Session 3

Classification of lathes

Kinematics system of centre lathe

Working principle of lathe machine

Classification of lathes

Lathes are very versatile of wide use and are classified according to several aspects: (a) According to configuration

• Horizontal

-Most common for ergonomic conveniences • Vertical

- Occupies less floor space, only some large lathes are of this type.

Classification of lathes

(b) According to purpose of use •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 : centre lathes •Single purpose

Only one (occasionally two) type of operation is done on limited ranges of size and material of jobs; example – f

acing lathe, roll turning lathe etc. •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.

Classification of lathes

(C)According to size or capacity • Small (low duty)

- In such light duty lathes (upto 1.1 kW), only small and medium size jobs of generally soft and easily machinable materials are machined

• Medium (medium duty) - These lathes of power nearly upto 11 kW are most versatile and commonly used

• Large (heavy duty) • Mini or micro lathe

- These are tiny table-top lathes used for extremely small size jobs and precision work; example : swiss type automatic lathe

Classification of lathes

(D)According to degree of automation • Non-automatic

- Almost all the handling operations are done manually; example: centre lathes

• 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.

• 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.

Classification of lathes

(E)According to type of automation • Fixed automation

- Conventional; example – single spindle automat, swiss type automatic lathe etc.

• Flexible automation - Modern; example CNC lathe, turning centre etc.

(f) According to configuration of the jobs being handled • Bar type

- Slender rod like jobs being held in collets • Chucking type

- Disc type jobs being held in chucks • Housing type

Odd shape jobs, being held in face plate

Classification of lathes

(g)According to precision • Ordinary • Precision (lathes)

- These sophisticated lathes meant for high accuracy and finish and are relatively more expensive.

(h) According to number of spindles • Single spindle

- Common • Multispindle (2, 4, 6 or 8 spindles)

- Such uncommon lathes are suitably used for fast and mass production of small size and simple shaped jobs.

Classification of Lathes

Bench LatheBench LatheBench LatheBench Lathe

Engine Lathe Engine Lathe

Tool room LatheTool room Lathe

Special purpose lathe (Gap bed)Special purpose lathe (Gap bed)

Kinematic System Of Lathes

Kinematic System and working principle Of Lathes

Lathe Components1. Bed:

• It supports all major components of lathe as it is the

base of machine.

• These have large mass, rigidly built as single piece

casting from gray/ toughened C.I to resist deflection &

absorb vibrations generated during cutting process.

• Three main parts head, tail stocks , carriage are

mounted on bed

2. Head stock:

• It is a part which secured permanently at left hand

end of bed which supports spindle & equipped with

power driving mechanisms (motors, pulleys, V-belts

) for spindle at various rotational speeds.

• It have a hollow spindle to which Work holding

devices such as chucks, collets are attached.

3. Tail stock/ Loose head stock/ Puppet head:

• It is mounted on inner ways at right hand end of bed

which can slide along the ways & can be clamped at

any position, supports the other end of w/p.

• It is equipped with a centre that may be fixed(dead

centre) or may be free to rotate with w/p called (live

centre)

• Drills & reamers can be mounted on tailstock quill (a

hollow cylindrical part with tapered hole) to drill axial

holes in w/p. Quill can move in & out with hand wheel.

4. Carriage:

• It slides along the guide ways between head stock,

tailstock & consist of assembly of saddle, cross

slide, tool post, compound rest, apron.

• Main function of carriage is to hold cutting tool &

move it to give longitudinal & / cross feed to it.

• Operator moves carriage manually by hand wheel/

automatically by engaging feed shaft with carriage

feed mechanism.

• Carriage consists of:

a)Saddle:

Part of carriage which slides along bed ways & support

the cross slide, compound rest, tool post.

b)Cross slide:

Mounted on top of saddle & always moves in direction

normal to axis of main spindle.

It can be either operated by hand by means of cross feed

screw or may be given power feed through apron

mechanism.

c) Compound rest:

• It is mounted on cross slide & carries a graduated

circular base called as swivel plate.

• Upper part is called compound slide can be moved

by means of compound rest feed screw.

d)Tool post:

• Top most part of carriage, used for holding tool/ tool

holder in position.

e) Apron:

• It is hanging part in front of carriage.

• It serves as housing for number of gear trains

through which power feeds can be given to the

carriage & cross slide.

5. Feed rod & Lead screw:

• Feed rod is powered by set of gears from head

stock.

• It rotates during operation of lathe & provides

movement to carriage & cross-slide by means of

gears, friction clutch, key way along the length of

rod.

• Lead screw it transmits power to carriage through a

gear & clutch arrangement in carriage apron.

Working Principle of lathe

• The lathe is a machine tool which holds the work piece

between two rigid and strong supports called centers or in a

chuck or face plate which revolves as shown in Fig.

• The cutting tool is rigidly held and supported in a tool post

which is fed against the revolving work.

• The normal cutting operations are performed with the cutting

tool fed either parallel or at right angles to the axis of the

work.

• The cutting tool may also be fed at an angle relative to the

axis of work for machining tapers and angles.

Working Principle of lathe

Working principle of turning