Lathe Machine Operation

Lathe Machine Operation

In this article, you will learn about what are the different types of lathe machine operations
performed on the lathe machine. Lathe machine performs the different operations such as turning,
facing, taper turning, knurling, grooving, parting off, thread cutting, reaming etc.

Let's discuss all lathe machine operations one by one as follows.

To perform different lathe machine operations on a lathe, the workpiece may be supported and
driven by any one of the following methods:

1. Workpiece held between centres and tool driven by carriers and catch plates.
2. Workpiece held on a mandrel which is supported between centres and driven by carriers
and catch plates.
3. Held and driven by chuck with the other end supported on the tailstock centre.
4. Held and driven by a chuck or a faceplate or an angle plate.

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The above methods of holding the work may be classified under two heading:

1. Workpiece held between centres.

2. Workpiece held by a chuck or any other fixtures.

Read Also:
1. The Complete List of Milling Machine Operations
2. 6 Different types of Shaper Machine Operations

Types of Lathe Machine Operations

The lathe machine operations are classified into three main categories and are as follows.

Following are the Lathe machine operations done either by holding the workpiece between centres
or by a chuck:

1. Turning Operation
1. Plain or Straight Turning
2. Rough Turning
3. Shoulder Turning
4. Taper Turning
5. Eccentric Turning
2. Facing Operation
3. Chamfering Operation
4. Knurling Operation
5. Thread cutting Operation
6. Filing Operation
7. Polishing Operation
8. Grooving Operation
9. Spinning Operation
10. Spring Winding
11. Forming

Lathe machine operations which are performed by holding the work by a chuck or a faceplate or an
angle plate are:

1. Drilling
2. Reaming
3. Boring
4. Counterboring
5. Taper boring
6. Tapping
7. Undercutting
8. Internal thread cutting
9. Parting-off

The operation which is performed by using special attachments are:

1. Grinding
2. Milling

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Read Also about Lathe Machine:

 Lathe Machine: Parts, Types, Accessories, Attachments

 7 Types Of Lathe Machine Chucks with [Images]
 Cutting speed, Feed, Depth of cut, Machining time in lathe machine
 14 Different Types of Lathe Cutting Tools

1. Operations Done by Holding Workpiece Between Centres

Turning:

It is the most common type of operation in all lathe machine operations. Turning is the operation of
removing the excess material from the workpiece to produce a cylindrical surface to the desired
length.

The job held between the centre or a chuck and rotating at a required speed. The tool moves in a
longitudinal direction to give the feed towards the headstock with proper depth of cut. The surface
finish is very good.

1. Straight Turning:

The workpiece is held on the chuck and it is made to rotate about the axis, and the tool is fed
parallel to the lathe axis. The straight turning produces a cylindrical surface by removing excess
metal from the workpiece.

2. Rough Turning:

It is the process of removal of excess material from the workpiece in minimum time by applying high
rate feed and heavy depth of cut. in rough turning the average depth of cut 2mm to 4mm can be
given and feed is from 0.3 to 1.5mm per revolution of the work.

3. Shoulder Turning:

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When a workpiece has different diameters and is to be turned, the surface forming steps from one
diameter to the other is called the shoulder, and machining this part of the workpiece is called
shoulder turning.

Eccentric turning:

When a cylindrical surface two separate axis of rotation, with the first axis, is offset to the other axis
then such a workpiece is machined by the operation called eccentric turning. Here three sets of
centre holes are drilled.

By holding the workpiece at these three centres the machining operation for each of the surface can
be completed.

Taper Turning:

 A ''taper'' is the uniform increase or decrease in the diameter of the workpiece and
measured along with its length.
 Taper turning means to produce a conical shape by a gradual reduction in diameter from a
cylindrical workpiece.

The amount of taper in the workpiece is usually specified on the basis of the difference in diameter
of the taper to its length. It is known as a cone and it is indicated by the letter K.

It has the formula K = D-d / 1 to produce the taper on the workpiece.

 D = Larger diameter of taper.

 d = Small diameter of taper.

In the case of a lathe, the taper on a given workpiece is obtained by tuning the job and feeding the
tool at an angle to produce a gradual increase or decrease in the diameter of the workpiece.

 The two important types of tapers are,

o ''More taper'' here, the angle is very small and varies from 1.4 to 1.5°.
o ''Metric taper'' is available in seven standard sizes with standard taper angles.
 Methods of taper turning,
o Form tool method
o Combined feeds method
o Compound rest method or swivelling compound rest method
o Tailstock set over method
o Taper turning attachment method

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Read Also: Capstan and Turret Lathes

1. Form tool method

Here the taper length obtain is equal to the width of the form tool. To obtain the required size of the
taper the form tool is fed slowly straight into the workpiece by operating the cross slide
perpendicular to the lathe axis.

This is the simplest method of taper turning. It is limited to obtain small taper length such as
chamfering the side of the workpiece. The method is done at a faster rate.

