1/1/2015

WORKSHOP

TECHNOLOGY

MANUAL

B.SUDARSHAN, M.TECH (Ph.D.) CENTURION UNIVERSITY OF TECHNOLOGY AND MANAGEMENT

pg. 1

Workshop technology syllabus

1. Introduction to welding, types of welding,

2. Oxyacetylene gas welding,

3. Types of flames,

4. Welding techniques and equipment.

5. Principle of arc welding, equipment and tools.

6. Casting processes.

7. Classification, constructional details of engine (or) center lathe,

8. Main accessories and attachments.

9. Main operations and tools used on center lathes.

10. Types of shapers, Constructional details of standard shaper.

11. Work holding devices,

12. Shaper tools and main operations.

13. Types of drilling machines.

14. Constructional details of pillar types and radial drilling machines.

15. Work holding and tool holding devices.

16. Main operations. Twist drills,

17. Drill angles and sizes.

18. Types and classification.

19. Constructional details and principles of operation of column and knee type universal milling

machines.

20. Plain milling cutter.

21. Main operations on milling machine.

pg. 2

PRACTICALS: 22. Introduction to welding equipment, processes tools, their use and precautions;

23. Jobs on ARC welding – Lap joint, butt joint;

24. T-Joint and corner joint in Arc welding;

25. Gas welding Practice – Lab, butt and T-Joints;

26. Introduction to metal casting equipment. Tools and their use;

27. Mould making using one-piece pattern and two pieces pattern;

28. Demonstration of mould making using sweep pattern, and match plate patterns;

29. Practical test; Introduction to machine shop machines and tools;

30. Demonstration on Processes in machining and use of measuring instruments;

31. Practical jobs on simple turning, step turning;

32. Practical job on taper turning, Drilling and threading;

33. Operations on shaper and planer,

34. Changing a round MS rod into square section on a shaper;

35. Demonstration of important operations on a milling machine, making a plot,

36. Gear tooth forming and indexing; any additional job.

pg. 3

WELDING

Introduction to Welding: A weld is made when separate pieces of material to be joined combine and form one piece when

heated to a temperature high enough to cause softening or melting. Filler material is typically added to

strengthen the joint.

Welding is a dependable, efficient and economic method for permanently joining similar

metals. In other words, you can weld steel to steel or aluminum to aluminum, but you cannot weld

steel to aluminum using traditional welding processes. Welding is used extensively in all sectors or manufacturing, from earth moving equipment to the

aerospace industry.

Welding Processes: The number of different welding processes has grown in recent years. These processes differ

greatly in the manner in which heat and pressure (when used) are applied, and in the type of equipment

used. There are currently over 50 different types of welding processes; we’ll focus on 3 examples of

electric arc welding, which is the most common form of welding.

The most popular processes are shielded metal arc welding (SMAW), gas metal arc welding

(GMAW) and gas tungsten arc welding (GTAW).

All of these methods employ an electric power supply to create an arc which melts the base

metal(s) to form a molten pool. The filler wire is then either added automatically (GMAW) or manually

(SMAW & GTAW) and the molten pool is allowed to cool.

Finally, all of these methods use some type of flux or gas to create an inert environment in which

the molten pool can solidify without oxidizing.

1.1. Classification Of Welding Processes:

I).Arc Welding:

Carbon arc, Metal, Tungsten, Plasma, Submerged, Electro Slag. Ii).Gas welding

Oxy-Acetylene, Air- Acetylene,Oxy-hydrogen iii).Resistance welding

Butt,Spot,Seam,Projection, iv). Thermit Welding

V). Solid State Welding

Friction, Ultra Sonic ,Diffusion, Explosive, vi). Newer Welding

Electro-Beam, Laser Beam vii). Related Process

Oxy-Acetylene Cutting, Arc- Cutting, Hard Facing,Brazing,Soldering, VARIOUS TYPES OF WELDING:

(a) Forge Welding: This welding is done by the black-smiths. In this two similar metal pieces are

heated up to the plastic stage in the furnace. Then it is hammered so that a homogeneous mixture

is formed at the joint.

(b) Gas Welding: Gas welding is the process in which a gas flame is used to raise the temperature

of the metals to be joined. The metals are heated up the melting. Many combinations of gases are

used in gas welding. But the most common of these is oxygen and acetylene.

(c) Arc Welding: The welding in which the electric arc is produced to give heat for the purpose

of joining two surfaces is called electric arc welding.

(d) Resistance Welding: Resistance welding is a group of welding processes where in

coalescence is produced by the heat obtained from resistance of the work to the flow of electric

pg. 4

current in a circuit of which is the work is a part and by the application of pressure. No filler metal

is needed. GAS WELDING:

Gas welding is the process in which a gas flame is used to raise the temperature of the metals to be joined.

The metals are heated up to melting. The metal flows and on cooling it solidifies. A filler metal may be

added to the flowing molten metal to fill up cavity made during the end preparation.

Many combinations of gases are used in gas welding. But the most common of these is oxygen and

acetylene.

Oxy-acetylene Welding

The process of oxy-acetylene welding can be used for almost all metals and alloys for engineering purposes.

A high temperature flame (3200°C) can be produced by this method. There are two systems of oxygen-

acetylene welding.

(a) High Pressure System: In this process the oxygen and acetylene are taken for use from high pressure

cylinders.

(b) Low Pressure System: In this system oxygen is taken from high pressure cylinder and the acetylene is

produced by the action of Calcium carbide and water.

CaC2 + 2H2O = Ca (OH) 2 + C2H2

(a) APPARATUS

Apparatus used for oxy-acetylene (high pressure) welding is shown in the fig. and consists of the following:

1. Oxygen cylinder 2. Acetylene cylinder 3. Pressure gauges 4. Valves 5. Hose pipes

6. Torch 7. Welding tip 8. Pressure regulators 9. Lighter 10. Goggles

pg. 5

(b) Principle of Oxy-acetylene Welding:

A very hot flame is produced by burning of the gases coming through the torch tip. The edges to be welded

are heated up to melting. A filler metal is also added to complete the welding. This molten metal mixture

when solidifies on cooling forms a welded joint.

Oxygen cylinder and acetylene cylinder are filled with gases. Both the cylinders are attached with pressure

gauges, regulators and cylinder valves. The cylinder containing oxygen is painted black whereas the

acetylene cylinder is painted maroon. Hose pipes, are provided with each cylinder. These pipes are

connected to welding torch.

Fig: Oxy-acetylene welding outfits

(c) Welding Process:

To start welding, the acetylene control valve is turned first. When acetylene comes out of the nozzle, it

should be ignited with spark lighter. It will give a yellow-colored smoke flame. After it, oxygen cylinder

valve is opened and supply is increased until a most suitable flame is obtained. Then the flame. The edges

and filler metal melt and a joint are formed after cooling of the molten metal.

The joint may be formed with or without using filler metal.

(d) Applications:

Oxy-acetylene welding is particularly used for sheet metal work. All the metals can be welded with proper

filler metals. Same equipment may be used for cutting purposes.

(e) Advantages of Oxy-acetylene Welding:

The main advantages of oxy-acetylene welding are given below:

1. Equipment is cheap as compared to other welding process.

2. It can be used for welding of all types of metals.

3. Maintenance of equipment is very less.

4. It is a portable process.

5. It can be used for cutting of metals of small thickness.

6. It is specially used for sheet metal work.

pg. 6

(f) Disadvantages:

1. It takes long time for heating the job as compared to the arc welding.

2. The heat affected area is more.

3. This is prone to corrosion and brittleness.

4. Gases are expensive and difficult to store.

Types of Gas Flames

There are three types of gas flames:

1. Oxidizing Flame 2. Carburizing Flame 3. Neutral Flame

1. Oxidizing Flame: When the volume of oxygen gas is more than the volume of acetylene mixed into the

torch. This flame is used for welding brass and is also used for cutting the metals.

2. Carburizing Flame: When the volume of acetylene mixed is more than oxygen, carburizing flame is

formed. This flame is used for welding nickel, Monel etc.

3. Neutral Flame: It is known as balanced flame. Oxygen and acetylene gases are mixed in equal volumes.

Neutral flame is used for normal welding of steel, cast iron etc.

Gas Welding Techniques

There are two types of gas welding techniques:

1. Left ward welding

2. Right ward welding

1. Left Ward Welding: In this welding the tip of the torch is held at 60 to 70°C to the plates. And the filler

rod is inclined at 30 to 40°C in opposite direction. In this method, the plate edges are heated immediately

after the molten metal. The torch tip and filler rod are moved slowly in the direction towards left. The

technique is illustrated in the Fig.

2. Right Ward Welding: In right ward welding the torch is kept at 40 to 50°C to the job to be welded.

Torch is moved towards right as shown in the Fig. Right ward welding is done for heavy sections only.

pg. 7

Flux

The chemicals which deoxidize the metal surface and provide inert atmosphere around the molten metal

are known as fluxes.

1. To prevent oxides on the hot surfaces.

2. To reduce the viscosity of molten metal.

3. It maintains a steady arc in case of arc welding.

Fluxes are available as liquid, powder, paste and gas.

Powder flux is sprinkled on the surfaces to be welded or the filler rod is dipped into the powder.

Liquid & paste fluxes are sprayed on the surfaces to be welded.

Gas fluxes are used to form inert atmosphere around the joint to be welded

Filler

The rod which provides additional metal in completing the welding is known as filler. The composition of

filler metal should be the same as that of the metals to be welded.

Gas Welding Equipment

Details of Gas welding equipment are as under:

1. Oxygen Cylinder: cylinder is made up of steel in capacity range 2.25to 6.3 m3. The cylinders are filled

with oxygen at about 150 kg/cm2 at 21°C. A safety valve is also provided on it. The cylinder can be opened

or closed by a wheel which operates a valve. A protector cap is provided on the top of a cylinder to safeguard

the valve.

Fig: Oxygen Cylinder

2. Acetylene Cylinder: Acetylene cylinders are also made up of steel. Gas is filled at a pressure of 18-20

kg/cm2. The capacity of the cylinder is about 10m3.Regulator valve and safety valve are mounted on

cylinder. Safety plugs are also provided on the bottom of the cylinder. When filled into the cylinder, the

acetylene is dissolved in acetone.

pg. 8

Fig. Acetylene cylinders

3. Regulator: Regulator is used to control the flow of gases from high pressure cylinder. A simple type of

regulator is shown in the Fig. 7.8.

Fig. Regulator

4. Torch: Torch is a device used to mix acetylene and oxygen in the correct proportion and the mixture

flows to the tip of the torch. Refer Fig.

There are two types of torches:

(a) Low pressure or injector torches

(b) Medium pressure or equal pressure torches

Fig. Welding Torch

pg. 9

(a) Low Pressure or Injector Torch: These torches are designed to use acetylene at low-pressure. The

pressure is kept very low up to 0.7 kg/cm2. But the oxygen pressure is very high.

(b) Medium Pressure or Equal Pressure Torch: In this type of torch the acetylene is taken at a pressure

equal to 1 kg/cm2, the oxygen is always supplied at high pressure. Both types of torches are provided with

two needle valves. One regulates the flow of oxygen and the second valve controls the flow of acetylene.

A mixing chamber is provided to mix the gases.

5. Torch Tips: For different types of jobs, different tips are used. The size of the tip is specified by the

outlet hole diameter. More than one hole is also provided in tips. The tip is screwed or fitted on the front

end of the torch. Various types of tips are shown in the Fig.

Fig. Torch tips

6. Goggles: Gas flames produce high intensity light & heat rays, which are harmful to naked eye. To protect

the eyes from these rays, goggles are used. Goggles also protect the eyes from flying sparks.

Fig. Goggles

7. Lighter: For starting the flame, the spark should be given by a lighter. Match sticks should not be used,

as there is risk of burning hand.

8. Fire Extinguishers: Fire extinguishers are used to prevent the fire that may break out by chance. Sand

filled buckets and closed cylinders are kept ready to meet such accidents.

Safety Precautions in Gas Welding

The following safety precautions must be observed while working in welding shop:

1. Always handle the gas cylinders with care.

2. The adjusting screw on the regulator must be fully released before opening a cylinder valve.

3. Never use matchsticks for lighting a torch.

4. Never lubricate the regulator valve with oil or grease, it may cause explosion.

5. Always use goggles while working.

6. Proper ventilation must be provided in the shop.

7. Acetylene cylinders should be stored in upright position.

8. Do not open acetylene cylinders near sparks or fire.

pg. 10

9. Never remove torch tips with pliers.

10. The cylinder should be leak proof.

11. Always use protective caps over the valves.

12. Keep in mind the location of the fire extinguishers.

ELECTRIC ARC WELDING

The welding in which the electric arc is produced to give heat for the purpose of joining two surfaces is

called electric arc welding.

