeturns and 8 degrees. As amovement of two holes in an 18-holecircle equals one degree, amovement of 16 holes is required for8 degrees. I f we want to index 1 13 degrees, the one-half degreemovement is obtained by turning the crank one hole in the 18

hole circle, after the 11 degrees have been indexed by makingone complete revolu tion (9 degrees) , and four holes (2 degrees) .Similarly, one and one-third degree can be indexed by using the27

-hole circle, three holes being required to index one degree, andone hole, one-third degree .

When it is necessary to index tominu tes, the requiredmovement can be determined by dividing . the total number ofminutes represented by one turn of the index crank, or 540 (9 X 60

by the number ofminu tes to be indexed. For example,

to index 16minutes requires approximately 31; turn (540 16

34, nearly) , or a movement of one hole in a 34-hole circle.

As the 33-hole circle is theonenearest to 34, this could be used andthe error would be very small.Rule for Angular Indexing. The following is a general rule

for the approximate indexing of angles, assuming that fortyrevolutions of the index crank are required for one turn of thespiral-head spindleDivide 540 by the number of minutes to be indexed. If the

164 MILLING MACHINES

quotient is nearly equal to the number of holes in any index circle

available, the angular movement is obtained by turning the crank

one hole in this circle; but, if the quotient is not approximatelyequal , multiply it by any trial number which will give a produc t

equal to the number of holes in one of the index c ircles,andmove

the crank in the circle asmany holes as are represented by the trialnumber.

I f the quotient of 540 divided by the number of minu tes tobe indexed is greater than the largest indexing c ircle

,it is not

Fig. 10. Diagrams Illustrating the Principle of Helical or Spiral Milling

possible to obtain the movement by the ordinary method ofSimple indexing .

Helical or Spiral M illing . The spiral head is not only u sedfor indexing or dividing, but also in connection with themillingof helical or “

spiral ” grooves . When a spiral is beingmilled,the work is tu rned Slowly by the dividing head as the table ofthemachine feeds lengthwise. As the result of these combinedmovements

, a spiral groove is generated by the milling cu tter.The principle of spiral milling is illustrated by the diagramsshown in Fig. 10 . I f a cylindrical partmounted between centers,as atA

,is rotated

,and

,at the same time ,moved longitudinally

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66 MILLING MACHINES

SPIRAL M ILLING 167

Example of Spiral M illing. As an example of spiralmilling,suppose we have a cylindrical cu tter blank 3} inches in diameterin which right-hand spiral teeth are to bemilled

, as indicated inFig. 12

,which Shows the cutter after the teeth have beenmilled.

The blank is firstmounted on an arbor which is placed betweenthe centers with a driving dog attached . The arbor should fittightly into the hole of the blank so that both will rotate as one

Fig. 12 . Universal Machine arranged for Spiral M illing

piece, and it is also necessary to take up all play between the

driving dog and faceplate .

The spiral head is next geared to the feed-sc rew. I f a tableof change-gears is available, it will Show what gears are needed ,provided the lead of the spiral is known . A small section of oneof these tables is reproduced in Fig. 13 to

'

illustrate the arrangement . Suppose the lead given on the drawing is 48 inches; then

168 MILLING MACHINES

this figure (or the nearest one to it) is found in the column headed,“Lead in Inches,

”and the four numbers to the right of and in

line with 48 indicate the number of teeth in the four gears tobe used . The numbers opposite 48 are 72 , 24, 64 and 40,

re

spec tively, and the position for each of these gears is shown bythe headings above the columns. As 72 is in the column headedGear onWorm,

”a gear d (see also Fig. 1 1) of this size is placed

on shaft W. The latter is referred to as the worm-shaft, al

though,strictly speaking, the worm-shaft W1 is the one which

Fig . 13 . Part of Tab le showing Gear Comb inations to use for

ob taining Spirals of Diderent Lead

carries the indexing crank and worm. The first gear c placed on

the stud E has 24 teeth , as shown by the table, and the secondgear b on the same stud has 64 teeth , whereas gear a on the sc rewhas 40 teeth.

After these gears are placed in t heir respective positions, the

first and second gears c and b on stud E are adjusted tomeshproperly with gears a and d by changing the position of the supporting yoke I’ . As a right-hand spiral is to bemilled, whichmeans that it advances by twisting or tu rning to the right, anidler gear is not used with the design of spiral head shown .

Whenmilling a left-hand spiral, it is necessary to insert an idlergear in the train of gears (as at i , Fig. 12

, Chapter V) , to rotate

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170 MILLING MACHINES

Setting the Cutter for M illing Spiral Flutes. A method ofsetting a double-angle cutter, for milling the teeth in Spiralmills, which is Simple and does not require any calcu lation , is

as follows: The pointer of a surface gage is first set to the height

of the index head center and then the work is placed in themachine . The cu tter is next centered with the blank

,laterally,

which can be done with a fair degree of accuracy by setting theknee to the lowest position at which the cu tter will just graze

the blank . The blank is then adjusted endwise until the axis of

Fig. 15 . Setting a Doub le-an e Cutter for Milling Teeth of a Spiralng Cutter

the cu tter is in line with the end of the work, as shown by the

side and plan views at A,Fig. 15 . Onemethod of locating the

cu tter in this position (after it has been set approximately) is toscribe a line on the blank a distance fromthe end equal to theradius of the cu tter. The blade of a square is then set to thisline, and the table is adjusted lengthwise until the cu tter justtouches the edge of the blade. The cu tter can also be centeredwith end (after it is set laterally) by firstmoving the blank endwise frombeneath the cutter

,and then feeding it back slowly

SPIRAL M ILLING 17 1

until a tissue paper feeler Shows that it just touches the comerof the blank . The relation between the cu tter and blank willthen be as Shown at A .

The table is next set to the angle of the spiral (as explainedlater) but its lengthwise position Should not be changed . Thesurface gage

,set as previously described , is then used to scribe

lines which represent one of the tooth spaces on the end of theblank where the cut is to start. This is done by first drawing ahorizontal line as at B . This line is then indexed downwardan amount equal to one of the tooth spaces , and another horizontal line is drawn as at C. The last line scribed is then indexed 90 1 2 degrees

,which locates itparallelwith the 12-degree

Side of the cu tter, as atD. The work is then adjusted laterally,

and vertically by elevating the knee, until the cu tter is so lo

cated that the 1 2-degree side cuts close to the scribed line, and,

at the same time,the required width of land w (see sketch E ) is

left between the top edge of the groove and the line representingthe front face of the next tooth .

Af ter the cu tter is centered,as at A ,

the longitudinal positionof the blank shou ld not be changed until the cu tter is set as at

E , because any lengthwise adjustment of the work would beaccompanied by a rotarymovement (as the spiral head is gearedto the table feed-screw) and the position of the lines on the end

would be changed .

Setting the Tab le to Angle of Spiral . The table of themachinemust also be set to the same angle that the spiral grooveswillmake with the axis of the work . This is done by looseningthe bolts which normally hold the saddle to the clamp-bed

,and

swinging the table around to the right position , as shown by thedegree graduations on the base of the saddle . The reason for

setting the work to this angle is to locate the cu tter in line withthe spiral grooves which are to bemilled by it. I f the cutterwere not in line with the spiral, the shape of the grooves would

not correspond with the shape of the cutter.The angle to which the table should be set, or the spiral angle,

varies according to the diameter of the work and lead of thespiral. AS the diameter of the cu tter illustrated in Fig. 1 2 is

1 72 M ILLING MACHINES

3} inches and the lead of the spiral is 48 inches, the angle is 12

degrees. The direction in which the table is turned dependsupon whether the spiral is right or left-hand . For a right-handspiral the right-hand end of the table should bemoved towardthe rear

,whereas if the spiral is left-hand, the left-hand end of

the table ismoved toward the rear.Milling Spiral Flutes. After the table of themachine is Set

to the requ ired angle and the saddle is clamped in position,the

work is ready to be milled . The actual milling of the spiralgrooves is practically the same as though they were straight orparallel to the axis. When a groove is milled

,it is well to

either lower the table slightly or turn the cu tter to su ch a positionthat the teeth will not drag over the work , when returning for

another cu t, to prevent scoring ormarring the finished groove.

If the work-table is lowered,it is returned to its original position

by referring to the dial on the elevating screw .

After each successive groove is cut,the work is indexed by

turning the indexing crank in the regular way. This operation

ofmilling a groove and indexing is repeated until all the teeth

are finished . I t should be mentioned that the difl'

erential

method of indexing cannot be employed in connec tion with Spiralwork

,because with this systemof indexing the worm-Shaft of

the spiral head is geared to the spindle. When milling spiralgrooves

,the position of the cu tter with relation to the work

should be such that the rotary movement for producing theSpiral will be toward that side of the cu tter which has thegreater angle. To illustrate

,the blank A

,Fig. 14, should turn

(as Shown by the arrow) toward the 48-degree Side of the cu tter,

as this tends to produce a smoother groove .

Calculating Change-gears for Spiral M illing . As was ex

plained in connection with Fig. 10,the lead of a Spiral cut in a

milling machine depends on the relation between the rotary

speed of the work and its longitudinal movement, and theserelative speeds are controlled by the change-gears a, b, c and d,

Fig. 1 1 , which connect the table feed-screw L with shaft W.

I f the combination of change-gears is such that 20 turns of sc rew

L are requ ired for one revolu tion of spindle S ,and the screw has

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174 MILLING MACHINES

numbers of teeth in available gears. Suppose 8 is chosen for

the secondmultiplier; we then have

i x i = i

The set of fractions obtained in this way, that is, H; and i i :represents the gears to use formilling a spiral having a lead of12 inches . The numerators equal the number of teeth in thedriven gears , and the denominators the number of teeth in the

driving gears . If numbers oc cu rred in either fraction which didnot correspond with the number of teeth in any of the changegears available

,the fraction should bemultiplied by some other

trial number until the desired result is obtained .

Relative Positions of the Change-gears . When the gears forcu tting a given Spiral are known ,

it remains to plac e theminthe proper place on themachine , and in order to do this, the distinction between driving and driven gears should be understood.

The gear a (Fig. 1 1) on the feed-screw is a driver and gear b,which is rotated by it

,is driven . Similarly , gear c is a driver

and gear d is driven . As the numerators of the fractions represent driven gears

,one having either 7 2 or 32 teeth (in this in

stance) should be placed on shaft W. Then a driving gear witheither 40 or 48 teeth is placed on stud E and the remainingdriven gear is afterwardsmounted on the same stud . The otherdriving gear is next placed on the screw L and yoke Y is adjusteduntil the gears mesh properly . The spiral head will then begeared for a lead of 1 2 inches

,the gear on the wormhaving 72

teeth,the first gear on the stud having 40 teeth , the second gear

having 32 teeth , and the gear on the screw having 48 teeth .

E ither the driving or driven gears could be transposed withoutchanging the lead of the spiral. For example, the driven gearwith 32 teeth could be placed on shaft W and the one having

72 teeth could be used as a second gear on the stud, if such an

arrangement were more convenient. As previously stated,a

reverse or idler gear is inserted in the train when cutting lefthand spirals

,bu t it does not affect the ratio of the gearing.

Determining the Helix or Spiral Angle. When the changegears for a given Spiral have been selected, the next step is to

SP IRAL MILLING 175

determine the angle to which the table of themachinemust beset in order to bring the milling cu tter in line with the spiral.This angle equals the angle that the spiralmakes with its axis

and it depends upon the lead of the spiral and the diameter ofthe cylindrical part to bemilled . The angle of a spiral can bedetermined graphically by drawing a right-angle triangle as

shown by sketch C,Fig. 10 . If the length e of one side equals

the circumference of the cylinder on which the Spiral is to begenerated, and the base L equals the lead, the angle a will bethe spiral angle . If such a triangle is wrapped around the

cylinder, the hypothenuse will follow a helical curve,as the

illustration indicates .

Another way of determining the angle of a spiral is to first getthe tangen t of the angle by dividing the circumference of thework by the lead of the spiral. When the tangent is known ,

thecorresponding angle is found by referring to a table of naturaltangents. For example

,if the circumference e is 1 2 inches

, and

the lead L is 48 inches, the tangen t equals 13 and the

angle a corresponding to this tangent is abou t 14 degrees. Evi

dently, if the circumference is increased or diminished, therewill be a corresponding change in angle a provided the lead Lremains the same. For that reason

,the ou ter circumference

is not always taken when calculating the spiral angle. The

angle for setting the table when cu tting spiral gears in amillingmachine is determined by taking the diameter either at the

pitch circle,or at some point between the pitch circle and the

bottoms of the teeth , rather than the ou tside diameter, in orderto sec ure teeth of the proper Shape .

Cutting Spiral Grooveswith an EndMill.— When a spiral groovehaving parallel sides is required it shou ld be cutwith an endmillas illustrated in Fig. 16. If an attempt were made to mill agroove of this kind by u sing a Sidemillmounted on an arbor, thegroove would not have parallel sides

,because the side teeth of the

mill would not clear the groove; in other words, they wou ld cu t

away the sides owing to the rotarymovement of the work and

forma groove having a greater width at the top than at the bot

tom. This can be overcome,however

,by using an endmill.

176 M ILLING MACHINES

Themachine is geared for the required lead of spiral, as pre

viously explained , and the work is adjusted vertically until its

axis is in the same horizontal plane as the center of the endmill.With the machine illustrated , this vertical adjustment can beobtained bymoving the knee up until its top surface coincides

with a line on the columnmarked center; the index head centerswill then be at the same height as the axis of themachine spindle.Use of Chuck on the Spiral Head. I t is often nec essary to

use a Spiral-head in connection withmilling of parts which can

Fig. 16. M illing a Spiral Groove with an End M ill

not be held between centers and must be attached directly tothe spiral-head spindle. A common method of holding work ofthis kind is to place it in a chuckwhich is screwed on to the spiralhead spindle. An example of chu ck work is shown in Fig. 17 .

The operation is that of milling a square head on bolt B . As

the illustration shows,the Spiral-head spindle is set in a vertical

position . This is done by loosening the clamp bolts C and tuming the head 90 degrees, as Shown by the graduations on thefron t Side. These bolts shou ld afterwards be tightened.

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178 MILLING MACHINES

Spiral-head spindle . The footstock center is used to supportwork of this class whenever feasible . When it is neces sary to

hold a part true with a bored hole,arbors of the expanding type

are often used . These have a taper shank which fits the taper

hole in the spindle, and the ou ter end is so arranged that it canbe expanded tightly into the hole in the work . Small chucks ofthe collet type are sometimes used for holding small parts

,in

stead oi a jaw chuck.

Attachments for the M illing Machine. The range of amillingmachine or the variety of work it is capable of doing can be

greatly extended by the use of special attachments . Many of

these are designed to enable a certain type ofmillingmachine toperformoperations that ordinarily would be done on a differen t

machine; in other words, the attachment temporarily convertsone type of machine into another. There are quite a numberof different attachments for themillingmachine, some of whichare rarely used in the average Shop. There are, however, threetypes that are quite common; namely, the vertical spindlemilling attachment, the slotting attachment and the circular milling and dividing attachment.Vertical M illing Attachment. The way a vertical spindle

milling attachment is applied to a horizontalmillingmachine isshown in Fig. 18. The base of the attachment is securelyclamped to the column of the machine by four bolts and the

ou ter end is inserted in the regular arbor support. The spindle

is driven through bevel gears connecting with a horizontal Shaft

inserted in themain spindle of themachine . The spindle of

this particular attachment can be set at any angle in a verticalor horizontal plane, and its position is Shown by graduationsreading to degrees.

For the operation illustrated , which is that ofmilling the edgeof the steel block shown

,the spindle is set at an angle of 45 de

grees fromthe vertical. The block is held in an ordinary vise

and it is fed past the cu tter by using the cross-feed. The oppositeedge ismilled by Simply swinging the spindle 45 degrees to theright of the vertical. Vertical attachments are used in connec

tion with horizontalmachines whenever it is desirable to have

MILLING MACHINE ATTACHMENTS 179

the cu tter in a vertical or angular position . There are severaldifferent types designed for diflerent classes of work. The

style shown in the illustration is referred to as a universal at

tachment because of its two-way adjustment,and it can be u sed

for a variety of purposes,such as drilling,milling angu lar slots

or surfaces,cu tting racks,milling keyseats, etc. The spindle of

many vertical attachments can only be adjusted in a planeparallel with the front face of the column or at right angles to

the axis of the spindle. A vertical attachment of this type

Fig. 18. Vertical Attachment Applied to a Horizontal M illing Machine

which is designed for comparatively heavy verticalmilling operations

,is illustrated in Fig. 2 1 .

Slotting Attachment. The Slotting attachment, as its name

implies,is used for converting amillingmachine in to a slotter.

The base B is clamped to the column of themachine as shownin Fig. 19. The tool slide S ,

which has a reciprocatingmovementlike the ramof a slotter, is driven fromthemain spindle of themachine by an adjustable crank which enables the stroke to bevaried. The tool Slide can be set in any position fromthe

180 M ILLING MACHINES

vertical to the horizontal, in either direction , the angle being

indicated by graduations on the base. When the attachmentis in use

,a slotting tool of the requ ired shape is clamped to the

end of the slide by the bolt shown ,and it is preven ted from

being pushed upward by a stop that is swung over the top of

the tool shank.

Fig. 19 shows the attachment slotting a rec tangular opening ina screwmachine tool which is held in the vise . AS this Opening

Fig . 19. S lotting Attachment Applied to a M illing Machine

mu st be at an angle,the tool Slide is inclined fromthe vertical,

as shown . A previously drilled hole forms a starting place forthe slotting tool.Fig. 20 shows another application of the Slotting attachment.

