Turning Workpiece (Basic)

Worksheet 9.2.2: Facing, Parallel turning and shoulder turning

Answer
1. (C) Machine a workpiece to the required length
2. (C) Produce a true cylindrical surface
3. (C) Filleted Shoulder
4. (D) Allow mating parts fit flatly onto each other
5. (B) Knife-edge tool

Code No. Turning Workpiece Date: Developed Date: Revised Page #
MEE722302 3

Information Sheet 9.2.2: Grooving and Parting-off

Learning outcomes:
1 Turn workpiece
Learning Activity:

1. Explain grooving and parting-off operation
2. Explain the procedures of grooving and parting –off operation

Grooving and Parting Off

1. Grooving
Grooving is also known as under-cutting, recessing or necking. There are many types of
grooves, among them square, round and bevelled ones.

Figure 10.1 – Grooving

Grooving is done for the following reasons:

 Permit full travel of the nut up to the shoulder.
 Provide easy access to the grinding wheel to grind the face and the cylindrical portion.
 Provide clearance for the tool to travel fully up to the shoulder for thread cutting.
 Ensure a proper fit for the mating components.
 Accommodate the retainer ring.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 1

Information Sheet 9.2.2: Grooving and Parting-off

Figure 10.1.1 – Purposes of Grooving

Common Types of Grooves
The three types of grooves are:

 Square groove
 Round groove
 Vee-shaped groove

When machining grooves, the tool bit is ground to the size and shape of the groove.

Figure 10.1.2 – Types of Grooves

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.2: Grooving and Parting-off

Tool Setup for Grooving
 Grind the tool to the desired size and shape.
 Set the lathe to half the speed used for parallel turning.
 Apply cutting fluid.

Figure 10.1.3 – Grooving Setup

2. Parting Off
Parting Off is the process of cutting a groove around a revolving workpiece in order to severe it
from the piece held in the chuck. It saves time in cutting-off the extra length of work.

Figure 10.2 - Parting Off

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.2: Grooving and Parting-off
Types of Parting Off Tool Holders

a. Straight Tool Holder
The straight tool holder is used for general purposes.

Figure 10.2.1a – Straight Tool Holder
b. Offset Parting Off Tool Holder
Similar to the normal tool holder, the offset tool holder is either:
 Right hand tool holder
 Left hand tool holder

Figure 10.2.1b – Offset Parting Off Tool Holder

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 4

Information Sheet 9.2.2: Grooving and Parting-off
Setting Up a Tool for Parting Off Operation

 Set the parting off tool to centre height and at 90 to the work axis.

Figure 10.2.2 – Setting Up

 Set the lathe to half the speed for turning.
 Reduce the in feed when the work is nearing the axis of the work.
 Never part off work that is held between centres.
 To prevent chattering, use low speed and feed.
 Apply cutting fluid.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 5

Information Sheet 9.2.2: Grooving and Parting-off
Figure 10.2.2 – Never Part Off Work Held Between Centres

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 6

Worksheet: 9.3.2- Grooving and parting off

Learning outcomes:
1 Turn Workpiece
Learning Activity:
1.2 Objectives

1. Identify the following lathe operation;
• Grooving
• Parting - off

Test Your Self

Direction: Identify the method use in setting tool.

(1) It is used to machine a recess or an undercut on a cylindrical surface.

A. Grooving
B. Parting
C. Facing
D. Threading

(2)It is the operation of cutting off one end of the work.

A. Grooving
B. Parting
C. Facing
D. Threading

( 3 ) The three common types of grooves are :Square Groove,Round Groove, and;
A. V-shaped Groove
B. Filleted Groove
C. Threaded Groove
D. I Groove

( 4) In parting operation, when the tool is nearing the
axis of the work. The feed should be;

A. Allow until it cut
B. Add more
C. The same
D. Reduce

Code No. Turn workpiece Date: Developed Date: Revised Page #
MEE722302 1

Worksheet: 9.3.2- Grooving and parting off

Answer Key:

1. A. Grooving
2. B. Parting
3. C. Filleted Shoulder
4. D. Reduce

Code No. Turn workpiece Date: Developed Date: Revised Page #
MEE722302 2

Information Sheet 9.2.3:

Learning outcomes:
1 Turn workpiece
Learning Activity:

1. Explain center drilling and drilling operation on lathe machine
2. Explain the procedures in center drilling and drilling operation on lathe machine

Drilling Operation on Centre Lathe

1. Centre Drilling

Centre drilling involves drilling and countersinking. When jobs are to be supported between
centres, centre drilling is necessary.