Principle

Power supply is given to electrode and the work. A suitable gap is kept between the work and electrode. A

high current is passed through the circuit. An arc is produced around the area to be welded. The electric

energy is converted into heat energy, producing a temperature of 3000°C to4000°C. This heat melts the

edges to be welded and molten pool is formed. On solidification the welding joint is obtained.

Fig. Arc Welding

Electric Power for Welding

AC current or DC current can be used for arc welding. For most purposes, DC current is preferred .In D.C.

welding, a D.C. generator or a solid state rectifier is used. D.C. machines are made up to the capacity range

of 600 amperes. The voltage in open circuit is kept around 45 to 95 volts and in closed circuit it is kept 17

to 25 volts. D.C. current can be given in two ways:

(a) Straight polarity welding.

(b) Reverse polarity welding.

In straight polarity welding work piece is made anode and the electrode is made cathode as shown in the

fig A. Electrons flow from cathode to anode, thus, heat is produced at the materials to be welded.

pg. 11

In reverse polarity system the work is made cathode and the electrode is made anode. This welding is done

specially for thin section.

AC welding has the advantage of being cheap. Equipment used is simpler than DC welding. A transformer

is used to increase the current output at the electrode. The current varies from 150to 1000 amperes

depending upon the type of work.

Effect of Arc Length

Arc length is the distance from the tip of the electrode to the bottom of the arc. It should vary from 3 to 4

mm. In short arc length, the time of contact will be shorter and will make a wide and shallow bead. The

penetration is low as compared to long arc lengths.

Equipment used for Arc Welding

Various equipment’s used for arc welding are as under:

1. D.C. Welding Equipment

(a) AC Motor - Generator set

(b) Diesel Engine - Generator set

(c) Transformer - Rectifier welding set

2. AC Equipment

(a) Welding transformer set

3. Equipment accessories

(a) Leads

(b) Holder

(c) Connectors (d) Ground Clamps

4. Operator’s tool

(a) Chipping hammer

(b) Wire brush

(c) Arc shield

(d) Closed shoe

The details of the above equipment and accessories are described below:

1. AC Motor Generator: In this a generator is driven by a suitable AC motor. The average voltage of the

generator is 25 volt. The current ranges from 25 to 100 amperes. The voltage in the generator is variable.

The voltage can be set to the desired value with the help of rheostat.

2. Diesel Engine Generator Set: In this set, the drive is given by a diesel engine. Rest of the system is

same as in case of A.C. motor generator. Diesel engine generator sets are used in the areas when electricity

is not available.

pg. 12

3. Transformer Rectifier Set: It allows the current to flow through it only in one direction because it has

a one way valve or solid rectifier installed on the electrode side of the secondary coil. The set can supply

straight polarity and reverse polarity power supply. The rectifier, are of two types

(a) Silicon diode

(b) Selenium plate

Fig: Transformer Rectifier Set

4. Welding Transformer Set: It is used to step down the voltage supply. It consists of a primary and

secondary circuit. The input is given to primary winding. By electromagnetic induction the current flows

through the secondary coil. The output can be controlled as per requirement.

Fig: welding Transformer Set

5. Cables or Leads: These leads are made up of copper or aluminum wire. The wires are insulated with

rubber & cloth fiber. A heavy insulation is necessary for these cables.

6. Face Shield: When arc is produced around the job, infrared rays and ultraviolet rays are produced. To

protect the face and eyes from these dangerous rays, a shield is necessary.

7. Other Accessories & Tools: Other accessories & tools used for arc welding are shown in the fig.

pg. 13

Fig: Other Accessories

2. Horizontal Position: In this position, the work piece is kept as in the fig 7.19. Two surfaces rest one

over the other with their flat faces in vertical plane. Welding is done from right side to left side. The axis

of the weld is in a horizontal plane and its face in vertical plane.

3. Vertical Position: In this position, the axis of the weld remains in approximate vertical plane. The

welding is started at the bottom and proceeds towards top. Welding process is illustrated in figure.

Types of Electrodes

Electrodes are of two types

1. Coated electrodes: Coated electrodes are generally applied in arc welding processes. A metallic core is

coated with some suitable material. The material used for core is mild steel, nickel steel, chromium

molybdenum steel, etc. One end of the coated core is kept bare for holding.

2. Bare electrodes: Bare electrodes produce the welding of poor quality. These are cheaper than coated

electrodes. These are generally used in modern welding process like MIG welding.

Electrode Size

Electrodes are commonly made in lengths 250 mm, 300 mm, 350 mm, 450 mm, and the diameters are 1.6

mm, 2 mm, 2.5 mm, 3.2 mm, 4 mm, 7 mm, 8 mm and 9 mm.

TYPES OF JOINTS:

Basic types of welding joints are classified as under:

(a) Butt Joint

In this type of joint, the edges are welded in the same plane with each other. V or U shape is given to the

edges to make the joints strong. Some examples of butt joints are shown in the figure.

pg. 14

Fig: Different Types of Butt Joints

(b) Lap Joint

This type of joint is used in joining two overlapping plates so that the corner of each plate is joined with

the surface of other plate. Common types of lap joints are single lap, double lap or offset lap joint. Single

welded lap joint does not develop full strength as compared to double welded lap.

Fig: Different Types of Lap Joints

(c) T-Joint

When two surfaces are to be welded at right angles, the joint is called T-Joint. The angle between the

surfaces is kept 90°.

(d) Corner Joint

In this joint, the edges of two sheets are joined and their surfaces are kept at right angle to each other. Such

joints are made in frames, steel boxes, etc.

(e) Edge Joint

In this joint two parallel plates are welded edge to edge.

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pg. 15

RELATED QUESTIONS

1. What is Welding?

Welding is a process of joining similar metals by the application of heat with or without applying

pressure.

2. What are the different types of welding?

There are two types:

1. Pressure welding (plastic welding) – without using filler metal.

2. Fusion welding – no pressure – without or with filler.

3. What is arc welding?

It is a welding process used to join two metals when electric current is used to generate the arc for

joining the metals.

4. What is an electrode?

Electrode is a metal rod coated with a flux. It is used to supply metal required for welding the

metal pieces. When the metal rod is not coated then it is referred to as filler rod or welding rod.

5. What is a flux?

Flux is a material capable of dissolving the oxides of metal formed during heating of weld. It

mainly consists of chlorates, fluorides, boarates, carbonates, borax etc.

6. What is the range of current and range of voltage used in arc welding?

In arc welding the normal current range used varies from 100-120 amps and voltage varies from

20-50 volts.

7. What are the different types of welded joints?

Butt joint –V, double U etc. Lap joint-joint, corner joint, angle joint etc.

8. What type of steel can be easily welded?

Steel with low carbon content (C<0.25%) can be easily welded

9. What is M.S? What is its composition?

M.S is the abbreviation for Mild Steel.

It contain Fe, less than 0.25% carbon, 0.5-0.8% is, 0.7-0.09% Mn approx. 0.05%max. S & P each.

10. Mention the arc welding energy sources.

Energy for arc welding is provided by transformers, generators, rectifiers and converters.

11. What is the formula for heat input in welding?

Q = 12RT where I = Current R == resistance, T = Time.

12. What is the principle of arc welding?

Electric arc is produced between metal electrode carrying high current and the work piece. Flow

of current takes place between the electrode and the work piece. Negative electrons are emitted

from the cathode (electrode) and they have to overcome the lionized gas column called plasma

(between the air gap).Hence, electrons trying to overcome the plasma move at higher velocity and

strike the work piece thus the kinetic energy is converted to heat energy.

13. What is the other classification of welding?

It can be classified as mainly (1) Plastic Welding & (2) Fusion Welding.

(1) Plastic Welding: Ex. Resistance welding – spot welding, seam welding, butt welding.

(2) Fusion welding: Ex. Gas welding, Arc welding.

pg. 16

CASTING PROCESSES

Introduction:

Foundries: The plant where jobs are prepared by melting and pouring the molten metals in to

moulds are known as foundries.

Mould: A mould is a cavity so prepared that it can be used to make casting by molten metal in to

it.

Pattern: Pattern is a facsimile model of anything, which is used to prepare moulds by placing it

in sand.

Casting Process: The process of poring molten metal in to a predefined cavity of a mould and

allowing it to cool is known as casting process.

Castings: The products made by casting process are known as castings.

HAND TOOLS

1. Showel: It consist of a iron pan with a wooden handle it can be used for mixing and conditioning

the sand and then transferring the mixture in some container

2. Trowels: These are used for finishing flat surface and corner inside a mould. Common shapes

of trowels.

3. Lifter: A lifter is a finishing tool used for repairing the mould and finishing the mould sand.

Lifter is also used for removing loose sand from mould.

4. Hand Riddle: It is used for ridding of sand to remove foreign material from it. It consist of a

wooden frame fitted with a screen of standard wire mesh at the bottom.

5. Strike of Bare: It is a flat bar made of wood or iron to strike off the excess sand from the top

of a box after riming

6. Vent Rod: It is a thin steel rod or wire carrying a pointed edge at one and a wooden handle or

a bent loop at the other. After ramming and striking of the excess sand it is used to make small

holes called vents in the sand mold to allow the exit of gasses and steam during casting.

7. Draw Spike: It is a tapered steel rod having a loop or ring at it is one end and a sharp point at

the other it is used to tap and draw patterns from the mould.

8. RAMMER: Rammer are used for striking the sand mass in the molding box to pack it closely

around one pattern.

a) Peen rammer

b) Floor rammer

c) Hand rammer

9. Slicks: These are used for repairing and finishing the mould surfaces and edges after the pattern

has been withdrawn the commonly used slices are heart and leaf square and heart spoon and bead

and heart and spoon.

10. Smoother and Corner Slicks: they are also finishing flat and round surfaces round or square

corners and edges.

11. Swab: It is a hemp fiber brush used for moistening the edges of sand mould which are in

contact with the pattern surfaces before withdrawing the pattern it is also used for coating the liquid

blocking on the mould faces in dry sand moulds.

12. Sprue Pin: It is a tapered rod of wood or iron which is embedded in the sand and later

withdrawn to produce a hole called runner through which the molten metal is poured into

themould.

13. Bellow; it used to blow but the loose or unwanted sand from the surface and cavity of themould.

14. Draw Screws and Rapping Plate: It is a long mild steel rod with a ring in one end and

threaded at the other, there is a plate known as rapping plate consisting of several tapped holes.

pg. 17

15. Moulding Boxes: The Moulding boxes or flasks used in sand Moulding are of two types;

(a) Closed Moulding boxes.

(b) Open type of snap flasks.

16. Ladles: They are used to receive molten metal from the melting furnace and pour the same

into the mould. Their size is designated by their metal holding capacity. Small hand shank ladles,

used by a single. Moulder, are provided with only one handle and are made indifferent capacities

up to a maximum of 20kg.

17. Crucibles: They are made of refractory material and are similar in shape to the ladles .They

are used as metal melting pots. The raw material or charge is broken into small pieces and placed

in them. They are then placed in crucible or pit furnaces which are coke fired.

Pattern Materials: 1. Wood.

2. Iron.

3. Aluminum; brass; zinc etc.

4. Plaster.

5. Plastic.

6. Wax.

Types of Patterns: 1. Solid or single piece pattern. 2. Two-piece or split pattern.

3. Multi piece pattern. 4. Match plate pattern.

5. Gated pattern 6. Skeleton pattern.

7. Sweep pattern. 8. Pattern with loose pieces.

9. Cope and drag pattern. 10. Follow board pattern.

11. Segmental pattern.

Fig: Types of Patterns

Single piece pattern:

It is the simplest of all the patterns. This has a flat surface on the cope side. This makes possible a

straight line parting on the joint between the cope and drag of the mould. It is used for making

simple castings.

Split pattern:

pg. 18

Split patterns are recommended for intricate castings, where removal of the pattern from the mould

is difficult. The two halves of the pattern are put together by dowel pins. If the two pieces are

similar in size and shape, it is called a split pattern, otherwise, it is known as a two-piece pattern.

The upper and lower parts of the split pattern are accommodated in the cope and drag parts of the

mold respectively.

NOTE:

In case of a split pattern, to be used with a core, the shape of the pattern will not be exactly the

same as that of the casting. This is because of the projection that has to be provided for core prints,

to provide bearing surface for the core.

Loose piece:

When a pattern cannot be withdrawn from the mould due to its complexity, loose pieces are

provided to facilitate this. The loose parts or pieces are attached to the main body of the pattern

with dowel pins. However, only two molding boxes are required for making a mould in this case.

Multi-piece pattern:

This type of pattern is made in three or more parts. The parts that makeup the pattern are held

together with dowel pins. The number of molding boxes required will be equal to the number of

pieces of the pattern.