The operation in this case is that of cu tting a square hole in theend of a rod . As this rod is too long to be placed in a verticalposition ,

it is inserted through the hollow spindle of the spiralhead and is held in a three-jaw chuck as shown . The Slottingattachment is swung around to the horizontal position

,and after

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182 MILLING MACHINES

and a dial just back of handwheel H is graduated to read to

11, degree or 5 minutes . These angular graduations are often

needed for dividing a circu lar surface or whenmilling to angles.

Some circular attachments have a power feed for the table ,which can be disengaged au tomatically at any poin t bymeans ofadjustable stOps which are bolted to the periphery of the table.

Spiral Milling with Universal Attachment. When milling a

spiral, it is not always possible to align the cutter with the helix

Fig. 2 1 . Comb ined u se of Vertical and Circular M illing Attachments

or spiral angle by swinging the table around, as illustrated in

Fig. I 2 . Withmost universalmillingmachines it is inconvenient

,if not impossible

,to swivel the table to a greater angle

than 45'degrees; hence for greater angles, it is the general prac

tice to leave the table In its normal position at right angles tothe spindle of themachine, and u se a special swiveling attachment for holding the cu tter at the proper angle. Fig. 2 2 illus

trates thismethod of spiralmilling.

The operation is that ofmilling sextuple threads on a worm.

MILLING MACHINE ATTACHMENTS 183

The pitch diameter of thewormis inches and the lead of thethread

, 6 inches. Therefore the tangent of the helix angle equalsX 6 which is the tangent of 62} de

grees. With this partic ular milling machine the table can beswiveled to an angle of abou t 50 degrees. Therefore, it is

necessary to use a universal attachment.The table is ’

set at zero and the attachment is swung around

27} degrees fromits position at right angles to the machinespindle (90 623 thus setting the c utter in line with

Fig. 22 . Milling S extuple Threaded Worms in Kempsmlth Machineby use of Universal Attachment

the helix angle. After one thread groove ismilled,the cu tter

is indexed one-sixth revolu tion formilling the next groove, and

so on un til the Six thread grooves are completed . Three wormblanks are held on the arbor at one time and roughing and finishing cu ts are taken . A plain blank and a finished wormmaybe seen on themachine table . The cu tter is 4 inches in diameterand runs 64 revolu tions perminu te for this particu lar operation .

The included angle between the sides of the wormthread is 29 degrees and the depth of the thread groove equals X pitch.

184 MILLING MACHINES

The spindle of the attachment illustrated can be set at any

angle throughout the entire circle. I t can be used formillingspiral gears or other work, the helix angle of which Is beyond

the range of the swiveling table . When cu tting threads in the

millingmachine the only limitation is similar to that imposedwhen cutting threads of large lead in the lathe , although in a

reverse order. Whenmilling wormthreads or Spiral gear teethof small lead as compared with the diameter, the rotarymovement of the blankmay be so great as compared with the slowmoving feed-screw

,that there will be difficu lty in transmitting

Fig. 23. 5A) Incorrect M ethod of Holdin Taper Blank for Fluting.

B) Correct Way. (C) Taper MfiIing Attachment

sufi cient power to feed the work against the cu tter,through the

gearing that is necessary to give the required speed of rotation .

Milling Taper Flutes. Whenmilling flu tes in taper reamers,milling cu tters

,etc .

,which are held between centers

,the axis

of the dividing-head spindle and the axis of the work should co

incide or be in line with each other . Sketch A ,Fig. 23 , Shows

an incorrectmethod of holding a taper reamermounted betweencenters for fluting. When a

“ plain ”indexing head is used

that does not have angular adjustment like a “universal” head,

taper work is sometimes held in this way; that is, the tailstockis blocked up on parallels to hold the reamer or cu tter blank

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186 MILLING MACHINES

same amount for each indexing and equal flutes aremilled;moreover, there is no movement of the dog relative to the driver

plate.

A simplemethod of aligning the reamer or cutter blank withthe dividing-head spindle is as follows : P lace the dog in a

vertical position and adjust it un til the end of the tail or driv

ing armjust touches the driver plate at the top; then index thedriver plate one-half revolution and againmake a test. If there

is space between the dog and driver plate, the tailstock center

is too high; inversely, if the dog bears heavily at the bottom,

the tailstock center is too low and should be adjusted accordingly

to secure an even contact at both top and bottom.

TaperMilling Attachment. Sketch C,Fig. 23 , shows a special

attachment for tapermilling. With this attachment, alignmentbetween the dividing-head spindle

,work

,and tailstock center is

assured and the desired angular setting can be obtained easily.

One end of the attachment is secured to the spindle of the dividing head and the Opposite end is bolted to a slotted knee

clamped to the table of themachine. This knee is graduatedto correspond with the graduations on the spiral head . Thefootstock of the attachment can be adjusted along a T-slot tosuit the length of the work . An attachment of this kind is

especially desirable when there is considerable tapermilling tobe done .

In determining the angular position of the work and dividinghead for milling taper reamers

,etc .

,the number of angles in

volved usually makes the calculation difficult and,ordinarily,

the setting can be obtained by the “c ut-and-try ”method in less

time than is required to compute the angle . When using a

single-angle cu tter for flu ting reamers, the angle of inclinationcan be determined by using the rule given in the paragraphheaded “M illing Angular Cu tters .

Multiple Index Centers. Multiple index centers are oftenused in preference to the single-spindle type

,for such operations

as fluting taps and reamers ,milling nu ts, cu tting small gears, orfor similar work . A design of multiple index center that iscommon has three parallel spindles which are geared together

COMPENSATING DOG OR DRIVER 187

and are indexed in unison . There are also three footstock cen ters

in alignment with the dividing-head spindles . Obviously, withcenters of this type three reamers or other parts can bemilledat the same time by using a gang of three cutters. For taper

milling,multiple index centers aremade with an independent

base or table which can be elevated to the required angle,the

same as the taper attachment illustrated at C in Fig. 23 .

Compensating Dog or Driver. When a taper part is heldbetween centers as illustrated at A , Fig. 23 , it is well to use

what is known as a compensating dog or driver,instead of the

ordinary type , in order to securemore accu rate indexing. The

Fig. 3 5 . Compensating Di'iver which Practically Eliminates Errorwhen Indexing Taper Work

compensating dog,which is illustrated in Fig. 25, has a forked

armwhich is secu red to the dividing-head spindle. This armisengaged by a ball-shaped partmounted on the cylindrical endof the driver. The latter is clamped in such a position that thecenter of the cylindrical driving end is approximately in linewith the end of the work. The ball fits closely between the

curved surfaces of the forked armand adjusts itself as the relation between the driver and armchange owing to the angularitybetween the axes of the work and the index spindle. The forkedarmc an b e adjusted to take up all play between the ball and thecurved surfaces of the slot which it engages . As the driving is

188 M ILLING MACHINES

done at a point opposite the end of the work, the irregularity of

the indexingmovement is very slight and negligible for ordinarymilling or fluting operations. Moreover

,there is no binding

action between the dog and driver plate such asmay occur withthe ordinary dog.

Milling Clutch Teeth. A common method of milling a

straight-tooth clu tch is indicated by the diagrams A,B and C ,

Fi 26. Diagrammatical Views showing S im e Method of Cutting8Clutch Teeth

pi

Fig. 26, which Show the first, second, and third cu ts required forforming the three teeth . The work is held either in the chuck

of a dividing head (the latter being set at right angles to thetable) , or in a plain vertical indexing attachment especially designed for this class of work . A plainmilling cu ttermay be used(unless the comers of the teeth are rounded) , the side of the cu tterbeing set to coincide with the center-line of the clutch. Whenthe number of teeth in the clu tch is odd

,the out can be taken

clear across theblank as shown ,

thus fin ishing the sides of twoteeth with one passage of thecu tter. When the number ofteeth is even, as at D

,it is

necessary tomill all the teethon one side and then set the

Fig. 27 . Dia amshowing Position of Cut cu tter forfinishing the oppositet" mM Mm“ emchTm”

side; therefore, clu tches of thistype commonly have an odd number of teeth . The maximumwidth of the cu tter depends upon the width of the space at the

narrow ends of the teeth . I f the cu ttermust be qu ite narrow inorder to pass the narrow ends

,some stock may be left in the

tooth spaces, whichmust be removed by a separate c ut.

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190 MILLING MACHINES

outer points of teeth cut as at B would hear at the bottomof

the grooves in the Oppositemember, and the inner ends of teethcut as at C would strike first

,thus leaving spaces between the

teeth around the outside of the clu tch . In order to securebetter contact between the clutch teeth

, they should be cut asindicated at D

, or so that the bottoms and tops of the teethhave the same inclination , converging at a central point x. The

teeth of bothmembers will then engage across the entire width .

The angle a required for c utting a clutch as at B can be determined by the following formula in which a equals the required

angle, and N ,the number of teeth

meg-97325) X cot cutter angle

1 + cases )Expressing this formula as a rule

,the cosine of the angle to

which themillingmachine index head is set equals the sine ofangle 6 (see sketch A)multiplied by the cotangent of the c utterangle divided by the cosine of angle 8 plus 1 .

Example. A saw-tooth clutch is to have 8 teethmilled witha 60-degree cutter. T0 what angle amust the dividing head beset"

COS aI cos 45

°

1

By referring to a table of sines and cosines we find thatis the cosine of 76 degrees 10minu tes which is the required angle.CamMilling in 9. Universal Milling Machine. P late cams

having a constant rise,such as are used on automatic screw

machines, can be cut in a universalmillingmachine,with the

spiral head either in a vertical position or set at an angle a,as

Shown in Fig. 29. When a camismilled with the spiral head

set in a vertical position,the “

lead ” of the cam(01_ its rise forone complete revolu tion) will be the same as the lead for whichthemachine is geared; but when the spiral head and cu tter areinc lined, any lead or rise of the camcan be obtained

,provided

it is less than the lead for which themachine is geared , that is,

MILLING PLATE CAMS 191

les s than the forward feed of the table for one turn of the spiralhead spindle . The camlead, then ,

can be varied within certainlimits by simply changing the inclination a of the spiral head andcu tter. In the following formulas for determining this angle ofinclination , for a given rise of camand with themachine gearedfor a certain lead

,let

angle to which index head andmilling attachment areset;

rise of camin given part of circumference;“lead ” of cam

,or rise

,if latter were continued at given

rate for one complete revolu tion ;

Fig. 29. M illing a Plate Cambl

use of Spiral Head and VerticalM illing ttachment

L spiral lead for whichmillingmachine is geared;N part of circumference in which rise is required , expressed

as a decimal in hundredths of camcircumference .

R r r

L’and R '

N’hence

,sma

N X L

For example,suppose a camis to bemilled having a rise of

inch in 300 degrees or in of the circumference,and that

themachine is geared for the smallest possible lead , or inch,

thenr

N X L Xsin a =

192 MILLING MACHINES

which is approximately the Sine of I 3 degrees. Therefore,to

secure a rise of 5 inch with themachine geared for inchlead

,the Spiral head is elevated to an angle of I 3 degrees and

the verticalmilling attachment is also swiveled around to locatethe cutter in line with the spiral -head spindle

,so that the edge

of the finished camwill be parallel to its axis of rotation .

When there are several lobes on a camhaving difl'erent leads,themachine can be geared for a lead somewhat in excess of thegreatest lead on the cam and then all the lobes can bemilledwithou t changing the spu d head gearing by Simply varyingthe angle of the spiral head and cu tter to suit the diflerent camleads. Whenever possible, it is advisable tomill on the under

Side of the cam,as there is less interference fromchips;more

over,it is easier to see any lines thatmay be laid out on the cam

face. T0 set the camfor a new cut, it is first tu rned back byoperating the handle of the table feed-screw

,after which the

index crank is disengaged fromthe plate and turned the re

quired amount .

Cammilling is generally done on machines designed for thispurpose

,such as are illustrated and described in Chapter VI .

Cutting Teeth in End and S ide M ills. Whenmilling the endteeth in endmills or the side teeth in Sidemills, the dividing headshould be set at su ch an angle that the “

lands ” or tops of theteeth will have a uniformwidth . This angle a (see Fig. 30)at which the dividing-head Spindle should be set fromits horizontal position can be determined as follows:Rule. Mu ltiply the tangent of the angle between adjacent

teeth (equals 360 No. of teeth requ ired) by the cotangent ofthe cu tter angle; the result is the cosine of the angle a at whichthe dividing headmust be set.

Expressing this rule as a formula,cos a tan 0cotB

in which

a angle of elevation of dividing head;0 tooth angle of cu tter blank 360 No. of teeth

6 angle of cu tter used for grooving.

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4 M ILLING MACHINES

Whenmilling the end teeth in an endmill, the angle aswould bedetermined in the same way as indicated by the preceding example for a sidemilling cu tter. The teeth on the cylindrical part ofthe cutter are usuallymilled first and then the end or side teeth(as the casemay be) are c ut tomatch those on the periphery.

Milling Angular Cutters. The angle at which the div iding

head should be set whenmilling the teeth of angular cutters, orfluting taper reamers with a

“single-angle ” cu tter

, can be de

termined as follows:Rule.

— Divide the cosine of the angle 0(Fig. 3 1) between adjacent teeth (equals 360 No . of teeth required) by the tangentof the blank angle 8; the quotient is the tangent of angle 7 .

Fig. 3 1 . Diagramsho Angles Involved in Calculation for DetPosition of Index sad when Milling Teeth in Angular Cutter

Nextmultiply the tangent of the angle 0between the teeth bythe cotangent of the grooving cu tter angle and thenmultiplythe resu lt by the Sine of angle 7 ; the product will be the sine of

angle 5 . Subtract angle 6 fromangle 7 to obtain the angle a at

which the dividing head should be set.

This rule is rather unwieldy and can bemore clearly expressedby formulas . Thus

,

sin 6= tan 0cot ¢ sin 7 .

Angle of elevation (1 7 6.

Themeaning of the letters used in these formulas and theforegoing rule is indicated by the illustration , Fig. 3 1 .

MILLING CUTTER TEETH 195

Example of Angular Cutter Milling . To illustrate the appii

cation of the rule and formulas given in the preceding paragraph,suppose that 18 teeth are to be milled in a 70

-degreemillingcutter blank, with a 60-degree single-angle cu tter. To what

angle a (see Fig. 32) must the dividing head he set to obtain“lands” of uniformwidth" In this example

, the angle 0 (Fig.

Fig. 32 . Index Head set at Angle of 15 Degrees for Cutting Teeth in7o—deg1ee Blank with 6o-deg1ee Cutter

3 1) between adjacent teeth 360 18 20 degrees; blankangle 6 70 degrees; cu tter angle a 60 degrees .

cos o0 . 2 .

tan s 2 -747434

The angle whose tangent is is 18 degrees 53minu tes.

sin e tan 0cot¢ sin 7 x X

The angle whose sine is is 3 degrees 53minu tes, approximately. Therefore angle a at which the dividing head Shouldbe set equals the difierence between angles 7 and 5 or 18° 53

'

3°

53'

15 degrees

CHAPTER V

GEAR CUTTING IN THE MILLING MACHINE

SPUR, spiral, and bevel gears are cut ordinarily in spec ial gearcu ttingmachines, but themillingmachine is often used in shops

not equ ipped with specialmachines, or for cu tting gears of odd

sizes, especially when only a small number are required .

Cutting a Spur Gear. Fig. 1 illustrates how a small spurgear is cut in the milling machine . The gear blank is firstbored and tu rned to the correct ou tside diameter and then it ismounted on an arbor which is placed between the centers of thedividing head. An arbor having a taper shank which fits thedividing-head spindle is a good formto use for gear work. I f

an ordinary arbor with centers in both ends is employed , all playbetween the driving dog and faceplate should be taken up toinsure accu rate indexing.

Cutter to use for Spur Gears. The type of cu tter that isused for milling the teeth of spur gears is shown in Fig. 2 .

This style of cutter ismanu factured in various sizes for gearsof difierent pitch. The teeth of these cutters have the sameshape or profile as the tooth Spaces of a gear of correspondingpitch; therefore , the cu tter to use depends upon the pitch ofthe gear to be cut. The number of teeth in the gearmust alsobe considered, because the Shape or profile of the teeth of a

small gear is not exactly the same as the shape of the teeth of alarge gear of corresponding pitch .

The cu ttersmanufactured by the Brown Sharpe Mfg. CO.,

for cu tting gears according to the involute system, aremade in

eight difl'

erent sizes for each pitch. These cu tters are numberedfrom1 to 8 and the different numbers are adapted for gears ofthe following sizes. Cu tter No. I

,for gears having teeth vary

ing from135 to a rack; No . 2,gears with from55 to 134 teeth;

No. 3 , from35 to 54 teeth; No . 4 , from26 to 34 teeth; No. 5,196

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198 MILLING MACHINES

position B and it is adjusted to barely touch or pinch a thintissue paper “ feeler ” j held between the arbor and the corner ofthe cu tter . The dial of the elevating screw is now set at zero

,

and the horizontal distance between positions A and B should benoted by referring to the cross-feed dial. For convenience thiswill be called dimension No. 1 as indicated by the illustration .

The arbor is next lowered and returned to position A hori

zontally, the vertical position not being particular . The arboris then raised un til the elevating screw dial is again at zero,after which it ismoved to position C, or un til it just touches a

tissue paper feeler” as

Fig. 2 . Cutter for M illing the Fig . 3 . Method of setting Cutter CentralTeeth of Spur Gears with Arbor

No . 2 is next noted by referring to the cross-feed dial; this isadded to dimension No. 1 and the sumis divided by 2 to getdimension No. 3 . The arbor is then returned to position A

(as far as the horizontal location is concerned) after which it islowered far enough to clear the cu tter and thenmoved inward adistance equal to dimension No. 3 , which is the central position.

