Introduction to Lathe - Turning Operations

An engine lathe is the most basic and simplest form of the lathe.  Besides the simple turning operation,  lathe can be used to carry out other operations  such as drilling, reaming, boring, taper turning, knurling, screw-thread cutting, grinding etc.

TYPES OF LATHE

1. Speed lathe

(a) Wood working
( b ) Spinning
(c) Centering
(d) Polishing


2. Centre or engine lathe

(a) Belt drive
( b ) Individual motor drive
(c) Gear head lathe

3. Bench lathe

4. Tool room Lathe

5. Capstan and Turret lathe

6. Special purpose lathe

(a) Wheel lathe
( b ) Gap bed lathe
(c) Duplicating lathe
(d) T-lathe

7. Automatic lathe

SPECIFICATION OF LATHE 

The size of a lathe is generally specified by the following means:

(a) Swing or maximum diameter that can be rotated over the bed ways

( b ) Maximum length of the job that can be held between head stock and tail stock centres

(c) Bed length, which may include head stock length also

( d ) Maximum diameter of the bar that can pass through spindle or collect chuck of capstan lathe.


(i) Maximum swing over bed
(ii) Maximum swing over carriage
(iii) Height of centers over bed
(iv) Maximum distance between centers
(v) Length of bed
(vi) Width of bed
(vii) Morse taper of center
(viii ) Diameter of hole through spindle
(ix) Face plate diameter
(x) Size of tool post
(xi) Number of spindle speeds
(xii) Lead screw diameter and number of threads per cm.
(xiii) Size of electrical motor
(xiv) Pitch range of metric and inch threads etc.



Introduction to lathe - Monash University Video
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CUTTING SPEED

Cutting speed for lathe work may be defined as the rate in meters per minute at which
the surface of the job moves past the cutting tool. Machining at a correct cutting speed is
highly important for good tool life and efficient cutting. Too slow cutting speeds reduce
productivity and increase manufacturing costs whereas too high cutting speeds result in
overheating of the tool and premature failure of the cutting edge of the tool. The following
factors affect the cutting speed:

(i) Kind of material being cut,

(ii) Cutting tool material,

(Hi) Shape of cutting tool,

(iv) Rigidity of machine tool and the job piece and

(v) Type of cutting fluid being used.

Calculation of cutting speed Cs, in meters per minute 

Cs = ((22/7) x D x N)) /1000

Where

D is diameter of job in mm.

N is in RPM

FEED 

Feed is defined as the distance that a tool advances into the work during one revolution
of the headstock spindle. It is usually given as a linear movement per revolution of the spindle
or job. During turning a job on the center lathe, the saddle and the tool post move along the
bed of the lathe for a particular feed for cutting along the length of the rotating job.




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Updated on 14 March 2020
27 October 2015