machine tools - avesİs

MACHINE TOOLS

1

WEEK 4 & 5Functions of Lathe

Working Principles of Lathe and its Mechanism

MAK4462 - MACHINE TOOLS


• The lathe machine is one of the oldest and most

important machine tools. As early as 1569, wood lathes were in use in

France.

• The lathe machine was adapted to metal cutting

in England during the Industrial Revolution.

LATHES



• Lathe machine also called “Engine Lathe” because the first type of lathe was driven by a steam engine.

LATHES



• Nearly, one third of machine tools operating in engineering plants are lathes.

• A lathe operates on the principle of a rotating workpiece and a fixed cutting tool.

• The cutting tool is feed into the workpiece, which rotates about its own axis, causing the workpiece to

be formed to the desired shape.

LATHES



• Lathes are normally robust in construction and they will, with good care, last for many years.

• It is not unusual for instance to see good lathes still in uses that are 50 years old.

LATHES



• To ensure good, accurate, trouble free use it is necessary that the correct maintenance routines are

regularly carried out and that important surfaces such as slide-ways are kept well protected so as to reduce wear and thus maintain good accuracy, and the lubricants used, are all factors that require your

attention.

LATHES



LATHESLathe Operations and Tools



LATHESLathe Operations




Knurling

It is used to produce regular patterned

rough surface. Knurling tool

containing a set of hardened steel rollers with teeth cut on them

is used.




Knurling

The metal is squeezed against the multiple edges. The speed should be low and plenty of lubricant should be used.



i. The overall length of the bed. This includes the head stock length also. Or the greatest length of

the work that can be held between the head stock and tail stock centers. (DISTANCE BETWEEN

CENTERS)

LATHESEngine Lathe Size and Specification



ii. The largest size of the workpiece that can be rotated without touching the guide ways of the bed.

(SWING OVER THE BED)




iii. Sometimes the workpiece diameter is considered from the saddle instead of the bed ways. In this

case the height of the center should be measured from the saddle or the largest size diameter of the

work should be measured from the saddle. (SWING OVER THE SADDLE)



• Height of the center:“C” Vertical distance

between the lathe bed & the center line of the

lathe spindle.

• Swing diameter over bed: “B”, largest

diameter of the work that can be revolved without touching bed.

Equal to 2C.




• Length between center: “A” Max.

length of workpiece that can be set

between centers.

• Swing diameter over carriage: “D” Largest diameter of workpiece that can be revolved over the lathe saddle.




• Max. bar diameter: Max. diameter of bar

stock that pass through the hole of

head stock “E”

• Length of bed: Total length of guide ways provided on the bed.




• A: Swing

• B: Distance between centers.

• C: Length of bed

• D: Radius (one half of swing)




a) According to configuration b) According to purpose of use c) According to size or capacityd) According to degree of automatione) According to type of automation f) According to configuration of the jobs being handled g) According to precision h) According to number of spindles

LATHESClassification of Lathes



a) According to configuration

i. Horizontal: Most common for ergonomic conveniences

ii. Vertical: Occupies less floor space, only some large lathes are of this type.




b) According to purpose of use

i. General purpose: Very versatile where almost all possible types of operations are carried out on wide ranges of size, shape and materials of jobs; example: center lathes

ii. Single purpose: Only one (occasionally two) type of operation is done on limited ranges of size and material of jobs; example: facing lathe, roll turning lathe etc.




b) According to purpose of use

iii. Special purpose: Where a definite number and type of operations are done repeatedly over long time on a specific type of blank; example: gear blank machining lathe etc.




c) According to size or capacity

i. Small (low duty): In such light duty lathes (up to 1.1 kW), only small and medium size jobs of generally soft and easily machinable materials are machined

ii. Medium (medium duty): These lathes of power nearly up to 11 kW are most versatile and commonly used

iii. Large (heavy duty): More powerful, used for big and heavy part turning

iv. Mini or micro lathe: These are tiny table-top lathes used for extremely small size jobs and precision work; example: Swiss-type automatic lathe




c) According to size or capacity

iii. Large (heavy duty): More powerful, used for big and heavy part turning

iv. Mini or micro lathe: These are tiny table-top lathes used for extremely small size jobs and precision work; example: Swiss-type automatic lathe




d) According to degree of automation

i. Non-automatic: Almost all the handling operations are done manually; example: center lathes

ii. Semi-automatic: Nearly half of the handling operations, irrespective of the processing operations, are done automatically and rest manually; example: capstan lathe, turret lathe, copying lathe relieving lathe etc.