This operation can be performed more quickly than described .

Whenmaking the adjustments, all dial readings should be takenat the end of the inward or upwardmovements

,to avoid errors

due to backlash or lostmotion in the elevating or feed-sc rews.

Testing P osition of Cutter. Amethod of testing the positionof a gear c utter, when considerable accu racy is required , is as

MILLING SPUR GEARS 199

follows: First mill a tooth Space in a trial blank having the

same diameter as the gear blank, and then ,withou t changing

theposition of the cu tter, remove the blank fromthe work arborand turn it end for end . The blank Should be loose on the arbor

to permit feeding it back so that the cu tter will enter the tooth

space previouslymilled. The cu tter is then revolved Slowly byhand

,in order tomark its position in the slot. I f it is set exactly

c entral, the second cu t will follow the first, but if it is not central,somemetal will be removed fromthe top of the space on one sideand the bottomon the other . In order to center the cu tter, it

should be moved laterally toward that side of the tooth fromwhich stock wasmilled at the top

,by adjusting the gear blank.

Another trial c ut is then taken and the test repeated. Whenthe cu tter is set, the saddle should be clamped in position .

Setting the Cutter to Depth. The next step is to set thecutter formilling tooth spaces of the proper depth. I f the outside diameter of the gear blank is acc urate, this can be done byfirst adjusting the blank upward until the revolving cu tter justgrazes its surface. The dial of the elevating screw is then set

at zero, af ter which the blank ismoved horizontally to clear thecu tter, and then vertically the required amount

,as shown by

the micrometer dial . This vertical adjustment should equalthe total depth of the tooth space

,which can b e found by

dividing the constant by the diametral pitch of the gear.For example, if the diametral pitch is 12

,the depth of the tooth

Space241—51 inch . After the blank has been raised12

this amount,the gear teeth are formed by feeding the blank hor

izontally and indexing after each tooth space ismilled . Aboutone quarter of the teeth have been milled in the gear blankshown in Fig. 1 . The accuracy of the gear

,assuming that the

cu tter is properly made, will depend largely upon setting thecu tter central and to the proper depth. When the depth is

gaged fromthe ou tside of the blank, the diameter of the lattershould be ac curate, as otherwise the teeth will not have the correct thickness. This diameter can be found by adding 2 to the

number of teeth and dividing by the diametral pitch.

200 M ILLING MACHINE S

Testing Thickness of Tooth at P itch Line. The spec ialvernier

,gear-tooth caliper

,Shown in Fig. 4, is sometimes used for

testing the thickness of the first tooth milled . This tes t isespecially desirable if there is any doubt abou t the accuracy

of the ou tside diameter. A trial cut is taken at one side of theblank and then the work is indexed for the next space

,after

which another trial cut is taken part way across the gear. The

vertical scale of the caliper is then set so that when it rests on

PITCH CiRGLE

Fig. 4. Vernier Caliper for M easuring the Thickness of Gear Toothat the Pitch Circle

top of the tooth (as shown in the illustration) , the lower ends ofthe caliper jaws will be at the height of the pitch line . The

horizontal scale then Shows the thickness of the tooth at thispoint. The height fromthe top of the tooth to the pitch lineequals the circular pitch multiplied by the constantThe thickness of the tooth at the pitch line

,for any gear, can be

d etermined by dividing the circular pitch by 2,or the constant

by the diametral pitch . With a diametral pitch of 12 the

thickness would equal 5521 inch.

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202 M ILLING MACHINES

returned to its starting poin t and the blank is indexed 1516 of a

revolution (as the gear is to have 90 teeth) formilling the nextspace. This operation is repeated until all the teeth aremilled.

Whenmilling gear teeth that are coarser than 6 or 7 diametralpitch

,it is advisable to first rough-mill all the teeth and then take

Pi 6. Dividing Head set in Vertical Position for Cutting 8 Gear18 inches in Diameter W

finishing c uts . Special “stocking” cu tters are often used for

rough-milling coarse gears preparatory to finishing with a regularcutter. The speed for cutting gear teeth depends on ,

the pitchof the teeth

,the kind ofmaterial beingmilled , and the rigidity

of the work andmachine.

MI LLING SPUR GEARS 203

When the diameter of a gear is referred to, it is understood to

mean the pitch dimeter or diameter of the pitch circle , and not

the ou tside diameter. The diametral pitch is the number ofteeth to each inch of pitch diameter, and the circular pitch isthe distance fromthe center of one tooth to the center of thenext,measured along the pitch line .

Gear Cutting Attachment When it is necessary to cut comparatively large spur gears on amillingmachine , a gear cu ttingattachment is preferable to the regular dividing head . Thisattachment, in its usual form, is similar to a dividing head, butis larger and heavier in construction . If the gear is too largeto clear themachine table when mounted between the centers

(as illustrated in Fig. the centers are sometimes raised farenough to provide roomfor the gear blank by placing parallelblocks beneath the index head and tail-center. I f the gearblank is so large that it will not pass under the cutter arbor withthe table in its lowest position ,

itmay be possible to cut the gearby using an under-cu tting attachment.” The centers are raisedfar enough to provide roomfor the cutter beneath the gear, andthe arbor is supported by a special out-board bearing.

Fig. 6 illustrates a simplemethod of cu tting a spur gear whichis too large to be held between the centers on a horizontal arbor.Instead of increasing the swing of the centers by placing parallelblocks beneath them,

the dividing-head spindle is set in a verticalposition . The gear blank is held on a short arbor inserted in

the spindle and the rimis supported to take the downward

thrust of the cu t,by two vertical studs or rods placed on the

cu tting side, as the illustration shows. Whenmilling the teeth,the gear blank is fed up against the cu tter by using the powervertical feed . The spur gear shown in this illustration has teeth

of 5 diametral pitch and is 18 inches in diameter.Cutting Spur Gear on Circular Attachment. Fig. 7 illus

trates how a circ ularmilling attachment is sometimes used for

holding a comparatively large gear whilemilling the teeth . Thegear is clamped in a horizontal position and it is centered bythe finished bore of the hub which fits over a plug inserted in the

central hole of the table.

204 MILLING MACHINES

The cu tter,which is held on the regu lar arbor, forms the

tooth spaces as the table is fed vertically by power. I t will be

noted that this particular attachment is equipped with an index

plate. By holding a large gear on the circular attachment, therimis more rigidly supported than when the gear is held on

an arbormounted between the centers of a dividing head.

Fig. 7 . Cutting Spur Gear b y use of Circular M illing Attachment

Rack Cutting in the M illing Machine.—Themethod of cut

ting a rack in themilling machine by the use of a rack- cuttingattachment is illustrated in Fig. 8 . This attachment is secu relyclamped to the face of themachine column and its cu tter spindleis parallel with the table . The spindle is driven fromthemainspindle of the machine through bevel and spu r gearing. Therack teeth are formed by cu tting tooth spaces straight across therack blank (using the au tomatic transverse feed) and after each

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206 MILLING MACHINES

Index Table for Rack-c utting Indexing Attachnmnt(B. S. Milling Machine)

space ismilled, pin B is withdrawn and feed-screw handle C is

turned until pin B again engages the notch in the disk, whichindexes the rack for cu tting the next tooth space

,provided the

disk and feed-screw are connected by the proper change-gears.

A No . 1 involute cu tter corresponding to the pitch of the gearingthat is tomesh with the rack should be used . The rack teethare cut to the same depth and width as spu r gear teeth of similarpitch. The total depth of a tooth space equals divided by

the diametral pitch,or times the circu lar pitch . The

rack to be cu t is held in a special vise or fixtu re D which is

bolted to themachine table . Several narrow racks can be held

MILLING WORM—WHEELS 207

in this fixture at the same time and the teeth be cut simultaneously.

The accompanying table shows what change-gears should beused for indexing difierent pitches. The left half of the tableis used when the diametral pitch of the rack teeth is given .

This pitch, which is listed in the first column,corresponds to the

diametral pitch of the gear which is to mesh with the rack.

The right half of the table is for circu lar pitches,the pitch in

this case being equal to the center-to-center distance between

adjacent rack teeth. This table also gives the number of turnsfor the indexing disk; with but three exceptions all pitches areindexed by a single turn of the disk. The gear E (Fig. 8) nextto the indexing disk

,and the first gear on the stud (which is

the onemeshing with gear E ) are the only gears which requirechanging for difi

'

erent pitches.

Gashing and Hob b ing a Worm-wheel. The universalmillingmachine is sometimes used for cu tting the teeth in wormwheels

,although when there ismuch of this work to be done,

regular gear-cu tting machines are generally used . The wormitself shou ld be finished first, as it can be used advantageously

for testing the center distance when bobb ing the worm-wheel.

We shall assume that the wormhas been made,and that the

wheel blank has been tu rned to the required size .

The teeth of the worm-wheel are formed by two operations,which are illustrated in Figs . 9 and 10 . First it is necessary togash the blank and then the teeth are finished by hobbing.

Gashing consists in cu tting teeth around the periphery of the

b lank, which are approximately the shape of the finished teeth.

This is done, preferably, by the use of an involu te gear cutter

of a number and pitch corresponding to the number and pitchof the teeth in the wheel. If a gear cu tter is not available , a

plain milling c utter,the thickness of which shou ld not exceed

three-tenths of the circu lar pitch,may be used . The corners ofthe teeth of the cu tter shou ld be rounded , as otherwise the fillets

of the finished teeth will be partly removed .

As the wormwhichmeshes with and drives the worm-wheel is

simmy a short screw,it will be apparent that if the axes of the

208 M ILLING MACHINES

worm-wheel and wormare to be at right angles to each other,the teeth of the wheel must be cu t at an angle to its axis

,in

order tomesh with the threads of the worm. After the dividinghead and tailstock have been clamped to the table and the

cu tter has been fastened on its arbor, the table is adjusted un til

the centers of the dividing head and the center of the cutter

lie in the same vertical plane . If the cu tter used has a cente

Fig . 9. Gashing a Worm-wheel in a Univeraal M illing Machine

line around its periphery , the table can be set by raising ithighenough to bring the index head center in line with the cutter;the table can then be adjusted laterally until the center coin

c ides wi th the center- line on the cu tter. When the table is set,it should be clamped to the knee slide.

The blank to be gashed is pressed on a true-running arbor

which ismounted between the centers of the dividing head and

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2 I O MILLING MACHINES

having a straight edge as at A A line having a length B equal

to the lead of the wormthread is drawn at right angles to the

edge A , and a distance C is laid 06 equal to the circumference of

the pitch c ircle of the worm. I f the diameter of the pitch circleis not given on the drawing, itmay be found by subtractingtwice the addendumof the teeth fromthe ou tside diameter ofthe worm. The addendumequals the linear pitch xThe angle a: is nextmeasured with a protractor

,as shown in

the illustration . The table of themachine is then swiveled to a

corresponding angle, as shown by the graduations provided on

all universal milling machines. If the front of the table is

repres ented by the edgeA and the wormhas a right-hand thread,the table should be swiveled as indicated by the line ab; whereas

Fig. 1 1. S imple Method of obtaining Helix Angle of Worm

if the wormhas a left-hand thread, the table should be tu rnedin an opposite direction .

The angle that the teeth of the worm-wheelmakes with itsaxis

, or the angle to which the table is to be swiveled ,may also

be found by dividing the lead of the wormthread by the circumference of the pitch circle; the quotient will equal the tangent of the desired angle . This angle is then found by referringto a table of natural tangents .

0

M illing the Gashes in a Worm-wheel. When the table isset and clamped in place, asmany gashes are cut in the peripheryof the wheel as there are to be teeth . I f the diameter of thecutter is no larger than the diameter of the hob to be used

,the

depth of the gashes should be slightly less than the whole depthof the tooth . This whole depthmay be found bymultiplying

M ILLING WORM-WHEELS 2 I I

the linear pitch by Before starting a cut, bring thecu tter into contact with the wheel blank, set the dial on theelevating screw at zero

,and sink the cu tter to the proper depth

as indicated by the dial. The blank is then lowered to clearthe cu tter and indexed for gashing the next tooth. When thec utter is larger than the hob , the whole depth of tooth should be

laid 03 on the side of the blank , and a gash cut into this line .

The depth as indicated on the dial should then be noted and all

the gashes cut to a corresponding depth .

B obb ing the Teeth of aWorm-wheel. When the gashing is

finished, the table is set at right angles with the spindle of the

machine, and the cu tter is replaced with a hob , as shown in

Fig. 10. The latter is practically amilling cutter shaped liketheworm

'

with which thewheel is tomesh , except that the threadon the hob has several lengthwise flutes or gashes to formcu ttingedges. The outside diameter of the hob and the diameter atthe bottomof the teeth are slightly greater than the correspond

ing dimensions of the worm,to provide clearance between the

wormand worm-wheel. Before hobbing, the dog is removedf romthe arbor to permit the latter to turn freely on its centers.

The hob is then placed inmesh with the gashed blank, and theteeth of the worm-wheel are finished by revolving the blank and

hob together. As the two rotate, the blank is gradually raiseduntil the body of the hob between the teeth just grazes thethroat of the blank . The latter is then allowed tomake a fewrevolutions to insure well-formed teeth.

Testing Center Distance between Wormand Wheel. I f

the center-to-center distance between the wormand wormwheelmust be acc urate

,this dimension can be tested by placing

the finished wormin mesh with the wheel (after the latter hasb een bobbed) , andmeasuring the center distance directly. Thewormis placed on top of the wheel

,after removing the chips

fromthe teeth, and it is turned along until its axis is parallel

with the top of the table . I t can be set in this position by testing the threads at each end with a surface gage. The distancefromthe top of the wormto the topof the arbor is thenmeasured ,and the diflerence between the radii of the arbor and wormis

2 I 2 M ILLING MACHINES

either added to or subtracted fromthis dimension,to obtain the

center-to-center distance. When the wormis larger in diameterthan the arbor, subtract, and when it is smaller, add the difference between the radii .

I f the wormis accuratelymade and the worm-wheel blank o f

the correct size , this center distance should be very close to the

dimension required . I f necessary,the hob may be again en

gaged with the wheel and another light out taken . When tes ting the center distance as explained in the foregoing, it is better

to lower the knee sufficrently tomake roomfor the wormbenea ththe hob , and not distu rb the longitudinal setting of the tab le .

The relation between thewheel and hob will then bemaintained ,

which is desirable in case it is nec essary to te-hob the wheel to

reduce the center distance.

The center-to-center distance can also be measu red with a

fair degree of accuracy (when u sing themachine shown in Figs .

9 and 10) at the time the wheel is being b obbed . This is doneby elevating the knee and blank until the distance fromthe topof the column knee-slide to the line on the column markedcenter

,equals the requ ired center-to-center distance . When

the knee coincides with this line, the index centers are at the

same height as the spindle; hence the position of the knee wi

th

relation to thismark shows the distance between the centers ofthe arbor on which the worm-wheel ismounted

,and the hob .

When worm-wheels are cu t inmachines especially designed forthis purpose, thewheelblanks, instead of beingmounted on a freerunn ing arbor

,are driven by gearing at the proper speed. This

makes gashing the blank previous to hobbing unnecessary, as thechange gears insure a correct spacing of the worm-wheel teeth .

Cutting a Spiral Gear. The teeth of spiral gears are often c utin universal milling machines

,as indicated in Fig. 12

,although

special gear-cutting machines are used ordinarily where spiralgears are constantly beingmade, because the specialmachines aremore efficient. As the teeth of a spiral gear are inclined to the

axis and follow helical or “spiral” curves

,they are formed by

milling equally-spaced spiral grooves around the periphery of theblank ,

the number of the grooves corresponding , of course, to

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2 14 MILLING MACHINES

The c ircular pitch of the teeth is the distance 0measu redalong the pitch circle at one end of the gear

,or in a plane at

right angles to the axis . AS will be seen ,the circular pitch in

the case of a Spiral gear is not the shortes t distance between the

adjacent teeth , as this minimumdistance 11 is along a line at

right angles to the teeth . Hence,if a cu tter is used having a

thickness at the pitch line equal to one half the c ircular pitch ,

as for spur gearing,the spaces between the teeth would be c u t

too wide and the teeth would be too thin . The distance 11 isreferred to as the normal circu lar pitch , and the thickness of

the cu tter at the pitch line shou ld equal one-half this pitch .

The normal pitch varies with the angle of the spiral,which is

equal to angle a; consequently, the spiral angle must be con

sidered when selecting a cutter.If a gear has 30 teeth and a pitch diameter of 6 inches

,what is

sometimes referred to as the real diametral pitch is 5 (30 6

5) and in the case of a spur gear,a cu tter corresponding to

this pitch wou ld be used; but if a 5-pitch cu tter were used for

a spiral gear,the tooth spaces would be cut too wide . In order

to secure teeth of the proper Shape, it is necessary to use a

cu tter of the same pitch as the normal diametral pitch .

The normal diametral pitch can be found by dividing the realdiametral pitch by the cosine of the spiral angle . To illus

trate,if the pitch diameter of the gear Shown in Fig. 1 2 is

and there are 38 teeth having a spiral angle of 45 degrees, thereal diametral pitch equals 38 56 then the

normal diametral pitch equals divided by the cosine of

45 degrees, or 8. A cutter,then

, of 8—diametral pitch is the one to use for this partic ular gear .This same resu lt could also be obtained as follows : If the

circu lar pitch c is inch,the normal circular pitch 1: can

be found bymu ltiplying the circ ular pitch by the cosine of thespiral angle . For example

,The nor

mal diametral pitch is next found by dividing by the

normal circular pitch . To illustrate,2 8, which is the

diametral pitch of the cu tter.