Figure 13.1 – Centre Drilling

Purpose of Centre Drilling
The purpose of drilling centre holes are :

 Provide support for long workpieces or turning between centres.
 Provide a guide for the subsequent drilling operations.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.3:

Figure 13.2 - Purposes of Centre Holes

Centre Drills
Centre drills are made from high speed steel ( HSS ) and come in sizes 1 to 7, with 1 being the
smallest and 7 the largest.

Figure 13.3 - Centre Drill

Setting Up for Centre Drilling Operation

 Hold the work in a chuck and mount the centre drill in a drill chuck in the tailstock.
 Move the tailstock to about 24 mm to the workpiece and lock it in position.
 Use spindle speeds from 600 to 800 rpm.
 Feed the centre drill into the work by turning the tailstock handwheel.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 2

Information Sheet 9.2.3:

Figure 13.4 – Centre Drilling Operation
Errors in Centre Drilling
A centre hole must be drilled to the proper depth to ensure that it provides a good bearing
surface on the lathe centre.
If the centre hole drilled is too deep, the bearing surface on the lathe centre will be poor.

Figure 13.5a – Centre Hole Drilled Too Deep

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.3:

If the centre hole drilled is too shallow, there is not enough bearing surface for the lathe centre
to support the work.

Figure 13.5b - Centre Hole Drilled too shallow

A correctly drilled centre hole provides a good bearing surface on the lathe centre. “ A ”
should be ¾ the drill diameter.

Figure 13.5c – Centre Hole Drilled Correctly

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.3:

2. Drilling Operation

Drilling is the process of producing a hole in solid stock, the usual method is to hold the
workpiece in the chuck and mount the drill in the tailstock spindle.

Figure 14.8 – Drilling on a Centre Lathe

Twist Drills
Generally, drills up to 13mm diameter have straight shanks. It has to be held in a drill chuck so
as to be held in the tailstock spindle for drilling operations.

Figure 13.6.1a – Straight Shank Twist Drills

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.3:

Drills bigger than 13mm diameter have taper shanks. It can be held directly into the tailstock
spindle. A sleeve is used to hold the tapered shank drill if it smaller than the tailstock spindle
taper.

Figure 13.6.1b– Drill Sleeve
A socket is used to hold a tapered shank drill if its shank is bigger than the tailstock
spindle taper.

Figure 13.6.1c – Drill Socket
A drift is used to remove the tapered shank drill from a sleeve or socket.

Figure 13.6.1d – Using a Drill Drift

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.3:

Setting Up for a Drilling Operation

 Hold the select drill in the tailstock spindle.
 The depth of the hole can be measured using the scale on the tailstock spindle.
 Select the spindle speed according to the size of drill.
 Generally, when the drill is smaller, the spindle speed would be faster.

Figure 13.6.2a – Drilling Operation

 Drill a pilot hole first if a big hole is to be drilled. The pilot hole guides the bigger drill into
the work accurately.

Figure 13.6.2b – Drilling a Pilot Hole

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.3:
 The size of the pilot hole should be slightly larger than the web of the drill.

Drill

Figure 13.6.2c – Web of the Drill
 Withdraw the drill from the work regularly to allow chips to clear the hole.
 This is also to allow cutting fluid to reach the drill point.
 Reduce the pressure from the handwheel when the drill is breaking through the hole.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 8

Information Sheet 9.2.4: Reaming

Learning outcomes:
1 Turn workpiece
Learning Activity:

1. Explain reaming operation
2. Explain the procedures in reaming operation

Reaming Operation on Centre Lathe
Reaming is the process of enlarging a drilled or bored hole. The operation is performed with a
tool called a reamer.