d) According to degree of automation

iii. Automatic: Almost all the handling operations (and obviously all the processing operations) are done automatically; example – single spindle automat (automatic lathe), Swiss-type automatic lathe, etc.




e) According to type of automation

i. Fixed automation: Conventional; example: single spindle automat, Swiss-type automatic lathe etc.

ii. Flexible automation: Modern; example: CNC lathe, turning center etc.




f) According to configuration of the jobs being handled

i. Bar type: Slender rod like jobs being held in collets

ii. Chucking type: Disc type jobs being held in chucks




g) According to precision

i. Ordinary (lathes): More economical lathes,accuracy and surface finish are moderate.

ii. Precision (lathes): These sophisticated lathes meant for high accuracy and finish and are relatively more expensive.




h) According to number of spindles

i. Single-spindle: Common

ii. Multi-spindle: (2, 4, 6 or 8 spindles)Such uncommon lathes are suitably used for fast and mass production of small size and simple shaped jobs.




• Engine Lathe- Universal lathe – Parallel lathe• Capstan and Turret Lathes• Automatic Lathes• Other Lathes

LATHE TYPES

• CNC Lathes• Boring Machine• Flat Lathes• Tracer/Copy Lathes• Heavy Duty Lathes• Bench Lathes

• Crankshaft Turning Lathes

• Roll Turning Lathes• …



Most frequently used lathe. Engine lathe is also calledas Universal Lathe. An engine lathe is a type of

machinery, shaped horizontally, and it is often used to cut metal. The metal is turned, and the machine uses

special cutting tools to create the desired shape.

LATHE TYPESEngine Lathe



Workpiece is held in a chuck or between centers and rotated about its axis at a uniform speed.

Cutting tool held in the tool post is fed into the workpiece for a desired depth and in the desired

direction.


There exists a relative motion between the

workpiece and the cutting tool. Therefore the material is removed in the form of

chips and the desired shape in obtained.



These machine tools consist of bed, spindle, gearbox, headstock, tailstock, carriage, lead screw, feed rod,

chuck, tool post, apron etc.





H e ad s to c k

S p in d le

F e e d ro d

B ed

C o m p o u n d re s ta n d s lid e (sw iv e ls)

C a rr ia g e

A p ro n

se le c to r

F e e d ch an g eg e arb o x

S p in d lesp ee d

L e a d sc rew

C ro ss s lid eD e ad c en te r

T o o l p o stG u id e w a y s

T a ils to c k q u illT a ils to c k

H a n d le



BASIC PARTS

1. Device to hold workpiece2. Device to hold cutting tool3. Device to rotate workpiece4. Device to give feed to tool (automatic or manual)5. Device to give depth of cut and/or cross-feed to cutting

tool6. Device to stop movements (rotation of workpiece and

movement of cutting tool)7. Device for cutting thread and some other devices




LATHE BED

The lathe bed carries the spindle box with the work-driving spindle and the main driving mechanism, the carriage with apron, saddle, cross slide, tool rest and lathe tool holder as

well as tailstock with quill.


1. Lathe feet,

2. Bridge,

3. Guideways,

4. Lathe bed



LATHE BEDTypes of lathe beds: • Inverted "V" beds,• Flat beds,• Combination "V" and flat beds.

"V" and combination beds are used for precision and light duty work.

Flat beds are used for heavy duty work




LATHE BEDImportant parts of the lathe bed are the guideways, of

which two basic kinds are distinguished - sliding and roller guideways.

The sliding guideways are characterized by simple manufacture, great strength and faultless localization of the groups to be led. Roller guideways have roll bodies, only little friction, but are complicated in manufacture, have a low stressability and, when worn, become useless due to

backlash.




LATHE BED




HEADSTOCK

The headstock carries the spindle with the bearings in it.

Bearings provide excellent control over minimum axial and radial movements.

The spindle gets power or drive through the cone pulley and belts or by the gears in the headstock.




SPINDLE

The spindle is located inside the headstock and creates the main motion.

It is a tubular shaft having a flange and allows mounting the mirror.