M ILLING SP IRAL GEARS 2 15

Of course, in actual practice, it is not generally neces sary tomake such calculations , as the pitch of the gear, the lead and

an gle of the spiral, etc ., are given on the drawing

, and the work of

themachinist is confined to setting up themachine and cutting

the gear according to specifications. I t ismuch easier,however

,

to do work of this kind when the fundamental principles are

understood .

Number of Cutter to Use for Spiral Gears. As previously

explained, the proper cutter to use for spu r gears depends not

Fig. 13 . The Circular Pitch of a Spiral Gear is the Distance c andthe Normal Pitch, the Distance 11

only upon the pitch of the teeth, but also upon the number ofteeth in a gear, because the teeth of a small gear do not have

the same shape as those of amu ch larger size of the same pitch.

Therefore,according to the B rown 81 Sharpe systemfor spu r

gears having involu te teeth , eight difi'

erent shapes of cu tters

(marked by numbers) are u sed for cu tting all sizes of gears of

any one pitch froma 1 2-tooth pinion to a rack. The same styleof cutter can be used for Spiral gearing

,bu t the cu tter is not

selected with reference to the actual number of teeth in the gear,as with spu r gearing.

2 16 MILLING MACHINES

By r eferring to the list of cutters given in the paragraphheaded “

Cu tter to use for Spur Gears,it will be seen tha t a

No. 3 would be used for a spur gear having 38 teeth . A spiral

gear with 38 teeth, however, might requ ire a cutter of someother number, because of the angular position of the teeth.

I f the actual number of teeth in a spiral gear is divided by the

c ube of the cosine of the tooth angle,the quotient will represen t

the number of teeth for which the cu tter Should be selected ,

according to the systemfor spu r gears. If we assume that agear is to have 38 teeth cut at an angle of 45 degrees, then the

cutter to use would be determined as follows: The cosine of

38107 . The

08 535

list of cutters previously referred to calls for a No. 2 cu tter forspur gears having any number of teeth between 55 and 134;

hence,that is the c utter to use for a spiral gear having 38 teeth

and a tooth angle of 45 degrees. I t will be understood that thisnumber has nothing to do with the pitch of the cu tter, which isdetermined as previously explained; it is simply that one of theeight cutters (according to the B . S . system) which ismadeformilling gears having numbers of teeth between 55 and 134.

The number obtained by the foregoing rule is much largerthan the actual number of teeth in the Spiral gear . This isbecause a line at right angles to the teeth

,along which the nor

mal pitch ismeasu red , has a larger radius of curvature than thepitch circle of the gear (strictly speaking, the termradius is incorrectly used

,as this line is a helix and not a circle) and the

cu rvature increases or diminishes for corresponding changes inthe spiral angle . Therefore

,the number of teeth for which the

cu tter is selected depends upon the angle of the spiral, as well

as the actual number of teeth in the gear . As the angle becomessmaller, the diflerence between the normal and circular pitchesalso diminishes until, in the case of Spur gears

,the normal and

c ircular pitches are equal.

Gearing the Machine for Spiral Milling. The change-gears

a,b,c and d, Fig . 1 2

,connect the spiral head and table feed—screw

and rotate the gear blank as the table feeds lengthwise, in order

45 degrees is and 38

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2 18 MILLING MACHINES

getting the tangent and then the corresponding angle froma

table of tangents . For example,if the pitch diameter of the

gear is and the lead of the spiral is 20 inches,the tan gen t

6will equalW and is the tangen t of

35 degrees, which is the angle to which the table is set fromthe

normal position at right angles to the spindle .

The table is adjusted by loosening the bolts which ordinarilyhold it to the clamp-bed and swiveling it around until the 35

degree graduation on the circular base coincides with the station

ary zeromark . Before setting the table to the spiral angle, thecu tter should be located directly over the center of the gearblank . An accu ratemethod of centering a cutter of this kindwas described in connection with Fig. 3 .

M illing the Spiral Teeth. The teeth of a spiral gear are

proportioned fromthe normal pitch and not the c ircular pitch.

The whole depth of the tooth,that is the depth of each cut

,can

be found by dividing the constant by the normal diametralpitch of the gear; the latter, as will be recalled, corresponds tothe pitch of the cutter. The thickness of the gear at the pitchline equals divided by the normal diametral pitch . Aftera c ut is completed the cu tter Should be prevented fromdraggingover the teeth when being returned for another cut. This can

be done by lowering the blank slightly or by stopping themachine and turning the cu tter to such a position that the teeth

will not touch the work . I f the gear has teeth coarser than 10

or 12 diametral pitch,it is well to c ut twice around; that is,

take a roughing and a finishn cu t.

When pressing a spiral gear blank on the arbor,it Should be

remembered that spiral gears aremore likely to slip when beingcu t than spu r gears. This is because the tooth grooves are at anangle and the pressure of the cu t tends to rotate the blank on

the arbor .

Milling Bevel Gears. Small bevel gears are occasionally

c ut in the milling machine with a formed cu tter, but as the

cu rve of a bevel gear tooth changes throughou t its length, obvi

ously a formed cu tter having a fixed cu rve will not produce teeth

MILLING BEVEL GEARS

of the theoretically correct shape. The inaccu racy,however, is

not so pronounced when the teeth are small,but the milling

process is unsatisfactory for forming teeth of coarse pitch,espec ially if the gears are to revolve rapidly when in u se.

When a bevel gear is cut bymilling, the gear blank ismountedon an arbor inserted in the dividing-head Spindle , and the latteris set to the cu tting angle as shown in Fig. 14. A formed cutter

Fig. 14. Milling Machine arranged for Cutting a Bevel Gear

is used, and it is necessary to take two cu ts through each tooth

space, with the gear blank slightly off Center,first on one side

and then on the other, to obtain a tooth of approximately thecorrect form. The gear blank is also rotated proportionatelyto obtain the proper tooth thickness at the large and small ends.

The different steps or operations connected with cutting a bevel

gear are as follows : setting the blank to the cutting angle;

2 20 M ILLING MACHINES

selecting the cu tter; taking a trial cu t; determining the amountof ofiset; andmilling the teeth . These difierent operations will

be referred to in the order given .

Angular Position of Bevel Gear Blank — The angle a (see Fig.

15) at which the dividing-head spindle should be set formillingthe teeth equals the pitch cone angle 19, minus the addendumangle 0 of the tooth . Ordinarily, the cu tting angle for bevel

gears equals the pitch cone angle minus the dedendumangle;when cu tting the teeth bymilling with a formed cutter, the firs trule is preferable as it gives a uniformclearance at the bottomof the tooth spaces and a somewhat closer approximation to

the theoretically correct tooth shape .

For bevel gears with shafts at right angles, the tangent of the

pitch cone angle of the pinion is found by dividing the numberof teeth in the pinion by the number of teeth in the gear; thetangent of the pitch cone angle of the gear equals the numberof teeth in the gear divided by the number of teeth in the pinion;the tangent of the addendumangle equals the addendumdividedby the pitch cone radius; the addendumequals divided bythe diametral pitch .

Selecting Cutter for Bevel Gears. The Standard bevel gearc utter ismade thinner than the standard spu r gear cutter be

cause itmust pass through the narrow tooth spaces at the innerends of the teeth . For 14§~ degree involu te teeth there are

eight cu tters numbered fromone to eight for each pitch and

suitable for cutting bevel gears froma twelve-tooth pinion to a

crown gear. The c utter to u se,in any case , must not only be

of the required diametral pitch but the right number in the

series. The number of the cutter depends upon the number ofteeth in the gear or pinion . When cu tting miter gears, onlyone cutter is needed , but if one gear is larger than the other,two cutters of the same pitch bu t of different numbersmay berequired.

The number of teeth for which to select the cu tter is not theactual number of teeth in the gear

, but is found as follows:Divide the actual number of teeth in the gear by the cosine ofthe pitch cone angle. For example

,what cutter would be used

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2 22 MILLING MACHINES

as shown at A in Fig. 15 . The dial of the elevating screw is

then set to zero and the table is elevated an amoun t dequal tothe whole depth of the tooth. This depth will not be exactlyright

, as it shou ld be measu red along the back edge e of the

tooth, but the error due to this slight angle is negligible. (The

whole depth diametral pitch or circular pitch XHaving thus cen tered the cu tter and set it to depth ,

two tooth spaces should be cut, thus forming a tooth upon whichtrial cu ts can bemade to obtain the proper relation between thecu tter and work formilling the remainder of the teeth .

Amount of Ofi-set for Milling Bevel Gear Teeth. Instead of

milling the teeth with the cu tter in a central position ,it is set

03 center slightly on first one side and then the other, in orderto formteeth which are nearer the correct shape . The amountthat the gear blank or cu tter should be off -set is usually deter

mined by trial . For the first trial cut the ofi-set should equal

abou t 5 or 6 per cen t of the tooth thickness on the pitch line at

the large end. The trial tooth is first moved away fromthe

cu tter an amoun t equal to the off -set,as indicated by arrow b,

Fig. 15 ; the dividing-head spindle is then rotated, as shown by

arrow bl , far enough to align the small end of the tooth space

previously c ut with the cutter. The first trial cut is then

taken,after which the blank is indexed to bring the second

tooth space into position . The blank is next set over on the

opposite side of the central position (as indicated by arrow 0)the same amount as for thefirst trial cu t, thusmoving the oppositeface of the trial tooth away fromthe cu tter. The dividinghead spindle is again rotated as shown by arrow 01, to return

the trial tooth toward the cutter until the latter is aligned withthe small end of the tooth space, as before . The second trial

cut is then taken .

The thickness of the trial tooth at the pitch line is nowmeasured with a vernier gear-tooth caliper, or a fixed gage, the

measurements being taken at the large and small ends. If thethickness at both ends is too great

,rotate the tooth toward

the cutter and take trial cu ts until the proper thickness at

either the large or small end is obtained. I f the large end of

MILLING EEVEL GEARS 223

the tooth is of the right thickness and the small end is too thick,the blank was off-set too much. Inversely, if the small end iscorrect and the large end too thick , the blank was not set

enough ofi cen ter and, in either case

,its position should be

changed accordingly. A trial off-set of 5 or 6 per cent of thetooth thickness at the large end probably will not be enough ,so that two or three trial cu ts will have to be taken on eachside of the tooth before the right amoun t of ofi-set is found .

Milling the Bevel Gear Teeth. When the off -set is determined

,tooth spaces aremilled around the gear blank by cu tting

a space and then indexing for each successive cut. The cu tteris then off-set on the opposite side

,the blank is rotated far enough

tomill teeth of the required width, and another series of cu ts is

taken around the gear. Fromthe foregoing, it will be seen

that the gear blank is off-set to produce a tooth shape that is

approximately correct, and it is rotated by turning the spindle

of the dividing head tomill a tooth of the right thickness. The

number of holes it was necessary tomove the index pin betweenthe first and second series of c uts to get the correct tooth thickness should be recorded; then if duplicate gears are to be cut

,

itwill only be necessary to off-set the blank the required amount,take a series of c uts around it

,off-set the blank on the opposite

side of the center-line, rotate the index crank the required number of holes as determined when cu tting the first gear

,and finish

the teeth by a second series of cu ts .

When milling cast-iron gears coarser than abou t 5 diametralpitch

,it is advisable to first cut central spaces clear around

the gear and then finish the sides by separate cuts,going around

the gear three times. These central cuts are sometimes takenby using a roughing or “

stocking ” cutter. When milling steelgears, the central cuts are usually taken .

When cu tting bevel gears of fine pitch and large diamaer,

the adjustment obtained by moving the indexing crank (formilling the teeth to the required thickness) may not be fine

enough; that is, one hole in the index circlemay not rotate theblank far enough

,whereas if the pin is engaged in the next

hole,the blank will be turned too far

,thus milling too thin a

224 MILLING MACHINES

tooth . To sub-divide the space between the holes,most divid

ing heads have a fine adjustment for rotating the wormindependently of the crank.

Finishing the Teeth by Filing— When bevel gears are cu t

as des cribed in the foregoing, the teeth at the small ends are a

little too narrow ,at the bottomand too wide at the top; therefore , they shou ld be finished by filing ofi

'

a triangular area ex

tending fromthe point of the tooth at the large end to the point

Fig. 16. Cutting Sprocket Teeth in a Milling Machine

at the small end, thence down to the pitch line and back diagonally to a point at the large end, as indicated by the Shaded area

f in Fig. I 5 . If the amount of set over is redu ced, thusmillingthe teeth too thin at the pitch line at the small end, filingmay notbe necessary

, although better running gears will be obtained by

finishing the teeth as described .

Milling Teeth in Chain Sprockets . The teeth of chain

Sprockets , such as are used on chain-driven au tomobiles, etc.

aremilled with formed cu tters . When a number of sprockets

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226 MILLING MACHINES

ance, and , if the latter kind is used , the sprocket Should bemilledas follows : First

, cut the teeth in the usualmanner; then re

volve the sprocket an amount equal to the pitch line clearancedes ired and take an additional series of cuts around the sprocket.

Cutter for Sprockets . A number of sprocket cu tters are

made for each pitch the same as for spur gears, and in order toobtain a tooth adapted for high speeds

,it is the common practice

to use cu tters made for fewer teeth than the number in thesprocket to be cut. In this way, the teeth are made morerounding

,which facilitates engagement and disengagement of

the chain rollers. When using B rown 81 Sharpe cu tters, the

cutter numbers for different numbers of teeth are as follows:To cut a 9

-tooth sprocket,use the cu tter marked 8 teeth; to

cut a I o-tooth sprocket, use cu ttermarked 9 teeth; for an 11

tooth sprocket,use cuttermarked 10

—1 1 teeth; for a I 2-tooth

sprocket a 10—1 1 tooth cu tter; for a 13

-tooth sprocket, a 12—13

tooth cu tter; for 14 and 15-tooth sprockets

, use a cutter

marked 1 2-13 teeth; for 16 17 and 18- tooth sprockets , a

cu ttermarked 14 to 16 teeth; for 19 to 25-tooth Sprockets, a

cu ttermarked 17 to 20 teeth; for a 26—tooth Sprocket and over,use cu ttermarked 2 1 to 34 teeth .

Chain SprocketDiameters. The pitch diameter of a sprocketwheel for a roller chain equals the pitch of the chain P Sin

of angle a (see Fig. Angle a 180 degrees number ofteeth. The base diameter B pitch diameter diameter Dof chain roller. The ou tside diameter for sprockets of 17 teethand over equals pitch diameter diameter D of chain roller.

The ou tside diameter of smaller sprockets Should be reduced

from31; to 4 inch, depending upon the pitch of the chain and

number of teeth in the sprocket. This is done so that the

sprocket teeth will readily clear the chain rollers at high speeds.

I f the chain pitch varies from5‘ to ii inch, reduce the diameter115 inch for 8 to 1 2-tooth Sprockets

, and 313 inch for 13 to 16

tooth sprockets. I f the chain pitch is between 1 and 2 in ches,reduce the ou tside diameter 31, inch for 8 to 1 2-tooth sprockets

and 113 inch for 13 to 16-tooth sprockets .

For block-center chains the pitch diameter equals the pitch x of

M ILLING SPROCKET TEETH 2 2 7

the side links sine B (see detail sketch in upper left-handcorner

, Fig. The tangent of B sine a (y x cos a ) .

Angle a 180 degrees number of teeth . Base diameterpitch diameter d; ou tside diameter pitch diameter d;

d diameter of round part of chain block.

Example of Sprocket M illing . AS a practical example ofsprocketmilling, suppose a 12-tooth roller-chain sprocket is tobe cut for a chain of I -inch pitch and having rollers inchin diameter. AS previously explained, the pitch diameter isfound by dividing the pitch of the chain by the sine of angle a

(see Fig. a1n 15 degrees. Sine 15 degrees

1hence pi tch di ameter

The base diameter B inches; theou tside diameter 0 .5625 5 inches. In

obtaining this ou tside diameter, 5 inch is subtracted owingto the small size of the sprocket. (This is done to provideextra clearance between the teeth and chain rollers as explainedin the preceding paragraph.)The B . S . cu tter ordinarily used for a 12-tooth sprocket

would be one marked 10—1 1 teeth. The depth of the toothspace for a Sprocket having over 16 or 17 teeth would equal thediameter of the chain roller. For smaller sprockets

,however

,

this depth is somewhat less as the teeth aremade shorter. The

total depth equals one-half the difierenc e between the ou tside

and base diameters, which, in this example, equals°1

2°1

0.5 inch. Therefore when milling the teeth,the cu tter

,

after being set directly over the center of the sprocket blank,

is set to this depth when taking the fin ishing cut.

When turning the sprocket blank, the width of the teeth at

the pitch line should be from51; to 39; inch less than the length

of the chain rollers to provide sidewise clearance, and the teeth

should be chamfered or rounded fromthe pitch line outward

to the points. This chamf ering or rounding is important because if the chain sways while running and the sprockets are notac curately aligned

,the chamfered ends easily engage the chain.

inches .