Figure 14.0 – Reaming

Purpose of Reaming
The main purposes of reaming a hole are :

 Produce a perfectly round hole with an accurate diameter
 Produce the hole with a straight and smooth wall

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 Aug 15, 2003
Mar 01, 2006 1

Information Sheet 9.2.4: Reaming

Figure 14.1 - Purpose of reaming
Machine Reamers
Machine reamers can have either straight or tapered shanks. The end of the reamer usually
has a chamfer.

Types of Machine Reamers

Machine reamers can be divided into two types:

 Roughing reamers which can cut on the end only.
 Finishing reamers which can cut on the end and along the length of the lands.

Figure 14.2.1 – Machine Reamers

a) Roughing Reamer - Roughing reamers are designed to produce a hole quickly within
0.1 mm under the nominal size of the hole.

The rose reamer which has teeth chamfered to about 45° is the most commonly used machine
reamer. All the cutting is done at the end of the reamer.

The circumference around the flutes is cylindrical to support and guide the reamer in deep
holes.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 Aug 15, 2003
Mar 01, 2006 2

Information Sheet 9.2.4: Reaming

Figure 14.2.1a – Rose Reamer
b) Finishing Reamers

Finishing reamers are used to finish a hole which has been bored or rough reamed to within
about 0.12 mm on the finish size.

Fluted chucking reamers have more teeth than rose reamers of a given diameter and may
have straight or tapered shanks. They are designed to cut along the full length of the land to
produce a smooth and accurately sized hole. The ends of the reamer teeth are slightly
chamfered for end cutting.

Figure 14.2.1b - Chucking Reamer

c) Shell Reamer - The shell reamer is used to finish large diameter bores. It consists of a
hardened body which is fitted to a soft low carbon shank, for the purpose of economy.

The floating reamer has some free movement within its holder. This makes it suitable for
reaming a previously machined bore, and for use when the headstock and tailstock are out of
alignment.

Figure 14.2.1c – Shell Reamers

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 Aug 15, 2003
Mar 01, 2006 3

Information Sheet 9.2.4: Reaming

Types of Flutes used in Machine Reamer
Machine Reamers comes with two types of flutes:

 Straight flutes – They are used for reaming plain holes.
 Helical flutes – They are used for reaming plain hole and holes with interrupted

surfaces, eg. hole with a keyway.

Figure 14.3 – Types of Flutes

Reaming Allowance
The amount of allowance for reaming depends on:

 The type of material to be reamed
 The size of the hole to be reamed
 The type of finishing required
 The condition of the lathe.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 Aug 15, 2003
Mar 01, 2006 4

Information Sheet 9.2.4: Reaming

Figure 14.4 – Reaming Allowance

Machine Reaming Allowance

Hole Diameter (mm) 5 10 25 40 50 75
0.6 0.75 1.1
Allowance (mm) 0.25 0.35 0.5

Figure 14.4 – Machine Reaming Allowance

Reaming Speed and Feed
The selection of reaming speed and feed depends on :

 The type of material to be reamed
 The type of finishing required
 The tolerance and accuracy required
 The size and rigidity of the work and reamer

The reaming speed should be half to two-thirds the drilling speed while the reaming feed is
about 2 times the feed used for drilling. Never reverse a reamer when removing it from the
work. Reduce the speed if the reamer chatters while cutting.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 Aug 15, 2003
Mar 01, 2006 5

Information Sheet 9.2.5: Boring Operation

Learning outcomes:
1 Turn workpiece
Learning Activity:

1. Explain boring operation
2. Explain the procedures in boring operation

Boring Operation on Centre Lathe
Boring is an internal machining operation where a single point cutting tool is used to enlarge a
hole. Boring may be used to enlarge a hole to exact size when a drill or reamer cannot be
used.

Figure 15.0 - Boring on a Centre Lathe

While the machining technique remains essentially the same as for external turning, several
conditions are encountered that cause difficulties if allowances are not made for them.

