What is lathe machine | Function | Types | Operation | Cutting speed | Feed | Depth of cut

The lathe machine is one of the oldest machine tools that rotate a workpiece about an axis of rotation to perform different operations such as turning, drilling, knurling, facing and many more. In this article, you can check it out function, types, and operations, cutting speed, feed, depth of cut, machining time of the lathe machine. 

Functions of the Lathe Machine


To remove metal from a piece of work to give it the required shape and size is the main function of a lathe.

This is done by keeping the work on the device securely and rigidly and then turning it against cutting tool which extracts metal from the work in the form of chips.


Types of Lathe Machine

  • Speed Lathe Machine
  • Engine Lathe Machine
  • Bench Lathe Machine
  • Toolroom Lathe Machine
  • Capstan and Turret Lathe Machine
  • Special purpose Lathe Machine
  • Automatic Lathe Machine

Lathe Machine

Lathe Machine


Lathe Machine parts and its function 

The bed

The lathe bed is the foundation of a lathe machine. The headstock and tailstock are on either end of the bed and the carriage lies on the bed and slides over it. It is the guiding member of the lathe machine so it should be rigid to prevent deflection, avoid distortion, and must be resisted to twisting. Nickel and chromium alloyed cast iron form a suitable material for lathe bed.

The headstock

The headstock is firmly fixed on the inner ways at the left end of the lathe bed consists of a hollow spindle and mechanism for driving and altering the spindle speed. 

The tailstock

The tailstock is at the right end of the bed on the inner ways. It supports the other end of the workpiece holds a tool for performing an operation. 

The carriage

The carriage consists of several parts such as saddle, cross-slide, compound slide, toolpost, and apron that serve to support, move and control the cutting tool. 

The saddle is an H-shaped casting fits over the bed and slides along with the ways carried the cross-slide and tool post. 

The cross-slide comprises of casting machined on the underside for attachment to the saddle. 

The compound rest is mounted on top of the cross-slide used for obtaining angular cuts and short tapper. 

The tool post is located on the top of the compound rest to hold the tool and enable it to be adjusted to a working position. There are different types of tool post such as single screw tool post, four-bolt tool post, open side tool post, and four-way tool post. 

The apron is linked with the saddle and hands over the front of the bed contains gears, clutches, and levers for operating the carriage by hand and power feeds. 

Feed Mechanism 

The movement of tool related to the work is called a feed. A lathe machine may have three types of feed such as longitudinal, angular and cross. 

Gearbox 

The gearbox is placed below the headstock and contains gears.

Operations performed on Lathe Machine


An operations which are performed in a lathe either by holding the workpiece between centres or by a chuck are following below. 
  • Straight turning
  • Shoulder turning
  • Chamfering
  • Thread cutting
  • Facing
  • Knurling
  • Filling
  • Taper turning
  • Eccentric turning
  • Polishing
  • Grooving
  • Spinning
  • Spring winding
  • Forming
Operations which are performed by holding the work by a chuck or a faceplate or an angle plate are following below. 
  • Drilling
  • Reaming
  • Borning
  • Counterboring
  • Taperboring
  • Internal thread cutting
  • Tapping
  • Undercutting
  • Parting-off
Operations which are performed by using special attachments are following below. 
  • Grinding
  • Milling

Lathe Machine precaution

  • Do not use hand to support the work piece you can using the work holding device.
  • Use the brush to clean the chip.
  • While the machine is in operating condition no any adjustment done by the operator. 
  • Before starting the operation makes sure that all parts are secured tightly. 
  • Not to keep a chuck handle attached by the chuck. 
  • Do not touch the table to a rotating chuck. 
A lathe is one of the most flexible machine tools in the manufacturing industry today due to its versatility. 

Cutting speed of Lathe Machine 


The speed of cutting tool at which the metal is removed by the tool from the workpiece is called the cutting speed. It is the peripheral speed of the work expressed in meters per minute. 

Cutting speed = ╬ádn/1000 m/min

Where, d = Diameter of the work piece 
n = RPM

A feed of Lathe Machine 


The distance the tool advances of each revolution of the work is called a feed of cutting tool. The feed is expressed in millimetres per revolution. 

Depth of cut of Lathe Machine 


The perpendicular distance measured from the machine surface to the uncut surface of the workpiece is called depth of cut. 

Depth of cut = d1-d2/2

d1=Diameter of the work surface before machining
d2=Diameter of the machined surface 

Machining time of Lathe Machine 


The machining of the lathe machine can be calculated for a particular operation if the speed of the job, feed and length of the job is known. It is calculated by the below formula. 

Machining time = l/s×n min 

Where, l=Length of the job 

s=Feed of the job 
n=RPM of the workpiece

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