workshop (practical)

Dr. Ikbal Bahar Laskar

Workshop (Practical)

Prepared By:

Ikbal Bahar Laskar

Department of Mechanical Engineering

Jorhat Engineering College (JEC), Jorhat, Assam, India


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






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






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.






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






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.



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.



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



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.



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.



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.



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.



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.



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.



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



Used to movecutting tool along lathe bed

Consists of five main parts

Saddle

Cross-slide

Compound rest

Tool post

Apron

CARRIAGE



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



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



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.



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



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.



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



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.



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



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



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



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



TYPES OF LATHE

Automatic Lathe

A lathe in which the work piece is

automatically fed and removed

without use of an operator.



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.



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.



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.



Cutting Tool

Tool Post

Tool Post



Turning

Facing

Boring

Drilling

Taper

Chamfering

LATHE OPERATIONS

Grooving

Forming

Reaming

Undercutting

Thread cutting

Knurling



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



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



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



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



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



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



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



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



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



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



Tapping: Tapping is the process of cutting a thread inside the hole. So that cap screw and bolt can be threaded

into the hole



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



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



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



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.



Taper turning method

Taper turning by form tool

Taper turning by setti8ng over the tailstock

Taper turning by swiveling the compound rest




Taper turning by form tool




Taper turning by swivelling the compound rest



(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.



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.



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.



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



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



Collet Chuck

Magnetic Chuck



Face Plate

Angle plate

Driving Plate

Angle plate



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



Lathe dog

Lathe dog



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



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.



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



Chamfering ToolChamfer Surfaces

Varioius Chamfer Surfaces



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



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



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



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



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



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



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.



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



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



End of bed gearing

Tumbler gear mechanism

Bevel gear feed reversing mechanism



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



Headstock

Cone pulley

Backgears and backgear lever

Main spindle or headstock spindle

Live center and

Feed reverse lever



Direct Speed or back gear out

Indirect speed or back gear in

Spindle Speed




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



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



Back Gear



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



Speed Ratios



Feed Mechanism




2. Feed gear box


4. Apron mechanism



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



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



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





Spindle Speed




Step cone pulley is mounted on the main spindle as shown in figure,

Cone pulley

Direct speed or back gear out



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



𝐷1

Total Distance= 𝑁1𝐷1

How 𝑁1𝐷1 = 𝑁2𝐷2 ?



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= ?



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



Feed Mechanism




2. Feed gear box


4. Apron mechanism



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.



End of bed gearing

Tumbler gear mechanism

Bevel gear feed reversing mechanism



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



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.

https://en.wikipedia.org/wiki/Helical_gear



Rack Railway



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



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



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



Apron mechanism



Apron

RackLead screw

Apron mechanism



Apron mechanism



Thank You

workshop (practical)

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