government polytechnic, meham

GOVERNMENT POLYTECHNIC, MEHAM

Branch: Mechanical Engineering

Semester: 4th Sem.

Subject: Workshop Technology -II

CONTENTS:

1. Cutting tools

2. Various types of single point cutting tools and their uses

3. Single point cutting tool geometry

4. Tool signature and its effect

5. Heat produced during cutting and its effect

6. Cutting speed

7. Feed

8. Depth of cut

9. Properties of the cutting tool materials

10. Study of various cutting tool materials viz. High-speed

steel, tungsten carbide, cobalt steel cemented carbides, stellite,

ceramics and diamond.

1. CUTTING TOOLS

It may be define as the tools which are used for cutting the metals in desired shaped and

size.

Types of cutting tool:

Single point cutting tool: The cutting tool which is terminated in a single point is

known as the single point cutting tool. These are used in lathes, shapers, planers.

Multi point cutting tool: The cutting tool which is terminated more than one point as

known as the multi point cutting tool. These are used in milling cutter, drills,

broaches, etc.

2. VARIOUS TYPES OF SINGLE POINT CUTTING TOOL AND THEIR USES

Turning tool: The tools which are use for turning or for reducing the diameter of

the job. They are of two type:

i. Left hand turning tool

ii. Right hand turning tool

Facing tool: The tool which is used for facing or for reducing the length of the

job.

They are of two types:

i. Left hand facing tool

ii. Right hand facing tool

Chamfering tool: The tool which is used for the bevelling the corners of the

workpiece for small length.

They are of two types:

i. Left hand chamfering tool

ii. Right hand chamfering tool

External threading tool: This tool is used for cutting the external threads on the

workpiece as per required shape and size.

Internal threading tool: It is used for cutting the internal thread in the holes.

Boring tool: It is used to enlarge an already existing hole in the workpiece.

Some important terms related to single point cutting tool

1. Shank; It’s the main body of the tool and it is that part of the tool which is

gripped in the tool holder.

2. Face: It is the top surface of the tool between the shank and the cutting edge.

3. Flank: It is the portion of the tool which face the work or it is the surface below

and adjacent to the cutting edge.

4. Heel: It is the curved portion at the bottom of the tool where the base and flank of

the tool meets.

5. Base: It is the bearing surface of the tool in which it is held in the tool holder.

6. Nose: It is the point where side cutting edge and end cutting edge meet or

intersect.

7. Cutting edge: It is the edge on the face of the tool which removes material from

the workpiece.

3. SINGLE POINT CUTTING TOOL GEOMETRY

Back rack angle = 𝛾𝑦

Side rack angle = 𝛾𝑥

End relief/clearance angle = 𝛼𝑦 Side relief/clearance angle = 𝛼𝑥 End cutting edge angle = ∅𝑒 Side cutting edge angle = ∅𝑠 Nose radius = 𝛾

4. TOOL SIGNATURE AND ITS EFFECT

It is used to denote a standardised system of specifying the principle tool angle of a

single point cutting tool.

Effect of tool signature:

1. It reduced the cutting force required to shear the metal increase tool life and

reduce power consumption.

2. It improves the surface finish.

3. It allow the chips to flow in a convenient direction

5. HEAT PRODUCED DURING CUTTING AND ITS EFFECT

1. Due to friction: A lot of friction takes place between the tool and work piece and

the tool and the chips. The passing of the chips over the tool contributes the

maximum friction.

2. Due to plastic deformation of metal: Due to sufficiently high pressure exerted

by the tool on adjacent grain of the work piece.

3. Chips deformation: In machining operation, the chip curls out and tensile and

compressive stresses are generated on the chips. This result in distortion of grains

and consequent generation of heat.

5.1 Effect of heat produced during metal cutting:

It reduces the tool life.

It reduces the surface finish.

It causes the welding of chips with the face of tool.

Repeat replacement of tools occurs which increase the cost.

6. CUTTING SPEED

It may be define as the speed at which the cutting edge passes over the material.

7. FEED

The distance through which the tool advance into or along the workpiece each time the

tool passes a certain position in its travel over the surface.

8. DEPTH OF CUT

The perpendicular distance measured from the machined surface to the in cut surface of

the work piece.

