popular mechanics - hobby lathe#2

8/14/2019 Popular Mechanics - Hobby Lathe#2

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A p r i l 9, 1942 355 W O R K S H O P

I do hope it will induce others to producea scale drawing of s imi lar in teres t . Nodoubt th ey will find as m an y snags as I did,when they come to put t h e ir ideas onpaper ; but , above al l , le t us have theoriginal ideas included and without fixingprice l imits , al though a measure of s im-plicity will have to be included, otherwisethe design will surely get out of hand, asthere would appear to be no limits whenonce a start is made_ Since no thought ofproduction is being contemplated, th ere isno need t o let pr ice ups et idea s. If, however,anyone does hope to see his design produced,no doubt the prospective manufacturer willwhittle down the design until it reaches hisprice limit. Any th ought of ma nu factu renever ent ered m y mind, so pr ice didntinterfere, though much thought was given

to simplifying the various parts. Hereshoping, therefore, that any interest takenin this article will form a bait for others t ocome forward with their lathe designs, notnecessarily ideals, th ough incorpora ting oneor two original ideas, or should I say ideasoriginal ly appl ied in case there i s anymisconception as to their origin. To this Ihad better add, that I claim no originalityin my own drawings.

D r a w i n g sNow a word about the drawings. I have

given plan, elevation and end views in pre-ference to a projected view, in case anyonewishes to read off dimensions. Sectionaldrawings of all the parts would take up toomuch space, although, of course, they hadto be made before the outl ine drawingscould be a r rived a t. In lieu of sections I ha veincluded a description so that readers mayform an idea of wha t is hidden from view.

G e n e r a l F e a t u r e s o f t h e D es i g nThe machine was designed to mount on

top of a bench, without cutting away anyof the latter and to operate as a completeunit without any separate motor, belting,countershaft, or overhead gear other thanthat which was part of the machine itself.There had to be no belts to change, and asmuch as possible of the mechanism to beenclosed. Also, there would have been nogear wheels to change, but that was foundto be impracticable unless some limit wasset on the number of threads to be cut.After considering tha t t he am at eur u ses hislathe to cut worms and spirals, the necessityof very fine feeds at times, and also, at oddtimes, the- driving of the leadscrew indepen-dent of the mandrel, not to mention manyother uses to which loose gear wheels can beput, the adoption of the simple quadrantand standard set of change wheels waspreferred to the quick-change version with

limited uses. Not a convincing argument Iadm it, but it scores in simplicity an d in itsuniversal application, and the more universalthe machine can be made the better, at leastfrom the amateurs point of view.

Electricity being available, advantage wasnaturally taken of this as a source of power.Normal accessories such as chucks, face-plate, a ngle-plates, etc., ar e ass um ed to beavailable and are therefore not included inthe drawings.

T h e B e dThis is a box form casting closed at the

top and open at the bottom, well ribbedinside, and with plenty of metal in it, toensu re rigidity. Exten sions cast with th ebed support the motor and columns. Three-point suspension is adopted, with rockers

at the headstock end and a sphere at thetail end. This form of anchorage provides aready means of upending the machine to getat the mechanism underneath necessary,since there are no inspection plates. As,however, there i s l i t t l e undernea th torequire inspection, that task will only occurat very long intervals and would be simpleenough when it did occur. Besides this, allbolting-down strains are relieved from thebed.

The a xis of th e ma ndr el is offset from th ecentre line of the bed, the principal objecthere being to get a dequat e support immedi-atelv underneath the turning tool withoutoverhanging the front edge o f the bed anymore than was reasonably necessary. Addedto this, the offsetting allowed for an entirelysepar at e way to be form ed, along which t hesaddle could travel without touching anypar t of th e bed tr aversed by the t ailstock.

Comparatively large wearing surfaces were

provided for a lathe of this size. vet even ifwear did -occur, this could not affect theoriginal alignment of the head- and tail-stock.

