Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
Dr. Ikbal Bahar Laskar
Workshop (Practical)
Prepared By:
Ikbal Bahar Laskar
Department of Mechanical Engineering
Jorhat Engineering College (JEC), Jorhat, Assam, India
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Course Code Course Title Hours per week L-T-P Credit C
ME181402 Workshop Theory
and Practice-I 3-0-2 4
Syllabus
MODULE 1: LATHE
. (a) Lathe- Functions, Classification and Specification, Different parts, Drive mechanisms for speed, feed, depth of cut, Taper turning, Machining time. Lathe Accessories and Attachments.
. (b) Semi-Automatics: Capstan and Turret lathes – Different parts – Tools ––Work and Tool holding devices. Indexing and Bar Feeding Mechanisms. Tool layout and Tool Schedule chart.
MODULE 2: SHAPER, PLANER, SLOTTING & BROACHING OPERATIOS
. (a) Shaper – Function, Classification and Specification – Quick
. (b) return and feed mechanisms – Shaper operations – Cutting speed and Machining time calculations.
. (c) Planer - Function, Specification Table drives and feed mechanism
. (d) Broaching: Purpose, broaching tool and machine
. (e) Slotting machine: Purpose, slotting tool and machine
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Course Code Course Title Hours per week L-T-P Credit C
ME181402 Workshop Theory
and Practice-I 3-0-2 4
Syllabus
MODULE 3: DRILLING
(a) Drilling machines – Classification – specifications – Parts drilling machine – spindle drive mechanisms – tool and work
holding devices for operation
(b) Types of drills and tool in hand nomenclature, Drill size and designation of drills.
(c) Deep hole drilling
(d) Introduction to reaming and tapping
MODULE 4: MILLING:
Introduction – Classification – Specifications - Principal parts of a milling machine. Elements of a milling cutter, milling
processes – Up-milling – Down milling – Face milling – End milling. Cutting Speed, Feed and Depth of Cut – Machining
Time. Indexing and Dividing Head
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Course Code Course Title Hours per week L-T-P Credit C
ME181402 Workshop Theory
and Practice-I 3-0-2 4
Syllabus
MODULE 5: GRINDING AND SURFACE FINISHING Grinding: Introduction – Kinds of grinding – Grinding Processes –
Centreless Grinders – Surface Grinders – Tool and Cutter Grinder – Specifications. Grinding Wheel – Composition and
specification. Selection of Grinding Wheel. Dressing, and Truing of grinding Wheel.
Assam Science and Technology University Page 3 of16
Surface Finishing:
Introduction – Classification – Principle and Operations of Lapping, Honing, Super finishing, Polishing, Buffing, Tumbling
and Burnishing
MODULE 6: PATTERN MAKING AND FOUNDRY
Pattern making and sand casting – Pattern materials – Types – Pattern allowances. Core prints. Moulding sand – ingredients
– classification – sand additives – properties of moulding sand – sand preparation and testing. Green sand mould
preparation. Cores and core making – Types of cores.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Course Code Course Title Hours per week L-T-P Credit C
ME181402 Workshop Theory
and Practice-I 3-0-2 4
Syllabus
Text/Reference Books:
Elements of Workshop Technology (Vol. I & II) – S.K. Hajra Choudhury and A.K. Hajra Choudhury.
A course in Workshop Technology (Vol. I & II) – B.S. Raghuwanshi
Manufacturing Technology – P.N. Rao – Tata McGraw Hill
Workshop Technology-I – P.K. Sapra and R.K. Kapur- Vikas Publishing
Elements of Manufacturing Processes – B.S. Nagendra Parashar and R.K. Mittal – PHI. Introduction to machining Science –
G.K. Lal, New Age International Limited
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Course Code Course Title Hours per week L-T-P Credit C
ME181402 Workshop Theory
and Practice-I 3-0-2 4
Syllabus
Course Outcomes: At the completion of the course the student will be able:
CO1: To use proper metal cutting tools and fixtures for producing desired parts.
CO2: To apply various workshop machines for production of parts according to job design.
CO3: To apply the concept of transmission system in a machine tool fixture work (MFTW) system for obtaining
desired motion for machine, tool and job.
CO4: To evaluate the effect of machining parameters on quality of machined components.
CO5: To apply techniques of sand molding and casting for production of metal parts.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Lathe is a machine, which is used to remove metal from theworkpiece to giveittherequired shape andsize.