SPINDLE

Universal and independent chucks are fitted to three types of

spindles:

1. Threaded spindle nose (screws on in a clockwise direction)

2. Tapered spindle nose (held by lock nut that tightens on chuck)




SPINDLE

3. Cam-lock spindle nose (held by tightening cam-locks using T-wrench, Chuck aligned by taper on spindle nose)




GEAR-BOX

Gear-box contains a number of different sized gears for providing various spindle speed.




GEAR-BOX

The power is transmitted from the motor via the toothed gears or the belt drive to the work-driving spindle

(workpiece) or the feeding mechanism, respectively.




GEAR-BOX


Main driving mechanism:1. Driving motor (flange-

mounted motor),

2. Main shaft,3. Chuck,4. 4. Coupling,5. Operating lever,6. Countershaft,7. Gears, 8. Work-driving spindle



NORTON GEAR-BOX

Norton gear-box has a Norton gear system in it. It transmits the movement to the lead screw or feed rod.

If the movement is transmitted to the feed rod, the carriage is moved based on the revolution speed.

If the movement is transmitted to the lead screw, the motion is performed based on the screw pitch and

threading operation is carried out.




NORTON GEAR-BOX


Feeding mechanism and change gear

mechanism:

1. Lead screw,

2. Toothed gears,

3. Change gear mechanism,

4. Switching lever



GUIDES/SLIDESThe carriage and tailstock move on the guides/slides.

450-500 HB hardness is desired.




CARRIAGEThe carriage moves parallel to the spindle axis and provides

the feed motion.




CARRIAGEThe carriage consists of three main parts as saddle, cross-

slide and apron.

Saddle: H shaped casting (or plate) mounted on the guideways of the bed of the lathe. The cross-slide is

mounted on saddle and the apron is put below.

Cross-slide: carry the tool post and the compound rest.

Apron: carry the carriage and cross-slide levers.




CARRIAGE




CARRIAGE


1. Cross-slide

2. Lathe tool holder

3. Tool rest

4. Guideways

5. Carriage

6. Lead screw

7. Feed rod

8. Hand wheel for longitudinal feed

9. Apron



LEAD SCREW, FEED ROD AND DRIVE SHAFT

The lead screw and feed rod (shaft) are located between Norton gear-box and the other end of the bed. They are

parallel to the guideways/slideways.

The lead screw is a screwed shaft and used for thread cutting operations.

The feed rod is used performing the feed motion except thread cutting operations.

The drive shaft adjusts the motion direction of carriage.




LEAD SCREW, FEED ROD AND DRIVE SHAFT




TAILSTOCK

The tailstock is used as a counter-holding device in turning of long workpieces.

The tailstock slides on the guideways of the lathe bed and can be fixed in any place to hold and support the workpiece.

The tailstock is also used for drilling operations and producing long taper.




TAILSTOCK




TAILSTOCK


1. Tailstock center (replaceable)

2. Quill

3. Clamping lever of the clamping nut

4. Hand wheel

5. Tailstock clamping nut

6. Spindle

7. Spindle nut



TAILSTOCK APPLICATION



TAILSTOCK APPLICATION


Feed

Drill

Quill clamp moving

quill

Tail stock clamp

Tail stock



RESTS

Steady and follower rests are used not to bend the long workpieces during external cylindrical turning process.

The rests eliminate the deformations caused by the cutting forces.




RESTSSteady RestThe base is made up of cast iron.

It is clamped on the lathe bed where the workpiece is to be supported.

Three jaws are provided.

All jaws can be radially moved with independent screw.




RESTSFollower RestIt is “C” type in shape.

Two adjustment jaws to support the workpiece.


It is fitted on the rear portion of the carriage by bolt, hence it moves along with the carriage.

Used during the finishing operations or for carrying out turning along the entire length of the jaw.



CHUCKSMajor part for holding workpiece:1. Universal or self-centering chuck (three jaw chuck)2. Independent or four jaw chucks3. Combination chucks4. Drill chuck5. Magnetic chuck6. Power chuck7. Faceplates8. Collet chuck




CHUCKSUniversal or self-centering chuck (three jaw chuck)


1. Three jaw chuck with turning jaws,

2. Three jaw chuck with boring jaws



CHUCKSIndependent or four jaw chucks


Generally has four jaws, which are adjusted individually on the chuck face by means of

adjusting screws. With the help of the four jaw chuck, quadrangular and octagonal parts are

clamped.



