The size of a lathe

Size of lathe machine expressed in following ways that illustrated below :

• The height of the centres measured from the lathe bed.
• The swing diameter over the bed. It is the largest diameter of work that will revolve without touching the bed and is twice the height of the centre measured from the bed of the lathe.
• The length between centres. This is the maximum length of work that can be mounted between the lathe centres.
• The swing diameter over the carriage. This is the largest diameter of work that will revolve over the lathe saddle and is always less than the swing diameter over the bed.
• The maximum bar diameter. This is the maximum diameter of bar stock that will pass through hole of the head stock spindle.
• The length of the bed. This is the approximate floor shape occupied by the lathe.

Feed depth of cut and machining time for lathe machine

Some important parameter keeps in mind while operating on a lathe machine.
Feed :
The feed of cutting tool in lathe work is the distance the tool advances for each revolution of the work. 
The feed is expressed in millimetres per revolution.

Depth of cut :
The depth of cut is the perpendicular distance measured from the machine surface to the uncut surface of the work piece. 

Depth of cut =  d₁-d₂ / 2

Where 

d1 = diameter of the work surface before machining

d2 = diameter of the machined surface

Depth of cut varies inversely as the cutting speed. 

for the general purpose, the ration of the depth of cut to the feed varies from 10:1

Machining Time :

The machining time in the lathe work can be calculated for a particular operation if the speed of the job, feed length of the job is known.

Machining time = l / s * n min

Where

l = length of the job in mm

s = feed of the job in mm 

n = r.p.m of the work 

Cutting speed of lathe machine

Cutting Speed :

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

In a lathe, it is the peripheral speed of the work past the cutting tool expressed in meters per minute.

Cutting speed = Πdn/1000 m / min

Where d = diameter of the work in mm

n = R.P.M of the work

Some example related to cutting speed : 

A steel shaft of 20 mm diameter is turned at a cutting speed of 40 m / min. Find the RPM of a shaft?

Cutting tool signature

The signature is a sequence of numbers listing the various angles, in degrees, and size of the nose radius.
This numerical method of identification has been standardized by the American Standard Association.
The seven elements that comprise the signature of a single-point cutting tool are always stated in the following order :

Back rake angle-Side rake angle-End relief angle-Side relief angle-End cutting edge angle-Side cutting edge angle-Nose radius

7-15-6-5-4-14-3

7 - back rake angle

15 - Side rake angle

6 - End relief angle

5 - Side relief angle 

4 - End cutting edge angle

14 - Side cutting edge angle

3 - Nose radius

Lathe machine cutting tools

There are different types of cutting tool used for various operation performed on a lathe machine.
For a general purpose work, the tool used in the lathe is a single point cutting tool.
For special-purpose operations, multi-point cutting tool may be used.

Nomenclature of single point cutting tool :

Various single point cutting tool used for different operation it classified under the following groups.

• According to the method of manufacturing the tool :

Forged tool
Tipped tool brazed to the carbon steel shank
Tipped tool fastened mechanically to the carbon steel shank

• According to the method of holding the tool :

Solid tool
Tool bit inserted in the tool holder

• According to the method of using the tool :

Turning
Chamfering
Thread cutting
Facing
Grooving
Forming
Boring
Internal thread cutting
Parting-off

• According to the method of applying feed :

Right hand
Left hand
Round nose

All tool having a different shape and size so the main question is how to identify the right tool for that problem all tool have different cutting tool signature according to that the tool may be identified and select appropriately.

Carriage in lathe machine

Carriage: 

The carriage is located between the headstock and tailstock and serves the purpose of supporting, guiding and feeding the tool against the job during operation. The main parts of carriage are:

The saddle is an H-shaped casting mounted on the top of lathe ways. It provides support to cross-slide, compound rest and tool post.

The cross slide is mounted on the top of the saddle, and it provides a mounted or automatic cross-movement for the cutting tool.

The compound rest is fitted on the top of the cross slide and is used to support the tool post and the cutting tool.

The tool post is mounted on the compound rest, and it rigidly clamps the cutting tool or tool holder at the proper height relative to the work centre line.


The apron is fastened to the saddle and it houses the gears, clutches and levers required to move the carriage or cross slide. The engagement of split nut lever and the automatic feed lever at the same time is prevented she carriage along the lathe bed.
Carriage is one of the main parts of the lathe machine.

lathe machine safety precautions

While using lathe machine a safety must be needed to avoid an accident.

When we use a lathe, the following things must take great care.

• Do not support the work piece by hand use work holding device.
• Instead of using hand use brush to clean the chip.
• No adjustment while the machine is operating.
• Do not measure to attempt revolving parts.
• Make sure that all parts are secured tightly in the lathe before starting the operation.
• Never place tools on the drilling table.
• Wear safety goggles and avoid loose clothing.
• Don't keep a chuck handle attached by the chuck. Next, it flies at the moment of turning a lathe. 
• Don't touch the byte table into the rotating chuck. Not only a byte but the table or the lathe are damaged.

Lathe machine working

How to lathe machine works? 