Introduction
The first useful form of Lathe, incorporating the essential features, was made by H. Maudslay, a Britisher in
1800. Later developments and researches led to a number of amendments, as years passed and the result is
what we see today.
Lathe was actually the first Machine Tool which came into being as useful machine for metal Cutting. Thus,
it formed the basis of production of all the other Machine Tools which are the results of later developments.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Parts of Lathe
the Lathe Carries the following Main Parts as illustrated by a block diagram in Figure. The main parts of Lathe
are
1. Legs 2. Bed 3. Headstock 4. Tailstock 5. Carriage 6. Feed Mechanism
Fig. Block Diagram of
Ram clamp
Hand wheel
Spindle
Dead centerLive Center
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
PARTS OF LATHE
Legs: all the parts of lathe is mounted on lathe
Bed: It is the main body of the machine. All components are bolted on it. It is usually made by cast iron
due to its high compressive strength. It is made by casting process.
Carriage: Slides along the ways and consists of the cross-slide, tool post, apron
Headstock:Holds the jaws for the work piece, supplies power to the jaws and has various drive speeds
Tailstock: Supports the other end of the workpiece.
Feed Rod and Lead Screw: Feed rod is powered by a set of gears from the headstock.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
PARTS OF LATHE
Legs: Legs are the bottom portion and carrying the entire load of the machine. Both the legs are
firmly secured to the floor by means of foundation bolts in order to prevent vibrations in the
machine. One of these legs, usually, the one on left hand side of the operator, serves as housing for
the electric motor and Countershaft, etc. Legs of lathe is made up of cast iron. Since cast iron has
more shock resistance and wear resistance. So it absorb the vibration during machining.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
LATHE BED
It is the base on which all other parts of lathe are
mounted.
On left end of the bed, headstock is located while on
right side tailstock is located.
The carriage of the machine rests over the bed and
slides on it.
Generally cast iron alloyed with Nickel & Chromium
material is used for manufacturing.
Made up by casting & it is heavy and rugged.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
HEADSTOCK
Clamped on left-hand end of bed
It comprises of the headstock casting to
accommodate all the parts within it including gear
train arrangement.
Function is to transmit power to the different
parts of a lathe.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Fig.. Headstock spindle,
1. Threaded end 2. Taper Sleeve
3. live centre, 4. Threaded nose, 5.
Spindle hole.
It comprises essentially a hollow cylinder and mechanism for
driving and altering the spindle speed. The main spindle
possesses live centre to which the work can be attached. It
supports the work and revolves with the work, fitted into the
main spindle of the headstock. The cone pulley is also attached
with this arrangement, which is used to get various spindle
speed through electric motor. The back gear arrangement is
used for obtaining a wide range of slower speeds. Some gears
called change wheels are used to produce different velocity ratio
required for thread cutting.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
TAILSTOCK
It is commonly used to support the
circular job being turned on centers.
It can be easily set or adjusted for
alignment with respect to the spindle
center & carries a center called dead
center for supporting one end of the
work.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
TAILSTOCK
It is commonly used to support the
circular job being turned on centers.
It can be easily set or adjusted for
alignment with respect to the spindle
center & carries a center called dead
center for supporting one end of the
work.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
The tail stock is located on the innerways
at the right hand end of the bed. This has
main two uses: 1) it supports the other
end of the work when it is being
machined between centres, and 2) it holds
a tool for performing operations such as
drilling, reaming, tapping, etc
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Used to movecutting tool along lathe bed
Consists of five main parts
Saddle
Cross-slide
Compound rest
Tool post
Apron
CARRIAGE
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
It consists of the following main parts.
1. Saddle : it is that part of the carriage which
slides along the bed ways and supports the Cross
slide, compound rest and tool post.
2. Cross slide: it is mounted on the top of the
saddle and always moves in a direction normal to
the axis of the main spindle. It can either be
operated by hand, by means of the cross feed
screw, or may be given power feed through the
Apron mechanism.
CARRIAGE
Carriage
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
3. Compound rest: it is also known as Tool rest. It is
mounted on the cross- slide and carries a graduated circular
base ( called the Swivel plate) graduated in degrees. The
swivel plate enables the cross-slide to swivel to any angle in
horizontal plane. It is used for obtaining angular cuts and
short tapers as well as convenient positioning of the tool of
the work. The compound slide can be moved by means of the
compound rest feed screw.