CHAPTER VI

VERTICAL, HORIZ ONTAL AND SPECIAL MILLING MACHINES

WHEN an end mill is driven directly by inserting it in thespindle of amillingmachine of the horizontal type, it is difficultto mill some su rfaces, espec ially if much hand manipulation isrequired, because themill Operates on the rear side where it cannot readily be seen when one is in the required position for con

trolling themachine. Moreover, it is frequently necessary toclamp the work against an angle-plate to locate it in a vertical

position or at right-angles to the end mill, when the latter isdriven by a horizontal spindle. In order to overcome thes eobjectionable features special vertical milling attachments are

used to convert a horizontalmachine temporarily into a verticaltype . These vertical attachments are very useful, especiallywhen the Shop equipment is comparatively small and a horizontalmachinemust be employed formilling a greatmany difierentparts , but where there is a great deal of work that requires endmilling, it is better to use amachine having a vertical spindle.

Construction of a Vertical Milling Machine. A verticalspindlemillingmachine is shown in Fig. I . The part to bemilledis attached to table T and the cutter is driven by the verticalspindle S ,

so that it is always in plain view. This is partienlarly desirable whenmilling an irregular ou tline, or any part thatrequires close attention . The table of this machine has longitudinal, crosswise and verticalmovements , all of which can be

efl'

ec ted either by hand or by the au tomatic power feeds. The

spindle and the slide which supports the lower end can also befed vertically, within certain limits , by hand or power. I t shouldbe mentioned thatmillingmachines o f this type do not always

have vertical movements for both the spindle and table . In

some designs the table , instead of being carried by a sliding kneeK ,ismounted on a fixed part of the base which extends forward

228

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230 MILLING M ACHINES

lever C, and lev er D doubles it again , thus giving a total of sixteen speeds . The direction of rotation is reversed by lever B .

The power feeds for the table are varied by the levers seen

attached to the feed-box F . The feedmotion is transmitted to a

reversing box on the side of the knee, by a teles c oping Shaft, thesame as with a horizontal machine. Lever R may be used to

start,stop or reverse the automatic table feeds; lever V controls

the verticalmovement of the knee and table; and lever N thecross-movement. The table is reversed by lever L at the front,the reversing lever R not being used for this purpose.The handwheelG is for raising and lowering the table , and the

smaller wheel E is for the transverse adjustmen t. Bymeans ofhandwheel J the table can be given a fast or Slowmovement, orthe wheel c an be disconnected entirely, a clu tch in the center ofthe hub being used tomake thes e changes. The handwheels E

and C can also be disengaged fromtheir shafts by knobs in thecenter of each wheel. This is done to preven t the table frombeing shifted after an adjustment ismade, in case the workmanshould accidentally turn one of the wheels.

The vertical feed for the spindle head is also varied by the

mechanismat F , the required motion being transmitted to thetop of themachine by a chain and sprockets which drive wormshaft W. This worm-shaft is connected with the upper sprocketthrough a clutch controlled by lever I This same clu tch is alsoOperated by adjustable stops clamped into T-slots in the side ofthe Spindle head , for au tomatically disengaging the vertical feedat any predetermined ‘point. Shaft W transmits the feeding

movement to the spindle,through wormgearing and a pinion

shaft " , and lever O engages or disengages the worm-wheel withthis pinion shaft. When the worm-wheel is disengaged the

large handwheel at the side of the columnmay be used to raise orlower the Spindle rapidly , and , at other times, the small bandwheel at the front gives a slow feedingmovement.Example of Vertical M illing . The vertical milling machine

illustrated in Fig. I is shown at work in Fig. 2 . The casting C,

which is beingmilled , is the saddle of amillingmachine , and theOperation is that of finishing the dovetail ways for the table.

EXAM PLES OF VERTICAL M ILLING 23 1

The ways on the under side have already beenmilled and thisfinished part is held by a plate or fixture F , having a slide similarto the knee upon which the saddle will be mounted when as

sembled.

The cu tter used for this job has radial end teeth formilling theflat or bottomsurfaces

,and angular teeth for finishing the dove

tail. The cutter revolves in a fixed position , and the slide is

Fig . 2 . Example of M illing on Vertical M illing Machine

milled by feeding the table endwise after it is adjusted to theproper vertical and crosswise positions. The fixture ismade intwo parts

,and the top section can be swiveled slightly so that

the dovetail can bemilled tapering on one side for the gib which

is inserted afterward . The top part of the fixtu re is located in

the proper position whenmilling either the straight or taper side ,b y a pin which passes through the upper and lower plates.

232 MILLING MACHINES

Use of Circular M illing Attachment on Vertical Machine.

The verticalmillingmachine is often used formilling circu lar surfaces or slots. In order to do this it is necessary to impart arotary movement to the piece being milled. This is done bymeans of a circular milling attachment which is bolted to themain table of themachine , as Shown in Fig. 3 . The table of the

Fig. 3 . M illing a Circular T-slot on a Vertical Machine

attachment c an be revolved by handwheel A or automatically.

The power feed is derived fromthe splined shaft which drives

the longitudinal feed-screw of the table,this shaft being connected

by a chain and Sprockets to shaft B which transmits themovement to the attachment . When the attachment is in use the

table feed-screw is disconnected fromthe splined shaft,so that

the feedingmovement is transmitted to the circular table only.

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234 M ILLING MACHINES

Work of this kind is often done in the shaper, but thes e smallbrasses can be finishedmore rapidly bymilling, as the bottomof

the grooves and the sides of the flanges aremilled simultaneously ,whereas, with the Shaper it would be necessary (with a Singlepointed tool) to c ut down each Side and plane the horizontalsurface at the bottomof the groove , separately. Fu rthermore,

Fig. 4. M illing Connecting-rod Bearing Brasses on Becker VerticalMachine

it is easier tomill these brasses to a uniformSize than to planethemin a shaper . Whenmilling, the width between the flangesis governed by the diameter of the cu tter

,but if a shaper were

used , this width would depend on the adjustment of the tool,whichmight not always be set in exactly the same position . Theverticalmillingmachine used for this operation is not the same

EXAMPLES OF VERTICAL M ILLING 235

as the one previously illustrated, although its construction is

Similar and it is used for the same class of work .

The vertical milling machine is often used for finishing theedges of straight or circular parts, and irregular shapes c an alsobe worked out by using the longitudinal and cross feeds alter

Fig. 5 . M illing the Edge of a S teel Forging

nately, asmay be required . Of course, if an irregular outline isto be followed

,the machine is fed by hand. At A ,

Fig. 5 , is

Shown an odd-shaped steel forging, the rough end and sides ofwhich are finished bymilling , as indic ated at B . The straightsides and part of the circu lar hub are firstmilled as shown in this

illustration . AS the hole through the hub has already been bored ,

236 M ILLING MACHINES

this is used for locating the forging in a central position,the bored

hub being placed over a close-fitting cylindrical piec e that isclamped to the table, as shown . The work is held by a bolt andheavy washer at the top,

and it is kept fromturnn by a smallangle-plate which is set against the flanged end .

As the illustration shows , the edge is finished by a spirally

Fig. 6. Finishing a Circular Fillet with a Rose M illing Cutter

fluted endmill. The table of themachine is fed longitudinallyformilling the straight part , and then the circular attachment isused for finishing the circular hub around as far as the projectingflanged end will permit . The circular end of the hub is thencompleted (as shown in Fig . 6) by using a difierent type of cutter

which rounds that part of the hub next to theprojecting end and

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238 MILLING MACHINES

many respects to the plain horizontal machine illustrated in

Fig. 2 , Chapter I II , excepting, of course , the changes nec essa ryon account of the vertical location of the spindle. The part tobemilled is bolted direc tly to the table , and , beforemilling th efirst casting, the knee is elevated, so that the spindle slide A will

Fig. 7 . Finishing Top Surface of a Casting on a Cincinnati Vertical Machine

not need to extendmuch below its bearing when the cutter is atwork . The Spindle and cutter are then lowered for the right

depth of cut by using the fine hand-feed which is Operated by thesmall wheel B at the right of the Spindle. After roughmilling thesurface by traversing the table longitudinally

,the feed is reversed

and a finishing c ut of an inch deep is taken , as the tablefeeds in the opposite direction .

EXAMPLES OF VERTICAL MILLING 239

Themicrometer stop D which engages an armE bolted to theside of the columnmakes it possible to set the cu tter to the samevertical position ,

whenmilling a number of castings of the sameheight. This same casting can also bemilled by using a smallercutter which covers a flange on one Side only, instead of the entirecasting. When the smaller cutter is employed, it is made tof ollow the rectangular flange byusing the longitudinal and cross

feeds, alternately .

Fig. 8. Machine Equipped with Two Work-holding Fixtures so thatOne Casting can be Chucked while the Other is being Milled

The example of vertical facemilling shown in Fig. 8 illustratesamodernmethod of chucking castings and operating themachine ,when large numbers of duplicate parts have to bemilled . There

are two independent work-holding fixturesmounted on the table,

and the cutter moves fromone casting to another . First a

roughing cut is taken about 133 inch deep, with the table feeding

75} inches per minu te. When the working side of the cutterreaches the end of the casting, the feed is reversed and increasedto 20 inches perminute for the return or finishing out which is

very light. Meanwhile, another casting is placed in the other

240 MILLING MACHINES

fixture , and when the cutter reaches it, the feed is reduced to 72inches. While this roughing cut is being taken

,a new piec e is

chucked in the other fixture , and so on , one casting being chu c kedwhile the other is beingmilled

,so that themilling Operatio n is

practically continuous. Of cou rse,thismethod of handling the

work cannot be employed unless it is possible to clamp the par tin the proper position in a comparatively Short time. The

fixtures Shown in this illustration aremade likemillingmach in e

Fig. 9. Another M illing Operation Employing Two Fixtures

vises and have Special jaws with angular faces which hold a cast

ing firmly against the base of the vise .

Fig. 9 shows a continuousmilling Operation similar to the onejust referred to

,as far as themethod of chucking the work is con

cerned . There are two independent fixtures, as before, and the

castings are inserted in each fixture alternately; that is, one isbeing chucked while the other is beingmilled . Themachine isfitted with an automatic reverse, and the table travels back and

forth without stopping . Two cuts are taken across each piece;first a roughing c ut and then a finishn c ut on the returnmove

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242 MILLING MACHINES

such a position that the row of forgings will pass beneath therear side of the cutter which then faces the top surfaces . AS thefinished parts come around to the front of themachine, they are

removed by the operator and replaced by rough forgings withou tstopping themachine, so that themilling operation is practicallycontinuous .

A fixture for continuous circ ularmillingmust be des igned so

that the work can be removed quickly and without stopping therotation of the table. In this instance , the forgings are locatedin the fixture by pins and they are held by the pivoted clampsShown . The inner surfac es of these clamps have fine teeth and

are eccentric to the pivot about which the clamps swivel, so thatthe forging is either released or gripped Simply by turning theclamp in one direction or the other.The face cutter used for this operation has high-speed steel

inserted blades and takes an average depth of cut of about 3 inch.

While themilling cu tter is at work, a streamof cooling lubricantflows onto it fromthe jointed pipe seen to the left of the Spindle.

In order to catch the lubricant as it falls fromthe table,the latter

is surrounded by a flanged pan .

Die-sinking Machine. The die-sinking machine,Shown in

Fig. 1 1,is a type of vertic al-spindle millingmachine especially

designed for the use of diemakers inmilling out the impressionsin drop forging dies , etc .

, or for finishing recesses of circ ular or

irregular shape. The part to be milled is held in a vise on the

machine table which has lateral, longitudinal, vertical and rotaryfeeding movements effected by the handwheels shown . As die

irnpressions are usually very irregular in form,the feedingmove

ments of thework-table are controlled entirely by hand , because,formostwork, the cuttermust bemade to follow a line the dircetion of which changes constantly so that an automatic feed wouldbe useles s. The handwheel at the front is for the lateralmovement, the one at the left side is for the longitudinalmovement,and the small wheel placed at an angle is for rotating the table.The large pilot wheel at the side of the knee is for feeding the

table vertically.

The cutters used for die-Sinking aremade in a great variety of

DIE - SINKING MACHINES 243

shapes for finishing impressions of diflerent forms and they are

ordinarily held in a collet or spring chuck which is inserted in thespindle. When milling out a die immession , the diemaker isguided by lines previously laid out on the face of the die blockand also by a graduated index on the pilot wheel. The lines

Fig. 11. Pratt a Whitney Die-sinking Machine

Show the outline and the index is used formilling to the requireddepth at various parts of the impression . Circular parts of the

die, especially if quite large, are often bored out in a lathe prior

tomilling, whereas small circular impressions are either cut outby using formed cu tters of the required size or bymeans of the

c ircular attachment which is set concen tric with the spindle.

244 MILLING MACHINES

The impres sion in a die is milled as close to size as possib le

but in order to finish it, considerable hand work is usually nec es

sary, especially when there aremany corners and irregular places .

The vertical stop-rod seen attached to the Side of the column isused for re setting the knee to the same vertical position af ter it

has been lowered for inspecting or gaging the die beingmilled .

Fig. 12 . Pratt Whitney Two-spindle Die-Sinking Machine

Two-spindle Die-sinking Machine. Some die-sinking machines which are intended formilling large dies are designed sothat the cutter spindle moves vertically instead of the worktable, this construction being adopted to avoid elevating thetable and the heavy dies which are generallymilled on the largermachines . A die-sinking machine of this type

,built by the

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246 MILLING MACHINES

line; hence, positive stops are used because it would not bepracticable to provide an au tomatic feed-tripping device whichwould be sufi ciently accu rate. The stops are carried on the

side of the table, and micrometer screws are provided which

makes it possible to obtain very fine adjustments. I f the Operator should neglect to disengage the feed

,the stop comes again st

an abutment I on the saddle, thus stopping the table . A feedfriction enclosed at J will then slip, thus preventing damage tothe machine. This friction is adjusted so as to provide amplefeed under ordinary working conditions . Ordinarily , the Opera

Fig . 13 . Thurston Die M illing Machine

tor would disengage the feed just before the cutter reached theline on the work ,

and then bring the table up to themicrometerstop by hand . By releasing the lock-bolt K and rotating thefeed-screw with a crank , a rapidmovement of the table is efiected .

The vise seen on the table of themachine is pivoted at the centerso that it can be swung to an angle of 15 degrees in either directionfromthe central position. The cherrying attachment for thismachine is clamped to the under-Side of the head and is drivenfromthe large Spindle. The Spindle of the cherrying attachmentcan be located in four difl

'

erent positions.

DIE-SINKING MACHINES 247

Under-cutting Die M illing Machine. This is a type of diemillingmachine having a cu tter which is driven frombeneath thework-table, and extends up into the die Opening instead of beingheld by a spindle fromabove

,in the usualmanner. One advan

tage of this construction is that lines on the die face showing theou tline or contour of the die opening are not obstructed by thec u tter or Spindle. One design of under-cut diemillingmachineis shown in Fig. 13 . Thismachine is intended formilling variousforms of blanking dies, trimming dies, etc. The die to bemilledis held on a table which is carried by cross and longitudinal slides.

The cutter spindle projects upward through the die opening, andby manipulating the handles which operate the two slides

,the

work is fed against themilling cutter in the required direction .

The vertical Spindle is adjustable, and the cutter projects throughan opening in the chuck in which the die is clamped. The cuttermay either be straight, or tapered to suit the amount of clearancerequired in the die.

Whenmilling out a die Opening,it is nec essary to drill a hole

through the die to forma starting place for the cutter. The

latter is then fed around the outline of the die Opening, as pre

viouslymentioned ,and the entire center is removed in the form

of a solid block . The raising and lowering of the cu tter-Slide is

eflec ted by means of the lower handle seen at the front of the

machine. The upper handle at the fron t and the one at the right

end of the machine control the crOSS and longitudinal movements, respec tively . There is a pointer on themachine whichremains in a fixed position with reference to the cutter

,so that

when the latter is operating below the su rface of the die,the

pointer indicates its exact position . The entire frame of the

machine is mounted on trunnions SO that the work can be in

c lined to any desired position ,in order to give the Operator the

best possible light on the surface of the die.

Combined Horizontal and Verti cal Machine. The millingmachine, a detailed view of which is shown in Fig. 14, has bothvertical and horizontal spindles which forman in tegral part ofthe machine. These spindles may b e run independently or in

unison ,so that themachine is adapted for either vertical or hori

248 MILLING MACHINES

zontalmilling and on some classes of work both Spindles a n b e

used at the same time . The illustration Shows how twenty-six eas t

links aremilled . The vertical spindlemachines fourteen links onthe flat side, whereas the horizontal spindlemills twelve links onthenarrow edge, both the verticalandhorizontal spindles operatingsimultaneously. Two 16-inch facemilling cu tters are used and

the depth of cut for each cutter varies fromi to 115 inch. As will

be seen , the links are held in special fixtures in double rows.

Thismachine is of the column-and-knee type , the work-tablebeing carried by a knee whichmay be adjusted vertically on the

Fig. 14. Ingersoll Comb ined Horizontal and Vertical Milling MachineBoth Spindles in Operation

column . The table has automatic longitudinal, transverse and

vertical feeding movements,all of which are reversible. The

rate of table feed as well as the spindle speed c an be varied withinwide limits bymeans of change gears which are shifted by controllevers at the side of themachine. Themachine is driven either bymotor or a single constant-speed belt pu lley at the rearwhich transmitsmotion to each spindle by shafts and connec ting gearing.

P rofiling Machines. A profilingmachine or profiler is a

type of verticalmillingmachine which is largely used formakingparts of guns , pistols, typewriters , sewingmachines and for simi

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2 50 M ILLING MACHI NES

two cutter spindles A and B are carried by a saddle tha t ismounted on a cross-rail, as Shown . One Spindle is used for taking roughing cu ts and the other for finishing cuts . The saddle

is traversed along the cross-rail by handle E for locating ei therspindle in the working position

,whereas handle D is used for

moving the table along theways of the bed at right angles to the

cross-rail. Each spindle is carried by a vertical Slide and is

lowered to the working position by a hand lever at the top. The

spindles can be set in the required vertical position each time a

new part is profiled by means of plungers or stop-rods operatedby handles H. These plungers slide out and engage notches in

the strips G which are attached to the spindle slide and are ad

justed in accordance with the position required for the cutter.