CHUCKSCombination chucks


Four jaw combination chucks combine aspects of four jaw independent chucks and scroll

chucks. In a four jaw combination chuck each jaw can be adjusted independently but all the jaws are opened and closed at the same time

using a key. These chucks work well for repetitive work on square, rectangular or irregular pieces that don't require regular

adjustments.



CHUCKSDrill chuck


Used for drilling, reaming, tapping operations. It is held in the sleeve of the tail stock or spindle of the headstock. It contains key operated centering jaws

for holding the tool.



CHUCKSMagnetic chuck


Thin jobs can be held by means of magnetic chucks.



CHUCKSPower chuck




CHUCKSFaceplates


A lathe faceplate is a flat round plate that threads to the headstock spindle to the lathe.

The faceplate is used for irregularly shaped workpieces that cannot successfully held by chucks.



CHUCKSFaceplates


1. Clamping of large disks

2. Clamping of square workpieces



CHUCKSCollet chuck


1. Clamping body

2. Workpiece

3. Lathe spindle

4. Clamping tube

5. Hand wheel

For clamping smaller workpieces and for working from the bar, especially on turret lathes and automatics, the collet

chuck is used.



CHUCKSCollet chuck


Outer portion of collet is tapered.



CHUCKSCollet chuck




CHUCKSLathe dogs


Lathe dogs are cast metal devices used to provide a firm

connection between the headstock spindle and the

workpiece mounted between centers.



Turret and capstan lathes are the natural development of the engine lathe, where the tailstock is replaced by an indexable multistation tool head, called the capstan or

the turret.

This head carries a selection of standard tool holders and special attachments.

A square turret is mounted on the cross slide in place of the usual compound rest in engine lathe.

LATHE TYPESCapstan and Turret Lathes



Sometimes a fixed tool holder is also mounted on the back end of the cross slide.

Dimensional control is effected by means of longitudinal (for lengths) and traversal (for diameters) adjustable stops.

Capstan and turret lathes bridge the gap between manual engine lathes and automated lathes and are most practical

for batch and short-run production.




Capstan and turret lathes are advancements over center lathes. The machining of a job on a center lathe takes

considerable time, which is avoided on these lathes by the incorporation of facilities for carrying eight or more tools.

Capstan and turret lathes are capable of performing multiple cutting operations on the same workpiece (turning, boring,

drilling, thread cutting, facing)




Capstan and turret lathes are production lathes used for the manufacture of a large number of similar components in the

least possible time.

The characteristic features of these machine tools is the capstan or turret head mounted on the bed.




The main advantages of turret and capstan lathes include the following:

• Less-skilled operators are needed, as compared with center lathes

• No need to change tooling or move the work to another machine, as many operations can be performed without

the need to change tooling layout




1.Capstan or Ram Type Lathe

2.Turret or Saddle Type Lathe




1. Capstan or Ram Type Lathe

• It is production lathe

• Used for light duty work pieces

• Small in size as compared to turret lathe





Capstan or ram type lathe consists of a hexagonal turret on a ram that slides longitudinally on a saddle positioned and

clamped on the lathe bedways.

This type of machine is light in construction and suitable for machining bars of small diameter.

The tools are mounted on all the faces of the turret (commonly, square or hexagonal).





The saddle movement is suitably controlled in such a way that the saddle need not be moved back of forth appreciably

to bring the tool to a cutting position.

When the ram is moved back a little and then moved forward, the next tool indexes automatically for the next

operation.




On the capstan lathe, the drive to turret is provided form an auxiliary slide clamped to the top of the bed. The turret is adjustable, so that its distance from the machine nose can

be varied.


Mounting the capstan head



2. Turret or Saddle Type Lathe

• It is more rigid and hence most suitable for heavier works.

• Jobs up to 300 mm diameter can be machined on it. Its design eliminates the turret slide overhang problem inherent in the ram-type lathes.

• The power rapid traverse reduces the operator’s handling effort.





In a turret or saddle type lathe, the hexagonal turret is mounted directly on the saddle and the whole unit moves

back and forth on the bedways to apply the feed.

The apron on the front of the saddle, houses all the controls of the turret head.





A turret or saddle type machine is heaver than a capstan or ram type machine and is thus used for heavier and longer

production jobs.


The turret of the turret lathe is mounted on the saddle

that slides directly on the bed in the same way as a lathe

saddle.





