Department of Mechanical Engineering - Gopalan Colleges · WORKSHOP PARACTICE LAB P AGE N O. FROM TO PART A: FITTING PRACTICE I. VTU SYLLABUS 3 3 II. About Safety precautions 4 4

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Department of Mechanical Engineering

I/ II SEMESTER

10MEL48B – MACHINE SHOP

Workshop Practice Lab (15WSL16 / 26)

Laboratory Manual

NAME OF THE STUDENT :

BRANCH :

UNIVERSITY SEAT NO. :

SEMESTER & SECTION :

BATCH :

Academic year: 2016-2017

2

INDEX

SL.

NO WORKSHOP PARACTICE LAB

PAGE NO.

FROM TO

PART A: FITTING PRACTICE

I.

VTU SYLLABUS

3

3

II. About Safety precautions 4 4

III. Introduction to fitting 5 5

IV. About Engineering material 6 6

V. About Fitting tools 7 18

VI. About Fitting operations 19 22

1. Rectangular model-1 23 25

2. Rectangular model-2 26 28

3. Triangular model 29 31

4. Triangular model 32 34

5. Semicircular model 35 37

6. Semicircular model 38 40

7. Dove-tail mode 41 43

8. Dove-tail mode 44 46

9. Model for practice 47 48

PART B: Welding Practice

I Introduction to Welding. 49 56

10 Lap- Joint 57 59

11 Butt -Joint 60 62

12 T- Joint 63 65

13 L- Joint. 66 68

PART C : Sheet Metal Fabrication

I Introduction to sheet metal fabrication 69 78

14 Rectangular Tray. 79 81

15 Cylinder. 82 84

16 Pentagon cylinder

85 87

17 Hexagon cylinder 88 90

18 Frustum of a cone 91 93

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I-VTU SYLLABUS

WORKSHOP PRACTICE (CBCS)

Sub Code : 15WSL16/26 IA Marks : 20

Hrs/ Week : 03 Exam Hours : 03

Total Hrs. : 42 Exam Marks : 50

1. Fitting:

a. Study of fitting tools

b. Study of fitting operations & joints

c. Minimum 5 models involving rectangular, triangular, semi circular and dovetail

joints.

2. Welding:

d. Study of electric arc welding tools & equipments

e. Minimum 4 Models- electric arc welding-Butt joint, Lap joint, T-joint & L-joint.

3. Study and demonstration of Sheet metal and soldering work.

4. Study & demonstration of power Tools in Mechanical Engineering

Scheme of Examination:

Fitting / Sheet metal 30 Marks

Welding 10 Marks

Viva Voce 10 Marks

-------------

Total 50 Marks

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II- ABOUT SAFETY PRECAUTIONS

DO’S & DONT’S

1. Wear shoes to protect your feet.

2. Do not wear wrist watch while working.

3. Beware of the live electrical wires don’t attempt or try to touch

them.

4. Use hand glows / Welding shield.

5. Handle the tools / machines as per the instruction given by the

Faculty.

6. Use proper/ right tools.

7. Keep the tools in the right place else that may hurt you.

8. Use fire extinguisher to put off the flame.

9. Do not touch or pour water on burning live electric wire.

10. Use first aid box or inform the faculty for need of medical

assistance.

*Strictly follow the above instructions.

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III- INTRODUCTION TO FITTING

Even in the most mechanized industry, although majority of the work can be finished

with the help of machines, there are certain operations, which have to be carried out manually

using hand tools.

For example,

i) In production shops, when two or more parts are to be assembled

ii) Sometimes it necessary to replace or repair a component, which must fit accurately

with another component on re-assembly.

Ex-Fitting

FITTING

Fitting is the process of assembling two or more metal parts together by removing excess

material so as to obtain a required fit.

OR

It is the process of removing unwanted material with the help of hand tools/ power tools,

from a given stock (work piece) for making a component or fitting one in the other to form a

matting or fitting pair.

Ex:- 1) key and key hole

2) A Bush and a shaft.

Fitting requires the use of various hand tools and considerable manual effort. Fitting

work involves a large number of hand operations to finish the work to desired shape, size and

accuracy. The hand operations in Fitting shop include

1. Marking.

2. Sawing.

3. Chipping.

4. Filing.

5. Scraping.

6. Drilling.

7. Tapping.

8. Dieing.

9. Fitting etc.

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Classification of

Engineering Materials

Metals Non-Metals

Ferrous Metals Non-Ferrous Metals

Iron Steel

IV-About Engineering Materials

Materials that are used in the engineering Practice are called Engineering Materials.

These have physical, mechanical and chemical properties.

Metals

A metal is a solid (Exception: Mercury) having weight. It is opaque and a good

conductor of heat and electricity.

Non-Metals These are available in the form of liquids, gases or solids such as wood, stone, Rubber,

plastic, ceramic, concrete, asbestos etc.

Ferrous Metals

Iron containing metals such as pig iron, cast iron, wrought iron, carbon steel, Alloy steel,

Nickel steel etc., are called ferrous metals. These can be attracted by magnets and are

susceptable to rusting.

Non-Ferrous Metals

Non-Ferrous metals are those, which do not contain iron. Metals like Gold, Silver,

Copper, Aluminium, Tin, Platinum, and Nickel, Bronze etc, and its alloys are Non-Ferrous

metals. These can neither rust nor can be attracted by magnets.

Cast iron

It is an Iron based material containing 91-94% iron and other elements such as Carbon

(2-4%), Silicon (0.4-2.8%), Manganese (0.25-1.25%), Sulfur (0.2%max) and Phosphorous

(0.6%max).

Types of Cast iron: - Gray cast iron, malleable iron, white cast iron.

Steel:

May be defined as an alloy of iron and carbon. Besides this, it also contains Silicon,

Manganese, Sulfur and Phosphorous.One of the differences between Cast iron and steel is the

amount of carbon percentage.Based on the carbon content, steel is divided into

a) Low Carbon Steels- the carbon content ranges from 0.03-0.35%.

Low carbon steels are also called as soft or Mild steel (M.S).

b) Medium Carbon Steels-the carbon content ranges from 0.35-0.6%.

c) High Carbon Steels-The carbon content ranges from 0.6-1.7%

Mild steel (MS) Mild steel may be defined as an alloy of iron (91-94%), and carbon (0.15-0.35%).

Besides this, it also contains Silicon, Manganese, Sulfur and Phosphorous. Low carbon steels

are also called as soft or mild steel. These steels are used for bolts and nuts, structural work,

axles, shafts etc

Alloy Steel

In alloy steel in addition to carbon and iron, alloying elements such as chromium, Nickel,

Vanadium etc. are mixed. Ex: - Stainless steel, High Speed steel (H.S.S) (Tool steel).

Tool steel is widely used in the manufacturing of cutting tools.

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V- FITTING TOOLS

The Tools used in Fitting practice may be classified into the following categories.

a) Holding Tools b) Marking and Measuring Tools

c) Cutting tools d) Finishing Tools

e) Striking Tools f) Miscellaneous Tools

Holding Tools

Vice: A Vice is a tool used to hold the wok piece (job) in position while various operations

are being carried out.

1) Bench vice 2) Machine vice

3) Leg vice 4) pipe vice and

5) Hand vice

Bench vice The vice used for bench work is called bench vice. The bench work includes filing,

sawing, and threading operations.

It consists of a cast iron body carrying a fixed jaw and movable jaw. Both the jaws are made

of cast steel and are brought together by means of hand operated Screw.Seperate cast steel

plates known as ‘jaw plates’ are fixed to the jaws my means of set screws which can be replaced when worn out. The face of the jaw plates have teeth (serrations), which helps in

gripping the work firmly.

Specification: - the width of the jaws determines the size of the vice.

Machine vice

Machine vice is used to hold work piece in Machine tools. Machine vice is able to tilt

and swivel. It is mounted on the table of a Machine. Ex:-Drilling Machine, Milling Machine

and Shaping Machine.

Leg vice or Black smith’s vice

It is used for holding work piece that has to be cut, chipped or hammered. It consists of a

fixed jaw with long leg and movable jaw that can be moved by means of a hand operated

screw.

Pipe vice

It is used for holding round section parts such as pipes, tubes.

Hand vice

It is used for carrying work on small jobs, such as screws, keys, rivets etc., which cannot

be held in the Bench vice. It consists of two jaws that can be operated by means of a wing

nut.

V-block with Clamp V-block is a rectangular or square block with v-groves on one or both the sides, opposite

to each other. The angle V is usually 90 degrees. V-blocks are used for checking the

roundness of cylindrical work piece and for marking centers accurately. Material- Hardened

Steel or Cast Iron.

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Marking and Measuring tools

Surface plate

Surface plate is a plain surface. The surface is machined to very fine limits. The plate is

constructed in such a way that it will not wrap or twist. It is used for –testing the flatness of

finished work piece. Providing a base support for ‘marking gauges’ or ‘scribing block’. Testing the accuracy of Try square.

Material- Cast iron or hardened steel or granite stone.

Specification: - It is specified by length x width x height x grade.

Angle plate

It consists of two faces machined at right angles (90 degrees) to each other. A number of

slots are cut on both the horizontal and vertical faces as shown in figure. These slots enable

the work piece to be held firmly by means of bolts and nuts. It is also used to support work

piece, when you are using the surface gauge for marking out.

Material- Gray Cast iron

Scribing block or Surface gauge

A scribing block has three parts-base, spindle and scriber. The base of the scribing block

is machined to have a flat surface. A Vertical spindle fitted on the base carries a scriber and

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by adjusting the screw, the scriber can be fixed to any inclination and height along the

spindle.

It is used for scribing lines on work pieces and also used for checking parallel surfaces.

The Scribing block can be used to locate accurately the centers of round bars in conjunction

with the Vee-block.

Specification- Height of the Vertical spindle

Scriber

A Scriber is a thin steel rod with a pointed end or ends, one of the ends may be bent at

right angles to allow access to holes. It is used to scribe (or) mark lines on the metal work

pieces. Scribers are available in several sizes and types. The point should be ground to a 30

degrees angle and kept sharp for accuracy.

Material- High carbon steel (Hardened &Tempered).

Specification-It is specified by its length and diameter.

Try Square or Engineers Square

Try square also called ‘Engineering Square’ is one of the basic tool used in fitting work.

It consists of a steel blade riveted exactly at 90 degrees into a hard steel stock of rectangular

cross section as shown in figure. The stock acts as a fence and the blade as guide for marking.