 Movement of the cross slide feed screw is reversed.
 The machinist must work by “feel” as the cutting action cannot be readily observed.
 Additional front clearance must be ground on the cutting tool to avoid rubbing, otherwise

the tool bit is similar as for external turning.
 Boring deep or small diameter holes require a long, slender tool holder. The overhang

makes the tool more likely to spring away from the surface to be machined; this makes it
necessary to take several cuts to remove the same amount of material.
 Internal measuring tools are more difficult to use than those for taking external
measurements.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 1

Information Sheet 9.2.5: Boring Operation

Purpose of Boring

The main purposes of performing boring operations are:
 To produce large holes of odd-sized holes, eg. 16.68mm
 To produce true holes
 To produce better surface finish holes

Types of Boring Tools

There are two categories of boring tools. They are:

 Solid forged boring tools
 Boring tool with inserted tool bit
a) Solid Forged Boring Tool

The solid forged tool is used on small diameter holes which cannot be bored with the
inserted tool bit and boring bar. This is due to the necessary small section of the bar being
further weakened by the hole which takes the tool.

The tool bit is integral with the shank, the whole usually being made of high speed steel.
Occasionally, tungsten carbide or high speed steel tips are brazed to low carbon steel bars.

Figure 15.2a – Solid Forged Boring Tool

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 2

Information Sheet 9.2.5: Boring Operation

b) Boring Tool with Inserted Tool Bit

A low carbon steel bar has a hole at one end to take an inserted tool bit or round or square
section, the size depending on the diameter of the bar. The square tool bits are set at angles of
30°, 45° or 90°. This is held by a set screw or a special threaded end cap.

The tool bit may be square to the axis of the bar for plain boring or at an angle for facing
a shoulder, or threading up to a shoulder. The bar is held in a split or V-block holder.

Figure 15.2b – Boring Tool with Inserted Tool Bit

Boring Tool Shapes and Angles

Boring tools should have the correct shape and angles in order to cut properly. For boring
small through holes and blind holes, use a forged boring tool. The boring bar is used for boring
big though holes.

The recommended tool angles are :

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 3

Information Sheet 9.2.5: Boring Operation

Figure 15.3a - Boring Tool with Positive Approach Angle
A boring tool used for boring through holes should have a positive approach angle. A boring
tool used for boring blind holes should have a negative approach angle. For general purposes,
grind the approach angle to about 5.

Figure 15.3b – Boring Tool with Negative Approach Angle

To have a longer tool life and a better surface finish on the work, grind a small nose radius on
the tool bit. A secondary clearance angle is ground to prevent the heel of the tool from rubbing
the work.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 4

Information Sheet 9.2.5: Boring Operation

Figure 15.3c – Primary and Secondary Clearance
Setting Up the Boring Tool
The boring tool cutting edge is set slightly above the centre height because the tool is likely to
spring downwards during cutting.

Figure 15.4a – Cutting Edge Set Slightly Above Centre Height

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 5

Information Sheet 9.2.5: Boring Operation

For boring big through holes, use the biggest suitable boring bar. Make sure that the
boring bar is long enough to go through the hole but with minimum overhang to reduce
chatter.

Figure 15.4b – Setting Up the Boring Tool

Effects of Boring Bar Overhang
Too much overhang of the boring bar causes chattering which will result in poor surface finish.

Figure 15.5a – Check for Chatterin

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.5: Boring Operation
Too much overhang may also cause “bell-mouthing” which is an effect of a hole which has its
end diameter bigger than its core diameter.

Figure 15.5b – Bell Mouth Effect
Good Practices in a Boring Process

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 7

Information Sheet 9.2.5: Boring Operation

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 8

Information Sheet 9.2.6 : Knurling operation

Learning outcomes:
1 Turn workpiece
Learning Activity:

1. Explain knurling operation
2. Explain the procedures in knurling operation

Knurling Operation on Centre Lathe

Knurling is the process of forming horizontal or diamond shaped serration on the
circumference of the work. Knurling is not a cutting operation. It is an embossing operation.