Cored pattern:

When a casting with holes or recesses is to be made, a cored pattern is needed. This type of pattern

is made with core prints added to the surface. After molding, the core prints leave impressions in

the sand for positioning a dry sand core. A sand core is prepared separately, dried and then

positioned in the mould before it is closed. When molten metal is poured into the mould, a cavity

or recess is formed in the casting, the shape of which is determined by that of the core.

Core print:

An impression in the form of a recess is made in the mould, to support a core in the mould. This

is obtained with the help of\a projection, suitably added to the pattern. This projection on the

pattern is known as the core print. Depending upon the casting shape, core print may be horizontal

or vertical.

Core box:

A core box is a pattern, made of either wood or metal, into which sand is packed to form the core.

Wood is commonly used for making a core box; but metal boxes are used when cores are to be

made in large numbers. Specially prepared core sand is used in making cores.

Fig: Core Box

Moulding Processes:

1. Moulding Processes:

a) Floor Moulding.

b) Bench Moulding

c) Pit Moulding

pg. 19

d) Machine Moulding

2. According To the Mould Materials

i) Sand Moulding

a) Green sand Moulding

b) Dry sand Moulding

c) Core sand Moulding

d) Cement bonded sand Moulding

e) Shell Moulding

f) Skin dried sand Moulding

g) Loam Moulding

ii) Plaster Moulding

iii) Metallic Moulding

Casting Processes 1. Sand mould casting

2. Plaster mould casting

3. Metallic mould casting

a) Gravity or permanent mould casting

b) Slush casting

c) Pressed casting

d) Die casting

4. Centrifugal casting

5. Precision casting

6. CO2 mould casting

7. Continues casting

Moulding Sand Moulding sand is one of the most important and materials in production of sand casting. Sand is

Formed by breaking up of rocks due to natural forces such as frost wind, rain and action of water.

a. Natural sand

b. Synthetic sand

Types of Sand Used In Mouldes 1. Dry sand 2. Green sand 3. Loam sand 4. Facing sand 5. Parting sand

6. Backing sand 7. Core sand 8. Oil sand 9. Molasses sand

Composition of Green Sand 1. Silica sand 75%

2. Coal dust 8%

3. Bentonite sand 12%

4. Water 5 to 6%

Properties of Moulding Sand 1. Porosity and permeability 2. Refractoriness 3. Adhesiveness 4. Cohesiveness

5. Chemical resistance 6. Plasticity 7. Moisture

Main Constituent of Moulding Sand The principal constituents of Moulding sand are

1. Silica sand

2. Binder

3. Additives

pg. 20

4. Water

Binders The purpose of adding to the binder to the Moulding sand is to impart it sufficient strength

&cohesiveness so to enable it to retain its shape after the mould has been rammed & the pattern

withdrawn. However it produce an obverse effect on the permeability of the sand mould.

The common binders used in foundry can be grouped as:

1. Organic binders

2. in organic binders

(ORGANIC) (INORGANIC)

1. Dextrin 1. Bentonite.

2. Linseed oil 2. Kaolinite.

3. Molasses 3. Limonite.

4. Certain binders 4. Ball clay.

5. Pitch 5. Fire clay

6. Resins, phenol formaldehydes 6. Fuller’s earth

CORES:

Core is a mass of sand that is put into the mould of from holes and cavities in the casting cores are

prepared separately in core box.

a) Horizontal Core: It is the most common and simple type of core. It is assembled into the mould

with its axis horizontal. It is supported in the mould at its both ends.

B) Vertical Core: It is quite similar to a horizontal core except that it is fitted in the mould with its

axis vertical.

C) Balanced Core: It is used to produce a blind holes along a horizontal axis in a casting. As a

matter of fact it is nothing but a horizontal core with the exception that it is supported only one

end the other end remaining free in the mould cavity. CORE BOXES:

A core box is a type of a pattern used for making cores. It is made of wood, brass, aluminum or

any suitable material.

TYPE OF BOXES:

1. Half core box.

2. Dump core box

3. Split core box

4. Right and left core box

5. Gang core box CORE MAKING MACHINES:

Fore production work machine are used for core making, where Jolting, squeezing or blowing

machine rams core sand mixture.

The most commonly core making machine are

1. Core blowing

2. Core shooter.

i). Shrinkage or contraction allowance: It is an allowance given to the pattern to compensate for

the change in dimensions of the casting due to shrinkage of the metal during solidification.

ii). taper or draft allowance: A taper should be provided to the vertical walls of a pattern, for its

easy withdrawal from the sand mold. This is known as draft allowance.

pg. 21

iii). machining allowance: This allowance is provided on the pattern, if the casting needs

machining operation. In general, ferrous metals require more machining allowance than non-

ferrous ones.

The following are the factors that govern the selection of the pattern material:

1. Quantity, quality and intricacy of castings that are to be produced

2. Nature of casting process and the type of molding process

3. Possibility changes in the design

The following are the characteristics of a good pattern material:

1 Ability to take good surface finish

2 Stability in dimensions in all weathers

3 Permissibility to work, shape and join easily

4. Strong, hard and durability

Wood

It is the widely used material for pattern making. It is used when the number of castings to be

produced is relatively less. Pine, teak, kail and mahogany are the commonly used \voods for

patterns.

Metals and alloys

Metal patterns are preferred when large number of castings are to be produced. Metal patterns are

more durable and produce dimensionally accurate molds. Cast iron, steel, aluminum and its alloys,

brass, etc., are the metals commonly used for pattern making.

Metal pattern is produced by using a wooden pattern called 'Master pattern'. The most commonly

used

Plastics

Thermo-setting plastics are becoming more popular now-a-days, for making patterns. The

commonly used plastics are: Polyester resin, epoxy resin and polystyrene.

Plaster

Plaster of Paris or gypsum cement can also be used as a pattern material, as it can be cast into

intricate shapes and can also be easily worked.

Waxes

These are excellent pattern materials for investment casting process these help in

Producing a high degree of surface finish for the pattern and hence dimensionally accurate casting.

pg. 22

Fig: Moulders Tools and Equipment

Fig: Sand Casting

pg. 23

LATHE

Introduction:

Lathe is one of the most versatile and widely used machine tools all over the world. It’s commonly

known as the mother of all other machine tool. The main function of a lathes to remove metal from

a job to give it the required shape and size. Fig.shows the working principle of lathe. An engine

lathe is the most basic and simplest form of the lathe. It derives its name from the early lathes,

which obtained their power from be used to carry out other operations also, such as drilling,

reaming, boring, taper turning, knurling, screw thread cutting, grinding etc.

Fig: Working Principal of Lathe Machine

Types of Lathe:

Lathes are manufactured in a variety of types and sizes, from very small bench lathes used for

precision work to huge lathes used for turning large steel shafts. But the principle of operation and

function of all types of lathes is same. The different types of lathes are:

1. Speed lathe

(a) Wood working (b) Spinning

(c) Centering (d) Po1ishing

2. Centre or engine lathe

(a) Be1t drive

(b) Individual motor drive

(c) Gear head lathe

3. Bench lathe

4. Tool room Lathe

5. Capstan and Turret 1athe

6. Special purpose lathe

(a) Whee1 lathe (b) Gap bed lathe (c) Dup1icating lathe (d) T-lathe

7. Automatic lathe

Some of common lathes are described as under.

1. Speed Lathe

Speed lathe is simplest of all types of lathes in construction and operation. The important parts of

speed lathe are following-

(1) Bed

(2) Headstock

(3) Tailstock, and

pg. 24

(4) Tool post mounted on an adjustable slide.

It has no feed box, 1eadscrew or conventional type of carriage. The tool is mounted on the

adjustable slide and is fed into the work by hand contro1.

2. Centre Lathe or Engine Lathe:

The term “engine” is associated with this lathe due to the fact that in the very early days of its

development it was driven by steam engine. This lathe is the important member of the lathe family

and is the most widely used. Similar to the speed lathe, the engine lathe has all the basic parts, e.g.,

bed, headstock, and tailstock. But its headstock is much more robust in construction and contains

additional mechanism for driving the lathe spindle at multiple speeds. An engine lathe is shown in

Fig. Unlike the speed lathe, the engine lathe can feed the cutting tool both in cross and longitudinal

direction with reference to the lathe axis with the help of a carriage, feed rod and lead screw. Centre

lathes or engine lathes are classified according to methods of transmitting power to the machine.

The power may be transmitted by means of belt, electric motor or through gears.

Fig: Principal Components of a Central Lathe

3 Bench Lathe

This is a small lathe usually mounted on a bench. It has practically all the parts of an engine lathe

or speed lathe and it performs almost all the operations. This is used for small and precision work.

4 Tool Room Lathe

This lathe has features similar to an engine lathe but it is much more accurately built. It has a wide

range of spindle speeds ranging from a very low to a quite high speed up to2500 rpm. This lathe

is mainly used for precision work on tools, dies, gauges and in machining work where accuracy is

needed.

5 Capstan and Turret Lathe

The distinguishing feature of this type of lathe is that the tailstock of an engine lathe is replaced

by a hexagonal turret, on the face of which multiple tools may be fitted and fed into the work in

proper sequence. Due to this arrangement, several different types of operations can be done on a

job without re-setting of work or tools, and a number of identical parts can be produced in the

minimum time.

6 Special Purpose Lathes

These lathes are constructed for special purposes and for jobs, which cannot be accommodated or

conveniently machined on a standard lathe. The wheel lathe is made for finishing the journals and

pg. 25

turning the tread on railroad car and locomotive wheels. The gaped lathe, in which a section of the

bed adjacent to the headstock is removable, is used towing extra-large-diameter pieces.

7 Automatic Lathes

These lathes are so designed that all the working and job handling movements of the complete

manufacturing process for a job are done automatically. These are high speed, heavy-duty, mass

production lathes with complete automatic control.

CONSTRUCTION OF LATHE MACHINE:

A simple lathe comprises of a bed made of grey cast iron on which headstock, tailstock, carriage

and other components of lathe are mounted. Fig. shows the different parts of engine lathe or central

lathe. The major parts of lathe machine are given as under:

1. Bed 2. Head stock 3. Tailstock 4. Carriage 5. Feed mechanism 6. Thread cutting

mechanism

Fig. Different Parts of Engine Lathe or Central Lathe

1 Bed

The bed of a lathe machine is the base on which all other parts of lathe are mounted. It is massive

and rigid single piece casting made to support other active parts of lathe. On left end of the bed,

headstock of lathe machine is located while on right side tailstock is located.

2 Head Stock

The main function of headstock is to transmit power to the different parts of a lathe. It comprises

of the headstock casting to accommodate all the parts within it including gear train arrangement.

The main spindle is adjusted in it, which possesses live center to which the work can be attached.

It supports the work and revolves with the work, fitted into the main spindle of the headstock.

3 Tail Stock

Fig. shows the tail stock of central lathe, which is commonly used for the objective of primarily

giving an outer bearing and support the circular job being turned on centers. Tailstock can be easily

set or adjusted for alignment or non-alignment with respect to the spindle Centre and carries a

center called dead center for supporting one end of the work. Both live and dead centers have 60°

pg. 26

conical points to fit center holes in the circular job, the other end tapering to allow for good fitting

into the spindles.

Fig. Tail Stock of Central Lathe

4 Carriage

Carriage is mounted on the outer guide ways of lathe bed and it can move in a direction parallel to

the spindle axis. It comprises of important parts such as apron, cross-slide, saddle, compound rest,

and tool post. The lower part of the carriage is termed the apron in which there are gears to

constitute apron mechanism for adjusting the direction of the feed using clutch mechanism and the

split half nut for automatic feed.. Fig. shows the tool post of center lathe.

Fig. Tool Post of Center Lathe.

5 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

pg. 27

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.

The feed gear box contains a number of different sizes of gears. The feed gear box provides a

means to alter the rate of feed, and the ration between revolutions of the headstock spindle and the

movement of carriage for thread cutting by changing the speed of rotation of the feed rod or lead

screw.

6 Thread Cutting Mechanism

The half nut or split nut is used for thread cutting in a lathe. It engages or disengages the carriage

with the lead screw so that the rotation of the lead screw is used to traverse the tool along the work

piece to cut screw threads. The direction in which the carriage moves depends upon the position

of the feed reverse lever on the headstock.

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 equipment’s

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 center (head stock center) and dead center (tailstock center). 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

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 set screw. 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

Fig. Lathe Dog

Chucks

Chuck is one of the most important devices for holding and rotating a job in a lathe. It’s basically

attached to the headstock spindle of the lathe. The internal threads in the chuck fit on to the external

pg. 28

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) Magnetic chuck

(4) Collet chuck (5) Air or hydraulic chuck operated chuck (6) Combination chuck

(7) Drill chuck.