It is used for

1) Checking squareness or perpendicularity of work piece.

2) Testing for Straightness and

3) Marking straight lines (at right angles) on work piece.

Material-Steel (hardened and tempered).

Specification-the Size of Try-square is specified by the length of the blade (100mm,

150mm, and 200mm).

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Steel rule or Steel scale

It is used for measuring and marking the required dimensions on the work piece. The

scale is graduated in millimeters, centimeters and inches. Least count of normal steel rule

is1mm.

Spring Divider

It is used for scribing (marking) circles, arcs, bisecting lines and perpendicular lines on

metal work piece. It also used for transferring dimensions from scales to objects.

Material- Tool steel (Hardened &Tempered).

Specification-Max length /radius which can be scribed

Spring caliper:

Caliper are devices used for measuring and transferring the inside \outside dimensions of

components. Calipers are of two types, viz, outside spring caliper and inside spring caliper.

Material- Tool steel

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Outside spring caliper-It is used for measuring the outer diameter of shafts (rods) and

thickness of parts.

Inside spring caliper- It is used to measure the inner diameter/dimensions of parts

.

Center Punch

It is used for marking round indentations on metal surfaces. This provides a center for

locating the sharp end of the divider point and center for holes that are to be drilled. It is also

used for marking points along a line, which enables to cut the work piece easily. The point

angle should be ground to 90 degrees

Material- High carbon steel.

Specification-By length and angle.

Dot punch

` It is used for marking points along a line which enables to cut the work piece easily.

The point angle should be ground to 60 degrees

Letter punch

It has square body with a tapered end. At this end, a projection, corresponding to the

replica of the letter to be marked is made. It is used to punch Alphabetic letters (A to Z) on

metal work piece

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Number punch

It is similar to letters punch in construction but has numbers at its end. The numbers used

are from 0 to 8 (six used as nine also). It is used to punch numbers on metal work piece.

Vernier caliper

These are used for measuring outside as well as inside dimensions accurately. It may also

be used as a depth gauge.

Example: to measure outer diameter of shafts and cylinders, to measure inner diameter of

holes and depth of holes.

The main scale is divided into millimeters. In this case 49 main scale divisions ie 49 mm is

divided into 50 vernier scale divisions.

One vernier scale division equal to (49/50) 0.98 mm

Hence, Least count of the vernier caliper (LC) = 1 main scale division – 1 vernier scale

division

= 1MSD - 1 VSD

= 1mm- (49/50) mm =0.02 mm

Total reading =Main scale reading (MSR) + Least count (LC) X Vernier Coinciding Division

Vernier height Gauge

The vernier height gauge, clamped with a scriber, is shown in Fig.Vernier height gauges

are particularly suitable for marking off accurate distances and center locations. It is also

used in inspection of work pieces. The accuracy and working principle of this gauge are the

same as those of the vernier caliper.

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Vernier Height Gauge

Micrometer:

External micrometer is used to measure external diameters and lengths. The degree of

accuracy is high.

Pitch = distance moved on barrel

No. of rotations given to thimble

= 0.5 mm

1

= 0.5 mm

Least count of micrometer = pitch/ No of divisions on the thimble.

= 0.5 mm / 50 = 0.01 mm.

Total reading =Barrel scale reading (MSR) + Least count X Thimble scale reading (TSR)

MICRO METER

Cutting tools

Hack saw frame with blade.

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The hacksaw is used for cutting metal by hand. The hacksaw blade has a number of teeth

ranging from 5 to 15 per centimeter. Lesser number of teeth is used for cutting materials like

Aluminium, brass and Bronze and large number of teeth is used for cutting hard materials

like steel, C.I etc. Hack saw blades are fitted either in a solid frame or adjustable frame to

accommodate different lengths of blade.

It is made of high-speed steel. The hacksaw blades are specified byits material, length,

width, thickness and pitch of the teeth. The common dimensions are length 250-300 mm,

width 13 mm-16 mm, thickness 0.6 to 0.8 mm, pitch 1 to 1.8 mm. The blades are fixed with

teeth facing forward and the teeth are staggered, which are known as ‘set of teeth’. These make slots wider than blade thickness, preventing the blade from jamming

Twist drill

The twist drills are used for making holes. The drills are made of HSS (high speed steel)

with a straight or taper shank. The straight shank drills are held in drill chuck and fitted to the

spindle of drilling machine and the taper shank is directly fitted to the spindle. The drills are

manufactured to standard sizes in specified steps. A bench-drilling machine is commonly

used in workshops

Twist drill.

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Taps and Tap wrenches

A tap is a hardened steel tool, used for cutting internal threads in a drilled hole.

Hand taps are usually supplied in sets of three for each diameter and thread size. Each set

consists of a i) Taper or first tap ii) Intermediate or second tap and iii) plug or bottoming or

third tap. In hand tapping, the tap is rotated with the help of a tap wrench. These taps are

identical in all features except in the taper lead. For identifying the type taps quickly the taps

are either numbered as 1, 2, and 3 or rings are marked on the shank.

Dies and die –holder

Dies are the cutting tools used for marking external threads. Dies are made either solid or

split type. They are fixed in a die –holder for holding an adjusting the die gap. They are made

of tool steel or high carbon steel.

Finishing tools

Files

A file is a cutting tool used to remove small amount of material from the surface of the

work piece and also helps in giving a smooth surface finish. A number of teeth, parallel and

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inclined at suitable angle are cut on the flat surface of the file. The various parts of a file are

shown in figure the main parts of the file include,

Tang-It is the pointed part that fits into the wooden handle.

Heel – It is end of the tang that forms a curved edge.

Face -It is the portion of the file on which cutting teeth are formed.

Point – It is the end opposite the tang

Files are often tapered along their length but they may also be parallel.

Material -tool steel (hardened)

Specification- length, single cut /double cut, shape and pitch.

Example Length (say 400 mm)

Single cut /Double cut

Shape (say square cross –section)

Pitch or grade (say smooth)

Files are classified and named according to

a) Size/length

b) cut

c) shape and

d) pitch /grade.

(a) Size: the size of the file is identified by its length. It is the distance from the point to the

heel excluding tang. The selection of the length of the file varies depending on the size

of the job .

Sl.no Size(length) Application

1 100-150mm Used for fine work and small sized jobs

2 150-250mm Used for medium sized work

3 250-400mm For general and large sized work

(b) Cut: Based on the cutting teeth , files are classified as single cut files and double cut files

Single cut file Double cut file

Single cut file: In single cut file, the teeth are cut in parallel rows across the faces of the file

and normally inclined at an angle of 60 degrees with the centerline of the face.

Double cut file: A double cut file has two sets of teeth crossing each other as shown fig. one

set of teeth are cut similar to a single cut file and the other set runs diagonally across the first

set and are normally inclined at an angle of 10 degree to the center line of the face .

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Single cut files gives better finish when compared to double cut files but at the same time

removes material at a comparatively slower rate.

(C)Shape of files -Files is classified based on the shape of their cross-section.

Various types of files.

Flat files are used for general work or finishing flat surfaces.

1) Squares files are used for filing square corners, rectangular slots, keyways,

enlarging a square or a rectangular holes etc.

2) Triangular file or three-square files are used mainly for filing corners with angles

less than 90 degrees.

3) Round files are used for filing concave surface and also for enlarging round holes.

4) Half-round file the curved face of the half-round file is used for filing concave

surfaces and the flat face is used for filing convex surfaces.

5) Knife edge file is used for filing narrow slots and corners having angles less than 90

degrees

(D) Pitch of teeth /grade

Pitch refers to the spacing between two consecutive teeth. Table shows the classification

of files based on their pitch. The files are listed in descending order of their roughness.

Description Single cut Double cut Uses

Rough.

8 teeth/cm

For rapid removal of

Large amounts of

material from softer

materials.

Bastard

12 teeth/cm

Rapid removal of

Small amounts of

material.

Second cut.

16 teeth/cm

Used for filing on

harder materials.

Gives good surface

finish

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Smooth.

20-24 teeth/cm

Used for smooth

surface finish.

Removes small

amounts of material.

Dead Smooth.

>40 teeth/cm

Used for accurate and

smooth surface finish.

Striking Tools

Hammers: The hammer is defined as a device used to deliver blows to an object or strike

another object, in the sense that it is used for driving nails, fitting parts and breaking up

objects. It is also used for striking purposes while punching, bending, chipping, and riveting.

Available in various shapes and structures, hammers are designed for specific purpose. The

hammer consists of a handle to which a heavy head, usually made of metal is attached, with

one or more striking surfaces. The hammer is specified by its weight (125 grams to 1500

grams) and the shape of the pein.

Different types of hammers are straight pein hammer, ball pein hammer, cross –pein hammer

Material Cast steel or carbon steel.

Ball pein hammer:-This is the most common type of hammer which has a ball-shaped end of

the head opposite to the striking face. It is used for all kinds of engineering works. The ball

end being useful for sheet metal forming and it is made in weights from 1000gm to 1.5kg. It

is used for riveting and chipping.

Cross –pein and straight pein hammer:-These have blunt, chisel-shaped ends on the head

opposite to the face. It is used for bending, stretching, hammering into shoulders, curves.

Miscellaneous Tools

Anvil : It provides the necessary support during punching and chipping by resisting the

heavy blows given to the work piece by hammer .The beak is used in sheet metal work for

bending the sheet metal to round shapes.

Material-The body is made of mild steel or cast steel with a hardened top face.

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File card: It is a metal brush used for cleaning the files.

FITTING OPERATIONS

Marking and Measuring

The marking is the first step in fitting. Marking on the work can be done by setting out

dimensions with the help of a working drawing. Generally one end of work piece is filed flat

and the measurements are taken from this reference end. The measuring instruments used in

fitting are scale, Calipers, vernier caliper, micrometer, height gauge etc. Marking tools used

in fitting are Scriber, Dot puntch, Scribing gauge etc..

Filing: Filling is the process of removing burrs from cuts; clean the face of cuts and to give

the final shape to a work piece. The flatness and square ness of the surfaces finished by filing

are checked with try square.

Methods of filing- a) Cross-filing b) Draw filing

Cross-filing- this method is used for efficient removal of maximum amount of metal in

the shortest possible time. It may be noted that the file must remain horizontal throughout the

stroke (long, slow and steady) with pressure only applied on the forward motion.