4. Tool post: It is the topmost part of the carriage and is
used for holding the tool or tool holder in position. Fig.11
shows the tool post of the lathe.
Tool Post
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
ARPON
It is fitted to the saddle.
It contains gears and clutches
to transmit motion from the
feed rod to the carriage, and the
half nut which engages with the
lead screw during cutting
threads.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Apron: It is the hanging part in front of the carriage. It
serves as a housing for a number of gear train
through which power feeds can be given to the
carriage and the cross slide. It also carries the Clutch
mechanism and the split half nut. Out of these two,
the former (clutch mechanism) is used to transmit
motion from the feed rod whereas the latter, in
conjunction with lead screw, moves the whole
carriage in thread cutting.
Apron
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
TYPES OF LATHE
Bench Lathe:
It is small sized engine lathe mounted on bench. It is used for turning small and light
weight work piece.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Speed Lathe:
It is a very simple in design.
It only has headstock, tailstock and a very simple tool
post.
It can operate in 3-4 speeds.
The spindle speed is very high.
It is used for light machine works like wood turning,
metal spinning and polishing.
TYPES OF LATHE
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Engine Lathe:
It is probably the most widely used type of Lathe. The name engine lathe is little confusing in modern practice as all
these Lathes are are now made to have an individual motor drive. However it carries a great historical significance
that in the very early days of its development it is driven by a steam engine. From this, it derived its name, which is
popular even today.
TYPES OF LATHE
It is designed for low as well as high power operation.
The machine length can be up to 60 feet.
It is commonly seen in every machine shop.
Various types of metal can be machined.
The machine can operates at a wide range of speed ratios.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Tool Room Lathe:
It is nothing but the same Engine Lathe but equipped with some extra attachments to make it suitable for a relatively
more accurate and Precision type of work carried out in Tool room. It used for production of small tools, gauges,
fixtures and accurate parts in tool room.
Coolant
TYPES OF LATHE
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Turret Lathe:
These lathes are used in mass production and for heavy duty work pieces. These machines are actually semiautomatic
type and a very wide range of operation can be performed on them. In operating on the a very little is required of the
operator
TYPES OF LATHE
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Turret Lathe: Capable of performing multiple
cutting operations on the same workpiece
It is a great machine for quick operations.
As a number of tools are setup on machine, the
job can be completed quickly with the help of a
single setup.
A sequential machining process can be done by
using the turret lathe without moving the
workpiece.
It eliminates the error that occurs due to
misalignment.
TYPES OF LATHE
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Capsten Lathe:
These lathes are used in mass production used for light duty workpieces.
Automatic Lathe:
Special Purpose Lathe:
These lathes are modification of engine lathes developed for machining special types of
workpieces.
Automatic Lathe
Engine Lathe
Tracer Lathe
Computer Controlled lathe
TYPES OF LATHE
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
TYPES OF LATHE
Automatic Lathe
A lathe in which the work piece is
automatically fed and removed
without use of an operator.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
TYPES OF LATHE
Computer Controlled Lathe
A highly automated lathe, where
both cutting, loading, tool
changing, and part unloading
are automatically controlled by
computer coding.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Application of special Purpose Lathe
Sl.
No
Name of
Machine
Special Description Application
1 Precision Lathe Capable of giving a dimensional accuracy
up to 0.002 mm
Precision turning of previously rough- turned
workpiece.
Can , in good many cases, easily replace a high
class Grinding machine on account of its fine
dimensional accuracy
2 Facing lathe In this, the carriage is driven by a separate
motor, independent of the main spindle. It
carries no Tail stock
Used to machine the end face of bulky
Cylindrical Jobs
3 Frontal Lathe In this two carriage are provided- one on
each end . Also two Tool heads are
provided. Thus enables machining of two
job simultaneously.
Its specific use is in machining short jobs
4 Production Lathe It distinguish itself by its bed which is
made inclined towards the rear for
ensuring an efficient chip removal
Its special design makes it suitable for mass
production of cylindrical parts. Its use increase
the rate of production of such items. However, it
is not very suitable for repair work.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
TOOL POST
There are two main types of tool post used for holding lathe cutting tools:
Four-way turret: It has four ways, or sides, which allow four cutting tools to be held at the same time.
Quick–change: No need for packing. The adjustment is done by means of screw. There are separate tool
holders that fit the four faces of the main block and are easily removed and returned to exactly the same
setting.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Cutting Tool
Tool Post
Tool Post
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Turning
Facing
Boring
Drilling
Taper
Chamfering
LATHE OPERATIONS
Grooving
Forming
Reaming
Undercutting
Thread cutting
Knurling
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
TURNING:
In this process the tool is fed along the axis of
the spindle.