When one cuthas been taken ,the locating plunger for that spindle

is withdrawn ; the spindle is then quickly forced upward by a

spring, far enough for the cutter to clear the work so that theother spindle c an bemoved over to the working position withou tdelay.

AS the cutters used for profilemilling are usually quite small,they revolve rapidly . The spindles of the machine illustratedare driven through spiral gearing froma horizontal Shaf t to whichcone pu lley C is attached . The spindles of some profilers are

driven directly by belts,especially when exceptionally high

speeds are necessary , and also by universally-jointed verticalshafts which transmitmotion froman overhead countershaft tothemachine.

Example of P rofileMilling . The profilingmachine illustratedin Fig. 15 is arranged for milling the ou tside of a rifle trigger

guard . When the machine is in operation ,one of the former

pins AI or B 1 (depending upon which cu tter is being used) isbrought into contact with the former plate ormodel F attachedto the work-table. The pin which is clamped to the cutterspindle slide andmoves with it is thenmade to follow the outline of the former plate by manipu lating the lateral and longitudinal feeds, handles D and E being used for this purpose. In

this way ,the cutter ismade to follow a path which corresponds

to the Shape of the former plate, thus reproducing this formon

PROFILING 25 1

the work . Roughing and finishing cu ts are taken by bringingfirst the roughing cu tter spindle and then the one carrying the

finishing cutter into contact with the former, each Spindle beingset in the correct vertical position by the stop-rods operated by

handles H.

The edge of the former plate is beveled or tapered and the pin

has a corresponding taper,so that the cu tter can be adjusted

laterally,within certain limits

,by simply adjusting the former

pin vertically. For instance,if when setting up themachine it

is desired tomove the cutter a little toward the work for taking

Fig . 16. Profiling Inside of Finger Lever for a Repeating Rifle

a deeper cut,this can be done by raising the pin slightly; a

smaller part of the taper will then come into contact with thebeveled edge of the former plate so that the relation betweenthe work and cutter is changed .

The Operation of a profiler is comparatively simple after it isproperly set and adjusted

,b utmany of thework-holding fixtures

and former plates required for certain classes of work are ln

genious and interesting. The following examples of profilingwill illustrate , in a general way, the nature and variety of workwhich is done on machines of this type . These examples are

Operations on rifle and pistol parts and represent the practice at

2 52 M ILLING MACHINES

the Savage Arms Co. Owing to the irregular Shapes of manyrifle and pistol parts , a great many profiling Operations are

necessary in connection with theirmanufacture .

Profiling Inside of Finger Lever. The method of profilingthe inside opening of the finger lever of a repeating rifle is illustrated in Fig. 16. A concave cutter is used to forma convexsurfac e on the work . The lever is held in the fixtu re by clampsA which are forced downward by the ec centric clamps B and it is

located by the two rods C and pin D. The latter enters the

WORK7

Fig. 17 . Diagramshowing M ethod of Profiling Outside of RifleFinger Lever

pivot hole of the lever, and rods C extend beneath the left clampA and bear against the left side of the lever. The opposite side,which has been rough-milled by a previous Operation , is held

firmly in to contact with the fixture by rods C which are forced

inward by an eccentric lever E that bears against a yoke connect

ing the two rods .

The formerF ,which is engaged by guide-

pin G and controls the

movement of the cutter , has a plain rectangular Opening which,of course, conforms to the shape of the hole to bemilled in thefinger lever. When the profiling operation is completed, clamps

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MILLING MACHINES

Still an other profiling operation on the outside of the fingerlever is Shown by the diagram,

Fig. 18. One continuous cu t istaken as indicated by arrow 0 to formthe edges of that end ofthe lever which enters the rifle receiver and connects with the

breech-bolt. The surfaces at the extreme endmust be accuratelymachined as this end enters between the breech-bolt and a lug

on the receiver (when the action is closed) to forma solid supportfor the bolt.

Fig. 19. Plan View of Fixture and Former used for ProfilingOperation on Rifle Receiver

The lever is located by pin A which enters the pivot pin hole,and also by a small boss or pin at B which is solid with the lever

and enters a hole in the base of the fixture. (This pin engages a

c amslot in the breech-plug when the rifle is assembled .) The

lever is held by a clamp C which is forced downward by a screw

and lever D. The circular edge of the lever which is beneaththis clamp ismachined in a separate operation by a formed cut

ter,a Lincoln typemachine being used. The former F is a plain

type,shaped to correspond with the surface to bemilled , and the

PROFILING’

255

path of the guide-pin is shown by the arrow 01. To removethe finished work

,clamp C is withdrawn after being loosened,

so that the lever can be lif ted ofl the locating pin .

Profiling Operations on Rifle Receiver. The profiling opera

tion illustrated by the diagram, Fig. 19, is on the receiver of arifle, which is that part between the barrel and stock that contains the action . Two separate cu ts are taken by diflerent

cu tters held in the two spindles of the profiler. One cut 0 formsa gu ide way for the breech-bolt when the action is being Openedor closed

, and the other cut b extends fromthe lever support

Fig . 20. Profiling Cartri dge Guide S lot in Rifle Receiver

back to the trigger slot. When taking the longer cu t a, a cutter

is used that willmill a Slot of the required width,and the path of

the guide-pin along the former F is Shown by the arrow 01. Theprojecting part C of the former is simply a guard to prevent thecu tter fromstriking end D of the receiver when it is being re

moved at the completion of the cu t. P late L also forms a guardand prevents the cu tter fromstriking the tang " .

Before taking the Shorter cut b , the plateG is swung across theformer slot (as indicated by the dotted lines) and acts as a stopfor the guide-pin SO that the cut will be started at the correct

256 MILLING MACHINES

point. This plate swivels on screw H and rests against a pin K .

A small screw in the end of plate G provides an ac curate adjustment in case it Should be nec essary to vary the point at whichthe c ut begins. The c urve at the beginning of cut b is equal tothe radius of the cu tter used .

The rec eiver is located for this operation by a pin in the baseof the fixture at S which enters the sear pin hole, and also by a

pin atM which enters the lever pivot hole. The work is furthersupported and located by a plunger N which is pushed into thetrigger Slot by lever O. The plunger is clamped in position bythe lever " and the rec eiver is held down against the base of the

fixture by clamp R .

Fig. 20 Shows how the cartridge guide Slot is milled in thereceiver. This is a narrow,

straight slot abou t 55; inch wide and

2} inches long , on the right Side of the receiver, which holds thecartridge guide. (This cartridge guide , in conjun ction with themagazine carrier and ejector holds the cartridge in the properposition .) The receiver is located by the left Side and the upper

surface . A clamp sc rew operated by handle A forces the re

ceiver against the vertical wall of the fixture and it is held upwardagainst locating lug B by a b ar C on the under Side which israised by cam-lever D. AS the Slot is straight

,the former F

sirnply has a straight , rectangular opening . The cutter is locatedin the correct vertical position by barGwhich engages a notch in

Slide J and is operated by lever H .

Themethod ofmilling themortise or Slot which forms a seatfor the cartridge ejector is illustrated in Fig. This Slot is

slightly tapering and is at an angle with the Side of the receiver;hence , the latter is held at an angle in the fixture as the illustration Shows. The former F has a plain

,tapering Slot which gives

the required Shape . Before this seat is profiled,c learance holes

are drilled at each end of the slot for the profiling cu tter. Rough

ing and finishing cutters are used . The illustration shows the

finishing cu tter in position ,the roughing cu tter having been

moved to the left. The cu tter is set for depth by the engagementof plunger Gwith Slide J as previously explained . When plunger

G is withdrawn by handle H ,the slide is forced upward by a

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258 MILLING MACHINES

illustration) , which prevents the operator frommoving the cu tterover into contact with the left side of the former base. By having

guards of this kind , the operator can shift the cutter-Slide rapidly

and withou t fear of feeding the cutter against some part of thework or fixture . The Slide is located in the fixtu re by pin L at

the end and the three half -pins along the right-hand edge , and

it is held by a single clamp which is cu t away and beveled to clearthe cutter.

Fig. 2 2 . Diagramshowing Comb ination Former used for Profilingas Indicated b y Shaded Areas A and B

P rofiling Bolt of Automatic P istol. An interesting profiling

fixture and former is shown by the plan view ,Fig. 23 . The opera

tion is on the bolt of an automatic pistol and consists of beveling the corners M of the opening and cutting a round groove

,as

Shown by the Shaded area N . The bolt is held between the plug

A and the end B of the fixture, and it rests on block C which has

a circular seat. End B is counterbored to receive the end of thebolt

,and plug A has a pilot or small projecting end which enters

the bore of the bolt. Lever D attached to plug A passes through

a camSlot (similar in formto a bayonet lock) and is used to forcethe bolt back into the coun terbored seat in block B . The open

PROFILING 259

ing or channel which is to be beveled is located in a central posi

tion by a close-fitting finger E which is turned down into the

Opening by lever G.

A double former plate is used for this operation . When bevel

ing edges M , plate F is in the working position as Shown by thefu ll lines . This plate swivels about screw pin H and is locatedb y pin J which passes through it. When the edges have beenb eveled by the tapering cu tter used for this operation ,

the other

Fig. 23 . Plan View of Profiling Fixture and Former for Bolt ofAutomatic Pistol

spindle carrying a cu tter of different shape ismoved over to theworking position and plate F is swung back as indicated by thedotted lines . The lower slot in themain former F1 is then usedfor profiling the seat N at the bottomof the bolt.P rofiling Dovetail Seat in P istol Frame. The vulcanized

rubber Side plates for the handle of a Savage automatic pistolare inserted into close-fitting dovetail seats .

‘

The plan view,

Fig. 24 , illustrates how the seat on the right-hand Side of a frameismilled on the profiler. The frame is located by the angular

MILLING MACHINES

strip A and the boss B on the Side of the frame , which enters acircu lar seat in the projecting lug shown . The frame is clampedagainst the bottomof the fixture by two hook c lamps C and C1.

These clamps enter themagazine opening and the lower ends

are attached to a connecting bar that is forced downward by a

camlever D. To insure c ontact between the frame and the endstrip A ,

bolt C and the work is forced against A (as indicated bythe arrow) by tightening clamp E .

The path followed by the cu tter is Shown by arrow 0 and the

movement of the guide-pin along the former F is indicated by

Fig. 24. Fixture and Former for Profiling Dovetail Seat in S ide ofPistol Frame

arrow b . Roughing and finishing cu ts are taken . The cutters

are small and revolve very rapidly . The actual time requiredfor taking one of these dovetail cuts is only abou t five seconds.

The former F is open on the right-hand Side so the guide-pin can

enter while the cutter is in the working position .

The fixture used formilling the dovetail seat on the oppositeSide of the frame is similar to the one just described , except thatthemethod of locating the work is di ff erent because the circularlocating bosses are on the lower side and enter holes in the base

of the fixture; consequently locating strip A and the auxiliary

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262 MILLING MACHINES

cu tter to strike the former along the side K . Themovementof the guide-pin around the former is indicated by the dottedline 6 .

Indexing h pe of Profiling Fixture. A profiling fixture of therevolving or indexing type is Shown in Fig. 26. The operationis that ofmilling the top and bottomends of themagazine opening in the pistol frame, to a depth of abou t i inch. The frame islocated on the circular faceplate of the fixture by the locatingbosses previously referred to , and it is held by a T-head clampbolt A which passes through it and is tightened by the handle B .

Fig. 26. Indexing Type of Profiling Fixture

When one end of themagazine ismilled , plunger C is withdrawnand armDwith the work is tu rned a half revolu tion by swingingarmD over to the opposite side of the fixture, where plunger C

engages another hole, thus locating the frame for the operationon the opposite end of the magazine opening. The profilingoperation is Simply that of forming a plain rectangular surface,former F being used to guide the cutter. The metal betweenthese milled surfaces at the ends is afterwards removed by a

Shaving operation in the shaper .

P rofiling with Indexing Former Plate. The profiling Operation illustrated in Fig. 27 is that of forming the sear trip seat in

PROFILING 263

an au tomatic pistol frame, and the surfaces above the sear tripseat . The nature of the operation is illustrated by the diagramsA ,B and C. The sear trip seat, which is abou t inch deep

, is

formed by two separate cuts as Shown by the sketches A and B ;

the surfaces above this seat, which are represented by the shadedarea at C, are thenmilled .

A c utter in one Spindle is used for the sear trip seat, and anotherc u tter in the other spindle for milling the top su rfaces. The

Fig. 2 7 . Profiling Operation requiring an Indexing Former Plate

former plate F contains two guide-pin holes G and H . Hole Gis used when profiling the seat (as at A and B ) and hole H for

the other operation ,the former plate F being indexed to locate

either of these holes in the working position . This plate swivels

abou t the screw pin D and is located by the spring plunger Ewhich enters holes J and K in the former base .

The frame to be profiled is held against an angle-plate (attached to the base of the fixture) by T-head clamp bolt L which

64 M ILLING MACHINES

passes through the frame and is tightened by lever M . Circular

locating bosses on the side of the frame engage holes in the ang leplate and locate the frame In the proper position . Whenmillingthe seat , the former plate IS in the position shown In the illustra

tion; that is , with plunger E engaging hole " ,thus loc ating the

former hole G in the working position . The cutter is droppeddown to the proper depth by the vertical locating device for the

spindle Slide . The guide-pin is then traversed around hole G,

but when the cu tter reaches corner a (see Sketch A) themovement is continued along a straight line , as indicated by the arrows ,thus forming a rectangular slot as the diagramshows.

The auxiliary plate N on the former is then swung across the

end of hole G, as Shown by the dotted lines, thus blanking off

this end . The seat is then finished as at B . If plate N were

not used and the gu ide-

pin simply followed the slot in the former ,the corner at 0 would be rounding instead of square . The end

of the plate N , however, causes the guide-pin and cu tter tomovestraight in ,

thusmilling a square corner.

When the sear trip seat is finished , plunger E is withdrawn andthe plate is indexed to loc ate hole H in the working position ,

plunger E being engaged with hole K . A cutter in the opposite spindle , which is located at a higher level, is then used to

mill the upper surfaces as indicated by the Shaded areas insketch C.

In practically all of the profiling operations desc ribed in theforegoing, both roughing and finishing cuts are taken . Someof the roughing cu ts are quite heavy , but the light finishing cutswhich follow insure accurate and smooth surfaces .

Semi-automatic Profiler. In armories, etc.,where large

numbers of irregular-shaped partsmust bemilled, semi-automaticprofilingmachines are used to some extent in place of the handoperated type previously described . The P ratt Whitneymachine is illustrated in Fig. 28. The head in which the cutter

Spindles aremounted is stationary while themachine is operating, and the required formor contour is obtained by themovement of the table . The latter is carried at the front end of a

swingn armwhich is journaled in the bed between the uprights .

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266 MILLING MACHINES

Fig. 29 shows a detail view of thismachine arranged formillingthe steel frames of automatic pistols. The operation illustrated

is that of profiling the outside of the grip or handle . (The underSide of the barrel, the trigger guard, and the inside of the grip are

alsomilled in this samemachine , by the use of a difierent fixtureand cam.) The blanks are located in the correct position bypins, as the illustration shows, and they are held by screwoperated clamps. The rounded edge is formed by the concave

Fig. 29 . S emi-automatic Profiling Machine milling Automatic Pistolramea

cu tters D and E , one being used for roughing and the other forfinishing . The roughing and finishing cutter Spindles are set in

the working positions by means of the stops G and H and the

stop-screws J and K . The latter are adjustable for aligningthe cu tter with the work .

When the cutter is traversing the spaces between the work,the table speed is au tomatically accelerated . This change of

Speed or feed is controlled by adjustable dogs Fmounted on the

LINCOLN-TYPE M ILLING MACHINE 267

periphery of the table . After the parts are rough-milled by one

of the cu tters, the other spindle is placed in the operating position for finishing the surfaces . The speed of table rotation or

the feed can be varied bymeans of a change-gearmechanism.

The Spindle Speeds can also be varied to suit the Size of themilling cu tters and thematerial beingmilled .

M illing Master Camfor Semi-automatic Profiler. When a

master camor former A Fig. 28, is required for profiling a certainpart, it is produced as follows: Roller B ,

against which the cambears when themachine is in operation ,

is replaced with amillingc utter of the same Size. The spindle of the cutter is connectedby a belt with themain shaft and amodel of the work is locatedin the fixture. A former pin of the same size as the roller andcu tter is then inserted in the cutter Spindle and placed in contact

with themodel. The camblank attached to the table is then

milled as the table feeds around . The cutter is revolved by an

independent drive . The former pin in the spindle does not

rotate while the c amis beingmilled . Several cu ts are usuallyrequired for this operation .

Lincoln Type of M illing Machine. The milling machineshown in Fig. 30 is intended especially formanufacturing; thatis

,it is not adapted to a great variety ofmilling operations but

is designed formachining large numbers of duplicate parts. The

construction is very rigid b ut comparatively simple,and , there

fore, this style ofmachine is preferable to themore complicateddesigns for work within its range. Millingmachines

,having the

same general construction as the one illustrated , are often referred

to as the Lincoln type . As will be noted , the work-table A ,

instead of being carried by an adjustable knee , is mounted on

the solid bed of themachine and the ou ter arbor-support is alsobolted directly to the bed . This construction gives a very rigid

support both for the work and cutter . The work is usually held

in a fixture or vise attached to the table , and themilling is doneas the table feeds longitudinally .