No GapNo gap was thought necessary, since the

cent res were ra ised to 4-1/2 in. This height wasadopted for two reasons, first it provides afair m aximum t urning size for a n a mat eurslat he, alt hough a gap could ea sily be got byscooping out the bed immediately under-neath the faceplate, whilst stil l retainingthe desired front way the entire length ofthe bed. The second and most importantreason was to get ample room over thesaddle. The top and vertical faces of thefront shear of the bed take practically allthe pressure of the turning tool, the balancebeing taken on a section of the bed nottouched by the tailstock.

(T o be cont inu ed)


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April 30, 1942 421

Mr . J . W. P a t t i son

D es ign s a L a t h e -

a n d s o m e G a d g e t s f o r i t

T HE lower half of the jig-saw is a casting,enclosine a disc crank which imparts a1-1/4-in. stroke to the saw. Supported by it is

a table which may be tilted and clamped atany conven ien t ang le . The un i t i s secured

t o t h e l a t h e b e d b y a s i n g l e b o l t p a s s i n gthrough a hole dr i l led there in . The upperhalf is brought into register with it by some

def ini te marking on the auxi l iary bed. In

* Continued from page 396, M.E.,ApriE 23,1942.

this way, the set-up should only be the work

of a moment .For sawing out in t r ica te shapes in sheet

metal the jig-saw is idea!, and any material

may be sawn, if a suitable blade or knife isemployed. Wood, bakelite, fibre, etc., maybe sawn, and such material as cloth, cut with

a knife blade. By using the lower half of the

machine alone with a sabre saw in its chuck,i n t r i c a t e s h a p e s m a y b e c u t i n t h i c k e r

mater ia ls and should be useful in pat ternmaking .

JIG SAW ffEAARM TO CARRY

DR/L 1 HEAD.

SPRING FOOT

RISING & FALLINGCIRCULAR SAW

D IA TO FIT AuXSAODLE

Universal arm shown carrying jig-saw

head, together with circular saw and

jig filing machine.


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W O R K S H O P 4 2 2 T HE MODE L E NGI NE E R

By removing the saw clamp, the remainingexposed socket becomes available for smallmachine files. With the mechanism set tothe bottom of its stroke. there is plen tv ofroom to swing the circular saw into position.Either metal or woodcutting saws may beused and the swing movement of the saw

ar m is, th e equivalent of a r ising a nd fallingtable ; an d added to this, there is th e tiltingmovemen t of th e ta ble itself. An ad iust able

suggesting that it would be amply strongenough t o perform th is task.

There are numerous other uses to whichthe machine and its gadgets could be put,.

fence is clamped to the front edge of thetable, and two slots are included for use withan angle-gauge. With a gap-piece removedfrom t he cent re of th e ta ble, it would appea rpossible to- attempt even surface grinding,although i ts scope would obviously belimited.

U n i v e r s a l d r i ll in g a n dm i l l i n g m a c h i n e b o r e dt o c a r r y a n y o f t h er o t a t a b l e t o o l s . S i m i -

l a r l y , a s m a l l fa c e p la t eo r s lo t t e d t a b l e or a n y -t h i n g f it t e d w i t h a 1 i n .d i a . h o l d i n g p i e c e

c ou l d b e m o u n t e d .

The other gadget is a universal millingslide and needs little description, except tomention that the gib-piece is adjusted byfour screws a nd ma y be locked by a h an dledclamping-screw. It will, of course, carry

any of the rotatable tools, being bored outI in. diameter for tha t purpose. Besides theus es to which t he a bove gadgets can be pu t,it would appear possible to do a little planingon anvthing mounted on the boring table,either-by moving th e work m oun ted th ereonagainst a tool held in the auxiliary saddle, orby swinging th e au xiliar y bed ra dially. Thislatter experiment su ggests, also, tha t with asuitable clapper-box the tailstock might beused as a shaper for anything within its

i h l di i f h

as indeed there are-many more gadgetswhich could be added. until the machinebecame a veritable concentrated machine-

shop ; but as these appear to be never-ending, imagination must be left to thereader to think th em out for himself.