1. Chuck, 2. Gear box, 3. Electrical push button starter, 4. Overarm support, 5. Front tool post, 6. Rear tool post, 7. Hand wheel for cross-

slide, 8. Hand wheel for longitudinal feed, 9. Carriage, 10. Feed bar, 11. Saddle, 12. Turret head, 13. Lever for locking the slide



DIFFERENCE BETWEEN A TURRET LATHE AND AN ENGINE LATHE


1.The headstock of a turret lathe is similar to an engine lathe in construction, except in the range of speeds. A turret lathe

possesses a wider range of speeds.

2.The tailstock of a turret lathe consists of a turret. It resembles a big six-sided nut and can carry six tools for turning a job. The

tailstock of an engine lathe can hold only one tool of limited size.




3.The tool post of a turret lathe can hold four tools that may be indexed by 90°. In addition, there is a rear tool post that can hold four more tools. In an engine lathe, the usual practice is to hold

one tool at a time.

4.In a capstan or turret lathe, the feed movement is regulated by stops or feed trips. This enables duplication of work without

further measurement.





5.The time required to finish a component on a capstan or turret lathe is less than on an engine lathe, i.e. components produced on

a capstan or turret lathe are cheaper.

6.On a turret or capstan lathe, two or more cuts can be taken at a time. In a center lathe, this type of arrangement is quite

uncommon.





7.On a capstan lathe, threads are usually cut by dieheads or taps, which enables speedy operation.

8.Capstan or turret lathes are designed to act as production machines, whereas an engine lathe is designed to machine many

types of jobs, within limits. Thus, an engine lathe is a general purpose machine.

9.The chucking and rechucking of jobs is time consuming in an engine lathe while the turret lathe works automatically.




DIFFERENCE BETWEEN CAPSTAN AND TURRET LATHES


The working principle, working mechanism and design of capstan and turret lathes are almost the same, except for the manner of

mounting multitool holding devices.

These lathes are semi-automatic and used for mass or batch production of identical parts.

These lathes are provided with a multiple tool holding device called the turret head in case of a turret lathe and capstan head in case

of a capstan lathe.





The capstan head is usually cylindrical in shape and carries six equiaxed bored holes along its periphery. The head can be

swiveled in the horizontal as well as the inclined plane. The axis of the slot is always horizontal, irrespective of the method of fixed

the head.

A turret head is used in square, hexagonal and octagonal shapes but the hexagonal shape is most common. The turret head is

always mounted with its axis in the vertical direction, except in the case of a vertical turret lathe.





Capstan and turret lathes also differ in the method of mounting the capstan and turret heads.

The capstan head is mounted on a ram or slide. It slides in the ways provided on the saddle. The saddle can be fixed anywhere

along the bed. The operating traverse of the tool is made by moving the slide and not the saddle.

The turret head of a turret lathe is directly mounted on the saddle.





A capstan lathe is used for small sized precision components and is mainly used for bar work while a turret lathe is used for producing

comparatively larger components in the form of castings and forgings.

The accuracy of components produced on a turret lathe is comparatively less than in a capstan lathe.



PRINCIPAL ELEMENTS OF CAPSTAN AND TURRET LATHES


1.Headstock2.Bed3.Turret Saddle4.Tooling Accessories5.Work Holding Attachments




1. Headstock


The headstock consists of a provision for rapidly stopping the work.

The speed changing device is complex and quick.

The starting of the machine is easier.

It incorporates an instant reversal mechanism.




1. Headstock





1. Headstock


The headstock of a capstan or turret lathe can be classified as:1.Multispeed electric motor driven headstock2.All-geared headstock3.Pre-selective headstock. In this system the speed required is selected before hand by setting a pointer on an indicating dial. When another speed is desired, the movement o another lever causes the spindle to change speed.




2. Bed


The bed of a turret lathe consists of a long box-like casting provided with accurate guideways.

Over the bed are mounted the carriage and turret saddle.

The bed of a turret must be rigid strong and possess good damping capacity.




3. Turret Saddle


The turret saddle replaces the tailstock of a center lathe and is mounted on the lathe bed on the same side as the tailstock in a center lathe.

The turret head is usually hexagonal in turret lathes and circular in capstan lathes.




3. Turret Saddle


The pilots or shanks of the tools are inserted into the holes of a turret head and fastened by means of screws or suitable fastening devices.

The tools are fixed properly in these holes and indexed for controlled motion.




3. Turret Saddle


The indexing of the tool is in the clockwise direction. After indexing, the automatic feed can be engaged and production operations started.