Face plates

Face plates are employed for holding jobs, which cannot be conveniently held between centers or

by chucks. A face plate possesses the radial, plain and T slots for holding jobs or work-pieces by

bolts and clamps. Face plates consist of a circular disc bored out and threaded to fit the nose of the

lathe spindle. They are heavily constructed and have strong thick ribbon the back. They have slots

cut into them, therefore nuts, bolts, clamps and angles are used to hold the jobs on the face plate.

They are accurately machined and ground.

Angle plates

Angle plate is a cast iron plate having two faces machined to make them absolutely at right angles

to each other. Holes and slots are provided on both faces so that it may be clamped on a faceplate

and can hold the job or work piece on the other face by bolts and clamps. The plates are used in

conjunction with a face plate when the holding surface of the job should be kept horizontal.

Mandrels

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. It is hardened and tempered steel shaft or bar

with 60° centers, so that it can be mounted between centers. It holds and locates a part from its

center hole.

Rests

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. The two types of rests commonly used for

supporting a long job in an engine lathe are the steady or center rest and the follower rest.

Main operations and tools used on center lathes.

For performing the various machining operations in a lathe, the job is being supported and driven

by anyone of the following methods.

1. Job is held and driven by chuck with the other end supported on the tail stock center.

2. Job is held between centers and driven by carriers and catch plates.

3. Job is held on a mandrel, which is supported between centers and driven by carriers and catch

plates.

4. Job is held and driven by a chuck or a faceplate or an angle plate.

The above methods for holding the job can be classified under two headings namely job held

between centers and job held by a chuck or any other fixture. The various important lathe

operations are depicted through Fig (a), (b) and (c). The operations performed in lathe can be

understood by three major categories

pg. 29

(a) Operations, which can be performed in a lathe either by holding the work piece between

centers or by a chuck are:

1. Straight turning 2. Shoulder turning 3. Taper turning 4. Chamfering 5. Eccentric

turning

6. Thread cutting 7. Facing 8. Forming 9. Filing 10. Polishing

11. Grooving 12. Knurling 13. Spinning 14. Spring winding

Fig (A): Lathe Operation

(b) Operations which are performed by holding the work by a chuck or a faceplate or an

angle plate are:

1. Undercutting 2. Parting-off 3. Internal thread cutting 4. Drilling

5. Reaming 6. Boring 7. Counter boring 8. Taper boring

9. Tapping

Fig (B): Lathe Operation

pg. 30

(c) Operations which are performed by using special lathe attachments are:

1. Milling 2. Grinding

Fig(C): Lathe Operation

TAPERS AND TAPER TURNING:

A taper is defined as a uniform increase or decrease in diameter of a piece of work measured along

its length. In a lathe machine, taper turning means to produce a conical surface by gradual reduction

in diameter from a cylindrical job. Taper in the British Systemic expressed in taper per foot or

taper per inch.

Taper per inch = (D – d) /2l

Where,

D = is the diameter of the large end of cylindrical job,

d = is the diameter of the small end of cylindrical job, and

l = is the length of the taper of cylindrical job, all expressed in inches,

When the taper is expressed in taper per foot, the length of the taper l is expressed in

Foot, but the diameters are expressed in inches.

A taper is generally turned in a lathe by feeding the tool at an angle to the axis of

Rotation of the work piece. The angle formed by the path of the tool with the axis of the

Work piece should correspond to the half taper angle. A taper can be turned by anyone of the

Following methods:

1. By swiveling the compound rest,

2. By setting over the tailstock center,

3. by a broad nose form tool,

4. by a taper turning attachment

5 By combining longitudinal and cross feed in a special lathe and

6. By using numerical control lathe

pg. 31

Taper Turning by Swiveling the Compound Rest:

This method uses the principle of turning taper by rotating the work piece on the lathe axis and

feeding the tool at an angle to the axis of rotation of the work piece. The tool is mounted on the

compound rest which is attached to a circular base, graduated in degrees. The compound rest can

easily be swiveled or rotated and clamped at any desired angle as shown in Fig. (a). Once the

compound rest is set at the desired half taper angle, rotation of the compound slide screw will

cause the tool to be fed at that angle and generate corresponding taper. This method is limited to

turn a short but steep taper because of the limited movement of the cross-slide. The compound rest

can be swiveled at 45° on either side of the lathe axis enabling it to turn a steep taper.. The complete

setup for producing a taper by swelling the compound rest is given in Fig.

pg. 32

Taper Turning Attachment Method:

This method is commonly employed for generating external tapers only. In this method, the taper

turning attachment is bolted back of the lathe machine as shown in Fig.. It has guide bar which

may be set at any desired angle or taper. As the carriage moves along the bed length aside over bar

causes the tool to move in and out according to setting of the bar. The taper setting on the bar is

duplicated on the job or work. The merit of this methods that the lathe centers are kept in alignment.

Fig.Taper Turning Attachment

Taper Turning with Tailstock set over Method

This method is basically employed for turning small tapers on longer jobs and is confined to

external tapers only. In this method, the tailstock is set over is calculated using Fig. 21.11by

loosening the nut from its center line equal to the value obtained by formula given below.

Fig. Tail Stock set over

Tail stock set over = Taper length × Sine of half of taper angle

pg. 33

(D – D) / 2 = l × sin (a/2)

Where, D = is the diameter of the large end of cylindrical job,

d = is the diameter of the small end of cylindrical job, and

l = is the length of the taper of cylindrical job, all expressed in inches,

a = taper angle

When a part length of the job is to be given taper then tail stock set

= ((D – d)/2)) × (total length of the cylindrical job/length of taper)

= l × sin (a/2) × (total length of the cylindrical job/length of taper)

THREAD CUTTING

Fig. shows the setup of thread cutting on a lathe. Thread of any pitch, shape and size can be cut on

a lathe using single point cutting tool. Thread cutting is operation of producing a helical groove on

spindle shape such as V, square or power threads on a cylindrical surface. The job is held in

between centers or in a chuck and the cutting tool is held on tool post. The cutting tool must travel

a distance equal to the pitch (in mm) as the work piece completes a revolution. The definite relative

rotary and linear motion between job and cutting tool is achieved by locking or engaging a carriage

motion with lead screw and nut mechanism and fixing a gear ratio between head stock spindle and

lead screw.

Fig: Thread Cutting

1. Work holding devices:

Three jaw chuck:

For holding cylindrical stock centered and for facing/center drilling the end of your aluminum

stock

pg. 34

Four-Jaw Chuck: This is independent chuck generally has four jaws, which are adjusted

individually on the chuck face by means of adjusting screws

Collet Chuck:

Collet chuck is used to hold small work pieces

Magnetic Chuck:

Thin jobs can be held by means of magnetic chucks

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RELATED QUESTIONS

1. Describe the working principle of the lathe.

2. Name the different types of the lathes available in machine shop? Describe the working ofl

center lathe.

3. Explain the parts of a center lathe using neat sketch.

4. Explain following parts of a lathe by neat sketches:

(i) Lathe Bed (ii) Carriage (iii) Headstock (iv) Tailstock

5. How can you specify a lathe?

6. Name the operations, which can be performed on a lathe.

7. Lists the accessories of a lathe? Explain them with neat sketches.

8. Describe any two work holding devices used on the lathe.

9. What is the use of follower rest and steady rest?

10. Explain the difference between three jaw chuck and four jaw chuck.

11. Using neat sketches, describe the various operations that can be carried on lathe machines.

12. With the help of a line diagram, describe the gear mechanism of an engine lathe.

13. Discuss the merits and demerits of a geared-head drive over cone-pulley drive.

14. Name and sketch the different types of the cutting tools of the lathe.

17. Name different methods of taper turning? Describe these methods using neat sketches.

18. Describe with suitable sketch the procedure for turning a taper using setting over the tailstock.

19. Define the following terms used in lathe operation.

(i) Cutting speed (ii) Feed

(iii) Depth of cut (iv) Machining time

Types of shapers, Constructional details of standard shaper.

pg. 35

SHAPER

Introduction:

Shaper is a reciprocating type of machine tool in which the ram moves the cutting tool backwards

and forwards in a straight line.

It is intended primarily to produce flat surfaces. These surfaces may be horizontal, vertical, or

inclined. In general, the shaper can produce any surface composed of straight-line elements. The

principal of shaping operation is shown in Fig. (a, b).

Fig. (A, B) Working Principal of Shaping Machine

Modern shapers can also generate contoured surface as shown in Fig.

Fig. job surfaces generated by shaper

A shaper is used to generate flat (plane) surfaces by means of a single point cutting tool similar to

a lathe tool.

Working Principle and Operation of a Shaper: We have already discussed that in a shaper, a single point cutting tool reciprocates over the stationary work

piece. The tool is held in the tool post of the reciprocating ram and performs the cutting operation during

its forward stroke. It may be noted that during the backward stroke of the ram, the tool does not remove

material from the work piece. Both these strokes (i.e., forward and backward strokes) form one working

cycle of the shaper.

pg. 36

For shaping in horizontal direction, as shown in Fig, (a), the clamped work piece is fed against the

reciprocating tool after every cutting cycle. The depth of cut is adjusted by moving the tool downward

towards the work piece. For shaping in vertical direction, as shown in Fig. (b).The tool is fed vertically

towards the work piece after every cutting cycle. The depth of cut is adjusted by moving the work piece

sideways.

Types of Shapers:

Shapers are classified under the following headings: 1. According to the ram driving mechanism

According to the ram driving mechanism, the shapers are classified as follows:

(a) Crank shaper: In a crank shaper, a crank and a slotted lever quick return motion mechanism is used to

give reciprocating motion to the ram. The crank arm is adjustable and is arranged inside the body of a bull

gear (also called crank gear).

(b) Geared shaper: In a geared shaper, the ram carries a rack below it, which is driven by a spur gear. This

type of shaper is not widely used.

(c) Hydraulic shaper: In a hydraulic shaper, a hydraulic system is used to drive the ram. This type of

shaper is more efficient than the crank and geared shaper.

2. According to position and travel of ram

According to the position and travel of ram, the shapers are classified as follows:

(a) Horizontal shaper: In a horizontal shaper, the ram moves or reciprocates in a horizontal direction. This

type of shaper is mainly used for producing flat surfaces.

(b) Vertical shaper: In a vertical shaper, the ram reciprocates vertically in the downward as well as in

upward direction. This type of shaper is very convenient for machining internal surfaces, keyways, slots or

grooves.

3. According to the direction of cutting stroke

According to the direction of cutting stroke, the shapers are classified as follows:

(a) Push-Cut shaper: In a push-cut shaper, the ram pushes the tool across the work during cutting

operation. In other words, forward stroke is the cutting stroke and the backward stroke is an idle stroke.

This is the most general type of shaper used in common practice.

(b) Draw-cut shaper: In a draw-cut shaper, the ram draws or pulls the tool across the work during cutting

operation. In other words, the backward stroke is the cutting stroke and forward stroke is an idle stroke.

Can be tilted about the other horizontal axis perpendicular to the first axis. This type of shaper is mostly

used in tool room work. 4. According to the design of the table

According to the design of the table, the shapers are classified as:

pg. 37

(a) Standard or plain shaper: In a standard or plain shaper, the table has only two movements i.e.,

horizontal and vertical, to give the feed. It cannot be swiveled or tilted.

(b) Universal shaper: In a universal shaper, in addition to the above two movements, the table can be

swiveled about a horizontal axis parallel to the ram and the upper portion of the table

Principal Parts of Shaper:

Fig. shows the parts of a standard shaper. The main parts are given as under.

Fig: parts of a standard shaper

Base

It is rigid and heavy cast iron body to resist vibration and takes up high compressive load. It

supports all other parts of the machine, which are mounted over it. The base maybe rigidly bolted

to the floor of the shop or on the bench according to the size of the machine.

Column

The column is a box shaped casting mounted upon the base. It houses the ram-driving mechanism.

Two accurately machined guide ways are provided on the top of the column on which the ram

reciprocates.

Cross rail

Cross rail of shaper has two parallel guide ways on its top in the vertical plane that is perpendicular

to the rai1 axis. It is mounted on the front vertical guide ways of the column. It consists mechanism

for raising and lowering the table to accommodate different sizes of jobs by rotating an elevating

screw which causes the cross rail to slide up and down on the vertical face of the column. A

horizontal cross feed screw is fitted within the cross rail and parallel to the top guide ways of the

cross rail. This screw actuates the table to move in crosswise direction.

Saddle

The saddle is located on the cross rail and holds the table on its top. Crosswise movement of the

saddle by rotation the cross feed screw by hand or power causes the table to move sideways.

Table

The table is a box like casting having T -slots both on the top and sides for clamping the work. It

is bolted to the saddle and receives crosswise and vertical movements from the saddle and cross

rail.

pg. 38

Ram

It is the reciprocating part of the shaper, which reciprocates on the guide ways provided above the

column. Ram is connected to the reciprocating mechanism contained within the column.