Draw filing-this method is used to remove file marks and for finishing operations. Here, the

file is Griped as close to the work as possible between two hands. In this method of filing, a

fine cut file with a flat face should be used.

Sawing: It is the method of removing excess material quickly with the help of hand hack –saw. The surfaces are to be finish filed after sawing

Chipping-It is the process of removing unnecessary thick layers of metal using cold chisel

and hammer.

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Drilling –It is the operation of producing circular holes in a metal piece with the help of

bench drilling machine and drilling tools.

Tapping- It is the process of generating internal threads in a ready hole using a set of three

hand taps.

Dieing-It is a manual operation of generating external threads on a round rod or pipe using a

die and die holder.

Fitting /Assembly: After finishing the individual pieces as per dimensions they are joined

/fitted for an assembly.

Safe and correct practices:

1) All the tools and measuring instruments are to be cleaned and kept in the respective

places when not in use.

2) The sliding parts and pins are to be properly lubricated.

3) The vice should not be over tightened; otherwise it may damage the spindle.

4) The sharp edges of a chisel or scriber are to be covered with a cap to avoid getting

damaged and to prevent accidents.

5) The handles of hammers are to be checked for cracks etc.

6) The surface plate has to be covered and kept when not in use and tools and jobs

should not be thrown on the surface plate to avoid damage to the surfaces

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Use of Different Types of Files

23

.

How to hold the Hacksaw

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Model No: 1 Date: ……./………/……….

Rectangular model-1

AIM: To fabricate the fitting model as per the drawing given below.

50

40

1517

,5

MATERIAL: Mild Steel ( L x B x t )

TOOLS REQUIRED

1. Scriber.

2. Steel rule.

3. Dot Punch

4. Hacksaw frame with hacksaw blade.

5. Bench vice

6. Rectangular rough file.

7. Rectangular smooth file.

8. L- Square.

Theory :

The marking is the first step in fitting. Marking on the work can be done by setting out

dimensions with the help of a working drawing. The measuring instruments used in fitting are

scale, Calipers, vernier caliper, micrometer, height gauge etc. Marking tools used in fitting

are Scriber, Dot punch, Scribing gauge etc..

Filing: Filling is the process of removing burrs from cuts, clean the face of cuts and to

give the final shape to a work piece. The flatness and squareness of the surfaces finished by

filing are checked with try square.

Sawing: It is the method of removing excess material quickly with the help of hand hack

–saw.

PROCEDURE

1. Check the dimensions of the given work piece with respect to the given model.

2. File the one edge of the given work piece to straightness and checked with Try square.

3. File the adjacent edge so that it is square with first edge filed and checked with Try

square. File the upper and bottom surfaces of work piece.

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4. Paste white color on the upper surface of the work piece (with chalk powder and

water).

5. By marking gauges (Scale, Try square, Scriber, Divider), mark the dimensions on the

given work pieces.

6. Using Dot punch and Hammer, make the punch marks (dots) on the marked

dimensions on the given work piece.

7. By using hacksaw remove the extra material from the work piece and use cold chisel,

if necessary to remove the material.. Removing small amount (1 mm to 2mm) of

material Files can be used.

Pre Viva Questions:

1. What is the difference between Metal and Non metal.?

2. What is the difference between Iron and Steel.

3. What is the difference between MKS system and SI system?

4. What is safety?

SKETCH OF THE FINISHED MODEL

Result: The model is prepared as per the drawing given.

Verification: The measurement of the model reveals that there is a deviation of X mm in L1, Y mm

in L2 and Z mm in L3 & L4.

Conclusion: The model prepared is within / beyond the tolerance.

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Post Viva question:

1) What do you mean by fitting? (or) Define fitting? Give practical example.

Fitting is the process of assembling two or more metal parts together by removing

excess material so as to obtain a required fit.

Ex: - 1) key and key hole 2) A Bush and a shaft

2) Name the tools, which are used in fitting?

a) Work holding tools b) Marking and Measuring tools c) Finishing and cutting tools

3) Name work holding devices used in Fitting. (or) What are the types of vices?

a) Bench vice b) Machine vice c) leg vice d) pipe vice e) hand vice

4) Name Marking and measuring tools used in Fitting

a) Surface plate b) Angle plate c) Scribing block/Surface gauge d) Scriber e) Try

square f) Divider g) Center punch h) Steel rule or Scale i) caliper (Inside caliper and

Outside caliper)

5) What is the purpose of Marking?

a) To Transfer measurements and Dimensions from drawing to workpice for further

operations.

b) To obtain shape on work piece to the design given in the drawing.

c) To check Dimensional suitability of raw material for a given Job.

6) What are the tools required for Marking.(or) Name Marking tools used in Fitting

a) Surface plate b) Angle plate c) “V” block d) Divider e) Scriber f) Punches g) Marking Hammer h) Try Square i) Steel Rule j) Scribing Block or Surface gauge

7) What is meant by Measurement?

Determining the Size of a job in terms of Standard unit is called measurement.

8) Name measuring tools used in Fitting.

a) Steel rule b) Vernier Caliper c) Micrometer d) Depth gauge e) caliper (Inside

caliper and Outside caliper)

9) Name Finishing and cutting tools used in Fitting.

a) Files b) Hack saw c) Chisel

10) What is the classification of materials?

Metals and Non-Metals.

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Model No: 2 Date: ……/……/……….

Rectangular model-2


50

50

17,5

15

10

MATERIAL: Mild Steel (M.S)

TOOLS REQUIRED

1. Scriber.

2. Steel rule.

3. Dot Punch


5. Bench vice



8. L- Square.

Theory :

Marking: The marking is the first step in fitting. Marking on the work can be done by

setting out dimensions with the help of a working drawing. The measuring instruments used

in fitting are scale, Calipers, vernier caliper, micrometer, height gauge etc. Marking tools

used in fitting are Scriber, Dot punch, Scribing gauge etc..





–saw.

PROCEDURE





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water).


given work pieces.






8. Then male and female work pieces are assembled (joined) in order to make firm joint.

Pre Viva Questions:

1. What is the difference between Metal and Non metal give example?

2. What is the difference between ferrous and nonferrous metal.


4. What is safety?






Post Viva question:

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1) What is the classification of metals?

a) Ferrous metals b) non-ferrous metals.

2) Differentiate between the ferrous and non-ferrous metals.

Ferrous Metals: Iron containing metals such as pig iron, cast iron, wrought iron,

Mild Steel, carbon steel, Alloy steel, Nickel steel etc., are called ferrous metals.

These can be attracted by magnets and are susceptible to rusting.

Non-Ferrous Metals: Non-Ferrous metals are those which do not contain iron.

Metals like Gold, Silver, Copper, Aluminum, Tin, Platinum, and Nickel, Bronze etc,

and its alloys are Non-Ferrous metals. These can neither rust nor can be attracted by

magnets.

3) What’s the composition of CI Material?

CI-Cast Iron – a) Iron (91-94%), Carbon (2-4%), Silicon (0.4-2.8%), Less

percentage of, Manganese, Sulfur and phosphorous

4) What’s the composition of MS Material?

5) What is the classification of steels based on carbon content?

Based on the carbon content, steel is divided into

a) Low Carbon Steels- The carbon content ranges from 0.03-0.35%. -Mild steel

(MS)

b) Medium Carbon Steels-the carbon content a range from 0.35-0.6.

c) High Carbon Steels-The carbon content ranges from 0.6-1.7%

6) Name the commonly used material for preparing fitting models.

Mild Steel (MS).

7) What is the use of Alloy steels?

In alloy steel in addition to carbon and iron, alloying elements such as chromium,

Nickel etc. are mixed. Ex: - Stainless steel, High speed steel, Tool steel (0.8 to 1.5%

carbon).etc.

Alloy steels are widely used in the manufacturing of Cutting tools .

8) Name the parts of the bench vice?

a) Body with Fixed Jaw b) Movable jaw c) Jaw Plate d) Screw spindle e) Handle f)

Base

9) How will you specify a bench vice?

Width of the jaws determines the size of the vice

10) Which material is used to make the vices?

Cast iron

Model No: 3 Date : ……./……../………..

30

Triangular model-1


17,5

50

17,5

15


TOOLS REQUIRED

1. Scriber.

2. Steel rule.

3. Dot Punch


5. Bench vice

6. Rectangular and triangular rough file.

7. Rectangular and triangular smooth file.

8. L- Square.

Theory :









–saw.

PROCEDURE






water).


given work pieces.

31






Pre Viva Questions:




4. What is safety?






Post Viva question:

32

1) What do you mean by leg vice?

It is used for holding work piece that has to be cut, chipped or hammered

2) What is the use of Pipe vice?

It is used for holding round section parts such as pipes, tubes.

3) Why is it named as V-block?

V-block is a rectangular or square block with V-groves on one or both the sides,

opposite to each other. The angle V is usually 90 degrees.

4) What is the use of V-block?

V-blocks are used for checking the roundness of cylindrical work pieces and for

marking centers accurately.

5) What is a surface plate? Why it is used?

Surface plate:-Surface plate is a plain surface.

It is used for –testing the flatness of finished work piece. Providing a base support

for ‘marking gauges’ or ‘scribing block’. Testing the accuracy of Try square.

Material- Cast iron or hardened steel or granite stone.

Specification: - It is specified by length x width x height x grade.

6) What is the use of try square?

It is used for 1) checking squareness or perpendicularity of work piece.2) Testing for

Straightness and 3) marking straight lines (at right angles) on work piece.

7) How will you specify a try square?

The Size of Try-square is specified by the length of the blade (100mm, 150mm, and

200mm).

8) Define least count?

A smallest measurement that can be obtained from measuring instrument.

Or.

A smallest measurement that can be measured by using measuring instrument.

9) What is the use of Vernier caliper?

It is used for measuring outside as well as inside dimensions accurately. It may also

be used as a depth gauge (to measure depth of holes).

Hence, Least count of the vernier = 1 main scale division – 1 vernier scale division.

10) What is the use of micrometer?

Micro meter: External micrometer is used to measure external diameters and

lengths. The degree of accuracy is high.

Model No: 4 Date : ……/……../……….

33

Triangular model-2


50

50

17,5

17,5

15


TOOLS REQUIRED

1. Scriber.

2. Steel rule.

3. Dot Punch


5. Bench vice



8. L- Square.

Theory :









–saw.

PROCEDURE






water).

34


given work pieces.







Pre Viva Questions:




4. What is safety?






35

Post Viva question:

1) What is the use of steel rule?