Turning is the removal of metal from the
outer diameter of a rotating cylindrical work
piece.
Turning is used to reduce the diameter of the
work piece, usually to a specified dimension,
and to produce a smooth finish on the metal.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
TAPER TURNING:
An operation performed on a lathe that feeds a
tool at an angle to the length of the work piece in
order to create a conical shape.
Taper turning falls into three categories, short
tapers of relatively obtuse angles generally turned
with the top-slide, longer tapers of a more acute
angle produced either by setting the tailstock over
or by use of a taper turning attachment, and
internal taper.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
FACING:
Facing is the operation of machining the ends of a
piece of work to produce a flat surface square with
the axis. This is also used to cut the work to the
required length.
The operation involves feeding the tool
perpendicular to the axis of rotation of the work
piece.
A regular turning tool may also be used for facing a
large work piece.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
DRILLING:
This is the process of making holes in the workpiece with the help of drills.
The drill is held in the tailstock and the drilling operation is carried out by advancing the
drill in the workpiece by rotating the handle of the tail stock.
On a lathe, drilling is generally done in the centre of the workpiece.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
BORING:
Boring produces circular internal profiles in
hollow workpieces
Boring mills are used for large workpieces
Holes can be bored up to 20M if needed
Machines are available with a variety of
features
Horizontal boring machines
Jig borers
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
REAMING:
It is the process of enlarging holes to accurate
sizes.
Reaming is always carried out after drilling.
It is similar to the drilling process - the reamer is
held in the tailstock to carry out the reaming
operation.
Two broad categories of commercial reamers are
generally available; these are hand reamers and
machine reamers.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
CHAMFERING:
Chamfering is the operation of beveling the extreme
end of a work piece.
This is done to remove the burrs, to protect the end of
the work piece from being damaged and to have a better
look.
The operation may be performed after knurling, rough
turning, boring, drilling.
Chamfering is an essential operation before thread
cutting so that the nut may pass freely on the threaded
work piece.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
THREAD CUTTING:
Threading is the process of creating a screw
thread.
Thread cutting on lathe is an operation that uses a
single-point tool to produce a thread form on a
cylinder or cone.
The tool moves linearly while the precise rotation
of the work piece determines the lead of the thread.
The process can be done to create external or
internal threads (male or female).
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
KNURLING:
The process of rendering rough the surface of a
work piece by making a series of indentations or
depressions on it is known as knurling.
The knurling tool which is held in the tool post
is pressed against the job to carry out the
operation.
The indentations are generally of a criss–cross
pattern and can be classified into three
categories -coarse, medium and fine.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
COUNTER BORING:
The process of boring a hole to more than one diameter on the same axis is known as counter
boring.
Counter boring is needed for receiving the head of a socket head cap screw.
This operation is also carried out with a boring tool.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Tapping: Tapping is the process of cutting a thread inside the hole. So that cap screw and bolt can be threaded
into the hole
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Taper Turning
A taper may be defined as uniform increase or decrease in diameter of a piece of work measured along its length. In a lathe
taper turning means to produce a conical surface by gradual reduction in diameter from a cylindrical workpiece.
Almost all machines spindle have taper hole which receive taper shank of various tools and work holding devices.
A tapered piece shown in Figure may be designated by the following
symbols:
D = large diameter of taper in mm
d = small diameter of taper in mm
l = length of tapered part in mm
2 α= full taper angle
α = angle of taper or half taper angle
α
α
E
A
F
B
αD
C
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Taper Turning
The amount of taper in a workpiece is usually specified by the ratio of the difference in diameters of the taper to its length.
This is termed as the conicity and its designated by the letter K.
K=𝐷 −𝑑
𝑙
Example: In fig D=90 mm, d= 80, and l= 100 mm, find the value of K
K=𝐷 −𝑑
𝑙
=90 − 80
100
=1
10
This,1
10means that the amount of taper is 1:10, or in a length of 10 mm, the diameter of the taper is reduced 1 mm.