Tool head

The tool head of a shaper performs the following functions-

(1) It holds the tool rigidly,

(2) It provides vertical and angular feed movement of the tool, and

(3) It allows the tool to have an automatic relief during its return stroke.

SHAPER MECHANISM

In a shaper, rotary motion of the drive is converted into reciprocating motion of the ram by the

mechanism housed within the column or the machine. The shaper mechanism is so designed that

it moves the ram holding the tool at a comparatively slower speed during forward cutting stroke,

whereas during the return stroke it allow the ram to move at a faster speed to reduce the idle return

time. This mechanism is known as quick return mechanism. The reciprocating movement of the

ram and the quick return mechanism of the machine are generally obtained by anyone of the

following methods:

(1) Crank and slotted link mechanism

(2) Whitworth quick return mechanism, and

(3) Hydraulic shaper mechanism

Crank and Slotted Link Mechanism

In crank and slotted link mechanism (Fig.), the pinion receives its motion from an Individual motor

or overhead line shaft and transmits the motion or power to the bull gear. Bull gear is a large gear

mounted within the column. Speed of the bull gear may be changed by different combination of

gearing or by simply shifting the belt on the step cone pulley. A radial slide is bolted to the center

of the bull gear. This radial slide carries a sliding block into which the crank pin is fitted. Rotation

of the bull gear will cause the bush pin to revolve at a uniform speed. Sliding block, which is

mounted upon the crank pin is fitted within the slotted link. This slotted link is also known as the

rocker arm. It is pivoted at its bottom end attached to the frame of the column. The upper end of

the rocker arm is forked and connected

Fig., Crank and slotted link mechanism

pg. 39

To the ram block by a pin. With the rotation of bull gear, crank pin will rotate on the crankpin

circle, and simultaneously move up and down the slot in the slotted link giving it a rocking

movement, which is communicated to the ram. Thus the rotary motion of the bull gear is converted

to reciprocating motion of the ram.

Surfaces Produced on Shaper:

1. Horizontal plain surface 2. Vertical plain surface 3. Inclined surface

4. Grooved surface 5. Slotted surface

Shaper Operations:

A shaper is a machine tool primarily designed to generate a flat surface by a single point cutting

tool. Besides this, it may also be used to perform many other operations. The different operations,

which a shaper can perform, are as follows:

1. Machining horizontal surface (Fig1)

2. Machining vertical surface (Fig. 2)

3. Machining angular surface (Fig. 3)

4. Slot cutting (Fig. 4)

5. Key ways cutting (Fig. 5)

6. Machining irregular surface (Fig. 6)

7. Machining Splines and Cutting Gears on Shaper (Fig. 7)

pg. 40

Fig: Machining Splines and Cutting Gears on Shaper

WORK-HOLDING DEVICES:

Since the cutting forces in planning a work are quite heavy, therefore, it is essential that the work

is connected rigidly to the table so that it does not shift its position during planning. The various

work holding devices are vices, step blocks, stops, stop pins, jacks, V-blocks, T-bolts and clamps

etc. Some of these devices are shown in Fig.

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QUESTIONS

1. Explain principal parts of a shaper by neat sketch.

2. How can you classify the shapers?

3. How can you specify a shaper?

4. Explain the principle of quick return motion mechanism of a shaper. What is need of this

mechanism?

5. Using neat sketches, describe the various operations that can be carried on shaping machines.

6. Explain various safety precautions associated with shaper.

pg. 41

DRILLING

Introduction:

Drilling is an operation of making a circular hole by removing a volume of metal from the job by

cutting tool called drill. A drill is a rotary end-cutting tool with one or more cutting lips and usually

one or more flutes for the passage of chips and the admission of cutting fluid.

A drilling machine is a machine tool designed for drilling holes in metals. It is one of the most

important and versatile machine tools in a workshop. Besides drilling round holes, many other

operations can also be performed on the drilling machine such as counter- boring, countersinking,

honing, reaming, lapping, sanding etc.

Working Principle of a Drilling Machine

We have already discussed that a metal cutting operation that produces cylindrical holes or

enlarges existing holes with an end cutting tool is called as drilling. The end cutting tool used for

drilling holes in the work piece is called as twist drill and is provided with two cutting edges. In

order to cut off chips, two motions are given to the drill simultaneously as shown in Fig.

1. Rotary motion: The rotary motion is called as main motion or cutting motion. In some cases,

this motion is given to work pieces also (e.g., while drilling on the lathe). The cutting motion is

generally measured in m/min. The highest cutting speed is on the periphery of the drill and it

decreases towards the center of the drill.

2. Liner motion towards the fixed work piece: The motion is called as feed and it controls the

thickness of the chip. In small bench type drilling machines, instead of giving feed to the drill, the

work piece is moved towards the rotating drill by raising the table. The feed is generally measured

in mm/rev. As the drill is provided with two cutting edges, the thickness of the chip is half the

feed. By the simultaneous double action of cutting (or main motion) and the feed, each cutting

edge of the drill describes a spiral and thereby produces a constant flow of chips.

pg. 42

Construction of Drilling Machine:

In drilling machine the drill is rotated and fed along its axis of rotation in the stationary work piece.

Different parts of a drilling machine are shown in Fig. and are discussed below:

(i) The head containing electric motor, V-pulleys and V-belt which transmit rotary motion to the

drill spindle at a number of speeds.

(ii) Spindle is made up of alloy steel. It rotates as well as moves up and down in a sleeve. A pinion

engages a rack fixed onto the sleeve to provide vertical up and down motion of the spindle and

hence the drill so that the same can be fed into the work piece or withdrawn from it while drilling.

Spindle speed or the drill speed is changed with the help of V-belt and V-step-pulleys. Larger

drilling machines are having gear boxes for the said purpose.

(iii) Drill chuck is held at the end of the drill spindled in turn it holds the drill bit.

(iv) Adjustable work piece table is supported on the column of the drilling machine. It can be

moved both vertically and horizontally. Tables are generally having slots so that the vise or the

work piece can be securely held on it.

(v) Base table is a heavy casting and it supports the drill press structure. The base supports the

column, which in turn, supports the table, head etc.

(vi) Column is a vertical round or box section which rests on the base and supports the head and

the table.

Fig: Construction of Drilling Machine

Types of Drilling Machine:

Drilling machines are classified on the basis of their constructional features, or the type of work

they can handle. The various types of drilling machines are:

(1) Portable drilling machine

(2) Sensitive drilling machine

(a) Bench mounting (b) Floor mounting

pg. 43

(3) Upright drilling machine

(a) Round column section (b) Box column section machine

(4) Radial drilling machine

(a) Plain (b) Semi universal (c) Universal

(5) Gang drilling machine

(6) Multiple spindle drilling machine

(7) Automatic drilling machine

(8) Deep hole drilling machine

(a) Vertical (b) Horizontal

Few commonly used drilling machines are described as under.

Portable Drilling Machine

A portable drilling machine is a small compact unit and used for drilling holes in work pieces in

any position, which cannot be drilled in a standard drilling machine. It may be used for drilling

small diameter holes in large castings or elements at that place itself where they are lying. Portable

drilling machines are fitted with small electric motors, which may be driven by both A.C. and D.C.

power supply. These drilling machines operate at fairly high speeds and accommodate drills up to

12 mm in diameter.

Sensitive Drilling Machine

It is a small machine used for drilling small holes in light jobs. In this drilling machine, the work

piece is mounted on the table and drill is fed into the work by purely hand control.

A sensitive drilling machine consists of a horizontal table, a vertical column, a head supporting

the motor and driving mechanism, and a vertical spindle. Drills of diameter from 1.5 to 15.5 mm

can be rotated in the spindle of sensitive drilling machine. Depending on the mounting of base of

the machine, it may be classified into following types:

1. Bench mounted drilling machine, and

2. Floor mounted drilling machine

Upright Drilling Machine

The upright drilling machine is larger and heavier than a sensitive drilling machine. It is designed

for handling medium sized work pieces and is supplied with power feed arrangement. In this

machine a large number of spindle speeds and feeds may be available for drilling different types

of work there are two general types of upright drilling machine:

(1) Round column section or pillar drilling machine.

(2) Box column section.

The round column section upright drilling machine consists of a round column whereas the upright

drilling machine has box column section. The other constructional features of both are same. Box

column machines possess more machine strength and rigidity as compared to those having round

section column.

Radial Drilling Machine

Fig. illustrates a radial drilling machine. The radial drilling machine consists of a heavy, round

vertical column supporting a horizontal arm that carries the drill head. Arm can be raised or

lowered on the column and can also be swung around to any position over the work and can be

locked in any position. The drill head containing mechanism for rotating and feeding the drill is

mounted on a radial arm and can be moved horizontally on the guide-ways and clamped at any

desired position. These adjustments of arm and drilling head permit the operator to locate the drill

quickly over any point on the work. The table of radial drilling machine may also be rotated

through 360 deg. The maximum size of hole that the machine can drill is not more than 50 mm.

pg. 44

Fig. Radial Drilling Machine

Depending on the different movements of horizontal arm, table and drill head, the upright drilling

machine may be classified into following types-

1. Plain radial drilling machine

2. Semi universal drilling machine, and

3. Universal drilling machine.

In a plain radial drilling machine, provisions are made for following three movements -

1. Vertical movement of the arm on the column,

2. Horizontal movement of the drill head along the arm, and

3. Circular movement of the arm in horizontal plane about the vertical column.

In a semi universal drilling machine, in addition to the above three movements, the drill head can

be swung about a horizontal axis perpendicular to the arm. In universal machine, an additional

rotatory movement of the arm holding the drill head on a horizontal axis is also provided for

enabling it to drill on a job at any angle.

TYPES OF DRILLS:

A drill is a multi-point cutting tool used to produce or enlarge a hole in the workpiece.It is usually

consists of two cutting edges set an angle with the axis. Broadly there are three types of drills:

1. Flat drill 2. Straight-fluted drill, and 3. Twist drill

Flat drill is usually made from a piece of round steel which is forged to shape and ground to size,

then hardened and tempered. The cutting angle is usually 90 deg. and the relief or clearance at the

cutting edge is 3 to 8 deg. The disadvantage of this type of drill is that each time the drill is ground

pg. 45

the diameter is reduced. The various types of twist drills (parallel shank type and Morse taper

shank type) are shown in Fig.

Fig.Types of twist drills

Twist Drill Geometry

Twist drill geometry and its nomenclature are shown in Fig... A twist drill has three principal parts:

(i) Drill point or dead center (ii) Body (iii) Shank.

Fig: Geometry and Nomenclature of Twist Drill

pg. 46

Drill axis is the longitudinal center line.

Drill point is the sharpened end of the drill body consisting of all that part which is shaped to

produce lips, faces and chisel edge.

Lip or cutting edge is the edge formed by the intersection of the flank and face

Lip length is the minimum distance between the outer corner and the chisel-edge corner of the lip.

Face is that portion of the flute surface adjacent to the lip on which the chip impinges as it is cut

from the work.

Chisel edge is the edge formed by the intersection of the flanks.

Flank is that surface on a drill point which extends behind the lip to the following flute.

Flutes are the grooves in the body of the drill, which provide lips, allow the removal of chips, and

permit cutting fluid to reach the lips.

Flute length is the axial length from the extreme end of the point to the termination of the flutes

at the shank end of the body.

Body is that portion of the drill nomenclature, which extends from the extreme cutting end to the

beginning of the shank.

Shank is that portion of the drill by which it is held and driven,

Heel is the edge formed by the intersection of the flute surface and the body clearance.

Body clearance is that portion of the body surface reduced in diameter to provide diametric

clearance.

Core or web is the central portion of the drill situated between the roots of the flutes and extending

from the point end towards the shank; the point end of the core forms the chisel edge.

Lands are the cylindrically ground surfaces on the leading edges of the drill flutes. The width of

the land is measured at right angles to the flute.

Recess is the portion of the drill body between the flutes and the shank provided so as to facilitate

the grinding of the body. Parallel shank drills of small diameter are not usually provided with a

recess. Outer corner is the corner formed by the intersection of the lip and the leading edge of the

land.

Chisel edge comer is the corner formed by the intersection of a lip and the chisel edge.

Drill diameter is the measurement across the cylindrical lands at the outer corners of the drill. .

Lead of helix is the distance measured parallel to the drill axis between corresponding points on

the leading edge of a flute in one complete turn of the flute.

Helix angle is the angle between the leading edge of the land and the drill axis.

Rake angle is the angle between the face and a line parallel to the drill axis. It is bigger at the face

edges and decreases towards the center of the drill to nearly 0°. The result is that the formation of

chips grows more un-favorable towards the center.

Lip clearance angle is the angle formed by the flank and a plane at right angles to the drill axis;

the angle is normally measured at the periphery of the drill. To make sure that the main cutting

edges can enter into the material, the clearance faces slope backwards in a curve. The clearance

angle is measured at the face edge, must amount to 5° up to 8°.