Amateur T o o l m ak i n g(Continued from page 420)

edges just down to the cutting edges, nomore and no less. Painting the lands with plumbers black or red lead facili-tates the accuracy of this filing operation.

After heat treatment, touch up the cuttingedge flats a nd t he flut es with Carborun dumoil slips, and again you have quite a pro-fessional-looking job.

T w i s t D r i l l sAgain flute a piece of silver-steel or reduced

stock of desired diam eter with two flutes, a salready described for t aps a nd r eamers a ndfinish bv grinding, but flute a longer lengththan that-required for finishing. Grippmg

the shank of the work tiehtlv in the chuckof the lathe and the other end in the tailstockchuck, form the twist, working back thetailstock to keep the work straight. Removethe damaged fluted part and, after straighten-ing and grinding the point, t h e drill is-readyfor ha rden ing an d tem pering. Sizes betweenabout 1/8in. and 5/16 in. can be successfullyma de, but th e absence of lands m akes t hesehome-made drills unsuitable for very deepdrilling, as th ey tend t o bind.

H e a t T r e a t m e n tA muffle fur na ce is a very useful adjun ct

for the amateur toolmaker. Procure half adozen firebricks approximately 4 in. x 6 in.x l i n . and secure four t oge the r wi thclamping straps to form a chamber approxi-matelv 4 in. wide, 2 in. deep and 6 in. longan d secur e an oth er of th e bricks t o close oneend of the chamber. With an old hacksaw,cut strips from the remaining brick to layacross th e bott om of th e cha mber to support

articles being treated.Moun t th e whole on a suita ble stan d

applicable to your gas burner or blowlamp,as t he case ma v be. With a half-Dint size ofth e lat ter , ta ps, dies, ream ers, etc., up t o1/2 in. can be sa t isfactori ly har dened a ndtempered, and, of course, the muffle issuitable for many other heat treatment jobs.The residual heat at the back of the muff leprovides all that is required for temperings m a l l t o o l s a t a t e m p e r a t u r e uniform

h h i h i


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376.

THE MODEL ENGINEER

* Mr . J . W. Pattison

D es ig n s a L a t h e -

a n d S u g g e s t s s o m e G a d g e t s f o r i t

WHEN the drawings were completed, thesesurfaces came in for a lot of criticism

from myself. Particularly, they did notachieve one of the objects desired, that beingslides which would remain entirely free fromchips or, even worse, grit if grinding was to beattempted. Any attempt to eliminate thisdisadvantage appeared to bring i n even

greater troubles. An open-top bed would dolittle to relieve the situation, as the slides would still remain exposed. Transferringthe slides to the front and rear face of thebed was thought of, but this meant no endof troubles, such as leadscrew mounting, tail-stock fixing, etc. On the whole, therefore,it was thought better to leave it alone, andpossibly provide some form of telescopicapron to cover the exposed parts ; but

whether this would be worth the trouble,

however, is doubtful.It is assumed that the bed would be

ground, and its accuracy would dependupon the parallelism of the vertical faces ofthe front and back shears of the bed, and,of course, the flatness of the top surface.As the head and tailstock are both locatedagainst the rear vertical face, and, as alreadymentioned, the saddle is located against thevertical face of the front shear, alignmentshould be preserved at all times.

The Headstock

First in importance is the mandrel. Ithad to be large because I particularly wanted l-in. collet capacity : therefore. theminimum diameter had to be 2 in.

Only when it was drawn out did I fullyrealise why a large mandrel would beexpensive, for almost everything else in theheadstock had to be increased in like propor-tion. Just imagine what diameter pinion isrequired and you will soon realise what

dimensions a 6 to 1 back gear will assume.Also, one cannot mount standard-size changewheels direct on so large a mandrel, assumingit is to be bored out maximum diameter asin this case. Quite a lot of scheming had tobe employed to keep everything withinreasonable dimensions and yet providelarge wearing surfaces.