α
α
E
A
F
B
αD
C
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Taper TurningExample: In figure, let D= 100 mm, d=80 mm, and the conicity or the amount of taper is 1\30
K =𝐷 − 𝑑
𝑙𝐷 = 𝐾𝑙 + d𝑑 = 𝐷 − 𝐾𝑙
Example: in Fig, let the conicity is 1/30, the length of taper 300 mm the small diameter 80 mm, find the large diameter
𝐷 = 𝐾𝑙 + d
=1
30× 300 + 80 = 90 𝑚𝑚
Example: in Fig, let the conicity is 1/50, the length of taper 250 mm the large diameter 55 mm, find the small diameter.𝑑 = 𝐷 − 𝐾𝑙
= 55 −1
50× 250 = 50 𝑚𝑚
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
AB=EF
D-d= AB+ EF
D – d = 2 AB
⸫AB = 𝑫−𝒅
𝟐
BC= 𝒍
From Figure,
𝐓𝐚𝐧 α =𝐀𝐁
𝐁𝐂
𝐓𝐚𝐧 α =𝐃 − 𝐝
𝟐𝐥𝐓𝐚𝐧 α =
𝐊
𝟐
K = 2𝐓𝐚𝐧 α
α
αE
A
F
B
αD
C
Example: In figure let D= 90 mm, d=80 mm and l= 100 mm. find taper angle and full taper angle
Solution: 𝑻𝒂𝒏 α =𝑫−𝒅
𝟐𝒍= Tan α =
90−80
2×100=10
200=
1
20
Example: find the taper per inch and taper per foot if the diameters of the taper are 3/5 and 1/5 and the length of taper is
3𝟏
𝟒inch.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Taper turning method
Taper turning by form tool
Taper turning by setti8ng over the tailstock
Taper turning by swiveling the compound rest
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Taper turning method
Taper turning by form tool
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Taper turning method
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Taper turning method
Taper turning by swivelling the compound rest
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
(L)
(D)
(d)
Chuck
BedCarriage
Tai
lsto
ck
The size of a lathe is designated in many different ways. The practice usually differs with different countries. For
example a S.S.S.C. (Sliding, Surfacing and screw Cutting ) lathe is specified in U.S.A by swing. The term swing
denotes the maximum diameter of the work which can be accommodate on the lathe.
Lathe specification and Sizes
This swing is specified at different positions on the
lathe as shown in Figure. It will be observed that the
swing is specified in the Gap (in case of Gap bed
lathes) over the Carriage and over the Bed. These
measurements indicate the maximum diameter of
the work which can be safely accommodated over
these positions during the operation.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
The size of a LatheThe size of a lathe is expressed or specified by the following items and illustrated in Fig. 2.
1. The height of the centers measured from the lathe bed.
2. The swing diameter over bed. This is the largest diameter of work that will revolve without touching the bed and
is twice the height of the center measured from the bed of the lathe.
3. The length between centers. This is the maximum length of work that can be mounted between lathe centers.
4. The swing diameter over carriage. this is the largest diameter of work that will revolve over the lathe saddle, and
is always less than the swing diameter over bed.
5. The maximum bar diameter. This is the maximum diameter of bar stock that will pass through hole of the
headstock spindle.
6. The length of bed. These indicates the approximate floor spaced occupied by the lathe.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Accessories and Attachments of Lathe:
There are many lathe accessories provided by the lathe manufacturer along with the lathe, which support the lathe operations.
The important lathe accessories include centers, catch plates and carriers, chucks, collets, face plates, angle plates, mandrels,
and rests.
These are used either for holding and supporting the work or for holding the tool. Attachments are additional equipments
provided by the lathe manufacturer along with the lathe, which can be used for specific operations. The lathe attachment
include stops, ball turning rests, thread chasing dials, milling attachment, grinding attachment, gear cutting attachment, turret
attachment and crank pin turning attachments and taper turning attachment.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Lathe Centers
The most common method of holding the job in a lathe is between the two centers generally known as live centre (head
stock centre) and dead centre (tailstock centre). They are made of very hard materials to resist deflection and wear and they
are used to hold and support the cylindrical jobs.
Carriers or driving dog and catch plates
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Chucks
Chuck is one of the most important devices for holding and rotating a job in a lathe. It is basically attached to the headstock
spindle of the lathe. The internal threads in the chuck fit on to the external threads on the spindle nose. Short, cylindrical,
hol1ow objects or those of irregular shapes, which cannot be conveniently mounted between centers, are easily and rigidly held
in a chuck. Jobs of short length and large diameter or of irregular shape, which cannot be conveniently mounted between
centers, are held quickly and rigidly in a chuck.