Point angle is the included angle of the cone formed by the lips.

Operations Performed On Drilling Machine

A drill machine is versatile machine tool. A number of operations can be performed on it. Some

of the operations that can be performed on drilling machines are:

1. Drilling 2. Reaming 3. Boring 4. Counter boring 5. Countersinking

6. Spot facing 7. Tapping 8. Lapping 9. Grinding 10. Trepanning.

pg. 47

Drilling:

This is the operation of making a circular hole by removing a volume of metal from the job by a

rotating cutting tool called drill as shown in Fig. 22.6. Drilling removes solid metal from the job

to produce a circular hole. Before drilling, the hole is located by drawing towlines at right angle

and a center punch is used to make an indentation for the drill point at the center to help the drilling

getting started.

Fig. Drilling

Reaming:

This is the operation of sizing and finishing a hole already made by a drill. Reaming is performed

by means of a cutting tool called reamer as shown in Fig. Reaming operation serves to make the

hole smooth, straight and accurate in diameter. Reaming operation is performed by means of a

multi tooth tool called reamer. Reamer possesses several cutting edges on outer periphery and may

be classified as solid reamer and adjustable reamer.

Fig. Reaming operation

Boring:

Fig. shows the boring operation where enlarging a hole by means of adjustable cutting tools with

only one cutting edge is accomplished. A boring tool is employed for this purpose.

Fig. boring operation

pg. 48

Counter-Boring

Counter boring operation is shown in Fig. It is the operation of enlarging the end of a hole

cylindrically, as for the recess for a counter-sunk rivet. The tool used is known as counter-bore.

Fig. Counter boring operation

Counter-Sinking

Counter-sinking operation is shown in Fig.This is the operation of making a cone shaped

enlargement of the end of a hole, as for the recess for a flat head screw. This is done for providing

a seat for counter sunk heads of the screws so that the latter may flush with the main surface of the

work.

Fig. Counter-sinking operation

Lapping

This is the operation of sizing and finishing a hole by removing very small amounts of material by

means of an abrasive. The abrasive material is kept in contact with the sides of a hole that is to be

lapped, by the use of a lapping tool.

Spot-Facing

This is the operation of removing enough material to provide a flat surface around a hole to

accommodate the head of a bolt or a nut. A spot-facing tool is very nearly similar to the counter-

bore

Tapping

It is the operation of cutting internal threads by using a tool called a tap. A tap is similar to a bolt

with accurate threads cut on it. To perform the tapping operation, a tap is screwed into the hole by

hand or by machine. The tap removes metal and cuts internal threads, which will fit into external

threads of the same size. For all materials except cast iron, a little lubricate oil is applied to improve

the action. The tap is not turned continuously, but after every half turn, it should be reversed

slightly to clear the threads.

pg. 49

Fig: Tapping Operation

CUTTING SPEED

The cutting speed in a drilling operation refers to the peripheral speed of a point on the surface of

the drill in contact with the work. It is usually expressed in meters/min. The cutting speed (Cs)

may be calculated as:

Cs = ((22/7) × D × N)/1000

Where, D is the diameter of the drill in mm and

N is the rpm of the drill spindle.

FEED

The feed of a drill is the distance the drill moves into the job at each revolution of the spindle. It

is expressed in millimeter. The feed may also be expressed as feed per minute. The feed per minute

may be defined as the axial distance moved by the drill into the work per minute. The feed per

minute may be calculated as:

F = Fr × N

Where, F = Feed per minute in mm.

Fr = Feed per revolution in mm.

N = R.P.M. of the drill.

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QUESTIONS

1. State the working principle of a drilling machine.

2. Explain principal parts of the drilling machine and sketch the mechanism of a drilling machine.

3. Give the classification of drilling machines.

4. How will you specify a drilling machine?

5. What operations can be done on a drilling machine? Discuss them with diagrams.

6. With the help of a line diagram, describe the construction of radial drilling machine.

7. List the devices commonly used for holding the work on a drilling machine, and describe any

three.

8. Define cutting speed, feed and machining time for drilling.

9. Sketch a twist drill and name its different parts.

10. What is boring? Sketch a boring tool.

11. What is the function of flutes on a twist drill bit? Why are straight flute drills used for

nonferrous materials and metal?

12. Draw suitable figure for a drill bit showing:

(i) Point (ii) lip clearance (iii) point angle (iv) flute (v) margin and (vi) body clearance

pg. 50

13 Write short notes on following:

(i) Drilling (ii) Boring, (iii) Reaming (iv) Tapping (v) Counter boring (vi) Counter sinking

14. Explain various types of operations performed on a drilling machine by neat sketches.

15. Define the following terms used in drilling operation.

(i) Cutting speed (ii) Feed

14. Constructional details of pillar types and radial drilling machines.

15. Work holding and tool holding devices.

16. Main operations. Twist drills,

17. Drill angles and sizes.

18. Types and classification

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pg. 51

MILLING

Introduction:

A milling machine is a machine tool that removes metal as the work is fed against a rotating

multipoint cutter. The milling cutter rotates at high speed and it removes metal at a very fast rate

with the help of multiple cutting edges. One or more number of cutters can be mounted

simultaneously on the arbor of milling machine. This is the reason that a milling machine finds

wide application in production work.

Milling machine is used for machining flat surfaces, contoured surfaces, surfaces of revolution,

external and internal threads, and helical surfaces of various cross-sections.

Principle of Milling

In milling machine, the metal is cut by means of a rotating cutter having multiple cutting edges.

For cutting operation, the work piece is fed against the rotary cutter. As the work piece moves

against the cutting edges of milling cutter, metal is removed in form chips of trochoid shape.

Machined surface is formed in one or more passes of the work.

The work to be machined is held in a vice, a rotary table, a three jaw chuck, an index head, between

centers, in a special fixture or bolted to machine table. The rotatory speed of the cutting tool and

the feed rate of the work piece depend upon the type of material being machined.

Milling Methods

There are two distinct methods of milling classified as follows:

1. Up-milling or conventional milling, and

2. Down milling or climb milling.

Fig: Principle of Up Milling

UP-Milling or Conventional Milling Procedure

In the up-milling or conventional milling, as shown in Fig. the metal is removed in form of small

chips by a cutter rotating against the direction of travel of the workpiece.In this type of milling,

the chip thickness is minimum at the start of the cut and maximum at the end of cut. As a result

the cutting force also varies from zero to the maximum value per tooth movement of the milling

cutter. The major disadvantages of up-milling process are the tendency of cutting force to lift the

work from the fixtures and poor surface finish obtained. But being a safer process, it is commonly

used method of milling.

pg. 52

Fig: Principle of down- Milling

Down-Milling or Climb Milling

Down milling is shown in Fig. It is also known as climb milling. In this method, the metal is

removed by a cutter rotating in the same direction of feed of the work piece. The effect of this is

that the teeth cut downward instead of upwards. Chip thickness is maximum at the start of the cut

and minimum in the end. In this method, it is claimed that there is less friction involved and

consequently less heat is generated on the contact surface of the cutter and work piece.

Types Of Milling Cutters

The following Fig. illustrates some types of milling cutters along with work pieces. Milling cutters

are made in various forms to perform certain classes of work, and they may be classified as:

(1) Plain milling cutters, (2) Side milling cutters (3) Face milling cutter (4) Angle milling

cutters,

(5) End milling cutter, (6) Fly cutter (7) T-slot milling cutter (8) Formed cutters,

(9) Metal slitting saw,

Milling cutters may have teeth on the periphery or ends only, or on both the periphery and ends.

Peripheral teeth may be straight or parallel to the cutter axis, or they may be helical, sometimes

referred as spiral teeth.

Plain Milling

It is also known by slab milling. A plain milling cutter is used to produce a plain, flat, horizontal

surface parallel to the axis of rotation. The work is mounted on a table and the tool is secured

properly on the spindle. The speed and feed of the machine is set up before starting the operation

and the depth of cut is adjusted by rotating the vertical feed screw of’ the table.

pg. 53

Face Milling

The face milling operation is used for machining flat surfaces by a face milling cutter which is

rotating in an axis perpendicular to the work surface. The depth of cut is adjusted by rotating the

tables cross feed screw.

Angular Milling

The angular milling is the operation used for machining flat surfaces at an angle. Depending upon

whether the machining has to be carried out in a single or two mutually inclined surfaces, a single

or double angle cutter may be used. The V-blocks of any size can be machined by this operation.

Staggered Milling

These types of cutters are narrow and cylindrical having staggered teeth and with alternate teeth

having opposite helix angles. These cutters are used for milling deep slots.

pg. 54

Form Milling

These types of milling cutters are used to cut some profile or contour on the work piece. These can be used

to cut convex, concave, corner rounding and gear tooth in the work piece.

End Milling

These types of cutters have teeth on the circumferential surface at one end. They are used for

facing, profiling and end milling operations.

Fig. Types of Milling Cutters

pg. 55

Types of Milling Machines

Milling machine rotates the cutter mounted on the arbor of the machine and at the same time

automatically feed the work in the required direction. The milling machine may be classified in

several forms, but the choice of any particular machine is determined primarily by the size of the

work piece to be undertaken and operations to be performed. With the above function or

requirement in mind, milling machines are made in a variety of types and sizes.

According to general design, the distinctive types of milling machines are:

1. Column and knee type milling machines

(a) Hand milling machine (b) Horizontal milling machine (c) Universal milling machine (d)

Vertical milling machine

2. Planer milling machine

3. Fixed-bed type milling machine

(a) Simplex milling machine. (b) Duplex milling machine. (c) Triplex milling machine.

4. Machining center machines

5. Special types of milling machines

(a) Rotary table milling machine. (b) Planetary milling machine. (c) Profiling machine. (d)

Duplicating machine.

(e) Pantograph milling machine. (f) Continuous milling machine. (g) Drum milling machine (h)

Profiling and tracer controlled milling machine

Constructional details and principles of operation of column and knee type universal

milling machines

Column and Knee Type Milling Machine

The following Fig.shows a simple column and knee type milling machine. It is the most commonly

used milling machine used for general shop work. In this type of milling machine the table column.

The knee is vertically adjustable on the column so that the table can be moved up and down to

accommodate work of various heights. The column and knee type milling machines are classified

on the basis of various methods of supplying power to the table, different movements of the table

and different axis of rotation of the main spindle

Fig: a simple column and knee type milling machine

pg. 56

(a) Horizontal Milling Machines: These machines can be further classified as plain or universal

milling machines. In a plain milling machine, the table cannot be swiveled in a horizontal plane.

The table maybe fed in a longitudinal, cross or vertical directions on a plain milling, machine. In

case of universal milling machine, and the table can be swiveled up to 45° in a horizontal plane to

the right or left. This arrangement makes the angular and helical milling operations by using the

universal milling machine. In addition to the three principal movements as incorporated in a plain

milling machine, the table can be fed at an angle to the milling cutter.

Fig: horizontal column and knee type milling machine

(b) Vertical Milling Machines: In vertical knee type milling machines, the position of the cutter

spindle is vertical. Though it has the same table movements as in plain milling cutter, the spindle

head swivel or it may be a combination of the sliding and swivel head type. These machines are

suitable for end milling and face milling operations.

Fig: vertical column and knee type milling machine

pg. 57

Base

It is a foundation member for all the other parts, which rest upon it. It carries the column at its one

end. In some machines, the base is hollow and serves as a reservoir for cutting fluid.

Column

The column is the main supporting member mounted vertically on the base. It is box shaped,

heavily ribbed inside and houses all the driving mechanism for the spindle and table feed. The

front vertical face of the column is accurately machined and is provided with dovetail guide way

for supporting the knee.

Knee

The knee is a rigid grey iron casting which slides up and down on the vertical ways of the column

face. An elevating screw mounted on the base is used to adjust the height of the knee and it also

supports the knee. The knee houses the feed mechanism of the table, and different controls to

operate it.

Saddle

The saddle is placed on the top of the knee and it slides on guide ways set exactly at 90°to the

column face. The top of the saddle provides guide-ways for the table.

Table

The table rests on ways on the saddle and travels longitudinally. A lead screw under the table

engages a nut on the saddle to move the table horizontally by hand or power. In universal machines,

the table may also be swiveled horizontally. For this purpose the table is mounted on a circular

base. The top of the table is accurately finished and T -slots are provided for clamping the work

and other fixtures on it

Overhanging arm

It is mounted on the top of the column, which extends beyond the column face and serves as a

bearing support for the other end of the arbor.

Front brace

It is an extra support, which is fitted between the knee and the over-arm to ensure further rigidity

to the arbor and the knee.

Spindle

It is situated in the upper part of the column and receives power from the motor through belts,

gears. And clutches and transmit it to the arbor.