9. PROPERTIES OF THE CUTTING TOOL MATERIALS

Tool material must be at least 30 to 50% harder than the work piece material.

Tool material must have high hot hardness temperature.

High toughness

High wear resistance

High thermal conductivity

Lower coefficient of friction

Easiness in fabrication and cheap

10. STUDY OF VARIOUS CUTTING TOOL MATERIALS

11.1 High speed steel (H.S.S)

General use of HSS is 18-4-1.

18- Tungsten is used to increase hot hardness and stability.

4 – Chromium is used to increase strength.

1- Vanadium is used to maintain keenness of cutting edge.

In addition to these 2.5% to 10% cobalt is used to increase red hot hardness.

https://me-mechanicalengineering.com/friction-coefficient-applications-advantages-disadvantages/#coefficent_of_friction

Cemented carbides

Produced by powder metallurgy technique with sintering at 1000°C. Speed can be used 6 to 8 times that of H.S.S.

Can withstand up to 1000°C.

High compressive strength is more than tensile strength.

They are very stiff and their young’s modulus is about 3 times that of the steel.

High wear resistance.

High modulus of elasticity.

Low coefficient of thermal expansion.

High thermal conductivity, low specific heat, low thermal expansion.

According to ISO the various grades of carbide tool materials grouped as

1. For cutting CI and non-ferrous metals are designated as K10 to K50

2. For cutting steel are designated as p10 to p50

3. For general purpose application are designated as M10 to M50.

The advantages of carbide tools are

They have high productivity capacity.

They produce surface finish of high quality.

They can machine hardened steel.

Their use leads to reduction in machining costs.

Ceramics and sintered oxides

Ceramics and sintered oxides are basically made of Al2O3, These are made by

powder metallurgy technique.

Used for very high speed (500m/min).

Used for continuous cutting only.

Can withstand upto 1200°C.

Have very abrasion resistance.

Used for machining CI and plastics.

Has less tendency to weld metals during machining.

Generally used ceramic is sintered carbides.

Another ceramic tool material is silicon nitride which is mainly used for CI.

Cermets

Cermets is the combination of ceramics and metals and produced by Powder

Metallurgy process.

When they combine ceramics will give high refractoriness and metals will give

high toughness and thermal shock resistance.

For cutting tools usual combination as Al2O3 + W + Mo + boron + Ti etc.

Usual combination 90% ceramic, 10% metals.

Increase in % of metals reduces brittleness some extent and also reduces wear

resistance.

Diamond

Diamond has extreme hardness, low thermal expansion, high thermal

conductivity and very low coefficient of friction.

Cutting tool material made of diamond can withstand speeds ranging from 1500

to 2000m/min.

https://me-mechanicalengineering.com/hookes-law-modulus-of-elasticity/#youngs_modulus_of_elasticity

https://me-mechanicalengineering.com/hookes-law-modulus-of-elasticity/

https://me-mechanicalengineering.com/ceramics/



https://me-mechanicalengineering.com/cutting-tool-materials/

https://me-mechanicalengineering.com/friction-coefficient-applications-advantages-disadvantages/#coefficent_of_friction

On ferrous metals diamond are not suitable because of the diffusion of carbon

atoms from diamond to work-piece.

Can withstand above 1500°C.

A synthetic (man-made) diamond with polycrystalline structure is recently

introduced and made by powder metallurgy process.



Semester: 4th Sem.

Subject: Workshop Technology -II

CONTENTS

11. Introduction

12. Function of cutting fluids

13. Properties of cutting fluids

14. Types of cutting fluids

15. The factor under consideration during selection of a

cutting fluid

16. Application of cutting fluids

17. Lubricant

18. Characteristics of good lubricant

19. Difference between cutting fluids and lubricants

CUTTING FLUIDS AND LUBRICANTS

INTRODUCTION:

Any substance applied to a tool during cutting operation release /decrease heat removal of

chips and increase tool life is known as cutting fluids.

The cutting fluids have little effect on cutting efficiency, when machine are made to

operate at high speed. Water based fluids are best suited for cooling action due to their high

specific heat and thermal conductivity. The rate of transfer of heat by water based fluid. The

cooling efficiency of any cutting fluids does not depend decided only by its thermal

conductivity other factor which considered are wetting action, cooling action and vapours

formation of fluids.