It is used for measuring and marking the required dimensions on the work piece.

2) What are the types of spring calipers?

a) Outside spring caliper b) inside spring caliper

3) What is the use of outside spring caliper?

It is used for measuring the outer diameter of shafts (rods) and thickness of parts.

4) What is the use of inside spring caliper?

It is used to measure the inner diameter/dimensions of parts

5) What is the use of angle plate?

It consists of two faces machined at right angles (90 degrees) to each other. A

number of slots are cut on both the horizontal and vertical faces as shown in figure.

These slots enable the work piece to be held firmly by means of bolts and nuts. It is

also used to support work piece, when you are using the surface gauge for marking

out.

6) What is the use of Dot punch?

It is used for marking points along a line which enables to cut the work piece easily.

7) What is the point angle of Dot punch?

60 degrees

Material- High carbon steel.

Specification-By length and angle.

8) What is the use of center punch?

1) It is used for marking round indentations on metal surfaces.

2) This provides a center for locating the sharp end of the divider point and center

for holes that are to be drilled.

3) It is also used for marking points along a line which enables to cut the work piece

easily.

9) What is the point angle of Center punch?

90 degrees

10) What is the use of number punch?

It is used to punch numbers (0 to9) on Metal work piece.

Model No: 5 Date :

……/……./……….

Semicircular model -1

36

AIM: To fabricate the fitting model as per the sketch given below

R15

1515

60

45


TOOLS REQUIRED

1. Scriber.

2. Steel rule.

3. Dot Punch


5. Bench vice



8. L- Square.

Theory :









–saw.

PROCEDURE






water).

37


given work pieces.






Pre Viva Questions:




4. What is safety?






Post Viva question:

1) What is the use of letter punch?

38

It is used to punch Alphabetic letters (A to Z) on Metal work piece.

2) What is the use of Universal Scribing block or surface gauge?

It is used for scribing lines on work pieces and also used for checking parallel

surfaces.

The Scribing block can be used to locate accurately the centers of round bars in

conjunction with the Vee-block

3) What is the use of scriber?

It is used to scribe (or) mark lines on the metal work pieces.

4) What is the use of spring divider?

It is used for scribing (marking) circles, arcs, bisecting lines and perpendicular lines

on metal work pieces

It also used for transferring dimensions from scales to objects.

5) What is the difference between divider and Caliper?

A divider is a marking device used to mark dimensions, But a caliper is a measuring

device used to measure dimensions.

6) Name finishing tools used in Fitting.

a) Files b) Sand Paper

7) What is a file?

A file is a cutting tool used to remove small amount of material from the surface of

the work piece and also helps in giving a smooth surface finish

8) Name the parts of the files?

Tang-It is the pointed part that fits into the wooden handle.

Heel – It is end of the tang that forms a curved edge.

Face -It is the portion of the file on which cutting teeth are formed.

Point – It is the end opposite the tang

9) Classification of files.

Files are classified according to a) Size or length b) Shape c) Grade d) Cut

10) Name the different types of files and their uses?

Round files are used for filing concave surface and also for enlarging round holes.

Half-round file the curved face of the half-round file is used for filing concave

surfaces and the flat face is used for filing convex surfaces.

Knife edge file is used for filing narrow slots and corners having angles less than 90

degrees

Model No: 6 Date : ……./……/………

39

Semicircular model -2


R15

60

60

1515


TOOLS REQUIRED

1. Scriber.

2. Steel rule.

3. Dot Punch


5. Bench vice

6. Rectangular and semicircular rough file.

7. Rectangular and semicircular smooth file.

8. L- Square.

Theory :









–saw.

PROCEDURE





40


water).


given work pieces.







Pre Viva Questions:




4. What is safety?






Post Viva question:

1) What are the methods of filing?

41

a) Cross Filing b) Draw Filing

2) Name the materials used in the manufacture of files?

Files are made of Hardened and Tempered Steel

3) Show me single cut file and double cut file.

4) What do you mean by single cut and double cut files?

A single cut file has rows of teeth in one direction across the face, which is useful

for filing soft materials like Aluminium, Brass, and Bronze.

A double cut file has 2 rows of teeth cut diagonal to each other .The double cut file

is useful in removing materials at faster rate in Harder Material.

Single cut files gives better finish when compared to double cut files but at the same

time removes material at a comparatively slower rate.

5) Differentiate between rough and smooth file?

A rough cut file has very coarse spaced teeth.It is used for rough work. It removes

more material.

A smooth cut file has more closely spaced teeth.It is used to get smooth surface.

6) What is the use of flat file?

Flat files are used for general work or finishing flat surfaces.

7) What is the cross-section of flat file?

Rectangle

8) What is the use of square file?

Squares files are used for filing square corners, rectangular slots, keyways, enlarging

a s quare or a rectangular hole etc.

9) A file removes the metal during ------ Stroke.

Forward stroke. The file removes metal during the forward stokes. No pressure is

applied on the Return Stroke, but the file is allowed to remain on the work piece.

10) What is the cross-section of Square file?

Square cross-section.

Model No: 7 Date : ……/……/………..

Dove tail model -1

42


30

15

45

60 1522

,5


TOOLS REQUIRED

1. Scriber.

2. Steel rule.

3. Dot Punch


5. Bench vice



8. L- Square.

Theory :









–saw.

PROCEDURE






water).

43


given work pieces.






Pre Viva Questions:




4. What is safety?






Post Viva question:

1) What is the use of triangular file?

44

Triangular file or three-square files are used mainly for filing corners with angles

less than 90 degrees.

2) How will you specify a file?

Specification- length, single cut /double cut, shape and pitch.

Example Length (say 400 mm)

Single cut /Double cut

Shape (say square cross –section)

Pitch or grade (say smooth)

3) The edge of a file that does not have teeth on it is called a --------.

Safe edge.

4) What is the material used to make a chisel

Material - High carbon steel or tool steel having octagonal or hexagonal cross-

section.

5) What are the types of hammers? What is the material used to make a hammers.

Different types of hammers are a) straight pein hammer, b) ball pein hammer, c)

cross–pein hammer. Material Cast steel or carbon steel

6) What type of hammer mostly used in fitting operations?

Ball pein hammer

7) What is a twist drill?

The twist drills are used for making holes.

The drills are made of HSS (high speed steel).A bench drilling machine is

commonly used in workshops .

8) What is a hacksaw?

The hacksaw is used for cutting metal by hand. The hacksaw blade has a number of

teeth ranging from 5 to 15 per centimeter. Hack saw blades are fitted either in a solid

frame or adjustable frame to accommodate different lengths of blade

9)Hacksaw blades having lesser number of teeth per cm are used for cutting -------- materials.

soft materials

Ex:-Aliminium.brass and Bronze.

10) Hacksaw blades having larger number of teeth per cm are used for cutting --------

materials.

Hard materials like steel, C.I etc.

Model No: 8 Date: ……./……./……….

45

Dove tail model-2


1522,5

60

60

15

30


TOOLS REQUIRED

1. Scriber.

2. Steel rule.

3. Dot Punch


5. Bench vice



8. L- Square.

Theory :









–saw.

PROCEDURE



46




water).


given work pieces.







Pre Viva Questions:




4. What is safety?




in

L2 and Z mm in L3 & L4.


47

Post Viva question:

1) Name the materials of hacksaw blade?

It is made of high speed steel. The hacksaw blades are measured by its length,

width, thickness and pitch of the teeth.

2) How hacksaw blades are specified?

The hacksaw blades are specified by its material, length, width, thickness and pitch

of the teeth.

3) What is the specification of try square?

Specification-the Size of Try-square is specified by the length of the blade (100mm,

150mm, and 200mm).

4) What is the use of Taps? Name the tap types in an each set?

A tap is a hardened steel tool, used for cutting internal threads in a drilled hole.

Hand taps are usually supplied in sets of three for each diameter and thread size.

Each set consists of a 1) taper tap 2) Intermediate tap and 3) Plug or bottoming tap.

5) With what tool internal threads are cut.

Taps

6) What is the use of Dies in fitting?

Dies are used for cutting external threads. They are made of tool steel or high carbon

steel.

7) With what tool external threads are cut.

Dies.

8) What are the steps to be carried out in fitting job?

1) Filing 2) Marking &Measuring c) Sawing d) Filing e)Fitting/Assembly.

9) What is the use of file-card?

It is a metal brush used for cleaning the files.

10) What is the use of Flat chisel?

Chisels are used for removing surplus metal from the work piece. They can be used

as a substitute when files and hacksaw blades are impossible to use.

Specification- Length and width of the edge.

The process of removing metal using a chisel is called ‘chipping ‘.

48

MODELS FOR PRACTICE

49

50

WELDING PRACTICE

INTRODUCTION

Process of joining two or more parts to make a single part termed as a Fabrication

process. A fairly large number of industrial components are made by fabrication processes.

Common examples are aircraft and ship bodies, building trusses, welded machine frames,

sheet metal parts etc.

The fabrication is often the most economical method and relies on raw material obtained

from one of the primary manufacturing process such as rolling and extrusion. Hence, it may

be called a secondary manufacturing process.

Classification Fabrication process

The Various fabrication processes can be classified according to Method of Joining as

follows.

1) Mechanical Joining by means of bolts and nuts , screws,rivets.

2) Adhesive joining by employing synthetic glues such as epoxy resins.

3) Metallurgical fusion process like Welding, Soldering and Brazing

The Various fabrication processes can be classified according to Type of assembly.

. .1) Temporary joining process

2) Permanent. Joining process

Temporary joining process: The joints obtained by these processes will be such that the

connected parts can be separated easily with out any damage. Example: - Joints obtained by

brazing, soldering, bolts and nuts. Studs and nuts, screws etc

Permanent Joining process: The joints obtained by these processes will be such that the

connected parts have to be broken in order to separate them. Example: - Joints obtained by

riveting, welding etc.

Welding: Welding is the process of joining similar metals by application of heat, with or

without application of pressure or filler material.

Applications of welding It is used in the manufacture of automobile bodies, aircraft frames, railway wagons,

machine frames, structural works, pressure vessels, furnaces, tanks, refrigerators, furniture,

boilers, and shipbuilding. Repair and maintenance work.

Example: joining broken parts, rebuilding worn out components etc.

Classification of welding process.