Arbor

It is like an extension of the machine spindle on which milling cutters are securely mounted and

rotated. The arbors are made with taper shanks for proper alignment with the machine spindles

having taper holes at their nose. The draw bolt is used for managing for locking the arbor with the

spindle and the whole assembly. The arbor assembly consists of the following components.

1. Arbor 2. Spindle 3. Spacing collars 4. Bearing bush

5. Cutter 6. Draw bolt 7. Lock nut 8. Key block

9. Set screw

Planer Type Milling Machine

It is a heavy duty milling machine. It resembles a planer and like a planning machine it has a cross

rail capable of being raised or lowered carrying the cutters, their heads, and the saddles, all

supported by rigid uprights. There may be a number of independent spindles carrying cutters on

the rail as two heads on the uprights. The use of the machine is limited to production work only

and is considered ultimate in metal re-moving capacity.

pg. 58

Special Type Milling Machines

Milling machines of non-conventional design have been developed to suit special purposes. The

features that they have in common are the spindle for rotating the cutter and provision for moving

the tool or the work in different directions.

DEPTH OF CUT

The depth of cut in milling is defined as the thickness of the material removed in one pass of the

work under the cutter. Thus it is the perpendicular distance measured between the original and

final surface of the work piece, and is expressed in mm.

Indexing And Dividing Heads

Indexing is the operation of dividing the periphery of a piece of work into any number of equal

parts. In cutting spur gear equal spacing of teeth on the gear blank is performed by indexing.

Indexing is accomplished by using a special attachment known as dividing head or index head as

shown in Fig... The dividing heads are of three types:

(1) Plain or simple dividing head,

(2) Universal dividing head and

(3) Optical dividing head.

Plain or Simple Dividing Head

The plain dividing head comprises a cylindrical spindle housed on a frame, and a base bolted to

the machine table. The index crank is connected to the tail end of the spindle directly, and the

crank and the spindle rotate as one unit. The index plate is mounted on the spindle and rotates with

it. The spindle may be rotated through the desired angle and then clamped by inserting the

clamping lever pin into anyone of the equally spaced holes or slots cut on the periphery of the

index plate. This type of dividing head is used for handling large number of work pieces, which

require a very small number of divisions on the periphery.

1. Swiveling block 2. Live center

3. Index crank 4. Index plate.

Fig: Dividing Head

pg. 59

MAIN OPERATIONS PERFORMED ON MILLING MACHINE

Unlike a lathe, a milling cutter does not give a continuous cut, but begins with a sliding motion

between the cutter and the work. Then follows a crushing movement, and then cutting operation

by which the chip is removed. Many different kinds of operations can be performed on a milling

machine but a few of the more common operations will now be explained. These are:

Plain milling or slab milling

Fig. (a) Illustrates the plain and slab milling operation. It is a method of producing plain, flat,

horizontal surface parallel to the axis of rotation of the cutter.

Face milling

Fig. (b) Illustrates the face milling operation. It is a method of producing a flat surface at right

angles to the axis of the cutter.

Side milling

Fig. (c) Illustrates the side milling operation. It is the operation of production of afloat vertical

surface on the side of a work-piece by using a side milling cutter.

Angular milling

Fig. (d) Illustrates angular milling operation. It is a method of producing a flat surface making an

angle to the axis of the cutter.

Gang-milling

Fig. (e) Illustrates the gang milling operation. It is a method of milling by means of two or more

cutters simultaneously having same or different diameters mounted on the arbor of the milling

machine.

Form milling

Fig. (f) Illustrates the form milling operation. It is, a method of producing a surface having an

irregular outline.

End milling

Fig. (g) Illustrates end milling operation. It is a method of milling slots, flat surfaces, and profiles

by end mills.

Profile milling

Fig. (h) Illustrates profile milling operation. It is the operation of reproduction of an outline of a

template or complex shape of a master die on a work piece.

Saw milling

Fig. (i) Illustrates saw milling operation. It is a method of producing deep slots and cutting

materials into the required length by slitting saws.

T-slot milling

Fig. (J) illustrates T-slot milling operation.

Keyway milling

Fig. (k) Illustrates keyway milling operation.

Gear cutting milling

Fig. (l) Illustrates gear cutting milling operation.

Helical milling

Fig. (m) Illustrates helical milling operation.

Flute milling

It is a method of grooving or cutting of flutes on drills, reamers, taps, etc.

Straddle milling

It is a method of milling two sides of a piece of work by employing two side-milling cutters at the

same time.

pg. 60

Thread milling

It is a method of milling threads on dies, screws, worms, etc. both internally and externally. As an

alternative to the screw cutting in a lathe, this method is being more extensively introduced now a

day in modern machine shops.

Fig: various types of milling operations

pg. 61

QUESTIONS

1. State the working principle of milling machine.

2. How will you classify milling machines?

3. using neat sketch, describe the principal parts of the milling machine by neat sketches.

4. Differentiate between up milling and down milling.

5. With the help of a neat sketch explain the column and knee type milling machine and name its

main parts.

6. Explain various types of milling operations using neat sketches.

7. Describe thread milling.

8. Sketch and describe the indexing head used for gear cutting.

9. Explain the principle of differential indexing.

10. What is indexing? Describe direct indexing, with example.

11. Single angle milling cutter (b) Slot milling cutter (d) convex milling cutter.

12. How will you index the gear teeth? Sketch the indexing set-up showing necessary calculations.

13. Sketch the machining set-up indicating tool work motions.

14. Sketch and specify the milling cutter indicating important tool geometry.

15. Define the following terms used in milling operation.

(a) Cutting speed

(b) Feed

(c) Depth of cut

(d) Machining time

pg. 62

PRACTICALS

Exercise 1

Single V ‐ Butt joint

Aim: To make a single v‐butt joint, using the given mild steel pieces of and by arc welding.

Material used: Two mild steel pieces of 80X40X5.

Equipment required:

A.C. Transformer with all welding accessories like Electrode holder, cables.

Tool Required:

1. Steel rule 2. Scriber 3. Flat file 4. Try square

5. Flat Tong 6. Chipping hammer 7. Ball peen hammer 8. Wire brush

9. Welding screen

Sequence of Operations: 1. Marking 2. Filing 3. Welding 4. Finishing

Sketch:

Figure: Single‐V butt joint

Operations to be carried out:

1. Cleaning the work pieces 2. Tack welding 3. Full welding

4. Cooling 5. Chipping 6. Finishing

Procedure:

1. Take the two mild steel pieces of given dimensions and clean the surfaces thoroughly from rust,

dust particles, oil and grease.

2. Remove the sharp corners and burrs by filing or grinding.

3. One edge of each piece is beveled, to an angle 30°.

4. The two pieces are positioned on the welding table such that, they are separated slightly for

better penetration of the weld.

5. The electrode is fitted in to the electrode holder and the welding current is set to a proper value.

6. The ground clamp is fastened to the welding table. The machine is switched ON

7. Wearing the apron, hand gloves, using the face shield, the arc is struck and the work pieces are

tack welded

At the ends and holding the two pieces together; first run of the weld is done to fill the root gap.

8. Second run of the welding is done with proper weaving and with uniform movement. During

the process of welding, the electrode is kept at angle of 15° to 25° from vertical and in the direction

of welding.

9. The slag formation on the weld is removed by chipping hammer.

10. Filing is done to remove spatters around the weld.

Safety Precautions:

1. Use welding screen leather apron and leather hand gloves while welding

2. Use flat tong and hand gloves for handling of work pieces during and after welding.

Result: Hence the single V‐Butt joint is made, using the tools and equipment as mentioned above.

pg. 63

Exercise 2.

Double ‐Lap joint

Aim:

To make a double lap joint, using the given mild steel pieces and by arc welding.

Material used:

Two mild steel pieces of 80X40X5 mm.

Equipment required:

A.C. Transformer with all welding accessories like Electrode holder, cables.

Tool Required:

1. Steel rule 2. Scriber 3. Flat file 4. Try square

5. Flat Tong 6. Chipping hammer 7. Ball peen hammer

8. Wire brush 9. Welding screen

Sequence of Operations: 1. Marking 2. Filing 3. Welding 4. Finishing

Sketch:

Figure: Double lap joint

Operations to be carried out:

1. Cleaning the work pieces 2. Tack welding 3. Full welding

4. Cooling 5. Chipping 6. Finishing

Procedure:

1. Take the two mild steel pieces of given dimensions and clean the surfaces thoroughly from rust,

dust particles, oil and grease.

2. Remove the sharp corners and burrs by filing or grinding and prepare the work pieces.

3. The work pieces are positioned on the welding table, to form a lap joint with the required

overlapping.

4. The electrode is fitted in to the electrode holder and the welding current is set to a proper value.

5. The ground clamp is fastened to the welding table.

6. Wearing the apron, hand gloves, using the face shield and holding the over lapped pieces the

arc is struck and the work pieces are tack‐welded at the ends of both the sides

7. The alignment of the lap joint is checked and the tack‐welded pieces are reset, if required.

8. Welding is then carried out throughout the length of the lap joint, on both the sides.

9. Remove the slag, spatters and clean the joint.

Safety Precautions:

1. Use welding screen leather apron and leather hand gloves while welding

2. Use flat tong and hand gloves for handling of work pieces during and after welding.

Result: The double lap joint is thus made, using the tools and equipment as mentioned above.

pg. 64

Exercise 3

T‐ Joint

Aim:

To make a T‐ Joint, using the given mild steel pieces and by arc welding.

Material used:

Two mild steel pieces of 80X40X5 mm.

Equipment required:

A.C. Transformer with all welding accessories like Electrode holder, cables.

Tool Required:

1. Steel rule 2. Scriber 3. Flat file 4. Try square

5. Flat Tong 6. Chipping hammer 7. Ball peen hammer 8. Wire brush

9. Welding screen

Sequence of Operations: 1. Marking 2. Filing 3. Welding 4. Finishing

Sketch:

Figure: T‐Joint

Operations to be carried out:

1. Cleaning the work pieces 2. Tack welding 3. Full welding

4. Cooling 5. Chipping 6. Finishing

Sequence of Operations:

1. Marking 2. Filing 3. Welding 4. Finishing

Procedure:

1. Take the two mild steel pieces of given dimensions and clean the surfaces thoroughly from rust,

dust particles, oil and grease.

2. Remove the sharp corners and burrs by filing or grinding and prepare the work pieces.

3. The work pieces are positioned on the welding table such that, the T shape is formed.

4. The electrode is fitted in to the electrode holder and the welding current is set to a proper value.

5. The ground clamp is fastened to the welding table.

6. Wearing the apron, hand gloves, using the face shield and holding the pieces the arc is struck

and the work pieces are tack‐welded at both the ends.

7. The alignment of the T joint is checked and the tack‐welded pieces are reset, if required.

8. Welding is then carried out throughout the length of the T joint as shown in the figure.

9. Remove the slag, spatters and clean the joint.

Safety Precautions:

1. Use welding screen leather apron and leather hand gloves while welding

2. Use flat tong and hand gloves for handling of work pieces during and after welding.

Result: Hence the Tee joint is made, using the tools and equipment as mentioned above.

pg. 65

Exercise 4

GAS WELDING OF MS PLATES BY CORNER JOINT METHOD

Aim:

To make a corner joint, using the given mild steel pieces .

Material used:

Two pieces of Mild steel (MS) flat of 80 X 40 X 5 mm.

Tools and equipment used:

File, scale, wire brush, hammer, gas lighter, welding torch, oxygen and acetylene cylinder with

nose pipe and fitting regulator, welding goggles, apron etc.

Sketch

Procedure: 1. Assemble all the materials needed to make the weld. This includes parts, AW equipment,

fixturing, tools, safety mask, gloves and filler rod.

2. Clean the parts to be welded to remove any oil, rust, or other contaminants. Use a wire brush if

needed to remove rust.

3. Cut the required size of piece from Mild Steel flat.

4. Place the two pieces in proper position and the welding table for lap joint.

5. Wear all the protective clothes.

6. Hold the electrode holder you plan to use welding.

7. Turn on the source, and touch the electrode on the sample work piece to get arc and weld the

specimen.

8. After completing the job, remove the slag from the welding joint by chipping hammer and clean

with wire brush.

Precautions: 1. Do not see the produced arc by naked eyes.

2. Use goggles at the time of chipping.

3. The joint of the cables should not be loose.

4. Make proper arc for welding carefully.

Result: The Corner joint is thus made, using the tools and equipment as mentioned above.

pg. 66

Exercise 5

PATTERNMAKING

Aim: To make V Block Pattern to be used in foundry shop.