FUNCTION OF CUTTING FLUIDS-

1. To reduce the cutting force.

2. To decrease wear and tear of the tool, so it’s helpful to increase the tool life.

3. Cutting fluids provided lubricating effect to the tool.

4. To improve the surface finished and machinability of any machine.

5. Cutting fluids protect the finished surface from oxidation.

6. To wash away the chips and dust from working surface.

7. Cutting fluids minimize friction at the mating surface, so its prevent increase the

temperature.

PROPERTIES OF CUTTING FLUIDS

1. It should be chemically stable

2. It should be non-corrosive.

3. It should have high flash point.

4. No skin irritation.

5. Anti -welding properties.

6. Low evaporation rate.

7. Deteriorate on storage.

8. Low viscosity.

9. No de-colorization.

10. It should be cheap.

TYPES OF CUTTING FLUIDS

1. Neat cutting oils-

These oils are not mixed with water for cutting operations. These cutting oils are a mixture of

number of different types of mineral oils together these are used when cutting speed is slow

and lowest feed are used or with externally tough material. These cutting oils have good

cooling properties. The main disadvantage of neat cutting oils that they are responsible for

dirty work areas by shipping from the machine.

2. Soluble oils-

These are the compounds of mineral oils an emulsified base when mix with water emulsified

base cause, the formation of oils water emulsion/solution. Water has excellent cooling

properties and oils have good properties of lubrication and corrosion resistance. The amount

of water varies with the types of operation. This is used for drilling, milling, lathe etc.

3. Synthetic fluids-

These fluids contain no oils but are mixer of chemicals mix in water to give lubricating and

anti-corrosion properties. These are a clear transparent solution with water, during grinding

operation ratio up to 8O%. They are easily mix with water and do not produce smoke during

cutting.

4. Semi-synthetic fluids-

These are recently by develop cutting fluids, these fluids has a small amount of oils mix in

water as well as dissolved chemical. These cutting fluids are safer to use, do not produce

smoke and no slippery film on work piece.

5. Mineral cutting oils-

These are composed one or more mineral oils, fatty oils or fatty acids. These oils are used in

some light machining operation. The fatty oils both animals and vegetable are used in

combination with mineral oils. They are not chemically acting.

6. Chemical additive oils-

Sulphur and chlorine increase the lubricating and cooling properties of cutting oils. They also

provide anvil properties to the cutting oils.

7. Sulphurised mineral oils-

These oils minimized tearing and rough finish, they are commonly used for machining low

carbon steel, but highly sulphurised mineral oils are not used for copper and its alloys.

8. Chemical compounds -

These are the oils mixture of sodium nitrate with water. They are generally used for grinding

operation. The water provides good cooling properties where lubricating properties are not so

important during grinding.

THE FACTOR UNDER CONSIDERATION DURING SELECTION OF A CUTTING

FLUIDS-

1. The process of machining.

2. The cutting tool materials.

3. The material of a work piece.

4. Speed of cut /cutting speed of machine.

5. Cutting fluids also depend on speed as well as depth of cut.

6. Requirement of surface finished.

7. Human interaction.

8. Economically available on low price.

APPLICATION OF CUTTING FLUIDS-

The cutting fluids may be applied of the cutting tools in following ways:-

1. By hand or brush:-

In case of low production, the cutting fluids may be applied by hand or brush either to

material being cut or the cutting tool.

2. Flood method:-

For the effective use of cutting fluids and for heavy and continuous cutting, the fluids should

penetrate into the cutting zone. for this pump is used to supply the cutting fluid. Here a

continuous stream of cutting fluids is directed at the cutting zone with help of nozzle jet.

The used cutting fluids drop into the tank at the bottom. Before it is recirculated by the pump,

it passes through many filters to remove chips and dirt.

3. Jet Method:-

It is also known as high jet method under suitable circumstances. This method gives a

significant increase in tool life. In this system cutting fluids is pumped under a pressure of 30

to 40 kg/cm2 from the cutting fluids take in the base of the machine the high-5 speed jet

depended upon slight irregularities in both the cutting edge of the tool and work surface.