There are a number of types of lathe chucks, e.g.
(1) Three jaws or universal
(2) Four jaw independent chuck
(3)Combination chuck
(4) Magnetic chuck
(5) Collet chuck
(6) Air or hydraulic chuck operated chuck
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Collet Chuck
Magnetic Chuck
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Face Plate
Angle plate
Driving Plate
Angle plate
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
These are used to drive a job when it is held between two
centers. Carriers or driving dogs are attached to the end of the
job by a setscrew. A use of lathe dog for holding and supporting
the job is shown in Fig. Catch plates are either screwed or
bolted to the nose of the headstock spindle. A projecting pin
from the catch plate or carrier fits into the slot provided in either
of them. This imparts a positive drive between the lathe spindle
and job
Carriers or driving dog and catch plates Catch plate
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Lathe dog
Lathe dog
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Mandrel
A mandrel is a device used for holding and rotating a hollow job that has been previously drilled or bored. The job revolves
with the mandrel, which is mounted between two centers.
It is rotated by the lathe dog and the catch plate and it drives the work by friction. Different types of mandrels are employed
according to specific requirements
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Rests
Steady rest
Follower rest
A rest is a lathe device, which supports a long slender job, when it is turned between centers or by a chuck, at some
intermediate point to prevent bending of the job due to its own weight and vibration set up due to the cutting force that acts on
it.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
CHAMFERING:
Chamfering is the operation of beveling the extreme
end of a work piece.
This is done to remove the burrs, to protect the end of
the work piece from being damaged and to have a better
look.
The operation may be performed after knurling, rough
turning, boring, drilling.
Chamfering is an essential operation before thread
cutting so that the nut may pass freely on the threaded
work piece.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Chamfering ToolChamfer Surfaces
Varioius Chamfer Surfaces
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
KNURLING:
The process of rendering rough the surface of a
work piece by making a series of indentations or
depressions on it is known as knurling.
The knurling tool which is held in the tool post
is pressed against the job to carry out the
operation.
The indentations are generally of a criss–cross
pattern and can be classified into three
categories -coarse, medium and fine.
LATHE OPERATIONS
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Cutting speed : Cutting speed for lathe work may
be defined as the rate in meters per minute at which the
surface of the job moves past the cutting tool. Machining
at a correct cutting speed is highly important for good tool
life and efficient cutting.
Unit: M/Min or mm/Min
Feed rate: It is simply called feed. It is the relative
velocity at which the cutter is advanced along the
workpiece.
Unit : mm/rev.
Tool
Direction of tool along the workpiece
Rotation of workpiece
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Depth of cut: It refers to the width of metal layer that
is sheared off from the workpiece during machining. The
calculated distance is perpendicular to uncut surface and the
machined surface Workpiece before machining
Workpiece after machining
Depth of cut
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Cutting speeds for various materials using a plain high-speed steel cutterMaterials Meters/Min Surface feet per minute
Steel (tough) 18–50 60–100
Mild Steel 3–38 10–125
Mild Steel (with
coolant)
6–7 20–25
Cast Iron
(medium)
1–2 6–8
Carbon Steels
(C1008–C1095)
4–51 0–70
Stainless Steels
(300 & 400 series)
23–40 30–75
Bronzes 24–45 10–80
Leaded Steel
(Leadloy 12L14)
91 30
Aluminium 122-305 400-1000
Brass 90–210 300–700
Machinable Wax 6 20
Acetal Copolymer
(Delrin)
11 35
Polyethylene 12 40
Wood 183–305 600–1000
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Mathematical form
C.S=𝜋𝐷𝑁
1000
C.S= cutting speed
D= Diameter of Workpiece
N= Speed in rpm
The rotational speed in turning is related to the desired cutting speed at the surface of the cylindrical workpiece
by the equation.𝑁 =
𝐶. 𝑆
𝜋𝐷
Do= original diameter of the part, m (ft.). The turning operation reduces the diameter of the work from its original diameter.
Final diameter Df as determined by the depth of cut d.
𝐷𝑓 = 𝐷𝑂 − 2𝑑
Outer or original
diameter
Final or Inner diameterd
d
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
The feed in turning is generally expressed in mm/rev (in/rev). This feed can be converted to a linear travel rate
in mm/min (in/min) by the formula.
𝐹𝑟 = 𝐹𝑁
Where 𝐹𝑟 = feed rate, mm/min (in/min); and 𝐹 = feed, mm/rev (in/rev). 𝑁 = rotational speed of cutting speed at surface of workpiece
The time to machine from one end of a cylindrical work-part to the other is given by.