2. Combined feeds method

The combined feed is made with the movement of a tool in longitudinal and lateral direction
simultaneously while moving the workpiece.

The taper, which we are going to obtain, is equal to the resultant to the magnitude of the
longitudinal and lateral feeds.

Changing the feeds rates in both directions can change the direction and the taper angle.

Read Also: Slotter Machine: Types, Parts and Operations [Complete Guide]

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3. Compound rest swivel method

Here the workpiece rotates and the cutting tool is fed at an angle by swivelled compound rest. The
base of the compound rest is graduated in degrees.

The taper angle is the angle at which the compound rest to be rotated is calculated by using the
formula tanα = D-d / 21, where, D= bigger diameter, d = smaller diameter, l = length of the
workpiece.

Compound rest can be swivelled to the required angle α. Once the compound rest is set to a
particular angle then the tool is moved by compound rest and wheel.

4.Taper turning attachment method

 This method is similar to the compound rest method.

 Here the job or workpiece rotates and the tool is fed at the taper angle α.
 In this, arrangement, which has guide block graduated in degrees, with the help of this the
block can be required taper angle to the lathe axis.
 The taper angle is calculated similarly to the compound rest method using the formula: tanα
= D-d / 21.

Advantages of taper turning attachment:

 Internal tapers can be obtained accurately.

 large size tapers can be easily obtained.
 Once the attachment is set the taper turning operation can do at a faster rate.
 By setting the taper angle to 'zero' we can carry out plain turning.

Disadvantages of taper turning attachment:

 It requires additional mounting facilities.

 Fitting and removing attachment consume more time.
 The attachment has to take large forces.

Tailstock set over method:

Here the workpiece on the job is tilted at the required taper angle. The tool is fed parallel to the axis.

The tilting of the workpiece or the job to the required taper angle is achieved by the movement of
the tailstock with the help of tailstock set over the screw. This method is useful for small tapers.

Facing:

It is an operation of reducing the length of the workpiece by feeding the perpendicular to the lathe
axis. This operation of reducing a flat surface on the end of the workpiece. For this operation, regular
turning tool or facing tool may use. The cutting edge of the tool should set to the same height as the
centre of the workpiece.

Read Also: Horizontal Boring Machine [Types, Tools and Operations]

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 Facing consist of 2 operations

o Roughing: Here the depth of cut is 1.3mm
o Finishing: Here the depth of cut is 0.2-0.1mm.

Chamfering operation:

It is the operation of getting a bevelled surface at the edge of a cylindrical workpiece. This operation
is done in case of bolt ends and shaft ends. Chamfering helps to avoid damage to the sharp edges
and protect the operation getting hurt during other operations. Chamfering on bolt helps to screw
the nut easily.

Knurling operation:

It is an operation of obtaining a diamond shape on the workpiece for the gripping purpose. This is
done to provide a better gripping surface when operated by hands. It is done using a knurling tool.
The tool consists of a set of hardened steel roller, and it is held rigidly on the toolpost.

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Knurling is done at the lowest speed available on a lathe. It is done on the handles and also in case of
ends of gauges. The feed varies from 1 to 2 mm per revolution. Two or three cuts may be necessary
to give the full impression.

Read Also: Drilling machine – Parts, It’s Types, Operations and More [Complete Guide] with PDF

Thread Cutting:

It is the important operation in the lathe to obtain the continuous ''helical grooves'' or '' threads''.

When the threads or helical grooves are formed on the out surface of the workpiece is called
external thread cutting. When the threads or helical grooves are formed on the inner surface of the
workpiece is called internal thread cutting. The workpiece is rotating between the two centres i.e.,
live centre and dead centre os the lathe.

Here the tool is moved longitudinally to obtain the required type of the thread. When the tool is
moved from right to the left we get the left-hand thread. Similarly, when the tool is moved from left
to the right we get the right-hand thread.

Here the motion of the carriage is provided by the lead screw. A pair of change gears drives the lead
screw and by rotating the handle the depth of cut can be controlled.

Filling:

It is the finishing operation performed after turning. This is done on a lathe to remove burrs, sharp
corners, and feed marks on a workpiece and also to bring it to the size by removing the very small
amount of metal.

The operation consists of passing a flat single-cut file over the workpiece which revolves at a high
speed. The speed is usually twice that of turning.

Polishing:

This operation is performed after filing to improve the surface quality of the workpiece. Polishing
with successively finer grades of emery cloth after filing results in a very smooth, bright surface. The
lathe is run at high speeds from 1500 to 1800m per min, and oil is used on the emery cloth.

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Grooving:

It is the process of reducing the diameter of a workpiece over a very narrow surface. It is done by a
groove tool. A grooving tool is similar to the parting-off tool. It is often done at the end of a thread
or adjacent to a shoulder to leave a small margin.