Everyone appears to be in general

* Continued from page 355, M.E., April 9,

1942

agreement that plain bearings are best forlathe mandrels, and as I have no faultto find with phosphor-bronze carrying ahardened and ground mandrel, that is whatis suggested. No doubt, cast-iron is equallygood. though I have never worked a latheso fitted long enough to form any opinionof my own. Personally, I would favour ball-

bearings. but dread the warnings of others.I have experienced some of the troubles

attributed to ball-bearings, but as thesebearings had seen a lot of service I was notconvinced that the faults could not berectified. Whatever the reason, it stillremains a mystery to me why the makersof some of the finest precision lathesemployed on the production of delicate

work, such as instrument making, use ball-bearing headstocks and expound their

virtues as though they were the main reasonfor the accurate work produced. Will some-one with experience of these small modernmachines let us have some facts ? It wouldappear to me that many of the troubles ofthe earlier machines must have been over-come in the modern type. However, hardphosphor - bronze adequately lubricated,appears satisfactory enough to specify inthis case, These bearings are coned on theoutside for adjustment and are of square

dimensions as regards length to diameter.Both front and rear bearings are of thesame size. A ball-thrust washer takes theend pressure on the mandrel.

The drive enters the headstock by avertical shaft, thence to a two-speed gearthrough a worm and wheel. A 5/8in. face isallowed on all gears in, the headstock. Thegear change is affected bv a lever on theoutside ofthe head, giving high, neutral andlow, the neutra l posi t ion a l lowing themotor to be run without turning themandrel.

From the top of the vertical shaft theauxiliary drive is taken through a clutch,controlled by a small spring-loaded leverplaced near the rear bearing. A correspond-ing lever near the front bearing works thetumbler gears.

Provision is made for dividing-plates at\the front of the head. The protruding shaft

rries at its rear end a steel worm 1-1/8 in. in

hi h h i h h d l


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April 16, 1942 377

gear. This shaft ishoused in an eccen-tric sleeve bearingto allow for the

worm being takenin and out of mesh,and for adjustmentof backlash. Thefront end of theshaft carries thequadrant-arm andspr ing p lunger ,whilst changeabledividing-plates andsectors are carriedon the front end ofthe bearing. It isalso possible to fixa handle in placeof the quadrant and

plunger and thusform a hand driveto use in conjunc-tion with the per-manently attachedplate situated at therear end of themandrel. Thislatter plate is 1/2 in.thick and 4 in.diameter, drilled

around its edge with24 holes, 1/4 in.diameter, which areentered at right-angles by an equalnumber of 1/8 in.t apped ho l eslocated around theside face of theplate. Being per-manently fixed, it

is always availablefor the direct divid-ing of work intosquares, hexagons,etc., the lockingplunger being a5/16-in. knurled-

h e a d e d sc r ew ,

turned 1/4 in. to enterthe holes in theplate, and workingin a lug cast in the

head. Check count-ing may be done byinserting set-screwsin the tapped holescorresponding tothose required f o rindexing.

Two adjustablestops, having 1/4-in.turned legs, may be

WORKSHOP


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WORKSHOP 378 THE MODEL ENGINEER

entered into any of the holes in the plate and of taking care of all the power likely to befound in an amateurs lathe motor.locked by set-screws. Set tangentially on the

plate, they come up against the cast lug whichacts as a stop. Thus by using the handle onthe other dividing gear to turn the mandrel,end-milling of an arc, or any similar work,may be performed on anything held on thechuck, the positive stops presentmg the

rotation of the work beyond a predetermineddistance. This idea is similar to one seen at the

M.E. exhibition some years ago, and Itrust the originator of this useful device willpardon my having used it here.

The only other item in the headstock is aclutch which connects the start of the screw-cutting train. Thus, everything is com-pletely enclosed and runs in oil, adequatelubrication being vitally necessary with such

a large mandrel running in plain bearings athigh speeds. A cover-plate is provided forinspection and assemblv. The headstock isbolted down to the lathe bed and occupiesthe full width of the latter.