4. Mist method:-

In this system cutting fluids is vaporized over the work piece and cutting tool. Due to high

velocity fluids application. The surface area of cutting fluids is much more than fluids

method, jet method the process of producing mist of the cut fluid is based on the venturi

principle as shown in fig. The high pressured air flowing by a syphon tube, draw the fuel into

the nozzle.

LUBRICANT:-

A lubricant is the substance which reduce the force of friction between two relatively moving

solid surface in the constant with each other.

CHARACTERISTICS OF A GOOD LUBRICANT:-

1. High viscosity.

2. Viscosity index.

3. Flash and fire point is high.

4. Pour point is high.

5. Oiliness is high.

6. Acid value is low.

7. Emulsification is high.

DIFFERENCE BETWEEN CUTTING FLUID AND LUBRICANT



Semester: 4th Sem.

Subject: Workshop Technology-II

INTRODUCTION

Lathe is one of the oldest important machine tools in the metal working industry. A lathe operates on the principle of a rotating work piece and a fixed cutting tool.

A rope wound round the work with its own end attached to a flexible branch of tree and other end being pulled by man caused job to rotate intermittently. With its further development a strip of wood called “lath” was used to support the rope and that is how the machine came to be known as “lathe”.

The cutting tool is feed into the workpiece, which rotates about its own axis, causing the workpiece to be formed to the desired shape.

TYPES OF LATHE

• Engine Lathe

• Bench Lathe

• Tool room Lathe

• Automatic Lathe

• Turret Lathe

ENGINE LATHE

• This term ‘engine’ is associated with the lathe owing to the fact that early lathes were driven by steam engine. It is also called centre lathe. The most common form of lathe, motor driven and comes in large variety of sizes and shapes.

Continue..

Engine lathes are classified according to the various

designs of headstock and methods of transmitting power to

the machine.

1. Belt Driven Lathe

2. Motor Driven Lathe

3. Gear Head Lathe

The power to the engine lathe spindle may be given with

the help of a belt drive from an overhead line shaft but

most modern machines have a captive motor with either

a cone pulley driven or an geared headstock

arrangement.

BENCH LATHE • A bench top model usually of low power used to make precision

machine small work pieces.

• It is used for small w/p having a maximum swing of 250 mm at the face plate. Practically it consists of all the parts of engine lathe or speed lathe.

a

d

or

es,

TOOL ROOM LATHE

A tool room lathe having

features similar to an engine

lathe is much more accurately

built and has a wide range of

spindle speeds ranging from

very low to a quite high spee

up to 2500 rpm.

This lathe is mainly used f

precision work on a tools, di

gauges, and in machining

work where accuracy is

needed.

AUTOMATIC LATHE

• A lathe in which the work piece is automatically fed and removed without use of an operator. It requires very less attention after the setup has been made and the machine loaded.

Continue..

Once tools are set and the machine is started it performs automatically all the operations to finish the job.

After the job is complete, the machine will continue to repeat the cycles producing identical parts.

An operator can maintain five or six such a types of lathes at a time simply look after the general maintenance of the machine and cutting tools.

TURRET LATHE • Turret lathe is the adaptation of the engine lathe where the

tail stock is replaced by a turret slide(cylindrical or

hexagonal). Tool post of the engine lathe is replaced by a

square cross slide which can hold four tools.

Continue..

It has heavier construction and provides wider range of speeds.

The saddle carrying the turret head moves along the whole length of the bed. Much longer jobs can be machined.

Turret head directly mounted on the saddle. The front tool post can carry 4 tools and rear tool post may have 1 or 2 tools. Turret may have4 to 6 tools.

More than one tool may be set to operate simultaneously. There is no lead screw.

Lathe Machine

Parts of Lathe Machine

Lathe Bed

• This is heavy rugged casting

made to support the working

parts of lathe and also guide

and align major parts of

lathe.

• Made to support working

parts of lathe.

• On top section are machined

ways.

• Guide and align major parts

of lathe.

Head Stock

• The headstock houses

the main spindle,speed

change mechanism, and

change gears.

• The headstock is

required to be made as

robust as possible due to

the cutting forces

involved,which can distort

a lightly built housing.

Head Stock

• Induce harmonic

vibrations that will

transfer through the

work piece, reducing the

quality of the finished

work piece.

QUICK CHANGE GEAR BOX • Contains number of different-size gears.