Figure 16.0 – Knurling

Purpose of Knurling

The main purposes of performing knurling are :

 Provide a better grip on the surface.
 Increase slightly the diameter of the workpiece to obtain a press fit.
 To make the surface look better.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 1

Information Sheet 9.2.6 : Knurling operation

Figure 16.1 – Purpose of Knurling

Knurl Patterns
Two types of pattern and three different pitches are available for knurling.
The two patterns are:

 Straight Line pattern
 Diamond shaped pattern

Figure 16.2.1 – Knurl Patterns

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 2

Information Sheet 9.2.6 : Knurling operation

The three pitches are:

 Fine
 Medium
 Coarse

Figure 16.2.2 – Knurl Pitches

Types of Knurling Tools

a. Single Roller Type - It has only one roller and is used to knurl straight-lined
pattern.

Figure 16.3a – Single Roller Knurling Tool

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.6 : Knurling operation

b. Self Centering Type - It has one pair of rollers and is used to knurl diamond-
shaped pattern.

Figure 16.3b – Self Centring Knurling Tool

c. Revolving Head Knurling Tool - It has 3 pairs of rollers (coarse, medium, fine)
and is used to knurl diamond shaped pattern.

Figure 16.3c – Revolving Head Knurling Too

Setting-Up the Knurling Tool

 Set the knurling tool to between 87 to 90 to the work axis and at approximately the
tool centre height.

 Use low spindle speed (About ¼ the turning speed).
 Use automatic feed.
 Apply cutting fluid.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 4

Information Sheet 9.2.6 : Knurling operation

Figure 16.4 – Setting-Up the Knurling Tool

Faults in Knurling

If the automatic feed is disengaged before the full length of the work has been knurled, the
knurl may be damaged.

Figure 16.5a – Damaged Knurl
“Double Impression” is caused by incorrect pressure and feed used.

Figure 16.5b – Double Impression

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 5

Worksheet: 9.7.2 –Knurling operation

Learning outcomes:
1 Turn Workpiece
Learning Activity:
1.2 Objectives

1. Identify knurling operation
2. Define knurling operation

Test Your Self

1. The process of machining straight-line or diamond-shaped patterns on the surface of a
cylindrical workpiece is known as

A. facing
B. knurling
C. reaming
D. threading

2. The main purpose of knurling a workpiece is to
A. provide a better fit
B. provide a better grip
C. increase the diameter
D. roughen the surface finish

3. The spindle speed used for knurling workpiece is about
1. 1/4 the normal speed of turning.
2. 1/2 the normal speed of turning .
3. twice the normal speed of turning .
4. more than twice the normal speed of turning.

4. A straight-lined pattern knurling tool has
A. 1 roller.
B. 1 pair of rollers.
C. 2 pair of rollers.
D. 3 pair of rollers.

5. A self-centering type of knurling tool has

A. 1 pair of rollers.
B. 2 pair of rollers.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Worksheet: 9.7.2 –Knurling operation

C. 3 pair of rollers.
D. 4 pair of rollers.

6. A knurling tool with three pairs of rollers is known as
A. Single roller type.
B. Self-centering type.
C. Revolving-head type.
D. Multi-head type.

7. Which one of the following operations should be done first on the workpiece before knurling it?
A. Facing operation.
B. Parting-off operation.
C. Taper turning operation.
D. Parallel turning operation.

8. ‘Double impression’ in knurling is caused by
A. setting the tool above centre height.
B. setting the tool below centre height.
C. incorrect pressure and feed used.
D. using wrong feed-rate and spindle speed.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 2

Worksheet: 9.7.2 –Knurling operation

Answer Key:

1. B Knurling
2. B Provide a better grip
3. A 1/4 the normal speed of turning.
4. A 1 roller.
5. A 1 pair of rollers.
6. C Revolving-head type.
7. D Parallel turning operation.
8. C Incorrect pressure and feed used.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 3

Information Sheet 9.2.7: Taper Turning

Learning outcomes:
1 Turn workpiece
Learning Activity:

1. Define taper turning
2. Explain methods of taper turning
3. Explain the procedures in taper turning
Taper Turning using Compound Slide
Tapers
A round work is considered to be a taper when its diameter increases or decreases at a
uniform rate. Cones, lathe centres and taper shank drills are examples of tapered components.
Taper turning on a lathe can be done with the work held in a chuck or between centres.