Tools used: Try square, steel rule, marking gauge, smoothing plane, flat file, dividers, Hand

saw, sand paper (soft wood)

Material: 100 mm × 55 mm × 55 mm

Procedure:

1. Prepare the layout of V block pattern as per drawing.

2. Take all the allowances and core prints on the job.

3. Mark out the job as per the patterns layout.

4. Cut with handsaw and plane with the jack plane as per marking done as per layout.

5. Finish the V block pattern with the help of rasp file as per dimensions.

6. Check the dimensions as per drawing.

7. Finally use sand paper to give smooth finish to C.I. bracket pattern.

Safety Precautions

1. Never feed the stock faster than its capacity.

2. Hold the job firmly with clamping devices while working at the machines.

3. Always keep the tools at proper position when not in use. They should not be scrapped on the

wood floor.

4. Keep the floor area free from obstructions.

All dimensions are in mm

Fig: V Block Pattern

Result: The V Block Pattern is thus made, using the tools and equipment as mentioned above.

pg. 67

Exercise 6

CASTING

Aim: To prepare a v-block mould by floor moldings process and sand mould casting.

Tools & Equipment used: Pattern, Moulding boxes, Rammer, Well prepared Moulding sand

green sand), Trowel, Wood smother, Strike off bar, Sprue cutter, Draw spike, Lifter, Slicks,

Bellow, Small brush, Mallet, Vent wire, Furnace, Chisel, Hummer, Wire brush, Hacksaw, Grinder,

and file.

Materials required: Aluminum

Procedure:

a) Select a mounding box suitable for then pattern provided. It should be large enough to allow

some space around the pattern for ramming of sand.

b) Place the drag part of the Moulding box upside down on the floor and place the lower part of

the pattern in the center of the drag. The drag is then filled and rammed properly with well –

prepared green sand. The excess sand is then cut off to bring it in level with the edges of the drug

with the help of a strike of bar. Then drag is turned downside up along with lower half pattern in

it and sprinkle small amount of parting sand over the top surface to avoid sticking. Now turn the

drag upside down with lower half of the pattern in it

c) Place the cope over the drag in its proper position in alignment with locking pins. Then assemble

top part of the pattern in it.

d) Sprinkle parting sand over the surface of the drag and the pattern.

e) Place the runner and riser in position and fill the cope with green sand and ram it properly.

Cut off excess sand to bring it in level with the edges of the cope.

f) Remove the runner and riser to from the pour basin.

g) Using a venting wire perform the venting operation. It is done to allow exit of gases and steam

generated during pouring.

h) Remove the cope from the drag, and three after remove the pattern from cope and drag.

i) Repair the mould cavity for any small damage caused while removing the pattern; cavity should

be free from any undesirable sand particles.

j) The cope and drag are then locked with locking pins. The mould is thus ready for pouring.

k) Melt the metal, and then pour the molten metal through pouring basin continuously till the riser

is filled and allow it to solidify.

l) The solidified casting is then removed by breaking the mould and cleaned by removing adhering

sand. The sand is recycled and reused.

1. Precautions

a) Ramming of filled sand should be proper and uniform throughout surface of drug and cope.

b) Place the pattern in the drag properly.

c) Make the gate properly with broadening at the gate point.

d) The cope and drag should fit properly.

e) Take out the pattern carefully causing minimum damage.

f) Molten metal should be poured in to the mould cavity carefully, to avoid any accident.

g) The riser should be filled completely.

h) Do not touch casting immediately after from the sand mould.

pg. 68

Fig: Casting of a V-Block

Result: The V Block casting is thus made, using the tools and equipment as mentioned above.

pg. 69

Exercise 7

SIMPLE AND STEP TURNING OPERATION

Aim:

To obtain required diameters (steps) on a cylindrical work piece with the given lengths.

Tools & Equipment

Lathe machine. Mild steel bar, right hand cutting tool, box key or tool post key, chuck key, steel

rule, outside calipers or vernier calipers.

Theory:

Step turning is the operation of creating various cylindrical cross sections on a metal blank. Rough

Turning operation is used where excessive stock is to be removed and surface finish is not critical.

For such a operation deep cuts with coarse feed are used. During rough machining maximum metal

is removed and very little oversize dimension is left for finishing operation.

The motion is known as the feed. These combined motions cause the work piece by adjusting the

feed so that the helical path of the tool tip overlaps and generates a cylindrical surfaceon the work

piece. A spindle rpm which gives a desired cutting speed at the circumference of thecylindrical

surfaces should be reflected.

This may be calculated using the following formula:

Feed is measured as advance of the cutting tool per revolution of the work piece.

Tools:

Steel rule, outside calipers, tool holder with key, chuck key, HSS cutting Tool bit.

Material:

Mild Steel round rod of diameter 30 mm

Procedure

1. The given work piece is held in the 3‐jawchuck of the lathe machine and tightened firmly with

Chuck key.

2. Right hand single point cutting tool is taken tightened firmly with the help of box key in the tool

post.

3. Machine is switched on and the tool post is swiveled and the cutting point is adjusted such that

it positioned approximately for facing operation then the tool is fed into the work piece and the

tool post is given the transverse movement by rotating the hand wheel of the cross slide.

4. with this facing is completed and the tool post is swiveled and cutting point is made parallel to

the axis of work piece.

5. Depth of cut is given by cross slide to the tool post and the side hand wheel is rotated to give

the longitudinal movement for the tool post and job is turned to the required length and diameters

According to the sketch shown in figure.

6. After completion of the job it is inspected for the dimensions obtained with the help of steel rule

and outside caliper or vernier caliper.

Precautions

pg. 70

1. Work piece should be held firmly.

2. In rough turning operation do not over feed the tool, as it may damage the cutting point of the

tool.

3. Exercise over hung of tool should be avoided as it results in chatter and causes rough

machined surface.

4. It is important to ensure that during facing operation the cutting is performed from center point

to the outer diameter of the work piece.

Result The job is thus made according to the given dimensions.

pg. 71

Exercise 8

TAPER TURNING, THREADING AND DRILLING OPERATION

Aim:

Test Procedure to perform Taper turning operation by Compound Rest Swiveling method on the

given cylindrical work piece.

Apparatus:

1. Lathe with standard accessories.

2. Work piece

Principle:

Cutting Tapers on a lathe is common application. A number of methods are available for cutting

tapers on a lathe.They are:

1. Compound rest Swiveling Method.

2. Using form tools.

3. Tail stock offset method.

4. Taper attatchment method.

These methods are used for turning steep and short tapers. There is a circular base graduated

indegrees which can be swiveled at any angle from the center line of the lathe centers.The amount

of taper in a work piece is usually specified by the ratio of the difference indiameters of the taper

to its length. This is termed as conicity and is designated by the letter K.

,

Where, D = Large diameter of taper in mm

d = small diameter of taper in mm

L = length of tapered part in mm

Referring to the above figure BC draw parallel to the axis and in the right angle Triangle ABC.

Tools:

Chuck key, high speed Steel (HSS) cutting tool bit, outside calipers, Tool Holder with key,

spanner etc.

Material:

Mild Steel round rod of diameter 30 mm

Procedure:

The work piece is fixed in the tool post tightly and the center of head stock and tail stock

iscoincided with the centers of head stock and tail stock. Facing and plain turning operations

areperformed to get the required diameter on the work piece.

The compound rest is set on the required half taper angle and is locked by the cutting rod isadjusted

to a fixed position for the best possible to the open hand wheel and cross feed.Then the carriage is

locked and first cut is made at the end of the cut, the tool is again crossfed is given for the next

cut. Cuts are repeated piece is then removed from the chuck and dimensionsobtained are noted.

Precautions:

1. The work piece should be fixed tight in the jaw.

2. The power supply switched off before measuring diameters.

pg. 72

Result:

The required steps are made on the work piece for the given dimensions.

pg. 73

Exercise 9

DRILLING AND INTERNAL THREADING

Aim: To drill the given work piece as required and then to perform internal

threading operations on the given specimen.

Materials Required: mild steel specimen, coolant (oil and water

mixture), lubricant oil, nut and bolt.

Machine Required: Drilling machine

Measuring Instruments: Vernier calipers

Cutting Tools:

1.Button pattern stock,2.Dies,3.Drill bids,4.Hand taps,5.Tap wrench.

Fig: Drilling and Tapping Operation

Marking Tools:

1.Dot punch

Work holding fixtures:

1.Bench vice,2.V-Block

Miscellaneous tools:

1.Brush,2.Allen Keys

Sequence Of Operations:

a. Mark the center of hole and center punching

b. Drill bid

Where,

Dh - dia. of the hole,

dd – dia. of drill bid,

p = pitch

pg. 74

c. Use the suitable drill size for required tapping

D=Dia. of tap

Tap Drill size = (D-1.3p)+0.2 – for metric threads

d. Chamfering of specimen

e. Use the sequential tapping as tap set 1,2,3

f. Internal taping of drilled specimen

g. Filling of specimen on which external threading to be done

h. Measuring the diameter of the specimen & choosing of dies

according to it

i. Dieing operation (external threading) of the specimen.

PRECAUTIONS:

1. Coolant has to be sued while drilling

2. Lubricating oil has to be used to get smooth finish while tapping.

RESULT: Required specimen obtained according to specifiedoperaions(drilling and tapping

operations) with given dimensions

pg. 75

Exercise 10

MAKING SQUARE FROM ROUND ROD USING SHAPER

Aim:

To generate a square from rounded on the given work piece in a shapermachine.

a). Facilities/material required to do the exercise:

Material required

Punching machine

Steel rule

Hammer

Shaper tool

Try Square

b)Procedure for doing the exercise:

Steps

1.The job was checked to the given dimensions.

2.The square was scribed in the outer circle of diameter of 50mm and

punching was done.

3.The job was attached in the vice of a shaper

4.The job was checked for perpendicular dimension.

5.Then the square from round was obtained in the shaper

6.The work piece was removed and burns are removed with accuracy

was checked.

Result:

Thus the square from round was performed on the given dimension in a shaper machine with the

required dimensions

pg. 76

Exercise 11

Gear tooth forming and indexing

Aim: To perform a spur gear milling operation in milling machine.

FACILITIES REQUIRED AND PROCEDURE

a. Facilities/material required to do the exercise

Steel rule

Milling cutter

Spanner

Mandrel

Dog carrier

b. Procedure for doing the exercise:

Steps

1. The raw blank is selected with reference to the number of teeth to be cut.

2. Indexing number is calculated to the position of the blank.

3. Gear blank is mounted on mandrel in milling machine.

4. Centering of the blank is done by upward and cross feed.

5. The depth of the cut is calculated for the given module.

Fig: Gear block

Result: Thus the spur gear cutting is performed in a milling machine.

pg. 77

Viva questions for Lathe:

1. What is meant by lathe?

Lathe is a machine which removes the metal from a piece of work to the required shape and size.

2. Write any six specifications in lathe machine?

The length of bed, swing over bed, swing over the cross slide, width of bed, spindle bore, spindle speed.

3. What are the main operations in lathe?

Facing, Forming, Turning, Reaming, chamfering, Boring, Knurling.

4. Why lathe bed is made up of cast iron?

To improve high strength.

5. What are the components of a lathe?

Bed, head stock, tail stock, carriage, feed mechanism.

Viva questions for Milling:

1. What are the main components in milling machine?

Base, column, knee, saddle, table.

2. Write any six specifications in milling machine?

The table length and width, power of driving motor, spindle nose taper size, type of milling machine, floor space and

net weight.

3. What are the types of milling machine?

Plain milling machine, vertical milling machine, universal milling machine, simplex milling machine, triplex milling

machine.

4. What are the types of milling cutter?

Plain milling cutter, slide milling cutter, arbor cutters, shank cutters, face cutters.

5. What is the purpose of indexing head?

The work piece held between center of head stock and tail stock. Short work pieces are held in chuck fitted to head

stock spindle.

Viva questions for Shaper:

1. What are the specifications of shaper?

Maximum length of the stroke, power of the motor, floor space required, total weight of the shaper.

2. Define cutting stroke?

The ram reciprocates along with the tool to remove the metal in the forward stroke called cutting stroke.

3. What are the types of shaper?

Horizontal shaper, vertical shaper, travelling shaper.

4. What are the main components of shaper?

Base, column, cross rail, table.

5. Why the time for forward stroke is greater than return stroke?

The metal is removed in the forward stroke, but no metal is cut during the return stroke. So the time for forward stroke

is high.

Viva questions for Drilling:

1. What are the components in radial drilling?

Base, column, radial arm, drill head.

2. What is meant by tapping?

Tapping is the operation of cutting internal threads in hole by cutting tool.

3. What is meant by counter boring?

The operation of enlarging of end of hole cylindrically is known as counter boring.

4. What is meant by counter sinking?

The operation of making a cone shaped enlargement of end a hole known as counter sinking.

5. What are the specifications of radial drilling machine?

Maximum size of drill head, Maximum spindle travelling, Power input of the machine (H.P), Floor space required m2.

pg. 78

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