• Provides feed rod and lead-screw with various speeds for turning and thread-cutting operations

TOP VIEW

Continue..

The arrangement which are employed in feed gear

boxes to obtain multispindle speeds and different

rates of feeds are:

I. Sliding Gear Mechanism

II. Sliding Clutch Mechanism

III. Gear Cone And Tumbler Gear Mechanism

IV. Sliding Key Mechanism

V. Combination of any two or more of the above

• Usually two or three levers must be moved to

obtain the desired combination within a given

range.

CARRIAGE • Used to move cutting tool along lathe bed.

• Consists of three main parts-

i. Saddle

ii. Cross-slide

iii. Apron

Continue..

Movement of entire carriage assembly along the bed provides feed for the tool parallel to the lathe axis.

The compound rest can be swivelled on the cross slide in the horizontal plane about vertical axis.

To the front of the carriage is attached the apron. It is fastened to the saddle and hangs over the front of the bed.

The apron houses the automatic feed mechanism for longitudinal and cross feeds and the split nut for thread cutting.

CROSS SLIDE

• Mounted on top of saddle. • Provides manual or automatic cross movement for cutting tool.

APRON

• Fastened to saddle.

• Houses gears and

mechanism required to

move carriage or cross-

slide automatically.

• Locking-off lever inside

apron prevents engaging

split-nut lever and

automatic feed lever at

same time.

• Apron hand wheel

turned manually to move

carriage along lathe bed

TAILSTOCK Upper and lower tailstock castings.

• Adjusted for taper or parallel turning by two screws set in base.

• Tailstock clamp locks tailstock in any position along bed of lathe.

• Tailstock spindle has internal taper to receive dead center.

• Provides support for right-hand end of work.

Continue..

In tail stock jobs of different lengths are provided

with quill which can be moved in and out by

means of a screw and then locked in position.

The movement of the quill is parallel to the lathe

axis.

The quill has a tapered bore into which is fitted a

hardened centre which locates and holds the w/p

when turning between centre.

This bore may also be used for supporting tools for

operations like drilling and reaming.

AUTOMATIC FEED LEVER

• Engages clutch that provides automatic feed to

carriage.

• Feed-change lever can be set for longitudinal

feed or for cross-feed.

• In neutral position, permits split-nut lever to

be engaged for thread cutting.

• Carriage moved automatically when split-nut

lever engaged

FEED OF AN ENGINE LATHE

• Distance carriage will travel in one revolution of

spindle.

• Depends on speed of feed rod or lead screw.

• Controlled by change gears in quick-change

gearbox.

• Obtains drive from headstock spindle through end

gear train.

• Chart mounted on front of quick-change gearbox

indicates various feeds.

Cutting Tool

Work Holding Devices

(a) and (b) Schematic illustrations of a draw-in-type collets. (c) A push-out type collet. (d) Workholding of a part on a face plate.

Types Of Chuck

- Forholding

cylindrical stock

centered.

- For facing/center

drilling etc.

- This is independent chuck generally has four jaws , which are adjusted individually on the chuck face by means of adjusting screws.

-Thin jobs

can be held

by means of

magnetic

chucks.

-Collet chuck

is used to

hold small

work pieces.

SAFTY PRECAUTIONS

Don’t touch cutter or chips while machine is running.

Make sure work is clamped tightly in chuck or collet.

Be careful to stay clear of chuck jaws.

Continue..

All lathe operators must be constantly aware of the safety.

Handle sharp cutters, centres, and drills with care.

Remove chuck keys and wrenches before operating.

Always wear protective eye protection.

Always stop the lathe before making adjustments.

Know where the emergency stop is before operating the

lathe.

Correct dress is important, remove rings and watches.

Do not change spindle speeds until the lathe comes to a

complete stop.



Semester: 4th Sem.


Chapter 2: Drilling

DRILLING

Drilling is the operation of producing circular hole in the work-piece by using a rotating cutter called DRILL.

The machine used for drilling is called drilling

machine.

The drilling operation can also be accomplished in

lathe, in which the drill is held in tailstock and the work is held by the chuck.

The most common drill used is the twist drill.

DRILLING MACHINE

• It is the simplest and accurate machine used in production shop.

• The work piece is held stationary ie. Clamped in position and the drill rotates to make a hole.