Plastic welding:

In plastic welding, the metal parts to be joined are heated to the plastic state (or above)

and then fused together by applying external pressure. No filler metal is used in this process

plastic welding is also called ‘pressure welding processes.

Example: -Forge welding, resistance welding.

Fusion welding

In fusion welding process, the parts to be joined are heated above their melting

temperature and then allowed to solidify without application of pressure. A filler material is

used during welding process.

Example: - arc welding and gas welding

51

Types of Arc welding process 1) Carbon arc welding

2) Metal arc welding

3) Metal inert gas welding

4) Tungsten inert gas welding

5) Plasma arc welding

6) Submerged arc welding

Electric Arc Welding (Metal Arc Welding):-

Arc welding is a fusion method of welding that utilizes the high intensity of the arc

(generated by current flow) to melt the work pieces. A solid continuous joint is formed upon

cooling.

In arc welding process makes use of ‘filler material’ to supply additional material to fill the

gap between the workspaces. The filler material used in welding process is called

‘Electrode’. It is made of a metallic wire called ‘core wire’, which is of the same material or nearly the same chemical composition as that of the work piece metal or base metal. The core

wire is uniformly coated with flux.

Principle of Arc Welding:

The source of heat for arc welding process is an ‘electric arc ‘.The arc is produced by striking the electrode on the work piece. The electrode is momentarily separated from the

work piece by a small gap such that the arc is still maintained between the work piece and the

electrode .The electrical energy is thus converted into heat energy. The high heat at the tip of

the electrode is sufficient to melt the work piece. The tip of the electrode melts and combines

with the molten metal of the work piece there by forming a homogeneous joint.

Welding process

In arc welding process the electrode holder holding the electrode forms one pole of the

circuit and the parts to be welded forms the other pole. The electrode serves both to carry the

arc and also acts as a filler rod to deposit the molten metal into the joint. An arc is struck by

touching the tip of the electrode with the work piece and instantaneously the electrode is

separated from the work piece by a small distance of 2-4 mm such that the arc is still

maintained between the electrode and the work piece. The temperature of the arc ranges from

5000-6000 0C. The high heat of the arc melts the work piece metal forming a small molten

metal pool. At the same time, the tip of the electrode also melts and the molten metal of the

electrode is transferred into the molten metal of the work piece in the form of globules of

molten metal. The deposited metal fills the joint and bonds the joint to form a single piece of

metal.

Applications: Arc welding process is used for fabrication work, repair and maintenance

work. The process finds applications in

boiler and pressure vessel fabrication.

Shipbuilding. Joining of large pipes and

penstock, building and bridge construction,

automotive and aircraft industries etc.

Arc Welding Machine

The source of heat for arc welding process

is an ‘electric arc ‘. To supply the current for welding, two types of power sources are

52

available, viz; alternating current

(A.C) and direct current (D.C).

Current requirements:-

20-200 amperes for thin materials

20-300 amperes for general work

300- 600amperes for heavy work.

Welding using A.C current: Fig

shows the schematic

representation of an A.C welding

circuit.

The welding circuit consists of

Step–down transformer-to reduce the usual supply voltage (220-440 V) to that

required for welding (15-90V)

Two cables – one cable, to the electrode holder holding the electrode and other, the

ground cable

Ground clamp– used to connect one end of the ground cable to the work piece or to

the table carrying the work piece

Electrode holder and

Electrode

Welding using D.C current:

The schematic representation of a D.C welding circuit is shown in fig

In D.C welding, the electrode acts as one terminal and the work piece as the other terminal

(either +ve or -ve) with D.C generator, greater heat is generated at the positive pole. Hence.

The work piece should be connected to the positive pole of the D.C generator and the

electrode to the negative pole in order to melt greater mass of metal in the work piece

material.

In A.C, the melting rate cannot be controlled, because equal heat is generated at the

electrode and the work piece.

Comparison between A.C and D.C in Welding

Alternating Current (from Transformer)

More efficiency

Power consumption less

Cost of equipment is less

Higher voltage – hence not safe

Not suitable for welding non ferrous

metals

Not preferred for welding thin sections

Any terminal can be connected to the

work or electrode

Direct Current (from Generator)

Less efficiency

Power consumption more

Cost of equipment is more

Low voltage – safer operation

53

suitable for both ferrous and Non ferrous metals

preferred for welding thin sections

Positive terminal connected to the work

Negative terminal connected to the electrode

Electrodes used in Arc welding:

Welding electrodes used in arc welding are of two types.

1) Consumable electrodes

2) Non-consumable electrodes.

Consumable electrodes:

These are made of metallic wire and are consumed during the welding process. The

selection of a particular metal for the electrode depends upon their purpose and the chemical

composition of the work piece metal to be welded. Consumable electrodes are further

classified as coated electrodes and plain/bare electrodes.

Coated electrodes

In these electrodes, the metallic wire is coated with ‘flux ‘.During welding, the work piece melts and at the same time, the tip of the electrode also melts. As the globules of

molten metal pass from the electrode to the work piece, they absorb oxygen and nitrogen

from the atmospheric air. This causes the formation of some non- metallic constituents that

are trapped in the solidifying weld metal and thereby decrease the strength of the joint. In

order to avoid this, a ‘flux’ is coated on the metallic wire.

Flux A flux is a “material used to prevent, dissolve, or facilitate removal of oxides and other

undesirable surface substances”.

Various constituents like titanium oxide, cellulose, manganese oxide, calcium carbonates,

mica, iron oxide etc. are used as flux materials for coating.

The flux coated on the electrode performs the following functions.

prevents oxidation of molten metal

helps in the removal of oxides and other undesirable substances present on the surface

of the work piece

Chemically reacts with the oxides and forms a slag. The slag floats and covers the top

portion of the molten metal thereby preventing it from rapid cooling.

To remove any oxide formed.

To stabilize the arc

To make welding easy.

To avoid difficulties in welding.

Plain / Bare electrode: The metallic wire (core wire) is left plain or uncoated with flux.

These electrodes do not prevent oxidation of the weld and hence the joint obtained is weak.

Non –consumable electrode: - Non-consumable Electrodes are made of carbon, graphite or tungsten that does not get

consumed during welding.

Oxidation

Metals in molten condition absorb oxygen from atmosphere and form metallic oxides.

This process is known as oxidation. The formation of metallic oxides must be prevented. To

prevent oxidation, we use coated electrodes.

Advantages of Arc welding:

54

Most efficient way to join metals

Lowest-cost joining method

Affords lighter weight through better utilization of materials

Joins all commercial metals

Provides design flexibility

Limitations of Arc welding:

Manually applied, therefore high labor cost.

Need high energy causing danger

Not convenient for disassembly.

Defects are hard to detect at joints.

Gas Welding Process:

Principle: Gas welding is a fusion type of welding that utilizes a strong flame, generated

by the combustion of gases to melt the work piece. The gases are mixed in proper

proportions in a welding blow pipe called ‘welding torch’. A solid continuous joint is formed upon cooling.

The combination of gases used in this process is

Mixture of oxygen and acetylene

Mixture of oxygen and hydrogen.

Oxy-Acetylene welding

Oxygen and acetylene mixture are most commonly used in gas welding and the process

is widely called oxy-acetylene process. It consists of supply of oxygen and acetylene under

pressure in cylinders, pressure regulators, a torch, hoses and accessories like goggles and

lighter. The oxygen and acetylene cylinders are connected to the torch through pressure

regulators and hoses. The regulator consists of two pressure gauges. One for indicating the

pressure with in the cylinder and the other shows the pressure of the gas fed into torch, which

may be regulated. The torch mixes the two gases and the flame may me controlled by

adjusting the oxygen and acetylene supply.

Gas Welding Equipment.

1. Gas Cylinders

Pressure

Oxygen – 125 kg/cm2

Acetylene – 16 kg/cm2

2. Regulators

Working pressure of oxygen 1 kg/cm2

Working pressure of acetylene 0.15 kg/cm2

Working pressure varies depends upon the

thickness of the work pieces welded.

3. Pressure Gauges

4. Hoses

5. Welding torch

6. Check valve

7. Non return valve

Some of the Important points related to Gas Welding.

Sound weld is obtained by selecting proper size of flame, filler material and method

of moving torch

The temperature generated during the process is 33000C

When the metal is fused, oxygen from the atmosphere and the torch combines with

molten metal and forms oxides, results defective weld

55

Fluxes are added to the welded metal to remove oxides

Common fluxes used are made of sodium, potassium. Lithium and borax.

Flux can be applied as paste, powder, liquid. Solid coating or gas.

Types of flames produced in gas welding

Three types of flames can be produced at the torch tip by regulating the ratio of oxygen to

acetylene.

(a) Neutral flame.

(b) oxidizing flame.

(c) carburizing or reducing flame.

Neutral flame (Oxygen and Acetylene are mixed in equal proportions)

A neutral flame is produced when approximately equal volumes of oxygen and acetylene

are burnt at the torch tip (I has a balance of fuel gas and oxygen). The flame has a nicely

defined inner whitish cone surrounded by sharp blue flame. The temperature of the neutral

flame is around 32000C. . Used for welding steels, aluminium, copper and cast iron etc and

can also be used for metal cutting.

Oxidizing flame (Excess of Oxygen)

If more oxygen is added to the Neutral flame, the cone becomes darker and more

pointed, while the envelope becomes shorter and fiercer is called Oxidizing flame. Has the

highest temperature about 34000C.Used for welding brass and brazing operation.

Carburizing flame (Excess of Acetylene):-

If the volume of oxygen supplied to the Neutral flame is reduced, the resulting flame will

be a Carburizing or reducing flame i.e., rich in acetylene. A reducing flame can be recognized

acetylene feather that exists between the inner cone and the outer envelope. Has the highest

temperature about 30000C .The outer flame envelope is longer than that of the neutral flame

and is usually much brighter in colour . This type of flame is used for welding non- ferrous

metals.

Soldering

Soldering is a method of joining similar or dissimilar metals by means of filler

metal whose melting temperature is below 450 0C. The filler metal usually called ‘solder’ is

an alloy of tin and lead in various proportions.

Soldering is commonly used for joining circuits in electronic components. In sheet metal

work and in sealing of metal containers

Brazing

Brazing is a method of joining similar or dissimilar metals by means of a filler metal

whose melting temperature is above 450 0C, but below the melting point of the base metal.

56

The filler metal called ‘spelter’ is a non –ferrous metal or alloy. Copper and copper alloys

Silver and silver alloys and aluminum alloys are the most commonly used filler metals for

brazing.

