workshopmanual.pdf

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ManualWorkshop Practice-1

Prepared by

Faculty Member

Mechanical Engineering Department

Galgotias University

Greater Noida, UP.


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Introduction to Workshop Practice-1

Introduction

The workshop technology gives the basic working knowledge for the production of various

engineering products. It explains the construction function and the use of various working tools,

measuring tools, equipment and machines as well as the technique of manufacturing a product

from its raw material. To understand the subject and to develop the skill, one has to practice the

workshop processes, starting from simple models to complicated products.

Classification of Manufacturing Processes

Metal is considered as the most important material for engineering objects and machines. The

term, manufacturing process is considered as the general name for the method of processing

metal in order to obtain various shapes. The whole manufacturing processes can be broadly

classified into the following five groups.

1. Primary shaping processes2. Secondary shaping (machining) processes3. Joining processes4. Surface finishing processes5. Processes changing the metal properties

Primary shaping process: Metal obtained by extraction of ores is refined and cast to form big

blocks, called ingots. These ingots are reduced to smaller size and shape by one or more of the

primary shaping processes. The following are the important primary shaping processes:

Metal casting; Rolling; Forging; Extrusion; Metal drawing; Powder metallurgy; Oxy-gas cutting;

Press work; Sheet metal work; Metal spinning etc.

Sheet Metal Work: Sheet metal work is basically a hand process of making objects of sheets of

metal with the help of hand tools and equipment. The object to be made is developed and drawn

on a plane sheet of metal. Then it is cut and folded to form the shape. The joints are made by

folding, riveting or soldering.


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Ferrous, non-ferrous and coated metallic sheets are used for the production of the sheet metal

objects. Machines like shearing machine, folding machine, bending machine are also used for

large scale production of sheet metal objects.

Examples of sheet metal works are hoppers, trays, guards, covers, funnel, bucket, measuring can,

boxes, pipe etc.

Welding: Welding is the process of joining metallic parts by the application of heat, with or

without the application of pressure or filler metal in such a way that the joint is equivalent in

composition and characteristics of the metals joined. The popular welding processes are

mentioned below:

Arc welding: Shielded metal arc welding; Submerged arc welding; Metal inert gas welding

(MIG); Tungsten inert gas welding (TIG); Carbon arc welding; Electro-slag welding etc.

Resistance welding: Spot welding; Seam welding; Projection welding; Butt and upset welding;

Flash welding; percussion welding etc.

Gas welding: Oxy-acetylene welding; oxy-hydrogen welding; Air-acetylene welding; Oxy-other

fuel gas welding.

Miscellaneous welding process: Thermit welding; Forge welding and Modern welding processes.

Soldering: Soldering is the process of joining similar or dissimilar metals by means of a fusible

filler metal or alloy called solder applied in the molten stage. The melting temperature of the soft

solder is about 3500C to 370

0C and that of the hard solder is about 600

0C to 900

0C. But the

melting temperature of solder is always lower than the melting temperature of joining metals.


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How to write lab report

Preparing for the Workshop Practice

An engineering student who is going to do workshop practice, has to prepare the following prior

to practice

1. The student has to posses the following materials;a. Work record of A4 sizeb. Fair record approved by the workshop authoritiesc. Pen, pencil, eraser and straight edge.

2. Students are advised to wear tight dress, preferably pants and shirts. Girl students have totie their hair and tuck neatly as a precaution against being caught against moving machine

parts. For good protection of clothing, a shop apron of dark colour may also be used.

Wearing of shoes instead of slippers is also recommended for the safety of legs from

sharp and hot chips and material other waste.

3. Study the relevant theory about the process, tools, equipment and the material being usedfor the practice. Usually the students are given a study of the workshop tools andequipment prior to the practice.

Writing of Work Record for Study

Before starting the actual practice in a workshop, the instructor gives description about the

different types of tools and equipment used for cutting, holding, measuring etc. Students are

allowed to handle the tools and thus to become familiar with the shape, name of parts, and the

method of using them. After the study the students are required to prepare the work record of the

study. The suggested layout of the work record is shown.


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1.Heading: It should be written by using capital letters on the top portion of the first rightside page.

2. Serial number and date: It should be written in the top portion of the left side margin ofthe first right side page.

3. Aim: Objective of the study is to be written on the right side page as the first paragraph.

4. Tools and Equipment: The list of tools and equipment studied showing the detailedspecification has to be furnished as the second paragraph under the title.

5. Neat sketches of the tools and equipment have to be prepared using pencil on the lefthand pages. The name of the parts should be marked on them. The appropriate caption

should be written below each drawing.