The table is not adjustable vertically, but the spindle-head B

with the Spindle can be raised or lowered as may be required.

This vertical adjustment of the spindle-head is effected by turning

268 M ILLING MACHINES

handwheel C which has a graduated collar.

reading to thou

sandths of an inch . After the Spindle has been adju sted verti

cally, the head is c lamped to the upright by the four bolts shown.

The Spindle is driven froma pulley at the rear which transmitsthemotion through Shafting and gearing. A friction c lutch is

located in this driving pulley and provides means for starting

Fig. so. Brown a Sharpe Plain M illing Machine of the Lincoln Type

and stopping themachine . This c lu tch is operated by the hand

lever D.

The table has a longitudinal power feed in either direction,which can be varied to suit requirements. This power feed canbe au tomatically disengaged at any point by setting the adjustable stops E in the proper position . The direction of the feedcan also be reversed by operating reverse-rod F . The large hand

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2 70 MILLING MACHINES

remaining sides . While these cuts are being taken , the duplicate

fixture is loaded with unslotted nu ts. The latter are held ontothe plate by studs and are prevented fromturning by smallblocks located between them. Lubricant for the gang of cutters

is supplied through the pipe seen just above the cutter arbor,which has a number of openings . This example of gangmillingillustrates the special fixtures which are commonly used in con

nec tion withmilling Operations.

Semi-automatic Lincoln-type Machine. The semi-au tomatictype of Lincoln milling machine, as built by the Cincinnati

Fig. 3 1 . Castellatiug Nuta on a Hendey Lincoln-type Milling Machine

Milling Machine CO.,is provided with an au tomatic intermittent

feed and a power quick return for the work-table . Bymeans oftrip dogs , a variety of cycles ofmovement can be obtained . The

Simplest of these is the one that would be used formilling a number of surfaces with spaces between . For an operation of thiskind , themachine is set to bring the work up to the cutter at arapid rate; the feed then slows down while the surface is beingmilled , after which it is accelerated while the cutter is movingacross the space to the next piece . The feed is then reducedagain for milling , and this operation is repeated until the last

HORI Z ONTAL MILLING MACHINES 271

su rface has beenmilled; the table then au tomatically reverses andquickly returns to the starting point. This feature greatly reducesthe idle or non-cu tting period and increases the production .

Horizontal Milling Machines. The machine illustrated inFig. 32 is des igned for heavymilling operations. This style ofmillingmachine is sometimes referred to as a planer or slab type;as the illustration shows, it is built somewhat like a planer. The

Fig. 32 . Ingersoll Horizontal or Planer-type M illing Machine

work-table T ismounted on a long bed , and the cutter arbor Cis carried by a cross-rail A which, in turn , is attached to verticalhousings. The cutter spindle is driven by gearing at the leftend, and it can be adjusted longitudinally by traversing themainsaddle S along the cross-rail. The outer end of the cutter arbor

is supported by a bearing B , and there is also an intermediatesupport. The work-table has an automatic feedingmovementalong the bed, and it can be traversed rapidly by power, in either

272 MILLING MACHINES

direction , when the position needs to be changed considerably.

The power feed can be automatically disengaged at the end of thecut by a tappet which is shifted along the Side of the bed to therequired position . The cross-rail can be raised or lowered to

locate the cutter at the required height, and it is counterbalancedby weights attached to wire ropes that pass over the pulleys at

the top of the housings .

Fig. 33 shows how a horizontalmachine of this kind is used formilling a large casting. The parti cular part illustrated is thebed of a turret lathe , and the operation is that ofmilling the V

Fig. 33 . M illing the Ways of a Turret Lathe Bed on a HorizontalMachine

shaped ways, the flat surfaces inside these ways and the outersides or edges. The arrangement of the gang of eight cu tters isclearly Shown by the illustration . The bed has been movedaway fromthe cu tters somewhat , in order to Show the shape ofthemilled surfaces . The V-shaped ways aremilled by angularcutters and the flat inner surfaces by cylindrical cu tters, whilethe edges are trued by large Side mills. This gang of cuttersrotates in a clockwise direction , as viewed fromthe operatingside of themachine , and the table feeds to the right or againstthe cu tter rotation .

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274 MILLING MACHINES

grooved to forman I -beamsection . This lightens the rod con

siderab ly but leaves it strong enough to res ist the various stressesto which it is subjected .

These channels aremilled fromthe solid , and the cutters usedfor this work have inserted spiral teeth which inc line in oppositedirections to neutralize the endwise thrust. They are 8} inchesin diameter and their width is 4} inches, which corresponds tothe width of the channel. When milling , these cutters revolve

36 revolutions per minu te , giving a peripheral Speed of 77 feetperminu te . The channel or groove is I % inch deep , and it

Fig. 34. Channeling the S ides of Locomotive Main-rods on Horizontal Machine

milled in two cuts , each having a depth of i inch . A constantstreamof lubricant pours on each cu tter through the hose andvertical pipes seen attached to the cross- rail. When setting upwork for an operation of this kind , itmust be held securely againstendwise movement , because the pressure of such heavy millingcuts is very great. In this case, the rods rest against a heavy

steel block which is fastened across the end of the table to resistthe endwise thrust of the cut.

M illing Locomotive Trailer Frames . The powerful millingmachines used inmodern Shopsmake it possible to removemetalvery rapidly , espec ially when the machine is equipped with

HORI Z ONTAL M ILLING MACHINES 275

properly designed cu tters . Fig. 35 illustrates how a millingmachine of the horizontal type is used in the "uniata Shops of the

P ennsylvania Rai lroad,formilling the trailer ” or rear frames

Of locomotives. These trailer frames are only used on locomotives of the passenger type having trailing ” wheels, which differ

fromthe driving wheels in that they simply carry weight and are

Fig. 35 . End View of Horizontal Machine arranged for M illingEight Locomotive Trailer Frames

not connected to the Side-rods. The frames are forged and are

not made very close to the finished Size,because the metal is

removed so rapidly bymilling that it would not be economicalto forge too close to the finished dimensions . The amount ofmetal removed in machining these frames is indicated by thefact that a rough frame weighs about 2 2 1 2 pounds

,whereas one

that is finished weighs only 1725 pounds.

MILLING MACHINES

The frames are firstmilled on the Sides, two being placed on

themachine at one time. The work is Shimmed up with linersor thin wedges and is held by ordinary clamps . A stop-bar isplaced across the ou ter end to take the thrust of the c ut and as

the milling c utter advances,the clamps are shifted fromone

point to another.After both Sides of all the frames in a lot have beenmachined ,

the edges aremilled to theproper contour . E ight of these framesaremilled on the edges simultaneously , and the way the work is

set up is indicated in the illustration . Two broad clamps are

placed across the top and the frames are held laterally by screwstops along the sides . The rear clamp is provided with eightset-sc rews which insure a bearing on each frame section . The

outer frame on the operator’s side has lines Showing the requiredou tline for the finished edges. These lines are transferred froma steel templet before the frames areplaced on themachine . The

frames are first set up as shown and are then turned over for

milling the opposite edges . The cu tter used is 33 inches wide,and practically the entire width of this cutter is in use whenmilling the edges of the eight frames. The cu tter consists of threeI I -inch units having inserted blades which are held in helical

or Spiral grooves , giving a constan t cutting action along thefull width of the cu tter .

The following figures will show the rate at which these roughforgings aremachined . The length of the section beyond the

second clamp is 5 feet 83 inches; this section is milled in 56

minutes, and the average depth of cu t varies from3 to 3 inch.

(I twill be understood that the time specified is for eight frames.)The lengths of some of the other sections together with approxi

mate depths of the cu ts and time required formilling themare as

follows: Length, 19 inches, depth of cut, g to it inch ,

time, 21minutes; length , 495 inches, depth of cu t, 5} to i inch , time, 1hour 6minu tes; length , 333 inches, depth of cut, to 23 inches,time , 1 hour 40minutes; length, 353 inches , depth of cut, § to 1

inch, time , 28minutes; length , 50 inches, depth of c ut, to gl

inch , time, 34minutes.

The amount of metal removed fromthe edges of the eight

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278 MILLING MACHINES

cally on the housings , and the vertical heads laterally along thecross-rail. This particularmachine will drive facemills up to 20

inches in diameter.Machines of the same general design are also built with three

heads, one being on the cross-rail and two on the housings, and

there are various othermodifications. Wi th themu ltiple-spindle

Fig . 37 . Three-head Machine M illing AluminumCasting.

machines, the number of spindles used at one time depends, ofcourse, on the nature of the work. For some jobs it is necessaryto use the horizontal spindles

,whereas other parts are milled

by using the horizontal and vertical spindles in combination.

This type ofmachine is very efficient for certain kinds ofmilling.

An example illustrating the nature of the work done on a

MULTIPLE-HEAD MILLING MACHINE 279

multiple-head machine is shown in Fig. 37 . This particularmachine has three heads and a fixed cross-rai l, the latter beingc ast solid with both housings in order to secure amore rigid constru ction . One spindle is carried by the cross-rail and the othertwo aremounted on the front faces of right and left housings.

This general type ofmachine is extensively used formilling thesu rfaces of duplicate parts, such as gasoline engine cylinders,crank cases, etc .

Themilling operation shown is that of finishing the surfacesof aluminumcastings for au tomobile engines . As will be seen ,these castings are clamped to the sides and top of a cast-ironfixture

, and the three rows of castings aremilled simu ltaneouslyas they are fed past the cutters . The cutters at the sides are 14

inches in diameter, and the one attached to the vertical spindlehas a diameter of 10 inches. They are rotated for this operationat a speed of 100 revolutions per minute, and the feed of thetable is 33; inch per revolution of the cu tters, or over 9} inchesper minute . Obviously, it is possible to mill these castingsrapidly after themachine is adjusted .

The principal difficulty inmachining aluminumand aluminumalloys 15 caused by the clogging of the chips which tend to wedgeb etween the teeth of tools , such as milling cutters, etc . Thisdifii culty can be largely avoided by the use of the right kind of

cu tting lubricant . Soap water and kerosene are often used.

The latter enables afine finish to be obtained,provided the cut

ting tool is properly ground . Formilling flat surfaces , it is preferable to use end or facemilling cu tters rather than the cylindricalforms. The cutting edges or corners should be sharp instead ofrounded, and themill will cut better if a high c utting speed and

moderate feed are employed . The depth and width of the cutare ofminor importance . A cu tting speed of 3 25 feet perminuteis practicable

,and from2% to 4 cubic inches of aluminumcan be

removed perminu te .

According to onemanufacturer who'

machines aluminumpartsin large quantities

,the cutting speed for aluminumcan be from

so to 60 per cent faster than the speeds and feeds for cast iron.

The lubricant used by this manu facturer is composed of one

280 MILLING MACHINES

part aqualine and twenty parts water. This lubricant not onlygives a smooth surface but insures a keen cu tting edge and al

lows tools to be usedmuch longer withou t regrinding. Formerlya lubricant composed of one part of high-grade lard oil and one

part of kerosene was used . This mixture costs approximately30 cents per gallon , whereas the cost of the aqualine-and-water

mixtu re is less than 4 cents per gallon , and'it has provedmore

effective than the lubricant formerly employed .

Fig . 38. M illing the Ways of a M illing Machine Bed Casting

Fig. 38 shows how two spindles of a four-spindlemachine areused for rough-milling the top surfaces of amillingmachine bedcasting . A gang of four cutters is used

,consisting of two side

mills for the edges of the ways and two cylindrical c utters forthe top surfaces. These cu tters are mounted upon an arborwhich is driven by the right and left-hand horizontal spindles.

The cylindrical cu tters have round,inserted teeth which are

driven into holes in the cu tter body. These holes are so locatedthat the cutters incline at an angle to the axis of the arbor, and

the teeth of one row are in line with the spaces between the teeth

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282 MILLING MACHINES

The function of the spindle when driving in this way is simplythat of supporting the driving gear, this being the arrangemen twhen cutters varying from18 to 36 inches in diameter are used .

Cutters of smaller diameter are attached to the spindle bymeansof a shank and draw-in bolt , and themachine is driven by themain Spindle gear .

Fig . 39. Open-aide Horizontal Milling Machine Facing Pump Castings

The saddle has an in-and-outmovement by hand and in orderto provide a fine adjustment

,it is equipped with amicrometer

stop which gives accurate adjustments for any position withinthe limits of the saddle travel. This machine is driven by a

motor located on the opposite side of the vertical column . Thetable has twelve feed changes and a rapid power traverse ineither direction of thirty feet perminute . The open-side type

DUPLEX MILLING MACHINE 283

of milling machine can often be used for milling large or longparts which could not be handled on amachine having a housingon each side of the table, owing to the interference between thework and the machine. Open-side milling machines are alsobuilt with vertical spindles which are mounted upon a shortheavy cross-rail, which projects fromthe column over the table:Duplex Milling Machine. The duplex type of milling ma

chine has been developed more particularly for manu facturingoperations which require two sides of a piece to bemilled paralleland to a given width. A duplexmachine is shown in Fig. 40

Fig . 49 . Example of Parallel Face M illing on a Duplex Machine

milling both sides of a vise jaw casting. As will be seen ,it has

two horizontal spindles A ,each of which carries a face c utter B

for this particular operation . The work is clamped in a fixture

so as to clear each cu tter, and both surfaces aremilled simultaneously as the table and work feed au tomatically at right

angles to the cu tter spindles.

Machines of this type are particularly adapted to such operations because parts can b emilled quickly and the accuracy ofthe work is not dependent upon the care and skill with which thework is reset formilling the second surface . Inasmuch as the

284 M ILLING MACHINES

two surfaces are milled at the same time, thus avoiding a sec

ond setting of the work , it will be evident that a considerableincrease of production is also obtained .

The spindles of the duplexmachine shown in Fig. 40 are drivenby cone pu lleys at the rear which are connected through gearing.

These spindles have independent vertical adjustments in orderto locate the cutters in accordance with the height of the work,

and the distance between the ends of the spindles can also be

varied for milling difi'erent widths. The rate of the table feed

is changed by shifting gears in the feed-box C. Amachine of

Fig. 41. Whitney Hand M illing Machine

this type is often used exclusively for one or two operations in

manu facturing plants requ iringmany duplicate parts.

Hand M illing Machine .- The hand milling machine is so

named because the table or cu tter is fed by hand instead of by anautomatic power feed . A typic al design is shown in Fig. 41.

The table can be fed in a lengthwise direction by hand lever A

or by tu rning the feed shaft with a crank . The spindle headalso has a vertical lever feed

,the lever being inserted at B . The

table can be adjusted laterally and vertically by turning thesquared shafts C and D, respec tively . The cutter spindle is

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286 MILLING MACHINES

ordinary profilingmachine, although the construction is difierent.This machine is used for milling disks, face and cylinder camsof various forms, and for all kinds of rotary and irregu lar formmilling. The two tables A and B are driven in unison bymeansof shaf t C and wormgearing. Table A carries the former ormodel and table B the part to bemilled. The cu tter spindle

and its slide ismounted on a c ross-rail, and a former pin D isattached to the slide a certain distance fromthe spindle whichdistance can be varied to suit the work, by adjusting the pin

holder horizontally. When themachine is in operation , pin D

Fig. 43 . M illing Face Camon Garvin Camor FormMilling Machine

bears against the former plate ormodel and, as the table revolves,the cutter is caused tomove laterally so as to reproduce the required outline on thework . At the right-hand end of the drivingshaft C for the tables , there is a reversingmechanismso that thetables can be rotated in whichever direction presents the least

abrupt angles for the former pin and cu tter to pass over. Forinstance, if a camwere beingmilled having a sudden rise at onepoint, the direction of rotation should be such that the formerpin will approach the rise fromthat side which has themostgradual ascent.

CAM MILLING MACHINES 87

Milling a Face Cam. The type of camor formmillingmachine illustrated in Fig. 42 is shown in Fig. 43 arranged formilling a face cam. The unmilled camblank is shown at A and thefinished camatB . The blank is c lamped to the right-hand table

,

as at C, and the former plate E on the table to the left. Boththemodel and work are centered bymeans of bushings which arefitted to holes in the centers of the tables. The pin D on thecu tter slide is held firmly against themodel by counterweight F

,

and the cu tter and pin follow the same path as both tables re

volve in unison . The cutter spindle is adjustable vertically forsetting the cu tter

,bymeans of handwheel G (see also Fig.

and horizontally along the cross-rail by handwheel H ,when set

ting up the machine . Stops are provided for both horizontaland vertical movements . The cross-rail of

”

the machine illustrated in Fig. 42 can be adjusted vertically on the front of theuprights by means of elevating screws that run on ball- thrustbearings. The method of mounting the slide on cross-rail isnoteworthy. The upper horizontal surface of the rail has a

hardened and ground tool-steel ball race carrying a long row ofballs. The opposing surface of the slide has a similar race

,thus

supporting the weight. At the lower edges of the slide and railare two opposed tool-steel surfaces, between which are two rowsof balls that take up the thrust, thus making the slide travel

b ack and forth with little friction , so that the cutting of sharp

angle cams is greatly facilitated .

Whenmilling small parts of irregular shape , sometimes severalc an be placed on the table at one time in order tomill themsu c

cessively. The parts are held near the circumference of the tablein a suitable fixture and a series of duplicate formers is arrangedsimilarly on the other table. Themilling operation is continuous

,the finished part being removed and replaced with rough

blanks while the others are beingmachined .