Welding Tools and Safety Equipments

Electrode holder:- It is used to hold the electrode during welding refer fig it consists of a

handle and a pair of jaws operated by means of spring. The electrode holder forms one

element of the welding circuit. One cable (wire) from the transformer is connected to the

electrode. Due to this reason, the electrode holder should be well insulated.

Chipping Hammer:-During welding, the flux coated on the electrode reacts with the oxides

and other impurities and forms a slag. The slag being lighter floats over the surface of the

molten metal and on solidification forms a thin layer over the weld bead.

A chipping hammer is used for removing the slag formed on the weld bead. One end of the

chipping hammer is sharpened like a cold chisel and the other end to a blunt, round point.

Material- Tool steel

Wire brush: - The wire brush usually made up of steel wire is used for cleaning the work

piece before and after welding.

Tong:-A tong is used for holding the work piece during/after welding.

Ground clamp: - Ground clamp is connected to the end of the ‘ground cable’. Ground cable forms one pole of A.C.

Goggles and Hand shields:-The sparks produced during welding are harmful and should not

be seen with naked eyes. Goggles are used to protect the eyes of the welder form the ‘rays of

the arc’ and ‘flying particles of hot metal’. Hand shields and helmet type shields are used to

protect the eyes and also the face of the welder.

Hand gloves:-Hand gloves are used to protect the hands from the sparks produced during

welding and also from the heat of the electrode holder.

C- Clamp

The C-Clamp shown in fig is used for holding the job firmly on the work table during

welding.

Common welding terms

Base metal: - The metal to be joined or cut is termed as the base metal.

Bead or weld bead:-Bead is the metal added during single pass of welding. The bead appears

as a separate material from the base metal.

Striking voltage: - The minimum voltage at which the arc may be struck.

Fillet weld:- The metal fused into the corner of a joint made of two pieces placed at

approximately 90 degrees to each other.

Tack weld- A small weld, generally used to temporarily hold the two work pieces together

during actual welding, is the tack weld.

57

.

Safe and correct practices.

1) Welding should be carried out in a well ventilated place and the place should be free

of inflammable materials.

2) All the safety gadgets are to be used strictly.

3) Care should be taken to avoid dragging the welding cable and checked periodically

for any open insulation.

4) The cables should be prevented from coming into contact with hot metal, water, oil

etc.

5) Always keeps fire fighting equipment like water, sand, gas fire extinguisher, for any

fire hazard emergency.

6) Before welding, the parts to be welded are thoroughly cleaned from dust, foreign

matter, oil grease, rust etc.

7) The instructions given in the manufacture’s catalogue are to be strictly followed.

58

Model practice

Model No – 1 Date: ……./……../……….

Lap Joint

AIM: To do lap joint by welding as shown in the sketch.

50

50

50

5

5


TOOLS REQUIRED:

1. Rectangular file.

2. Steel rule.

3. Scriber.

4. Welding Electrode.

5. AC Welding Machine.

6. Metal brush.

7. Welding shield.

8. Hand glows.

9. Tong.

10. Bench vice.

11. Chipping hammer.

Theory: Welding is the process of joining similar metals by application of heat, with or without

application of pressure or filler material. In arc welding process the electrode holder

holding the electrode forms one pole of the circuit and the parts to be welded forms the other

pole. The electrode serves both to carry the arc and also acts as a filler rod to deposit the

molten metal into the joint. An arc is struck by touching the tip of the electrode with the work

piece and instantaneously the electrode is separated from the work piece by a small distance

of 2-4 mm such that the arc is still maintained between the electrode and the work piece. The

temperature of the arc ranges from 5000-6000 0C. The high heat of the arc melts the work

piece metal forming a small molten metal pool. At the same time, the tip of the electrode also

melts and the molten metal of the electrode is transferred into the molten metal of the work

piece in the form of globules of molten metal. The deposited metal fills the joint and bonds

the joint to form a single piece of metal.

Current requirements:



59


PROCEDURE

1. The given M.S work pieces are thoroughly cleaned of rust ,scale and other foreign

materials

2. Two work pieces are positioned on the work table (welding table) as shown in the

figure.

3. Connect the earth clamp of the welding machine to work table or base metal.

4. Select the proper size of the Electrode according to the thickness of the metal piece and

amperage.

Thickness of metal piece Current Range Size of the Electrode

5. Use hand shields, hand gloves and apron etc

6. After Selecting Proper size of the Electrode, place it in the Electrode holder.

7. Switch on the main and then the starter of the machine.

8. Bring the electrode near the weld joint and complete the circuit to maintain the correct arc

length. Move the electrode on the weld joint until the molten metal fills the parent metal.

9. Cool the joint for few minutes and remove the slag by chipping hammer

10. Brush the weld joint by the wire brush.

Pre viva questions:

1. What is welding?

2. Difference between current and voltage.

3. Difference between temporary joint and permanent joint.

4. Difference between rod, plate and sheet.

5. What is meant melting point?


60

Result:

Verification:

Conclusion:

POST VIVA – QUESTIONS

1) Define Fabricating process.

Joining two or more elements to make a single part termed as a Fabrication process.

Example: aircraft and ship bodies, building trusses, welded machine frames, sheet metal

parts etc.

4) Define Temporary joining process and give Example.

Temporary joining process: - The joints obtained by these processes will be separated

easily with out any damage to the connected parts. Example: - Joints obtained by

brazing, soldering, bolts and nuts. Studs and nuts, screws etc

5) Define Permanent Joining process and give Example.

Permanent Joining process: - . The joints obtained by these processes will be such that

the connected parts have to be broken in order to separate them. Example: - Joints

obtained by riveting, welding etc

6) What is welding?

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

application of pressure or filler material.

8) Classification of welding. Or. Mention different types of welding process.

1) Plastic welding 2) Fusion welding

9) Is welding a permanent or temporary fastening method.

Permanent fastening method.

12) Define pressure welding or plastic welding.

Name some pressure welding process.

In plastic welding, the metal parts to be joined are heated to the plastic state (or above)

and then fused together by applying external pressure. No filler metal is used in this

process. Plastic welding is also called ‘pressure welding processes. Example: -Forge welding, resistance welding.

13) Define fusion welding, name some fusion welding process.

In fusion welding process, the parts to be joined are heated above their melting

temperature and then allowed to solidify without application of pressure. A filler material

is used during welding process.

Example: - arc welding and gas welding

14) Differentiate between gas welding and arc welding.

In gas welding process combustion of oxy-acetylene (oxygen-hydrogen) gases in

different proportions is used for heating the work pieces. In gas welding filler rod is used

for joining work pieces.

In case of Arc welding Electrical Arc (AC OR DC) is used for heating the work pieces.

In arc welding electrode is used for joining work pieces.

61

Model No – 2 Date: ……./……./……

Butt Joint

AIM: To do butt joint by welding as given in the drawing.

50

50

5

50


TOOLS REQUIRED:


2. Steel rule.

3. Scriber.



6. Metal brush.

7. Welding shield.

8. Hand glows.

9. Tong.

10. Bench vice.

















62


PROCEDURE


materials


figure.



amperage.










Result:

Verification:

Conclusion:

63


1) List the different types of arc welding process?

1) Carbon arc welding 2) Metal arc welding 3) Metal inert gas welding4) Tungsten inert

gas welding 5) Plasma arc welding6) Submerged arc welding

2) Name some of the sources available for heating in arc-welding process.

1) Transformer (A.C)

2) Motor Generator (D.C)

3) Rectifiers (converts AC into DC).

3) What is the minimum Arc-gap should be maintained between electrode and work piece for

existence of arc. 2mm to 4mm.

4) Draw an A.C arc-welding circuit. (OR) Name the components used in welding ac-circuit

5) The amount of current required for arc welding circuit.

50 to 500 Appears

6) The amount of voltage required for arc welding circuit.

20Volts – 40 Volts

7) What type of Transformer used in Ac arc welding process.

Step down Transformer

8) What is the function of Step down Transformer?

Decrease the voltage to from 230V to50v-90v.

Increase the current to 50Amps-400 Amps.

9) The temperature developed in the arc welding process.

5000 degrees-6000 degrees.

10) Draw a DC circuit for arc welding process.

11) What is DCSP? OR DCEN-Direct current Electrode Negative.

Direct current straight polarity. In this case work piece is connected to the positive

terminal of the welding Machine. Electrode holder is connected to the negative terminal

of the welding machine. DCSP gives greater depth of penetration, more heat at job, used

for weld thicker plates. Or Electrode is cathode, work piece is cathode.

12) How many number cables required in arc-welding process.

Three cables are required in arc-welding.

1) Cable for connecting Main supply to Transformer.

2) Cable for connecting Transformer to electrode Holder.

3) Cable for connecting Transformer to work piece Table (for Farthing).

64

Model No – 3 Date: ……/……/……..

T- Joint

AIM: To do T joint by welding as given in the drawing..

50

5

550

50


TOOLS REQUIRED:


2. Steel rule.

3. Scriber.



6. Metal brush.

7. Welding shield.

8. Hand glows.

9. Tong.

10. Bench vice.














65





PROCEDURE


materials


figure.



amperage.










Result: The model is welded as per the drawing.

Verification: The welding is poor/ discontinuous/ good

Conclusion: The reason is ……………..

66


1) What is oxidation?

Metals in molten condition absorb oxygen from atmosphere and form metallic oxides.

This process is known as oxidation. The formation of metallic oxides must be prevented.

To prevent oxidation, we use coated electrodes.

2) Mention the current requirements for thin and thick materials.



300 -600amperes for heavy work (thick materials).

3) What is an electrode?

A welding electrode is defined as a component of the welding circuit through which

current is conducted.

OR.

Electrode forms one pole of the electric circuit, while work piece forms the other pole.

Electrode is used in Arc welding process.

4) What is Filler rod?

Filler metal supplies additional material to fill the gap between work pieces.

Material of the filler rod is same as the base metal. Filler rod is used in gas welding

process.

5) What is the difference between electrode and filler metal.

Electrode forms one pole of the electric circuit, while work piece forms the other

pole.

Filler metal supplies additional material to fill the gap between work pieces.

In case of arc welding process, the filler metal apart from supplying additional metal

also acts as an electrode by forming a component of the electric circuit.

6) Name parts of electrode.

7) specify a welding electrode, you have used.

Electrodes are specified by its diameter (diameter of core wire) and length.

