A lathe is an all rounder machine tool used widely by industries today. It is an important machine tool in manufacturing industries due to its versatility. A number of operations can be performed on lathe machine.

What is a lathe machine ?

The lathe is a machine tool which holds the work piece between two rigid and strong supports. To remove metal from a piece of work to give it the required shape and size is the main function of the lathe.

This is accomplished by holding the work securely and rigidly on the machine and then turning it against cutting tool which will remove metal from work in the form of chips.

Construction of Lathe Machine


Lathe machine - explained | The Mechanical post

1. The Bed


The lathe bed forms the base of the machine, the headstock and tailstock are located at either end of the bed and the carriage rests over the lathe bed and slides over it.

The lathe bed is the guiding member of the lathe machine so it needs to satisfy the following condition.

  • It should be sufficiently rigid to prevent deflection
  • It must be massive with sufficient depth and width to absorb vibration
  • It must resist the twisting
  • To avoid distortion the bed material should have a high compressive strength, should be wear resistant and absorb vibration. For this purpose Cast iron is alloyed with nickel and chromium is used for mnufacturing lathe bed.

2. The Headstock


The headstock is secured permanently on the inner ways at the left-hand end of the lathe bed.

It comprises essentially a hollow spindle and mechanism for driving and altering the spindle speed.


3. Tailstock


The tailstock is located on the inner ways at the right-hand end of the bed.
This has two main use:

  • It supports the other end of the work
  • It holds a tool for performing an operation such as drilling, reaming, tapping etc.

4. Carriage


The carriage of a lathe has various parts which serve to support, move and control the cutting tool. Parts are following below :

  • Saddle
  • Cross-slide
  • Compound slide
  • Tool post
  • Apron
The saddle is an H-shaped casting that fits over the bed and slides along the ways. It carried the cross-slide and tool post.

The cross-slide consists a casting, machined on the underside for attachment to the saddle and carries location on the upper face for the tool post or compound rest.

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

The tool post located on the top of the compound rest to hold the tool and to enable it to be adjusted to a working position.

The apron is fastened to the saddle and hangs over the front of the bed.

Apron contains gears, clutches, and levers for operating the carriage by hand and power feeds.

5. Feed Mechanism


Feed is the movement of the tool relative to the work.

A lathe tool may have three types of feed :

  • Longitudinal (For length)
  • Latitudnal (For depth)
  • Angular (For taper)


Working of Lathe machine


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.

In a tool post which is fed against the revolving work, the cutting tool is rigidly held and supported.

With the cutting tool fed either parallel or at right angles to the work axis, the normal cutting operations are performed.

Operations performed on Lathe

The operation which is performed on a lathe either by holding the workpiece between centres or by a chuck is the following :
  • Straight turning
  • Shoulder turning
  • Chamfering
  • Thread cutting
  • Facing
  • Knurling
  • Filling
  • Taper turning
  • Eccentric turning
  • Polishing
  • Grooving
  • Spinning
  • Spring winding
  • Forming

The operation which is performed by holding the work by a chuck or a faceplate or an angle plate is the following :
  • Drilling
  • Reaming
  • Borning
  • Counterboring
  • Taperboring
  • Internal thread cutting
  • Tapping
  • Undercutting
  • Parting-off

More operations can be performed on lathe by adding special attachments like :

  • Grinding
  • Milling


Cutting Speed 


The cutting speed of lathe is cutting tool is the speed at which the metal is removed by the tool from the work piece.

Feed


In a lathe work, the feed of the cutting tool is the distance the tool advances for each revolution of the work.
Feed is expressed in millimeters per revolution.

The depth of cut 


The depth of cut is the perpendicular distance from the machine tool surface to the surface of the workpiece.

Depth of cut = d1-d2 / 2

Where,

d1 = Diameter of the surface before machining

d2 = Diameter of the machined surface

A depth of cut varies inversely with the cutting speed.

Types of Lathe Machine

1. Speed Lathe

2. Engine Lathe

3. Bench Lathe

4. Toolroom Lathe

5. Capstan and Turret Lathe

6. Special purpose

7. Automatic Lathe

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