• Types :-

a) Based on construction:

Portable, Sensitive,Radial, up-right, Gang, Multi-spindle

b) Based on Feed:

Hand and Power driven

SENSITIVE DRILLING MACHINE

Drill holes from to 15mm

Operator senses

the cutting action so sensitive drilling machine

UP-RIGHT DRILLING MACHINE

• Drill holes upto 50mm

• Table can

move vertically and radially

RADIAL DRILLING MACHINE

It the largest and most versatile used fro drilling medium to large and heavy work pieces.

DRILL MATERIALS The two most common types are

1. HSS drill

- Low cost

2. Carbide- tipped drills

- high production and in CNC machines

Other types are

Solid Carbide drill, TiN coated drills, carbide coated masonry

drills, parabolic drills, split point drill

Drilling And Drills

Types of drills

– Twist drill: most common drill

– Step drill: produces holes of two or more different diameters

– Core drill: used to make an existing hole bigger

DRILL FIXED TO THE SPINDLE

Drilling operations

Drilling Centre Hole

Drilling Deep Holes

Drilling Thin

Material

Drilling Pilot Hole

TOOL NOMENCLATURE

TOOL HOLDING DEVICES

The different methods used for holding drill in a

drill spindle are

By directly fitting in the spindle

hole.

By using drill sleeve

By using drill socket

By using drill chuck

WORK HOLDING DEVICES

DRILLING OPERATIONS…

Operations that can be performed in a drillin g machine are

Drilling

Reaming

Boring

Counter boring

Countersinking

Tapping

OPERATIONS IN DRILLING MACHINE

TYPES OF CUTTERS

Reamers :-

Multi tooth cutting tool

Accurate way of sizing and finishing the pre-existing hole.

Accuracy of 0.005mm can be achieved

Boring Tool:-

Single point cutting tool.

Boring tool is held in the boring bar which has the shank.

Accuracy of 0.005mm can be achieved.

TYPES OF CUTTERS

Countersinks :-

Special angled cone shaped enlargement at the end of the

hole

Cutting edges at the end of conical surface.

Cone angles of 60°, 82°, 90°, 100°, 110°, 120°

Counter Bore Tool:-

Special cutters uses a pilot to guide the cutting action .

Accommodates the heads of bolts.

COUNTER BORE AND SPOT FACING

TYPES OF CUTTERS

Combined Countersinks and central drill :-

Special drilling tool to start the hole accurately.

At the end it makes countersinks in the work piece.

Gun drill :-

Machining of lengthy holes with less feed rates.

To overcome the heating and short life of the normal drill to l

o

TYPES OF CUTTERS

Tapping:-

For cutting internal

thread

Multi cutting edge tool.

Tapping is performed

either by hand or by

machine.

Minor dia of the thread

is drilled and then

tapping is done.


1. Machine Table

Vice


Step Blocks

Clamps

V-Blocks

Angles

Jigs

T- Slots Bolt

DEFINITIONS

Cutting Speed (v):-

It’s the peripheral speed of the drill

v = *D*N where

D = dia of the drill in m

N = Speed of rotation in rpm

Feed Rate (f):- It’s the movement of drill along the axis (rpm)

Depth of Cut (d):- The distance from the machined surface to the drill axis

d = D / 2

Material Removal Rate:- It’s the volume of material removed by the drill per unit time

MRR = ( D2 / 4) * f * N mm3 / min

Machining Time (T) :- It depends upon the length (l) of the hole to be drilled , to the

Speed (N) and feed (f) of the drill

t = L / f N min

PRECAUTIONS FOR DRILLING MACHINE

Lubrication is important to remove heat and friction.

Machines should be cleaned after use

Chips should be removed using brush.

T-slots, grooves, spindles sleeves, belts, pulley should be cleaned.

Machines should be lightly oiled to prevent from rusting

SAFETY PRECAUTIONS

Do not support the work piece by hand – use work holding device.

Use brush to clean the chip

No adjustments while the machine is operating

Ensure for the cutting tools running straight before starting the operation.

Never place tools on the drilling table

Avoid loose clothing and protect the eyes.

Ease the feed if drill breaks inside the work piece.



Semester: 4th Sem.


Chapter 3: Lathe