The size of the electrode is measured in Standard wire gauge (SWG).

8) Classification of electrodes.

1) Consumable electrodes

a) Coated electrodes b) plain/bare electrodes

2) Non-consumable electrodes

9) Amount of arc length required between electrode work pieces.

The distance through the center of the arc from the lip of electrode to the bottom of arc

crater is termed as arc length. It ranges from 3mm to 4mm.

67

Model No – 4 Date : ……/………/…….. L- Joint

AIM: To fabricate L joint by welding as per given drawing.

50

50

50

5

5


TOOLS REQUIRED:


2. Steel rule.

3. Scriber.



6. Metal brush.

7. Welding shield.

8. Hand glows.

9. Tong.

10. Bench vice.


















68

PROCEDURE


materials


figure.



amperage.










Result:

Verification:

Conclusion:


69

1) What are the sizes of electrodes?

Core wire diameter-3.15, 4.0, 5.0, 6.3,10 mm and 12.5 mm.

Core wire length-350mm and 450 mm

as per Indian standard.

2) Differentiate between consumable electrode and non-consumable electrode.

Consumable electrode-These are made of metallic wire and are consumed during the

welding process.

Non-consumable electrode- Non-consumable Electrodes are made of carbon,

graphite or tungsten that does not get consumed during welding.

3) Why electrodes are not coated fully.

One end of the electrode is left bare (uncoated with flux) which is usually held in the

electrode holder.

The uncoated part helps in transmitting full current from the electrode holder to the

front end of the electrode coating. The flux coating acts as an insulator

ofelectricity.Hence, electrodes are not coated fully.

4) What are the functions of flux on flux coated electrode?

prevents oxidation of molten metal helps in the removal of oxides and other

undesirable substances present on the surface of the work piece

Chemically reacts with the oxides and forms a slag. The slag floats and covers the

top portion of the molten metal thereby preventing it from rapid cooling.

To stabilize the arc

To avoid difficulties in welding.

5) Name the material of core wire of electrode.

Material of the core wire is same as the work pieces to be welded.

6) What is the material of flux used in the electrode?

Titanium oxide, cellulose, manganese oxide, calcium carbonates, mica, iron oxide

etc. are used as flux materials for coating.

7) What is a flux? Why is it used?

A flux is a “material used to prevent, dissolve, or facilitate removal of oxides and other undesirable surface substances”. prevents oxidation of molten metal

8) What are the defects that will result if flux is not used in welding?

a) Reduce the Strength of the joint.

b) Oxidation of molten metal will take place.

9) Define base metal.

The metal to be joined or cut is termed as the base metal.

10) What is the use of chipping hammer?

A chipping hammer is used for removing the slag formed on the weld bead

11) What is the use of electrode holder?

It is used to hold the electrode during welding

12) What is the use of wire brush?

The wire brush usually made up of steel wire is used for cleaning the work piece

before and after welding.

13) What is the use of goggles?

Goggles are used to protect the eyes of the welder from the rays of the arc and flying

particles of hot metal.

14) What is the use of hand shields?

Hand shields and helmet type shields are used to protect the eyes and also the face of

the welder

70

SHEET METAL FABRICATION PRACTICE

INTRODUCTION:

When the thickness of a material is much smaller than length and width, it is known as

sheet or plate. When the thickness is less than 6mm it is categorized as sheet and when

thickness is greater than 6mm it is categorized as plate.

Sheet metal work is the shaping or forming operations of mostly sheet. These sheet metal

processes are very much different from the processes for shaping thick bars, rods, blooms,

billets etc.

THEORY OF SHEET METAL WORK:

When an elastic material is subjected to increasing force, it deforms and stress

within the material keeps on increasing. A typical stress strain diagram of an elastic material

is as shown in the figure. Material follows Hooke’s law up to point A called yield stress.

When stress in the material exceeds yield stress, material deformation becomes permanent

and when the stress reaches ultimate or fracture stress, the material fails. These materials are

known as ductile materials which on increasing stress then yield and deform and then only

fail. But there are materials which do not yield much but fail prematurely and they are called

brittle materials.

In sheet metal forming in some operations, forces are applied such that stress in the

metal exceeds just the yield stress but well below ultimate stress called plastic state, so that

metal is deformed to the required shape but does not fracture. These processes are :

Bending,drawing,coining,embossing,stretch forming,spinning,deep drawing, roll bending

and super plastic forming and all these processes takes place in plastic state. But in some

processes, so heavy forces are applied that the stress in the material exceeds ultimate stress

and the material fractures. These processes are shearing, punching and piercing.

SHEET METAL WORK:

The metal forming processes such as cutting, shearing,

punching, piercing, embossing, drawing, coining, deep drawing,

stretches forming, spinning, roll bending, super plastic forming

are all sheet metal operations. Compared to machining or forging

or extruding processes, the sheet metal processes are much

cheaper as the machines required are much cheaper or they are

suitable for large scale production. The machines used for sheet

71

metal forming are: Shearing machine, 3 roll/4roll bending machine, arbor press, hydraulic

press, fly press, stretch forming machine, flow forming machine etc.

THE MATERIALS:

Used in sheet metal forming are: M.S, Aluminium alloys, copper alloys, zinc alloys,

Magnesium alloys, Tin alloys, G.I, Stainless steel (SS) etc. Material should have good

ductility for sheet metal forming. Galvanized iron is steel coated with zinc to protect it from

rusting an also can be soldered. Stainless steel is highly ductile material specially in an

annealed state it has 40% elongation. Steel sheet coated with tin is called tin plate and rust

proof and also used in making food containers, cans, pans and dairy equipments.

Several industrial, household and consumer products are made by sheet metal forming.

Storage tanks, pressure vessels, oil tankers, cooking utensils such as pressure cookers,

instrumentation boxes, containers, small as well as big packing boxes, trunks, suit cases,

boiler parts, heating ducts, air ducts, gutters etc all are sheet metal products.

DEVELOPMENTS:

Most of the sheet metal parts are formed by flat sheets. All the 3 dimensional

bodies(hollow) can be formed by correctly making corresponding shape in flat condition and

then it is folded and made to yield and final 3 dimensional body is made. After folding, the

joints are of standard joint configurations as shown in the figures.

72

SHEET METAL ALLOWANCES:

If a sheet metal of thickness ‘t’is bent to 90° with radius R from a flat sheet as shown in the fig., the total length in flat condition and after bending are not same.

Length of the flat sheet=l

Length after bending=x1+x2+x3 and x1,x2 are straight distances and x3 the length at bend

and this varies for outer layer, inner layer and central/neutral layer. Hence to calculate correct

length l to be taken to get final bend as shown in the fig,

Mid layer length is taken as L=x1+x2+ ∏(R+t/2) 2

The difference of l and L is called bend or sheet metal allowance. The sheet metal allowance

varies based on the bend radius, the thickness of sheet, bend angle, material condition etc.

there are empirical estimations available for sheet metal allowances and are tabulated and are

readily available.

SHEET METAL TOOLS AND FITTING TOOLS:

1) Marking tools: Steel rule, vernier calipers, scriber, divider, try square, universal

scribing block, surface plate, vernier height gauge, bench vice, bevel protractor,

punches, wire gauge.

2) Cutting tools: snips/shears, chisel, files.

3) Bending tools: mallet, stakes: beak horn stake, hatchet stake, half moon stake,

creasing stake, funnel stake, pipe stake, horse stake, pliers etc.

Steel rule, vernier calipers, vernier height gauge: These are measuring instruments used

for various measurements. The accuracy of scale being 1mm and that of vernier caliper and

vernier height gauge being 0.02 mm. They are made of steel.

Bevel protractor: it is made out of steel and is used for measuring and marking angles in

drawing developments.

Try square: it is made by hardened steel and used for marking perpendicular lines and

checking perpendicularity.

Wire gauge: it is made of steel hardened and used for checking the thickness of sheet metal

and wires. Most commonly used gauge is called imperial standard wire gauge(SWG) and the

markings vary from 4 to 24. Higher the gauge no. lesser is the thickness and standard wire

sizes are as given in the table.

73

SWG No Size in mm SWG No Size in mm SWG No Size in mm

4 6.0 11 3.0 18 1.25

5 5.5 12 2.7 19 1.05

6 4.8 13 2.4 20 0.95

7 4.5 14 2.1 21 0.85

8 4.0 15 1.9 22 0.72

9 3.6 16 1.65 23 0.62

10 3.3 17 1.45 24 0.58

Surface plate: it is a flat base of granite (or cast iron). It has high surface finish, flatness and

hard and used for placing sheet etc for marking and measurement.

Bench vice: it is a holding device made of C.I and M.S. it is used to hold jobs, sheet and also

pressing at bend line to form a bend.

Scriber, caliper and divider: These are marking tools made of iron tool steel material.

Universal scribing block or surface gauge: it consists of casting from base and M.S

spindle, clamp etc. it is very convenient marking tool. The base with v-groove is useful to

take reference dimensions on round bodies.

Snips/shears: it is similar to scissors but stronger and heavier and straight as well as

contoured. Cuts can be made along the already marked profiles and cut in to pieces. It is

made of carbon steel or tool steel.

Chisels: When there is no approach or access to line to be cut by snips/shears from an edge

the material can be cut using chisel. Chisels are made of high carbon steel, tool steel or alloy

steel. There are varieties of chisels for different applications.

Files: these are cutting tools to remove metal from surfaces.

Mallet: a wooden or plastic or hyde hammer is generally known as mallet. Thin sheet metal

bending and shaping is done by softer hammer such as wood or plastic to avoid or minimize

deep dents, marks pr scratches. Mallets are of different shapes to suit sheet metal forming.

Stakes: in the absence of sheet metal forming machines such as fly press, bending, folding,

rolling machines, for hand forming, stakes are the tools used. These are tools made of steel

and are of anvil shape. They are for forming the shapes by bending, forming, riveting,

seaming. Using mallet, the sheet to be shaped are placed over the stakes of appropriate shape

and hammered by mallet to permanently deform the sheet to the required shape. Stakes act as

supporting tools or mandrel for the sheet to be formed. Stakes are made in different shapes

and sizes.

A stake consists of a shank, a horn and head. The formation of sheet metal items

requires forming a corner with radius and contours of circular,conical,tapered etc and

different types of stakes are available to form all the types of corners, profiles etc.