4. Tooling Accessories


In addition to various tools and accessories used in a center lathe, the following tools are used for production work on a capstan or turret lathe:1.Multitool holder having six slots2.Long and short holders 3.Shaft tool holder (straight)4.Shaft tool holder (adjustable)






5. Shaft tool holder (inclined)6. Adjustable tool holder7. Split bushes8. Adapter sleeves9. Rear tool holder10.Tap and die holder11.Adapter flange






12.Centering and facing tool holder13.Recessing tool holder (hand operated)14.Roller steady centering and chamfering tool holder (and

operated)15.Boring heads16.Roller steady17.Floating reamers holder




5. Work Holding Attachments


Since the turret lathe is a production machine, the process of holding the work between centers finds no place in its practice. Practically all the work is held in the spindle in one form of fixture or the other.

Chucks: All the chucks used in a turret lathe are of self-centering variety with three and sometimes two jaws.






An essential requirement of the chuck used in turret lathes is that it must be strong and rigid.

Chucks are classified according to controlling mechanism as (a) pneumatic chucks,(b) mechanical chucks, and(c) hydraulic chucks.






Collet: A collet is used for feeding the bar through the hollow spindle for turning and parting off operations. The collets commonly used are either air operated or hand operated. The equipment is provided with a special handle to easily loosen and tighten the barstock by moving it leftward and rightward. This helps in the quick gripping and relieving of work.






Arbors: Arbors are used to hold short pieces of stock havng accurate previously machined holes.

Fixtures: Special or irregular components require special holding devices.






Work stops or bar stops: For the mass production of identical parts, it is necessary that the same length of the bar stock be projected out each time. Although it is not difficult to adjust the length every time, but it is time consuming. For such purposes, workstops or bar stops are used.






Centering and chamfering tools: The commonly used centering tools are (a) flat centering tool, (b) roller steady centering tool, and (c) combined bar stop and centering tool. A flat centering tool consists of a solid shank provided with a flat drill at its front.A roller steady centering tool consists of the main body having the shank at its back.






A combined bar stop and centering tool consists of a cast body having the shank at its rear and carrying an adjustable drill at its center.

A commonly used chamfering tool consists of a cast body fitted with a conical bush and a cutter. On a turret it is used for chamfering at a rapid rate with heavy feeds.






Drill and reamer holder: The commonly used drill and reamer holders are (a) plain drill holder, and (b) floating drill and reamer holder.

A plain drill holder consists of a hollow cylindrical body and a shank.






The floating holder is made in two pieces to enable it to make slight adjustment in the drill or reamer positions so as to make it concentric with workpiece.

An improved form of a drill and reamer holder is the self-centering drill chuck. This possesses a firm grip and automatically brings the drill or reamer into the required alignment.






Tap and die holders: a large variety of tap and die holders are used on turrets. The commonly used ones are (a) sensitive type tap holder, (b) self-releasing type tap holder, and (c) collapsible type tap holder.

The two types of die holders are the self-opening type and the combination type die holder.






Tap and die holders:



Automated machine tools have played an important role in increasing production rates and enhancing product quality.

They have contributed to mass production of spare parts and machine components.

In automated lathes, the data required for the machining of the workpiece are transferred to the workbench by

mechanical parts such as cam, shaft etc. The automated lathes can be single-spindle or multi-spindle.

LATHE TYPESAutomated Lathes



Automatic and semiautomatic lathes are designed to produce parts of complex shapes by machining the blank (or

bar stock). They are designed to perform the following machining operations:


• Turning• Centering• Chamfering• Tapering and form turning• Drilling, reaming, spot facing, and counter boring

• Threading• Boring• Recessing• Knurling• Cutting off



It is important to realize that during the automatic machining operation, the operator is free to operate another machine or to inspect the finished part without loss of time.




The automated lathes may be classified according to the following features:

1. Spindle location (horizontal or vertical)2. Degree of automation (fully or semi-automatic)3. Number of spindles (single-spindle or multi-spindle)

a. Single-spindle automated lathe are classified as fully automatic (Swiss-type and turret-screw automatics) and semi-automatic

b. Multi-spindle automated lathes. They can be classified as fully automatic and semi-automatic.




The automated lathes may be classified according to the following features:

4. Nature of workpiece stock (bar or magazine)a. Automatic bar machine. b. Magazine loaded machine

5. Workpiece size and geometry.6. Machining accuracy.




1. Spindle location (horizontal or vertical)

Vertical machines are heavier, more rigid, more powerful, and occupy less floor space. They are especially designed for

machining large diameter work of comparatively short length.