Tm = L/F r
Where Tm =machining time, min;
and L = length of the cylindrical work-part, mm (in).
F r = Feed rate
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
FACTOR EFFECTING CUTTING SPEED
Material of work piece
Material of tool
Depth of cut
Rigidity of work piece and cutting tool
Shape of cutting tool
Cutting fluid used.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Maximum permissible amount of tool wear.
Type of machining being performed
Kind of material being cut
Cutting tool material,
Shape of cutting tool
Rigidity of machine tool and the job piece
FACTOR EFFECTING CUTTING SPEED
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Feed Mechanism
Feed mechanism is the combination of different units through which motion of headstock spindle is transmitted
to the carriage of lathe machine. Following units play role in feed mechanism of a lathe machine.
1. End of bed gearing
2. Feed gear box
3. Lead screw and feed rod
4. Apron mechanism
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
End of bed gearing
Tumbler gear mechanism
Bevel gear feed reversing mechanism
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
The gearing at the end of bed transmits the rotary motion of headstock spindle to the feed gear box. Through
the feed gear box the motion is further transmitted either to the feed shaft or lead screw, depending on
whether the lathe machine is being used for plain turning or screw cutting.
End of bed gearing
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Headstock
Cone pulley
Backgears and backgear lever
Main spindle or headstock spindle
Live center and
Feed reverse lever
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Direct Speed or back gear out
Indirect speed or back gear in
Spindle Speed
Direct Speed or back gear out
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Indirect speed or back gear in
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Cone pulley
A pulley is a wheel that carries a flexible rope, cord, cable, chain, or belt
on its rim.
Pulleys are used singly or in combination to transmit energy and motion
A pulley in the form of a truncated cone :
A series of pulleys forming a stepped cone or conoid that are used
in pairs (as for varying the velocity ratios of shafts).
Cone Pulley
Cone Pulley
Direct speed or back gear out
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Gear9 speed gearbox for the turret head of a lathe machine operating in the spindle speed range of 1000 rpm to 30 rpm
and operated by a motor at 720 rpm.
Turret head Gear Box
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Back Gear
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Step cone pulley is mounted on the main spindle which carries spur gear B
at one end pinion A at other. Gear B is firmly keyed to the spindle so that it
never revolve free of the same. The spindle carries a sleeve over it which is
loose feet. The cone pulley is firmly secured to this sleeve.. This arrangement
forces the pinion to revolve with the cone pulley under all condition. A spring
knob “k” engages the gear with the cone pulley. The cone pulley is driven by
means of a belt, through a countershaft by an electric motor as shown in
figure. This arrangement enables 4 different speeds of the spindle.
Cone Pulley
BC
D
A
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Speed Ratios
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Feed Mechanism
Feed mechanism is the combination of different units through which motion of headstock spindle is transmitted
to the carriage of lathe machine. Following units play role in feed mechanism of a lathe machine.
1. End of bed gearing
2. Feed gear box
3. Lead screw and feed rod
4. Apron mechanism
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Apron: The apron is fitted to the saddle. It contains gears and clutches to transmit motion from the feed rod to the carriage,
and the half nut which engages with the lead screw during cutting threads.
Apron
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
The gearing at the end of bed transmits the rotary motion of headstock spindle to the feed gear box. Through the feed gear box the
motion is further transmitted either to the feed shaft or lead screw, depending on whether the lathe machine is being used for plain
turning or screw cutting.
End of bed gearing
Layout diagram of Feed drive
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Apron mechanism: The apron is fitted to the saddle. It contains gears and clutches to transmit motion from the feed rod
to the carriage, and the half nut which engages with the lead screw during cutting threads.
Apron
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Direct Speed or back gear out
Indirect speed or back gear in
Spindle Speed
Direct Speed or back gear out
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Step cone pulley is mounted on the main spindle as shown in figure,
Cone pulley
Direct speed or back gear out
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Example: A lathe has four steps, the diameter of each being 90 mm, 130 mm, 170 mm and 210 mm. the
countershaft pulley Revolves at 100 rpm. The gears A, B, C and D have 16, 48,16, 48. find the various speeds of
the spindle
Countershaft (N1)
Spindle (N2)
Countershaft connected to motor
• Because of rotation of
spindle, chuck will
rotate and then
workpiece will rotate
as workpiece is fitted
on chuck
Speeds without back gear:𝑁2𝑁1
=𝐷1𝐷2
𝑁1= r.p.m of countershaft
𝑁2= r.p.m of Spindle
D2
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
𝐷1
Total Distance= 𝑁1𝐷1
How 𝑁1𝐷1 = 𝑁2𝐷2 ?