The various types of stakes are : blow horn stake, beak horn stake, candle mould stake,

creasing stake, hollow mandrel stake, solid mandrel stake, double seaming stoke, conductor

stake, hatchet stake, bevel edge stake, common square stake, copper smith stake, bottom

stake, hand dolly stake.

Pliers: Pliers are used in sheet metal work for holding, cutting and bending work. Various

types of pliers are:

74

(a) Flat nose pliers: It has flat jaws rounded on the outside. It is used for holding and

forming work.

(b) Round nose plier: It has long jaws rounded on the outside. It is used for holding and

forming various shapes and patterns.

(c) Slip joint combination plier: It has an adjustable jaw. It is general purpose tool.

75

76

77

78

79

SOLDERING:

It is a process of permanent joining or coalescence of two similar or dissimilar metals. A

filler metal called solder, an alloy of lead, silver, tin and antimony whose melting point is less

than 450° c is used. Generally solders melt around 100-200°c. Metal to be joined is heated

but much below its M.P. the joint is well cleaned by flux and heated along with solder and

liquid solder metal, a thin layer is deposited along the joint. Due to surface tension and

capillary action at the joint, the liquid solder diffuses in to the metal and solidifies and forms

a permanent joint.

Solders:

The strength of soldered joint is poor. Different solder alloys and fluxes are available for

dfferent metals. Lead tin alloys, tin-zinc alloys, tin-silver, tin copper cadmium – silver alloys,

indium tin alloys etc are the solder materials. Lead-tin alloys melt 150-350°c are called soft

solders and give less strong joints. Alloys of copper melt at 600-900°c and give stronger

joints and are called hard solders.

Fluxes:

Zinc chloride, ammonium chloride, tin chloride, organic fluxes, rocasin fluxes are

generally used. Fluxes clean the joint surface; protect the metal from oxidation and helps in

creating capillary action so that metal diffusion takes place.

Methods:

Soldering is done by soldering iron in furnace or by torch or by dip, wave, induction,

resistance and infrared soldering processes.

80

MDEL NO: 01 Date: ……./……/……….

RECTANGULAR TRAY

AIM: To draw the development of sheet metal tray, cut the development, bend and form to

final tray shape and solder the joint.

`

`

Material:

The material used is G.I which is steel coated with Zinc and of …….. Gauge (…..mm). Size of sheet used is ………mm x………..mm

Solder material of lead-tin alloy (60% Tin and 40% Lead)

Tools used:

1. Steel rule vernier

2. Caliper,

3. Scriber,

4. Punch,

5. Ball peen hammer,

6. Mallet,

7. Divider,

8. Protractor,

9. Shears/snip,

10. Bending tools form blocks, stakes,

11. Bench vice,

12. Soldering gun, lead and flux.

THEORY:

Ductile materials can be formed into different shapes by permanent deformation by

subjecting the metal sheet beyond its yield stress. Galvanized iron, tin, MS or SS sheets of

thin cross sections are the materials generally used for sheet metal forming. G.I is a steel

sheet coated with zinc which protects it from rusting and also improves its appearance.

The 3D model of the sheet metal (tray) can be made by marking the development in flat

condition by geometrical and drawing methods. The sheet can be cut into the developmental

profile and then folded and bent along bend lines and the model (tray) shape can be formed

and then it can be soldered at the joints.

100mm

50mm

50mm

81

Pre viva questions:

1. Name few tools used to cut the material.

2. What do you mean by fabrication?

3. What do you mean by elasticity?

4. What do you mean by shearing?

Development:

The sheet development is made on paper by CAED method. The development of this

model is as shown in the sketch.

Procedure:

1. The development including calculations of the model is done and drawn on a

sheet and sketch book.

2. Using the development sketch the same is redrawn on the sheet metal to be

formed by using scale, scriber, divider etc.

3. Using stakes, form blocks bends are made by mallet on all bend lines.

4. Using a final shaped form block, hammer, the exact shape is formed by

hammering on all the bend lines by trial and error.

5. Each joint is held tightly by pliers and soldering is done by a soldering gun, flux

and solder by heating suitably.

6. The soldered joint is then cleared of flux, slag etc and the model is complete.

100 mm

70mm

50mm 50mm

50mm

200

mm

120mm

50mm

82


Verification: The measurement of the model reveals that there is a deviation of X mm in L1, Y

mm in L2 and Z mm in L3 & L4.


Post viva question

Q.1 Name of any five measuring instruments?

(i) Try square (ii) Vernier caliper (iii) Micrometer (iv) Divider (v) Inside caliper

Q.2 Name the gauges?

ANS:- (i) Depth gauge (ii) Filler OR slip gauge (iii) Radius gauge (iv) Vernier height

gauge (v) Thread OR pitch gauge (vi) Wire OR thickness gauge

Q.6 What is least count?

ANS:- Minimum dimension that can be expressed on vernier caliper

Q.7 What is the use of outside micrometer?

ANS:- To measure outside diameter & thickness of any job

Q.8 What is the use of divider?

ANS:- It is used for marking arc, dividing a line or transferring the dimension.

83

MODEL NO: 02 Date: ……/……./…….

FRUSTUM OF CONE

AIM: To draw the development of sheet metal frustum of cone, cut the development, bend and

form to final frustum of cone shape and solder the joint.

Material:

The material used is G.I which is steel coated with Zinc and of …….. Gauge (=…..mm). Size of sheet used is ………mm x………..mm


Tools used:

1. Steel rule vernier calipers

2. Caliper,

3. Scriber,

4. Punch,


6. Mallet,

7. Divider,

8. Protractor,

9. Shears/snip,


11. Bench vice,


THEORY:





The 3D model of the sheet metal frustum of cone can be made by marking the

development in flat condition by geometrical and drawing methods. The sheet can be cut into

the developmental profile and then folded and bent along bend lines and the model shape can

be formed and then it can be soldered at the joints.

D=30mm D=60mm

h=60mm

84

Pre viva question:

1. What is the use of try square?

2. What is the use of combination set?

3. What is the use of C- clamp?

Development:



Procedure:















85

Post viva question:

1. What is sheet metal work?

ANS: Sheet metal work is used for making, Cutting and bending

2. Which are the sheets of metals?

ANS: (I) Galvanized iron (ii) Stainless steel (iii) Copper (iv) Aluminum

3. Name the sheet metal hand tools?

ANS: (I) Steel rule (ii) Vernier caliper (iii) Micrometer (iv) Scriber (v) Divider (vi)

hammer (viii) mallet (ix) Shears

4. What is G.I.?

ANS: G.I. is galvanized iron

5.l What is shearing?

ANS: Shearing means for sheet metal cutting

86

MODEL NO: 03 Date: …../……./………

PENTAGONAL PRISM

AIM: To draw the development of sheet metal pentagonal prism, cut the development, bend

and form to final frustum of cone shape and solder the joint.

Material:



Tools used:

1. Steel rulevernier

2. Caliper,

3. Scriber,

4. Punch,


6. Mallet,

7. Divider,

8. Protractor,

9. Shears/snip,


11. Bench vice,


THEORY:





The 3D model of the sheet metal pentagonal prism can be made by marking the




h=70mm

h=70mm

87

Pre viva question:

1. What is the included angle of dot punch?

2. What is the included angle of centre punch.?

3. What is the use of spring divider?

Development:



procedure:















88

Post viva question:

1.Name of any five measuring instruments?

ANS:- (i) Try square (ii) Vernier caliper (iii) Micrometer (iv) Divider (v) Inside caliper

2 Name the gauges?

ANS:- (i) Depth gauge (ii) Filler OR slip gauge (iii) Radious gauge (iv) Vernier height

gauge (v) Thread OR pitch gauge (vi) Wire OR thickness gauge

3 What is least count?

ANS:- Minimum dimension that can be expressed on vernier caliper

4 What is the use of outside micrometer?

ANS:- To measure out side diameter & thickness of any job

5 What is the use of divider?

ANS:- It is used for marking arc, dividing a line or transferring the dimension.

89

MODEL NO: 04 Date: ……/……/……..

HEXAGONAL PRISM

AIM: To draw the development of sheet metal hexagonal prism, cut the development, bend and

form to final frustum of cone shape and solder the joint.

Material:



Tools used:


2. Caliper,

3. Scriber,

4. Punch,


6. Mallet,

7. Divider,

8. Protractor,

9. Shears/snip,


11. Bench vice,


THEORY:





The 3D model of the sheet metal hexagonal prism can be made by marking the




70mm

50mm

90

Pre viva question:

1.What do you mean by riveting?

2.What is the difference between sheet and plate.?

3.How many mm is equal to one inch?

4. how do you convert mm in to m?

Development:



Procedure:















91

Post viva questions

1 What is sheet metal work?

ANS Sheet metal work is used for making, Cutting and bending

2 Which are the sheets of metals?

ANS (I) Galvanized iron (ii) Stainless steel (iii) Copper (iv) Aluminium

3 Name the sheet metal hand tools?

ANS (I) Steel rule (ii) Vernier caliper (iii) Micrometer (iv) Scriber (v) Divider (vi)

hammer (viii) mallet (ix) Shears

4 What is G.I.?

ANS G.I. is galvanized iron

5 What is shearing?

ANS Shearing means for sheet metal cutting.

92

MODEL NO: 05 Date: ……/……/……..

TRUNCATED SQUARE PYRAMID

AIM: To draw the development of sheet metal truncated square pyramid, cut the development,

bend and form to final frustum of cone shape and solder the joint.

Material:



Tools used:


2. Caliper,

3. Scriber,

4. Punch,


6. Mallet,

7. Divider,

8. Protractor,

9. Shears/snip,


11. Bench vice,


THEORY:





The 3D model of the sheet metal truncated square pyramid can be made by marking the




70m

m

50m

m

30mm

93

Pre viva question:

1.What is mallet?

2. What is spelter ?

3. what is stakes.?

Development:



Procedure:











94





Post viva question:

1.What is SWG?

Ans: Standard Wire Gauge.

2.Why flux is used during soldering?

Ans: to remove oxide formation and contaminations on the surface.

3.What is hard soldering?

Ans: Brazing.

4.What is snips?

Ans: tool sued to cut t5he thin sheet.

5.What is the coating present on the GI sheet?

Ans : molten zinc.

Documents

Department of Mechanical Engineering - Gopalan Colleges · WORKSHOP PARACTICE LAB P AGE N O. FROM TO PART A: FITTING PRACTICE I. VTU SYLLABUS 3 3 II. About Safety precautions 4 4