Read Also: Planer Machine: Parts, Types and It’s Working Principle

Spinning:

it is the process of forming a thin sheet of metal by revolving the job at high speed and pressing it
against a headstock spindle. Support is also given from the tailstock end.

Spring Winding:

Spring winding is the process of making a coiled spring by passing a wire around a mandrel which is
revolved on a chuck or between centres. A small hole is provided on the steel bar, which is
supported by Tool Post and the wire is allowed to pass through it.

Forming:

It is the process of turning a convex, concave or of any irregular shape. Form-turning may be
accomplished by the following method:

1. Using a forming tool.

2. Combining cross and longitudinal feed.
3. Tracing or copying a template.

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Forming tools are not supposed to remove much of the material and is used mainly for finishing
formed surfaces. Generally, two types of forming tools are used straight and circular. Straight type is
used for wider surface and the circular type for narrow surfaces.

Read Also: Grinding Machine: Types of Grinding Wheel And Grinding Machine Operation

2. Operations Done By Holding The Work By A Chuck

Lathe machine operations performed by holding the work by a chuck or a faceplate or an angle
plate are:

Drilling:

Drilling is the operation of producing a cylindrical hole in a workpiece. It is done by a rotating tool,
the rotating side of the cutter, known as drilling drill. In this operation, The workpiece is revolving in
a chuck or a faceplate and the drill is held in the tailstock drill holder or drill chuck.

The feeding is adopted is affected by the movement of the tailstock spindle. This method is adopted
for the drilling regular-shaped workpiece.

Reaming:

Reaming is the operation of finishing and sizing a hole which has been already drilled or bored. The
tool is used is called the reamer, which has multi-plate cutting edges.

The reamer is held on the tailstock spindle, either directly or through a drill chuck and is held
stationary while the work is revolved at a very slow speed.

Read Also: 15 Different Types of Milling Machines [Full Guide]

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Boring:

Boring is the operation of enlarging the hole which is already drilled, punched or forged. It cannot
produce a hole. Boring is similar to the external turning operation and can be performed in a lathe.
In this operation, the workpiece is revolved in a chuck or a faceplate and the tools which are fitted to
the tool post is fed into the work.

It consists of a boring bar having a single-point cutting tool which enlarges the hole. It also corrects
out of roundness of a hole. This method adopted for boring small-sized works only. The speed of this
process is slow.

Counterboring:

Counterboring is the operation of enlarging the end of the hole through a certain distance. It is
similar to a shoulder work in external turning.

The operation is similar to boring and plain boring tools or a counterbore may be used. The tool is
used called a counterbore. The speed is slightly less than drilling.

Taper Boring:

The principle of turning a tapered hole is similar to the external taper turning operation and is
completed by rotating the work on a chuck or a faceplate. The feeding tool is at an angle to the axis
of rotation of the workpiece.

A boring tool is mounted on the tool post and by swivelling the compound slide to the desired angle,
a short taper hole is machined by hand feeding.

Tapping:

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Tapping is the operation of cutting internal threads of small diameter using a multipoint cutting tool
called the tap. In a lathe, the work is mounted on a chuck or on a faceplate and revolved at a very
slow speed. A tap of required size held on a special fixture is mounted on the tailstock spindle.

Undercutting:

Undercutting is similar to grooving operation when performed inside a hole. It is the process of
boring a groove or a large hole at a fixed distance from the end of a hole.

This is similar to the boring operation, except that a square nose parting is used. Undercutting is
done at the end of an internal thread or a counterbore to provide clearance for the tool or any part.

Read Also: What is Shaper Machine and The 4 Major Types of Shaper Machines

3. Lathe Operations Done By Using Special Attachments

Lathe machine operations are performed by using special attachments:

Milling:

Milling is the operation of removing metal by feeding the work against a rotating cutter having
multiple cutting edges.

For cutting keyways or grooves, the work is supported on the cross-slide by a special attachment and
fed against a rotating milling cutter held by a chuck. The depth of cut is given by vertical adjustment
of the work provided by the attachment.

The depth of cut is given by verticle adjustment of the work provided by the attachment. The
feeding movement is provided by the carriage and the vertical movement of the cutter is arranged in
the attachment.

Grinding:

Grinding is the operation of removing the metal in the form of minute chips by feeding the work
against a rotating abrasive wheel known as the grinding wheel.

Both internal and external surface of a workpiece may be ground by using a special attachment
mounted on the cross slide. For the grinding external surface, the work may be revolved between
centres or on a chuck. For internal grinding, the work must be revolved on a chuck or faceplate.

The feeding is done by the carriage and the depth of cut is provided by the cross slide. Grinding is
performed in a lathe for finishing a job, sharpening a cutter, or sizing workpiece after it has been
hardened.

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Read Next:

 Drilling machine The complete guide – It’s Types, Operations and more [with pictures]
 Types of lathe machine.

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