From the headstock the vertical shaftextends doivnwards into the bed, andexpanding Vee-pulleys connect it to themotor. This form of drive is a similararrangement to that found on the oldZenith and Rudge motor-cycles. The former

employed an expanding pulley on the engineshaft, and the back wheel with its belt rim was moved in or out to preserve the tensionon the belt. The Rudge was similar, onlyhere both pulleys expanded and contractedalternately to get the variable ratio andmaintain the tension on the belt at the sametime. It is this latter arrangement which isused here.

Two 6-in. pulleys give an infinitelyvariable speed between 30 and 2,200 r.p.m.

to the mandrel, the two-speed gear in thehead giving a slight overlap in the middleof this range. Variation of speed is con-trolled by turning the hand-wheel placedconveniently at the front of the bed.

The motor is mounted vertically on anextension of the lathe bed, and thus exposesthe free end of its shaft, which is equipped with a pulley for use at any time should anextra auxiliary drive be required. Tomention one example, should it b e necessaryto drive the leadscrew independently of themandrel, a belt could be taken from hereto a worm drive, connecting with the geartrain.

The main auxiliary drive is by flexiblecable taken off the top of the vertical shaftin the headstock. Judging from my ownshort experience of a home-made versionof this type of drive, it should be a real boon.It certainly is more adaptable than anyoverhead, and standard cable of no morethan 5/8-in. outside diameter is quite capable

Among other reasons, it was to exploitthis form of drive fully that l-in. colletcapacity was wanted in the mandrel andtailstock, since it was thought that if a well-made head of l-in. diameter carrying screwo n collet chucks was attached to this drive,

this head could be slipped into- the mandreland some quite delicate work turned with it.To go a step farther and get down to work ofthe watch-making variety, possibly a furtherhead would be required, together with a barbed, this latter fitting into a hole bored inthe headstock casting. Whether thenecessary accuracy could be attained, how-ever, is quite another matter. In any case,such an arrangement is only mentioned as apossibility, and no provision is made for

anything of the sort here. The speed range available from theflexible shaft is variable between 480 and4,350 r.p.m.

The Tailstock

In capacity, this could duplicate the head-stock, when all accessories would b e inter-changeable. A solid tailstock is to bepreferred to ensure preservation of theoriginal alignment, as it may well be called

upon to perform other jobs than thatusually associated with a tailstock. Slighttaper turning could be accomplished byusing an adjustable offset centre, or bydisengaging the slide nut and using theauxiliary bed, set at an angle, as a saddleguide. The tailstock spindle, is equipped with the usual screw and hand-wheel, whichmay be disengaged and a lever brought intouse. This lever could be swung out of the

way when not in use. Rotation of the

mandrel is prevented by a block, sliding ina machined slot in the casting. The tailstockassembly is held firmly against the verticalrear face of the bed. being drawn up tight

the top surface at the same

use-w uld be made of this fitment for boringand m ling. The longitudinal motion alongthe lat e bed was of first importance. Noless than 14 in. of sliding surface is used,and as this is onlv 2 in. wide. perfect slidingmotion should be obtained, the rear of thesaddle merely acting as a steady to keep itlevel. Adjustment is by gib-piece along thefront, whilst a stiff gib holds the rear of thesaddle up to its work.

(To be con tin ued)


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394 T H E M O D E L ENGINEER

*Mr . J . W. P a t t i son

Designs a L a t h e -

a n d S u g g e s t s s o m e G a d g e t s f o r i t

DUE to the exceptional length of the frontslide, the rear of this saddle is not

called upon to take any of the side thrustoccasioned in use ; therefore, binding andchatter should not occur. Long cross-traverse was required to provide for millinglong lengths at one setting. A small table didnot provide facilities for holding long workand traversing past the mandrel, with a full

length bearing all the way, hence theadoption of an extreme ly long tabl e.Almost 12 in. of traverse can be obtained

with full bearing all the way, and to attainthis, the angle of the slides would have tobe reversed so as to retain a reasonable sizedgib strip. For normal turning, this slide

would be well back out of the way, and would not appear to have any disadvantage,therefore.A n o t h e r necessity is some form of

rising movement to bring the work tocentre height and put on cuts. To achievethis, the saddle has a false base and thatpart containing the slide can be raised byhand-wheel and securely locked at the rear,to form a variable triangle with the bed. Thebearings which form the axis of this risingand falling movement are 7/8 in. diameterand are adjustable.