Milling a Cylinder Cam. The machine shown in Fig. 42

can be used for cutting cylinder or “ barrel” cams by replacingthe circular tables A and B with the attachment K seen on thefloor. The horizontal spindle of this attachment is rotated bygearing connecting with shaft C on themachine . The cylindri

288 MILLING MACHINES

cal former ormas ter camis attached to faceplate L and the camto faceplate M . P in D engages the former , and the cu tter inthe spindlemills grooves of the required cu rvature as the attachment rotates.

Fig. 44 shows a cylinder camattachment in place on another

machine which is similar to the one just described,except for

minor details. Shaft C connects with shaft N by a chain and

Fig. 44 . Milling Cylinder Cams on Garvin Machine

sprocket and shaft N,in turn , drives the horizontal spindle of

the attachment through the wormgearing shown . The cylindri

cal former has c amsurfaces corresponding in shape or curvatureto those requ ired and it is engaged by pin D attached to the cutterslide; hence, the cu ttermills a groove corresponding to the c amsurface engaged by the pin . The mechanismfor driving theattachment is operated by belt O,

and the cu tter spindle is ro

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290 MILLING MACHINES

as shown in Fig. 45 . For cu tting cylinder or barrel earns the

mandrel is held in a vertical position as Shown in Fig. 46 , and an

ou tboard support is used for steadying the upper end . Flatformer plates are used for cu tting all types of cams .

Power is transmitted to the work-head by means of a shaft

at the rear of themachine, and the horizontalmovement of thehead along the ways of the bed is eff ected by a screw. The

machine is driven by a single belt pulley at the rear . Speed

Fig. 46. Rowb ottomMachine Milling a Cylinder Cam

changes are obtained by means of a gear box, correspondingvariations being made for the former plate and work arbor

,in

order to retain theproper relation between the cutter and the

cambeing milled . The cutter speed can also be changed to

suit the size of the mill and material being cut. These speedchanges for the cu tter spindle are effected by lever E . The adjustment for the depth to which the cutter enters the work ismade on the work slide

,the squared shaft K being provided for

THREAD MILLING 291

this pu rpose . This shaft has amicrometer collar for acc uratelygaging the depth of themilled groove.

I f necessary , the relative position between the cu tter and c amblank can be varied. Suppose it is desired to alter the positionof the camgroove slightly fromthat arbitrarily fixed by the location of the driving pin which passes through the work into thefaceplate. Thefirst step would be tomove lever L to the neutralposition which disengages the clu tch which drives the workspindle. Lever M is then turned through one-twelfth of a revolution , after which the clu tch is te-engaged by lever L . Thisclu tch has twelve teeth and the result of this operation is to temesh the clutch one tooth ahead of

.

its former position . By

means of gearing in the work head,the resultantmovement of

the camrelative to the cutter amounts to one-fou rth degree.

Thismachine has a pump for supplying lubrican t to the cut

ter, but a strong blast of air for removing the chips and coolingthe cu tter has been found an excellent substitu te for a lubricant

,

even whenmilling steel cams .

Thread M illing. In many lines of manufactu re threadswhich were formerly cut with a single-pointed tool in an enginelathe are now formed bymilling inmachines designed for threadmilling. The thread ismilled by a cutter of the required Shapewhich is set to correspond with the helix angle of the thread .

Somemachines are so designed that the work rotates in a fixed

position and the cu tter slide ismoved along themachine bed bya lead- screw that is connected with the work-spindle throughsuitable change gears. There is also another type of machine

,

the cu tter of°

which rotates in a fixed position while the workrevolves and at the same time feeds forward at a rate proportionalto the lead of the thread beingmilled .

Pratt Whitney Thread Milling Machine . This machine,

which is shown in Fig. 47 , is the type in which the part to bethreaded rotates in a fixed position while the thread ismilled bya cuttermounted on a cu tter head which is fed along the bed at

the proper rate by suitable gearing. The cu tter is set in linewith the angle of the thread bymeans of a wormand worm-gear

adjustment. This particular machine is designed for milling

292 MILLING MACHINES

large screws of coarse pitch , such as elevator worms,worms for

gun mounts and for other heavy threading operations . I t is

driven froma cone pulley (seen at the left-hand end of themachine) which ismounted on the end of a horizontal splined shaftextending along the rear of the bed . Fromthis shaft the cutterspindle , headstock spindle and lead-screw are rotated . Motionis transmitted to the cutter spindle through a vertical telescopicshaft and bevel gears, and to the headstock spindle through a

gear-box which enables the speeds to be varied .

Fig . 47 . Pratt Whitney Thread Milling Machine

The lead-screw,which traverses the carriage and the cutter

head along the bed at the required rate , is rotated through change

gears so that threads or spirals,in a great variety of pitches or

leads, can b emilled . The headstock and the tai lstock spindles

aremade hollow so that work up to 3% inches in diameter canpass through . This featuremakes it possible to mill screws ofalmost any length , provided the overhanging ends are suitablysupported . The part to b e threaded is gripped by a chuck of thedrawback collet type

,in the headstock spindle . Whenever

possible,the ou ter end of the work should be supported by a

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294 MILLING MACHINES

the cu tter for depth of cut, and it is provided with amicrometerdial graduated to thousandths of an inch . There is also a stopat C which can be used for locating the cutter in the same position or at the same depth

, either whenmilling duplicate threadsor the grooves ofmu ltiple-threaded worms or screws . The traverse of the carriage is au tomatically controlled by two stopsseen on the rod extending along the front of themachine . The

hand lever D, to which the trip-rod is connected is used to con

Fig . 48 . Lees-Bradner Thread M illing Machine

trol the traverse of the carriage . When this lever is in the neutral

position,as shown ,

the carriage remains stationary , and whenit is thrown to the right , the carriagemoves to the left. Whenthe small stop collar is engaged by the carriage the feed clutchis disconnected; then if a thread were being milled ,

the cutter

would be backed out of the thread groove and lever D thrown tothe left

,thus causing the carriage to return to the starting point

for another cu t. The stop collar at the right of the handwheel

should be set for stopping the return movement at the properpoint, by throwing the lever D to the neutral position .

THREAD MILLING 295

The work is either held on the centers or in a collet chuck at theheadstock end and on a center at the tailstock end. The collet

chuck should be used if possible . The index plate E is for indexing when cutting multiple threads or spiral gears. Thestarting and stopping of themachine is controlled by hand leverF . Whenmilling very fine threads a hob type of cu tter is usedin stead of a regular formed cu tter. A follow-rest is suppliedwi th thismachine for supporting flexible parts . This is attachedto the cutter slide and has an independent side adjustment sothat the work c an be supported either ahead of or behind the

Fig. 49. Universal Thread M illing Machine

cutter . This machine will mill threads or grooves varying inlead from5

16 inch to 96 inches.

Universal Thread M illing Machine. The threadmillingmachine illustrated in Fig. 49 is the type in which the lead-screw

and work revolve and feed forward together, while the thread is

milled by a cu tter rotating in a fixed position . The lead-screw

L ismounted over the center of the bed and in direct line withthe screw that is beingmilled . The latter is gripped in a chuck

mounted upon a carriage which slides along the ways of the bed.

The cutter-head is located at the right-hand end of themachine,

296 M ILLING MACHINES

and the work is supported near the point where themilling cu tteroperates by an expansion bushing or steadyrest.

Themachine is driven by two pulleys A and B ,which transmit

power to the lead-sc rew and cu tter, respectively, by the univer

sally-jointed shafts C and D. Shaft C connects with a shaft on

which a friction roller ismounted , and this roller, in turn , bears

against and rotates disk F. The shaft carrying the friction disktransmits power through a wormto a worm-wheel having a

threaded hub through which the lead-screw passes . A key in

the worm-wheel engages a spline in the lead-screw, thus caus

ing the latter to revolve . The lead-screw also passes through a

split nut, the position of which is fixed so that the rotation of the

lead-screw results in a longitudinal movement. The handle G

serves to engage or disengage the split nut and the lead-screw.

The speed at which the lead-screw rotates can be varied bychanging the radial position of the friction driving roller by

means of a connecting screw and crank. This change does not

aff ect the lead or pitch of the thread beingmilled , b ut serves tovary themilling speed . Difi

'

erent pitches are obtained bymeansof a gear-box on the carriage through whichmotion is transmittedfromthe lead-screw to the work. There is a gear on the end

of the lead-screw which drives , through the gear-box , a large

spur gear located back of the chuck . This last gear of the train

is fastened to a cylindrical part to which the chuck is also at

tached,and it rotates both the chuck and work. Obviously,

the speed at which the work revolves and,consequen tly, the

pitch of the thread that ismilled , depends upon the ratio of thegears in the gear-box. For instance , if the gears were so proportioned that the lead-sc rew and work rotated at the samespeed

,a thread would b emilled having the same lead as the thread

on the lead-screw. I f the work rotated faster than the lead

screw,a finer lead of thread wou ld be obtained, whereas, if it

rotated slower,the lead or pitch would be coarser than that of

the lead-screw.

The cu tter arbor is driven fromshaftD through bevel and Spurgearing, so arranged that the cu tter can be swiveled about a

pivot, 90 degrees either to the right or left of the central posi

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298 MILLING MACHINES

it is necessary to take asmany separate cu ts as there are Singleor independent threads or grooves in the screw . For instance

,

a double thread would require two cuts, a triple thread threecu ts

, and so on . In order to hold the blank secu rely and prev en tit fromslipping in the chuck , an auxiliary dog or coupling issecured to the work and fits over one of the chu ck jaws to give a

positive drive.

Fig. 50 illustrates examples of work done on the universalmachine, which can be used not only for threadmilling b ut formany other spiral milling operations. The same general typeofmachine

,illustrated in Fig. 49, is alsomade in a simpler form

which is not equipped wi th a gear-box for varying the pitch of

the threadmilled , b utmust be provided with a lead-screw havinga pitch corresponding to the pitch of the thread to be milled .

This “ duplicating ” type of machine is especially adapted for

milling large numbers of screws of the same pitch . It is providedwith an indexing coupling similar to the one previously referredto

,for use whenmillingmultiple threads.

INDEX

A lina -Boswell radius planing attachmentAluminum,

formofmilling c utter to use for

lubricant to use whenmilling .

Angular cutters ,method ofmilling teethAngular indexing .

Angular planing .

Arbors for holding c utters onmillingmachineAttachment, c ircularmillingc ircularmilling , applied to verticalmachinefor circ ular planing on shaper .

for cutting large gears inmillingmachineformachining clutches on shaper

formilling taperfor planing c urved surfaces

for planing spiral flutes .

Slotting, formillingmachineuniversal

,applied to spiralmilling

verticalmilling

Betts slottingmachineBevel gear, angular position of b lank formilling teethc utting teeth inmillingmachinefinishingmilled teeth by filing .

offset of cutter formilling teethselec ting cutter formilling teeth

Braces and stop-

pins for planer

Brasses for oonnec ting-rod,milling on verticalmachine

Brown Sharpe Lincoln- typemillingmachine

Brown Sharpe universalmilling machineBrowne 8: Sharpe verticalmillingmachine

Cam, cylinder,milling on Garvinmachinefaoe

,milling on Garv inmachine

Cammilling in a universalmillingmachine .

Cammillingmachine, Rowbottomvertical typeCamor formmillingmachine, Garv inCenters, indexing for planer work .

Centering cutter formilling keyway

300 INDEx

Centering c utter with work arborChain sprockets ,method ofmilling teethChange-gears, calculating for helical or spiralmillingfor diflerential indexing

Channeling connecting-rods on horizontalmachineChordal thickness of Spur gear tooth,method of determining

Chuck for planer

planer, points on using

Cincinnati plainmillingmachineCincinnati verticalmillingmachine

Circularmilling, continuousCircularmilling attachmentapplied to verticalmachine

Circular planing attachments

Clamps and bolts for holding work on planer

Clamps, finger, application of .

Clamping , distortion of work caused by

Clamping thin plates for planing .

Clearance angle for planer tools .

Clearance and slope angles for slotter tools

Clutch teeth,methods ofmillingClutches , shaper attachment formachiningCochrane-Bly universal shaper

Compensatingmillingmachine dog or driverCompound indexingrule for determining indexingmovements .

Concave planing attachment for ShaperConnec ting-rod brasses,milling on verticalmachineConnecting-rods , channeling on horizontalmachineContinuous circularmilling .

Crank shaper, general desc ription of .

Cross-head set up for planing

Cross-rail, planer,methods of testing alignmentposition relative to work .

Cutters, angular,method ofmilling teethmethod of centering with work arbor

milling flutes in straight-fluted type

milling , rotation of relative to feed

milling spiral flutes in c utter blankCylinder cammilling on Garv inmachineCylinders,method of planing locomotiveCylindrical parts,methods of holding, on planet

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302 INDEX

Helix or spiral angle,method of determiningHobbing and gashing a worm-wheel inmillingmachineHorizontal and verticalmillingmachine, Ingersoll

multiple-spindle type .

open-side type .

Independent housing or planer floor stand

Index centers , applied to planer

Index head equipped with chuck for holding work

Index plates , high-number reversible typeIndex table for rac k-c utting attachmentIndexing, angular or in degrees

Brown Sharpe diflerentialmethod of

by combining simple and compound systemscompoundmethodcompound , rule for determining indexingmovementsdiflerential, determining sizes of change-gears

plain or simplemethoduse of sec tor in connec tion with

Indexing former plate for profiling fixtureIndexing or spira l head , construc tion of

example illustrating application of .

Indexing planing tool when c utting racks

Indexing type of profiling fixture .

Inserted-c utter planing tool .

Interlocking sidemillInternal stresses in castings, distortion caused by

"ack for supporting work on planer

Keywaymilling , centering c utter for

in shafts and other cylindrical work

method of setting cutter to depth

Lincoln-typemilling machine .

semi-automatic design .

Links for valvemotion , attachment for planingLub ricants formilling

INDEX 303

Magnetic chuck applied to planer

M illing , direc tion of feed and relative rotation of c utter

M illing c utters , angular,method ofmilling teeth .

c utting teeth in end and sidemillsdifferent types of .

making spirally-fluted typemilling flutes in straight-fluted typeright and left-hand types

M illingmachine, adjusting and Operating column-and-knee type

plain column-and-knee type

construc tion of vertical type .

‘

difference between plain and universal types .

horizontal duplex designhorizontalmultiple-head type .

horizontal Open-side typehorizontal typeIngersoll, combined horizontal and vertical type

M illing speeds and feeds

Morton draw-c ut shaper

M ultiple—head type ofmillingmachineM ultiple index centers

Multiple or gangmethod of planing

Nicked-tooth milling c utter .

Niles-Bement-Pond planer with reversingmotor drive

Open-side horizontalmillingmachineOpen

-side type of planer

Parallel strips for planer .

P itch of c utter to use for spiral gears

Plainmillingmachine of column-and-knee type

P laners , alignment of cross-railapplication of doub le-head type .

construc tional features of .

different forms of clamps and bolts fordouble-c utting typedouble-head type .

holding castings of irregular shape on

holding work on .

method of adjusting and Operating

Open-side type .

Spiral-geared type .

304 11mm:P laners , use of aide-heads

variable speed drives for . .

Planer chuck ,magnetic type and its application .

Planer index centers, application of .

Planer jack for supporting work .

points on grindingunder-c utting, with lifting latch

various forms of .

holding work for, by imbedding in plaster of Paris or wax

multiple or gangmethod .

P laning curved surfaces

Planing rack teeth

P laning spiral flutes with special attachmentsP laning vertical and angular surfaces

P laning speeds, average.

net or ac tual cutting speed

Pratt Whitney semi-automatic profilingmachinePratt Whitney threadmillingmachinePratt Whitney two-spindle profilingmachinePratt Whitney vertical shaper ”

Profilemilling ,miscellaneous examples ofProfiling with combination former . .

Profiling fixture, indexing typewith indexing former plate

P rofiling fixtures and formers, different types of

P rofilingmachine, Pratt Whitney two-spindle

Rack cutting in themillingmachiRack cutting on the planer .

method of indexing the tool .

Rack-c utting attachment, index table forRadius planing

Reversingmechanismof planer .

Reversingmotor drive for planer .

Rosin and wax, use of for holding planer work

Rowbottomvertical cammillingmachine

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306 INDEX

Spur gear.methods of cutting large sizes inmillingmachinesetting cutter to depth of

tes ting thicknes s of tooth at pitch line

Spur gear c utter, tes ting position .

Stop-pins and braces for planer .

Surface gage and its application

Surfacemilling in verticalmachine

Thread millingmachine, Lees-Bradner .

Pratt WhitneyUniversal

Thurston under-cutting diemillingmachineTools for planing , points on grinding

various forms ofTools for slottingmachineTrailer frames , locomotive,milling on horizontalmachineT-slots , c irc ular,milling on vertical machinec utting inmillingmachine

Under-cutting diemillingmachine, ThurstonUnder-c utting planer tool with lifting latch .

Universal attachment applied to spiralmillingUniversal millingmachine, Brown Sharpe .

Universal shaper, Cochrane-BIyUniversal threadmillingmachineUniversal vise formillingmachine

Variable speed drives for planersV-b locks for holding cylindrical parts on planer

V-b locks,method of planing acc urate .

Vertical and horizontalmillingmachine, comb inedVertical cammillingmachine, Rowbottom.

Verticalmilling , examples of t

Verticalmilling attachment .

Verticalmillingmachine, applied to surfacemillingconstruc tion of .

milling a c ircular T-slot

Vertical planing .

tools used for .

Vises for holding work onmillingmachine

Walkermagnetic planer chuck .

Wax and rosin, use of for holding planer work

Whitney hand millingmachine .

Worm-wheel,angle of table for gashing .

gashing and hobbing inmillingmachine 207- 2 1r