2. Degree of automation (fully or semi-automatic)

The decision to choose between fully and semi-automatic depends mainly on the lot size.

These are mainly based on mechanical control systems and are characterized by a rigid linkage between the working

and auxiliary operations.




2. Degree of automation (fully or semi-automatic)The two following mechanical systems are frequently

employed: 1. A control system composed of a single camshaft, which provides all the working and auxiliary motions. This is the simplest arrangement and is further classified into two types:

a. Systems in which the camshaft speed is set up and remains constant during the complete cycle

b. Systems in which the camshaft speed is set up for the working movements




2. Degree of automation (fully or semi-automatic)

2. A control system composed of a main and an auxiliary camshaft. The machining cycle is completed in one revolution of the main camshaft. Trip dogs on the main camshaft perform the auxiliary operations through signals that link the operative devices for auxiliary movements to the auxiliary camshaft. This system is more complex than the preceding one due to the very large number of transmission elements and levers. It is used in automatic screw machines and vertical multi-spindle semiautomatic chucking machines.




3. Number of spindles (single- or multi-spindle)

Single-spindle automated lathes are classified as fully automatic (Swiss-type and turret-screw automatics) and

semi-automatic.




3. Number of spindles (single- or multi-spindle)Swiss-type automatics (fully automatic)


This type of automated lathes was originally developed by the watch-making industry of Switzerland to produce small

parts of watches.

It is now extensively used for the manufacture of long and slender precise and complex parts.



3. Number of spindles (single- or multi-spindle)Swiss-type automatics (fully automatic)





Multi-spindle automated lathes 2–8 horizontal or vertical spindles. Their production capacity is higher than that of single-spindle machines, but their machining accuracy is generally lower than single spindle automatics due to the errors in indexing of spindles and large number of spindle

head fittings.






Multi-spindle automated lathesSingle-spindle automated lathes



3. Number of spindles (single- or multi-spindle)Multi-spindle automated lathes are further classified

as follows:Fully automatic:

These machines are suitable for both bar and magazine work. They are widely used for mass production and need a

lot of setup work. Large multi-spindle automatics are equipped with an auxiliary small power motor, which serves to drive the camshaft when the machine is being set up. The

rate of production of multi-spindle automatic is less than that of a corresponding sized single-spindle automatic.




3. Number of spindles (single- or multi-spindle)Multi-spindle automated lathes are further classified

as follows:Fully automatic:

The production capacity of a four-spindle automatic, for example, is only 2.5–3 times (not 4 times) as large as that of a single-spindle automatic, assuming the same product

size, shape, and material.Semi-automatic:

Semi-automatic multi-spindle machines are mostly of vertical type.




4. Nature of workpiece stock (bar or magazine)

Automated lathes use either coiled wire stock (up to 6 mm in diameter), bar, pipe, or separate blanks.

Bar stock is available in great variety of shapes and sizes; however, it is considered poor practice to use bar stock over 50 mm in diameter, as the waste metal in the form of chips

will be excessive.




4. Nature of workpiece stock (bar or magazine)

Separate blanks are frequently used in semi-automatics. The blanks should approach the shape and size of the

finished product; otherwise, the cycle time increases, thus increasing the production cost.




5. Workpiece size and geometry

The size and geometry of the WP determine the suitable machine to be used. In this regard, long accurate parts of

small diameters are produced on the Swiss-type automatics, whereas parts of complex external and internal surfaces are

machined using turret-type automatic screw machines.




6. Machining accuracy

Generally, bar automatics are employed for machining high-quality fastenings (screws, nuts) bushings, shafts, rings, etc.

The design configuration of the Swiss-type automatics makes them superior with respect to the production

accuracy, especially when producing long slender parts.




DESIGN AND LAYOUT OF CAMS FOR FULLY AUTOMATICS

Setting up an automatic involves all the preparatory work required to manufacture a workpiece in accordance with the

part drawing and specifications.




DESIGN AND LAYOUT OF CAMS FOR FULLY AUTOMATICS

Setting up includes the following steps:

1. Planning the sequence of operation2. Working out the calculation sheet for the set up3. Manufacturing the necessary cams and tooling4. Setting up the kinematic trains to obtain the required

speeds and feeds5. Installing and adjusting cams and tools on the machine




CAM DESIGN

The cam design for automated lathes is a tedious work including definite steps depending on the type of automated

machine.