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Therefore, Spindle Speed is
𝑁2 = 𝑁1 ×𝐷1𝐷2
𝑁2 = 𝑁1 ×𝐷1𝐷2
1. 𝑁2= 100 ×210
90= 233.3
2. 𝑁2= 100 ×170
130= 130.7
3. 𝑁2= 100 ×130
170= 76.5
4. 𝑁2= 100 ×90
210= 42.8
In 1st case 𝐷1=210 and 𝐷2 =90, 𝑁1= 100 and 𝑁2= ?
In 2nd case 𝐷1=170 and 𝐷2 = 130, 𝑁1= 100 and 𝑁2= ?
In 3rd case 𝐷1=130 and 𝐷2 = 170, 𝑁1= 100 and 𝑁2= ?
In 4th case 𝐷1=90 and 𝐷2 = 210, 𝑁1= 100 and 𝑁2= ?
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Indirect speed or back gear in
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Speed with Back Gear
𝑁𝐷𝑁𝐴
=𝑍𝐴𝑍𝐵
×𝑍𝑐𝑍𝐷
𝑁𝐷233.3
=16
48×16
48
𝑁𝐷 =1
9× 100 × 233.3
=25.9 r.p.m
𝑁𝐷=233.3, 130.7, 76.5 and 42.8
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Feed Mechanism
Feed mechanism is the combination of different units through which motion of headstock spindle is transmitted
to the carriage of lathe machine. Following units play role in feed mechanism of a lathe machine.
1. End of bed gearing
2. Feed gear box
3. Lead screw and feed rod
4. Apron mechanism
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Example: A lathe having cone pulley drive carries a 4- stepped cone pulley. The diameter of 4 the four steps are
100 mm, 140 mm, 180 mm and 220 mm. the pinion on the spindle and back gear shaft each carry 20 teeth while
the meshing gears carry 60 teeth each. If the machine motor drives the countershaft at a speed of 300 r.p.m.
calculate the different speeds which can be obtained for the lathe spindle.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
End of bed gearing
Tumbler gear mechanism
Bevel gear feed reversing mechanism
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
The gearing at the end of bed transmits the rotary motion of headstock spindle to the feed gear box. Through the feed gear box the
motion is further transmitted either to the feed shaft or lead screw, depending on whether the lathe machine is being used for plain
turning or screw cutting.
End of bed gearing
Tumbler gear mechanismEnd of bed gearing
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Rack and Pinion
Rack
Pinion A rack and pinion is a type of linear actuator that comprises
a circular gear (the pinion) engaging a linear gear (the rack),
which operate to translate rotational motion into linear
motion.
Helical gears are preferred due to their quieter operation and
higher load bearing capacity. The maximum force that can be
transmitted in a rack and pinion mechanism is determined by
the tooth pitch and the size of the pinion.
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Rack Railway
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Worm Drive
A worm drive is a gear arrangement in which aworm (which is a gear in the form of a screw)meshes with a worm wheel (which is similar inappearance to a spur gear). The two elementsare also called the worm screw and worm gear.The terminology is often confused by impreciseuse of the term worm gear to refer to the worm,the worm wheel, or the worm drive as a unit.
Like other gear arrangements, a worm drive canreduce rotational speed or transmit highertorque. A worm is an example of a screw,
worm
worm wheel
worm drive
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
One of the major advantages of worm drive units are that they can transfer motion in 90 degrees. The worm
in the worm drive may have single or multiple starts. Each full 360-degree turn of a single-start worm
advances the wheel by one tooth. For a multi-start worm, the gear reduction equals the number of teeth on
the wheel divided by the number of starts on the worm
worm
worm
worm wheel
worm drive
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Apron mechanism: The apron is fitted to the saddle. It contains gears and clutches to transmit motion from the feed rod
to the carriage, and the half nut which engages with the lead screw during cutting threads.
Apron
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Apron mechanism
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Apron
RackLead screw
Apron mechanism
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Apron mechanism
Dr. Ikbal Bahar Laskar
Jorhat Engineering College, Jorhat, Assam, India
Thank You