The purposes of producing tapers are :
 To allow fitted parts to be self centring
 To allow fitted parts to be self holding
 To allow fitted parts to separated easily.
 Tapers also permit the interchangeability

of certain cutting tools or attachments
with extreme accuracy.

Figure 18.1.1 – Purpose of Tapers
Expressing a Taper

Figure 18.2 – Symbols Used for
Calculating Tapers

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning

The following symbols are to be used:

L = Total length of workpiece in mm
I = Length of portion to be tapered in mm
D = Large diameter of taper in mm
d = Small diameter of taper in mm
T = Taper expressed as a ratio
 = Included angle of taper in degrees

There are three ways to specify Non-standard Tapers.

 Taper is the change in diameter per unit axial length ( D-d ) and can be expressed as a
ratio, for example: 1:10, 3:100

 The included taper angle (  ) expressed in degrees can be given. This method is used
when the taper angle is large.

Ratio
A 1:10 taper has a difference in diameter of 1mm for every 10mm of axial length.

Taper Ratio  Big Diameter - Small Diameter
Tapered Length

Figure 18.3.1 – Taper Expressed in Ratio

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning
From

Taper Ratio  Big Diameter - Small Diameter
Tapered Length

Taper Ratio  44 - 41  3  1
30 30 10

Taper Ratio = 1: 10
Included Angle
The taper is expressed in degrees and minutes.

Figure 18.3.2 – Taper Expressed in Included Angle

Millimetres per Metre
The taper is expressed by the change in diameter per metre length.

Figure– Taper expressed in millimeters per meter

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning

Standard Tapers
Various standards for taper are in common use; the most commonly used are :

 Morse Taper
 International Taper
 Brown and Sharp Taper
 Jarno Taper

Morse Tapers
The taper is approximately 1:9.2. It is probably the most widely used taper in the machine
industry. It is most commonly found on drills, reamers and lather centre shanks. The standard
sizes are Nos. 0,1,2,3,4,5,6, and 7. No. 0 is the smallest and No.7 is the largest.

Figure 18.4.1a – Morse Tapers

Figure 11.7 – Morse Tapers

International Tapers
They are self-releasing tapers with big included angles. The standard sizes are Nos. 30,40,50
and 60.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning

Figure 11.8 – International Tapers

Brown and Sharp Tapers
The taper, approximately 1:24 is used on Brown and Sharp machines and accessories.

Jarno Tapers
The taper is 1:20. It is not as commonly used as some other standard tapers.

Methods of Turning Tapers

Taper turning on a lathe can be done on work held between centres or with a lathe chuck.

There are four methods by which tapers can be turned on a centre lathe. The four methods
are:

 Using a form tool.
 Swiveling the compound slide.
 Using the taper turning attachment.
 Offsetting the tailstock.

The choice of taper turning methods depends on the:
 Work length
 Taper length
 Taper angle
 Number of pieces to be machined
 Type of taper ( External or internal )

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning
1. Off-Setting the Compound Slide

This method is used for short tapers only. The compound rest is set to half the included angle
and then locked. Since there is no power feed for the compound rest, the job is done manually.
It is usual practice to turn from the small diameter to the large diameter.

Figure 18.5a - Half Included Angle
For example; to turn a component with an included angle of 60, we need to find the half
included angle. In this case it would be 30.

Figure 18.5b – Half Included Angle

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning

Figure 18.5c - Off-setting the Compound Slide

The advantages of this method are:
 It can be used for turning external and internal tapers.
 It is easy to set up.

The limitations of this method are:
 It cannot use automatic feed.
 It is not suitable for machining tapers having lengths longer than the compound slide
travel.