The feed screw has a bearing at both endsand a graduated dial at the front end,

which can be set at zero. This feedscrew can be instantly disengaged fromits gunmetal nut by giving a few turnsto the set-screw, set in the right-hand sideof the saddle. By releasing this nut, and

with a piece of 1 in. diameter rod boltedvertically on top of the table, to engage acorresponding hole provided in the saddleof the auxiliary bed: then if this latter is setto a predetermined angle, the tool willfollow this angle in taper turning. Anotheraddition to the slide rest which would beuseful when milling would be an adjustablestop. Though not shown in the drawing, itsfitting should be obvious to anyone.

The Apron

Simplicity is in evidence here, as noprovision is made for automatic feed, exceptthat normally obtained by change-wheels

* Continued from page 378, M.E., April 16,1942.

and the leadscrew. Rack-and-pinion is addedfor quick traverse along the bed and isassisted by a large hand-wheel. Two half-nuts, each 3 in. long, are used to engage theleadscrew, but they are mounted on rockersinstead of slides. Although this does not givea true up and down movement, the error isso slight, and the advantages so great, thatit was adopted. The difficulty here was to

get a long bearing surface, and as the lead-screw was to be tucked away well up under-neath the front shear of the bed, long slides

were impracticable, due to the heightavailable ; thus, rockers with long shaftsappeared to be a much better arrangement.Engagement would be facilitated by theadoption of an Acme threaded leadscrew.A projection cast flush with the forwardedge of the apron engages the automatictrips.

The Leadscrew

This is substantial, being 7/8 in. diameter,and has an Acme thread, 8 per inch. Theadoption of 8 t.p.i. is open to criticism, butit nevertheless has many advantages. Al lthrust is taken at the headstock end, wherethe plain portion runs in a bronze bush andhas an adjustable thrust-washer. The drivecan be put in and out of engagement by adog clutch, operated by a small knob at the

front which has a snap action so that itremains positively in or out. The shaft on which this knob is carried is extended alongthe bed, and thus can be set to operateautomatically. The main purpose of thisclutch is to have the leadscrew entirelyfree from the gear train so that it can beoperated manually by the graduated wheelat its far end without dismantling the geartrain. The single-toothed dog clutch in theheadstock, which works at the beginning ofthe screwcutting train, also has its controlbrought to the front of the lathe andoperated similarly. The more normal methodof screwcutting could be used by disregardingthis last clutch and fitting an indicator atthe end of the saddle apron. Either method,however, requires only a simple fitment.

The Gear Train

This is a standard arrangement wherebyloose change-wheels are mounted on aquadrant. A single slot is all that is required,


10/13

STEADY COLUMN

REVOL V/ NC SADDLF

REVERSIEL EBRACKET _ZSPEED GEAR CHANGE

CLUTCH CONTROL.

Two end views : Left, headstock ; Right, tailstock of t he self-contained universal model engineers lathe.


11/13

WORKSHOP THE MODEL ENGINEER

due to the long length of the quadrant. Itmight be advantageous to have the studsmilled to slide in this slot, to prevent thetendency to revolve when being tightenedup. Splined sleeves are suggested, and asquare-holed washer and knurled-headedscrew would appear to be as good a methodas any other, to secure the wheels. A ball-

handled screw is used to lock the quadrant.

Gadgets

The third hand arrangement, pre-viously referred to, could take the form of

FL EXIBL E D R I V E

coNNEGr .oNs

BOX

\DRILLING HEADWITHJAW CHUCK.

TURNING O R M I L L I N G H E A D

WITH COLLET C H O C K . .