A lathe is a machine tool which holds the work piece between two rigid and strong supports called centres or in a chuck or faceplate which revolves. 

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.

Depth of cut, feed and cutting speed and machining time is also important parameter in machining on a lathe.

When we use a lathe, the following things must take great care.

(1) Don't keep a chuck handle attached by the chuck. Next, it flies at the moment of turning a lathe.
(2) Don't touch the byte table into the rotating chuck. Not only a byte but the table or the lathe are damaged.

Operation on lathe machine

Lathe machine performs different machining operation on a lathe.

In operation the work piece may be supported and driven by anyone of the following methods :

• Held between centres and driven by carriers and catch plates.
• Held on a mandrel which is supported between centres and driven by carriers and catch plates.
• Held and driven by chuck with the other end supported on the tailstock centre.
• Held and driven by a chuck or a faceplate or and angle plate.

Operations which are performed in a lathe either by holding the workpiece between centres or by a chuck are :

• Straight turning
• Shoulder turning
• Chamfering
• Thread cutting
• Facing
• Knurling
• Filling
• Taper turning
• Eccentric turning
• Polishing
• Grooving
• Spinning
• Spring winding
• Forming

An operation which is performed by holding the work by a chuck or a faceplate or an angle plate is:

• Drilling
• Reaming
• Borning
• Counterboring
• Taperboring
• Internal thread cutting
• Tapping
• Undercutting
• Parting-off

Operations which are performed by using special attachments are :

• Grinding
• Milling

Who invented lathe machine

The lathe machine Invented by

• Henry Maudslay

Jacques de Vaucanson built the first all-metal lathe around 1751, according to Book Rags. 

Henry Maudslay, who is considered the "father of the industrial lathe," invented the first screw-cutting engine lathe in 1797.

Henry Maudslay laid an important foundation for the Industrial Revolution with his machine tool technology. 

Lathe machine types

Types of Lathe machine :

1. Speed Lathe 

• Woodworking
• Centring
• Polishing
• Spinning

2. Engine Lathe

• Belt drive
• Individual motor drive
• Gear head lathe

3. Bench Lathe

4. Toolroom lathe

5. Capstan and Turret Lathe

6. Special purpose 

• Wheel lathe
• Gap bed lathe
• T-lathe

7. Automatic lathe

Lathe machine function

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 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.

Lathe machine introduction

Origin to Invented :

The lathe machine is one of the oldest machine tools.

The origins of lathe can be traced back to Ancient Egypt and ancient Greece. In ancient Egypt, two-person lathes were extensively used. 
In a two-person lathe, one person would turn the wood (work piece) and the other person would cut the wood with a single-point cutting tool. Cutting operation in this lathe involved a lot of manual labour and consumed a large amount of time.

Lathe machine came into existence from the early tree lathe which was then a novel device for rotating and machining a piece of work held between two adjacent trees.

A rope wound round the work with its one end attached to a flexible branch of a tree and the other end being pulled by a man-caused the job to rotate intermittently. then had tool arrives.

With its further development, a strip of wood called Lathe. it used to support the rope and that is how the machine came to be known as Lathe.

As early as 1569, the wood lathe was used in France. after that lathe machine adapted to metal cutting in England during the industrial revolution. 

In the year 1797 Henry Maudslay, an Englishman, invented the first screw-cutting lathe which is the forerunner of the present-day high speed, heavy-duty production lathe.

Lathe machine is also known mother/father of the entire tool family.

Basic Introduction :

A lathe is a machine tool which spins a block of material to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the work piece to create an object which has symmetry about an axis of rotation. 

On the lathe machine, the various operation is done by the different types of cutting tool for lathe machine with the Lathe machine safety precautions

Nowadays different Lathe machine types are available all lathe have different parts   so we choose according to the purpose which Operation we have to done and then select lathe machines. All lathe machine have different functions and different working.

Nowadays automatic CNC lathe machine is invented. It makes a big impact on manufacturing industries.

Common types of the lathe are used :

• Engine lathe 
• Bench lathe 
• Tracer lathe 
• Automatic lathe
• Turret lathe
• Computer-controlled lathe 

Lathe machine parts and function

Description and function of lathe parts :

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 main guiding member of the lathe machine so it must 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

For this point of view, the bed material should have high compressive strength, should be wear-resistant and absorb vibration.

Cast iron alloyed with nickel and chromium forms a good material suitable for 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. The 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 several parts that serve to support, move and control the cutting tool. 
Parts are following below :

• Saddle
• Cross-slide
• Compound slide
• Toolpost
• Apron

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

The cross-slide comprises 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. It is used for obtaining angular cuts and short tapper.

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.

Type of tool post :

• Single screw tool post
• Four-bolt tool post
• Open side tool post
• Four-way tool post

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 

The movement of the tool relative to the work is termed as "feed".

A lathe tool may have three types of feed :

• Longitudinal
• Cross
• Angular

6. Gear Box

The quick-change gear-box is placed below the headstock and contains a number of different sized gears.

This is the main parts of lathe machine. according to different lathe machine types are available in the market so different types to have different parts are there for various operations on lathe machine with the safety precaution.