2. Using a Form Tool

The tool bit is ground to the shape of the tapered angle and is fed directly to the work to
obtain the shape required. It is usually used for producing short tapers, eg. chamfers
and bevels.

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning

Figure 17.2a – Using a Form Tool

Figure 17.2a – Using a Form Tool

The advantages of this method are:
 It can be used for turning external and internal tapers.
 It is easy to set up.

The limitations of this method are:
 It is not suitable for machining long tapers.
 Chattering will occur if the contact area between the tool and the work is big.

3. Taper Turning Attachment Method
This method can only be done on lathes with this
attachment. Long tapers are usually machined
this way. The taper turning attachment is attached to
the cross slide of the lathe.The clamp when tightened
locks the carriage to the attachment so that the tool
follows the angle at which the guide bar has been
set.

Figure 17.3a - Using the Taper Turning Attachment

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 8

Information Sheet 9.2.7: Taper Turning

The attachment is set to half the included angle of the taper. The tool follows the angle at
which the guide bar has been set.

Figure 17.3b – Setting the Taper Turning Attachment

The advantages of this method are:
 It can be used for turning external and internal tapers.
 It can use automatic feed.
 Work can be held in a chuck or between centres.

The limitations of this method are:
 It cannot be used to cut steep tapers.

4. Offsetting the Tailstock Method
The offsetting tailstock method is normally used for turning long tapers when other methods
are not available. When the centres are out of alignment, the workpiece gets taper turned
because the centre line of the work is at an angle with the movement of the tool. The amount
of taper depends upon the amount the tailstock is offset.

Figure 17.4 - Off-Setting the Tailstock

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 9

Information Sheet 9.2.7: Taper Turning

To calculate the amount of tailstock offset, you can use this formula :

Tailstock Offset  L(D-d)
2

where D = Diameter of the large end

d = Diameter of the smaller end

L = Total length of workpiece

I = Length of tapered part

TPM = (D - I

Figure 17.4.1 - Tapered Component

Example:
a. Determine the tailstock offset for a workpiece with a TPM of 0.005 mm and the
length of work is 400 mm.

Tailstock Offset

= 1.0 mm

b. Calculate the tailstock offset for the following job.
D = 30 mm

d = 20 mm

L = 250 mm

I= 75 mm I
Tailstock Offset = {Lx(D–

= { 250 x ( 30 – 20 )

= 16.66 mm

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning

Exercises
a. Calculate the amount of tailstock offset to cut a taper for a work with large diameter
of 22 mm, small diameter 20 mm, length of taper 40 mm and length of workpiece
200 mm. ( Ans : 5 mm)

b. Calculate the tailstock offset required to turn a 1:30 taper with 60 mm taper length on
a workpiece 300 mm long. The smaller diameter of the taper section is 20 mm. ( Ans
: 5 mm )

The advantages of this method are:
 It can be used for turning long tapers.
 It can use automatic feed.

The limitations of this method are:

 It cannot turn internal tapers.
 The amount of tailstock offset is limited which will limit the tapered angle.
 The centres may be damaged if plain centres are used.
 It can cut tapers on work held between centres only.

Methods of offset Tail;stock
When the amount of offset is determined, the tailstock can be offset accurately with a dial
indicator or with a feeler gage

Figure 17.4.6a – Offset the Tailstock
Using Dial Indicator

Figure 17.6.4c – Offset the Tailstock

Code No. Turn Workpiece Date: Developed Date: Revised Page #
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Information Sheet 9.2.7: Taper Turning

Figure 17.4.6b – Offset the Tailstock using the feeler gauge

Turning Larger Diameter
When turning a taper that has the larger diameter at the tailstock end, offset the tailstock away
from the operator.

Figure 11.19 – Tailstock Offset Away from the Operator

Turning smaller Diameter
When turning a taper that has the smaller diameter at the tailstock end, offset the tailstock
towards the operator.

Figure 11.20 – Tailstock Offset Towards the Operator

Code No. Turn Workpiece Date: Developed Date: Revised Page #
MEE722302 12