Drilling, milling and grinding heads adopted for

universal mounting on the lathe.

an auxiliary bed mounted at the rear of thelathe and normally parallel to it.A truncated triangular bar is suggested,

clamped in a suitable bracket and mountedon a substantial vertical column, the latterbeing rigidly fixed to the main bed casting.A similar column fixed at the tail

end of the bed would act as a steady,keeping the auxiliary bed normally parallel with the lathe bed, yet allowing it to be setto any angle and clamped in position.

Clamping would be affected bv a locking bolton themain column, assisted by a radius-rodextending from the remote end of the bedto the other column. A screw and hand- wheel are provided to assist in raising andlowering the bed on the column. On thistriangular bed slides a saddle, traversed byanother screw and hand-wheel. The outer

part of the saddle is capable of movingaround its base and can be clamped inposition. It has a l-in. diameter hole boredin it to take any of the other accessories,including a slotted table. Work may bebolted to this table, or, alternatively, a toolmay be mounted here. It does not requiremuch imagination to realise the amount ofwork tha t could be accomplished by the aidof the flexible drive and with work mountedin full view.

Little need be said of the flexible drive, asit simply consists of a 3/8-in. diameter multi-stranded steel wire core, enclosed in anouter flexible casing which is oil tight, andhaving suitable solid splined ends to take upthe drive.

Drilling, Milling and Grinding Heads

Three heads for attachment to this driveare shown in the drawings, one geared forinternal grinding, as this requires anextremely high rate of revolutions ; another

for general work, such as drilling up to 1/2 in.capacity, and yet another, this time fitted with collet chucks, to be used for fineturning or to carry small milling cutters.All are 1 in. outside diameter and theirmounting is almost universal. Li ke theother gadgets, they will fit into the auxiliarysaddle, the collet chuck in head or tailstock,or the universal milling and drilling attach-ment. Hand drilling, sanding, buffing,polishing, etc., can be done, either on the

lathe or at a limited distance from it.

A Metal-cutting Jig-saw

Another gadget is the drill-arm which hasa lever feed, the lever remaining out of the

way when the arm is used for other purposes.A further gadget, fitting into this arm is theupper half of a metal-cutting jig-saw, whereit is secured by a set-screw. Adjustabletension on the saw blade can easily beobtained by raising or lowering the auxiliary

bed. This head contains the spring whichpreserves the tension on the saw bladeduring its return stroke. It also has aplunger which provides a blast of air at thepoint of sawing, thus keeping the workclear of cuttings. An adjustable rod,carrying a spring foot and roller saw guide,is inserted in the bracket, immediatelyalongside the head.

(To be continued)


12/13

April 30, 1942 421

* Mr . J . W. P a t t i son

D es ig n s a La t h e -

a n d s o m e G a d g e t s f o r i t

T HE lower half of the jig-saw is a casting,enclosing a disc crank which imparts a1-1/4-in. stroke to the saw. Supported by it is

a table which may be tilted and clamped ata n y convenient angle. The uni t i s secured

t o t he l a t he bed by a s i ng l e bo l t pa s s i ngthrough a hole dr i l led therein. The upperhalf is brought into register with it by some

defini te marking on the auxi l iary bed. In

* Continued from page 396, M.E.,April 23,1942.

this way, the set-up should only be the work

of a moment.For sawing out int r icate shapes in sheet

metal the jig-saw is idea!, and any material

may be sawn, if a suitable blade or knife isemployed. Wood, bakelite, fibre, etc., maybe sawn, and such material as cloth, cut with

a knife blade. By using the lower half of themachine alone with a sabre saw in its chuck,

i n t r i c a t e s h a p e s m a y b e c u t i n t h i c k e r

materials and should be useful in pat ternmaking.

JIG SAW ffEAARM TO CARRY

DR/L 1 HEAD.

SPRING FOOT

RISING & FALLING

CIRCULAR SAW

O/A TO FIT AUXSADDLE

Universal arm shown carrying jig-saw

head, together with circular saw and

jig filing machine.