CAM DESIGN

The following main guidelines are to be generally observed in the cam design process:

1. Determine the number of spindle revolutions required for each operation and idle movements.

2. Overlap those operations and idle movements that can take place simultaneously.

3. Proportion the balance of spindle revolutions on the surface of the cam so that the total of these revolutions equals the full circumference of the cam.




CAM DESIGN


Blank Cam Shaped Cam



Automatic Lathe Features 1. Minimum man-power utilized, meant for mass production 2. Manual machine controls replaced by various

mechanisms to eliminate the amount of skilled labor. 3. Mechanisms enable to follow certain prescribed frequency 4. Parts are fed and removed automatically, minimizing the

loading and unloading time 5. May have single or multiple spindles 6. Tool set up may be permanent 7. May have horizontal or vertical spindles 8. More accuracy can be obtained




CNC LATHE AUTOMATED LATHES C& T LATHES UNIVERSAL LATHE



Advantages1. Greater production over a given period. 2. More economy in floor space. 3. Improvement in accuracy. 4. Floor space maintenance and inventory requirements are

reduced. 5. More consistently accurate work than turrets. 6. More constant flow of production. 7. Scrap loss is reduced by reducing operator error. 8. During machine operation operator is free to operate

another machine or can inspect completed parts.




Boring is the machining process in which internal diameters are generated in true relation to the centerline of the spindle

by means of single-point tools.

It is the most commonly used process for enlarging and finishing pre-drilled or precast holes or other circular

contours.

Although most boring operations are performed on simple straight-through holes, the process may be also applied to a

variety of other configurations.

LATHE TYPESVertical Boring (Jig Boring) Machine



Boring offers three main benefits.It can bring the size of a hole to a specified diameter,

straighten a hole that has wandered off-center, or make it more concentric with an insert piece.

Compared to other ways of achieving these goals, boring is fast, accurate and cost-effective, making it ideal for

mass production.




Jig boring machines are extra-precise vertical boring machines intended for precise boring, centering, drilling, reaming, counter boring, facing, spot facing, and so on in

addition to lay-out work.

They are mainly designed for use in tool making, jigs and fixtures, and machining of other precisions parts.




The jig borer is generally built lower to the floor and is of much more rigid and accurate construction than any other

machine tool.

The table and saddle ensure the longitudinal and cross movements, X and Y. The machine has a massive column that supports and accurately guides the spindle housing in

the vertical direction, thus achieving the third position adjustment, Z.




The jig boring machines are rigid enough to perform heavy cuts and sensitive enough for précising.

They are equipped with special devices ensuring accurate positioning of the machine operative units including a

precision lead screw-and-nut and are supplemented by vernier dials and precision scales in combination with optical read-out devices, inductive transducers, and also optical and

electrical measuring devices.




To prevent the influence of ambient temperature changes on the machining accuracy, jig borers are installed in special

environmental enclosures with temperature maintained at a level of 20°C.

Currently, jig boring machines are often replaced by CNC machining centers to do similar work.




Flat lathes are used for machining large parts. The chucks connected to the spindle are of a large scale.

LATHE TYPESFlat Lathes



LATHE TYPESFlat Lathes



• Computer controlled • Wide variety of process capability• Multiple axis• Indexing and contouring head• On-line and off-line programming available• Equipped with one or more turrets• Each turret is equipped with a variety of tools• Performs several operations on different surfaces of the

workpiece

LATHE TYPESCNC Lathes



LATHE TYPESCNC Lathes



It is small sized engine lathe mounted on bench. A bench top model usually of low power used to make

precision machine small & light weight workpieces.

LATHE TYPESBench Lathes



• Hydraulic attachment used to copy the shape of a part from a master.

• Tracer/copy lathes have the ability to follow a template to copy a shape or contour.

• Machine tools with attachments • Capable of turning parts with various contours • A tracer finger follows the template and guides the

cutting tool

LATHE TYPESTracer/Copy Lathes



LATHE TYPESTracer/Copy Lathes



LATHE TYPESHeavy Duty Lathes



LATHE TYPESRoll Turning Lathes



LATHE TYPESCrankshaft Turning Lathes



Description of machine tool Classification Sections/parts Machining operations



machine tools - avesİs

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