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WORKSHOP 422 THE MODEL ENGINEER

By removing the saw clamp, the remainingexposed socket becomes available for smallmachine files. With the mechanism set tothe bottom of its stroke. there is plenty ofroom to swing the circular saw into position.Either metal or woodcutting saws may beused and the swing movement of the sawar m is, th e equivalent of a r ising and fallingtable ; an d added to this, t here is the t iltingmovement of th e ta ble itself. An adiu sta ble

suggesting that it would be amply strongenough to perform this task.

There are n um erous other uses t o whichthe machine and its gadgets could be put,.

fence is clamped to the front edge of thetable, and two slots are included for use withan angle-gauge. With a gap-piece removedfrom t he cent re of th e ta ble, it would a ppearpossible to attempt even surface grinding,although its scope would obviously bel imited.

, Un ive r sa l d r i ll ing a ndm i l l i n g m a c h i n e b o r e dt o c a r r y a n y o f t h ero t a t a b l e t o o ls . Simi -

l a r ly , a sm a l l f a c e p l a t eo r s l ot t e d t a b l e or a n y -

t h i n g f it t e d w i t h a 1 in .d i a . h o l d i n g - p iece

c o u ld b e m o u n t e d .

The other gadget is a universal millingslide and needs little description, except tomention that the gib-piece is adjusted byfour screws an d ma y be locked by a ha nd ledclamping-screw. It will, of course, carryany of the rotatable tools, being bored outI in. diameter for tha t purpose. Besides theuses t o which t he a bove gadgets can be put ,it would appear possible to do a little planingon anvthing mounted on the boring table,either-by moving th e work mounted t hereonagainst a tool held in the auxiliary saddle, orby swinging th e au xiliary bed ra dially. Thislatt er experimen t su ggests, also, th at with asuitable clapper-box the tailstock might beused as a shaper for anything within its

as indeed there are-many more gadgetswhich could be added. until the machinebecame a veritable concentrated machine-shop ; but as these appear to be never-ending, imagination must be left to thereader to think th em out for h imself.

Amateur T o o l m ak i n g(Continued from page 420)

edges just down to the cutting edges, nomore and no less. Painting the lands with plumbers black or red lead facili-tates the accuracy of this filing operation.After heat treatment, touch up the cuttingedge flats a nd t he flut es with Carboru ndumoil slips, and again you have quite a pro-fessiona l-lookin g job.

Twist Dr i l l s

Again flute a piece of silver-steel or reducedstock of desired dia met er with two flut es, asalready described for taps and reamers andfinish b y grinding, but flute a longer lengththan that-required for finishing. Grippingthe shank of the work tiehtlv in the chuck

of the lathe and the other end in the tailstockchuck, form the twist, working back theta ilstock t o keep th e work str aight. Removethe damaged fluted part and, after straighten-ing and grinding the point, t h e drill is-readyfor ha rden ing an d tempering. Sizes betweenabout 1/8in. and 5/16 in. can be successfullyma de, but th e absence of lan ds ma kes th esehome-made drills unsuitable for very deepdrilling, as th ey tend t o bind.

H e a t T r e a t m e n t

A muffle furnace is a very useful adjunctfor the amateur toolmaker. Procure half adozen firebricks approximately 4 in. x 6 in.x l in. and secure four together withclamping st ra ps to form a cham ber approxi-matelv 4 in. wide, 2 in. deep and 6 in. longan d secur e an oth er of th e bricks t o close oneend of the chamber. With an old hacksaw,cut strips from the remaining brick to layacross t he bott om of the chamber to supportar ticles being treat ed.

Moun t t he whole on a suit able sta ndapplicable to your gas burner or blowlamp,as t he case mav be. With a half-Dint size ofth e lat ter, ta ps, dies, reamer s, etc., up t o1/2 in. can be satisfactorily hardened andtempered, and, of course, the muffle issuitable for many other heat treatment jobs.The residual heat at the back of the muff leprovides all that is required for temperings m a l l t o o l s a t a t e m p e r a t u r e uniform

popular mechanics - hobby lathe#2

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