6. A brief description of each tool or equipment studied has to be prepared on the right sidepages under an underlined subheading.

NO.

L R

HEADING

AIM:

TOOLS & EQUIPMENT:

DESCRIPTION OF.......:

1. ............2. ............3. ............

DT:

SKETCHES


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Writing of Work Record for Practice

Similar to study a work record has to be prepared for workshop practice also. In this work record

a student copies the drawing of the model to be completed and prepares a sketch of the raw

material piece to be used for the model.

1. Heading, Serial number, Date and Aim: It should be written by using capital letters onthe top portion of the first right side page.

2. Work material: Details about the work material and other requirements are written underthis subheading. This should include the size, number of pieces or quantity, material

specification etc.

3. Tools and Equipment: The list of tools and equipments required for the practices is givenunder this subheading.

4. List of operations: The operations to be carried out for making the model have to begiven as a list below the subheading.

5. Procedure: After completing the work on the model the procedure followed for makingthe model has to be written in the second right page using past tense and in third person.

This should contain all details about the operations, controls, safety measure etc, related

to the making of model.

6. Results: It is a custom to write the result of the practice as the last paragraph of therecord. This include the statement that whether the content of the aim is achieved or not

by the practice.


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NO.

L R

HEADING

AIM:

TOOLS & EQUIPMENT:

LIST OF OPERATIONS:

DT:DIMENSIONEDSKETCHE OF

MODEL

WORK MATERIAL:

PROCEDURE:

RESULTS:


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Welding Shop


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ASSIGNMENT-1

Objective: To study about the oxy-acetylene gas welding process.

Introduction

The welding is a process of joining two similar or dissimilar metals by fusion, with or without

the application of pressure and with or without the use of filler metal. The fusion of metal takes

place by means of heat. The heat may be obtained from blacksmiths fire, electric arc, electrical

resistance or by chemical reaction.

The welding is extensively used in fabrication as an alternative method for casting and forging

and as a replacement for bolted and riveted joints. It is also used as a repair medium e.g., to

reunite metal at a crank, to build up a small part that has broken off such as gear tooth or to

repair a worn surface such as bearing surface.

Applications of Welding

1. Automobile construction2. Rail road equipment3. Ships4. Aircraft construction5. Bridges construction6. Storage tanks7. Piping and pipe lines8. Household furniture9. Repair of broken and damaged parts etc.

Safety Precautions in Gas welding Shop

1. Always wear welding gloves while doing gas welding2. Never play or get careless while using the gas welding equipment.


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3. Combustible gas must be handled carefully.4. Always use the spark lighter to light the torch5.

Strictly follow the procedure laid out in handling the cylinders, regulators and torches.

Oxy acetylene gas welding

Acetylene is a carbonaceous combustible gas. When it is burnt in presence of oxygen gas in a

controlled manner the combustion produces intense heat by means of flame at the torch tip with a

temperature of about 33000C which is sufficient to melt a metal. The flame is long, smoky and

yellowish in color. However when oxygen is also supplied in the mixing chamber and the

mixture is ignited, the size of the flame is reduces and it is not smoky. The flame is bluish in

color. The heat is produced due to following exothermic chemical reaction that takes place when

mixture of acetylene and oxygen is burnt at the tip of the gas torch.

2C2H2 + 5O2 = 4CO2 +H2O + 624000 cal

The heat so produced melts the metal.

Typical application of Oxy-acetylene welding includes welding of root run in pipe and other

multi-run welds, light fabrications like ventilation and air-conditioning ducts, and motor vehiclerepairs.

There are two ways for the Oxy-acetylene welding

1. High pressure system: In this method both oxygen and acetylene are derived for use fromhigh pressure cylinder.

2. Low pressure system: In this system, oxygen is taken out as usual from high pressurecylinder but acetylene is generated by the action of water on carbide in a low pressure

acetylene generator.


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Figure: Oxy-acetylene welding outfits

Types of Flames

Three types of flames are produced when the mixture is ignited at the tip of the gas torch.

Neutral flame

The neutral flame is most often used for the welding of most of the materials like low carbonsteels, cast steels, cast iron etc.

The flame is produced when the gas mixture has equal volumes of acetylene and oxygen. This

flame has two distinct zones, a sharply outlined luminous cone and an outer flame surrounding

the cone.

Oxidizing flame

The flame is produced when the amount of oxygen is slightly more than the acetylene. In other

words the oxidizing flame has higher proportion of oxygen than acetylene. This flame is very

short in length and sharper in shape. During the combustion a hissing sound is produced at the tip

of the torch. Again there are two distinct zones; the inner flame is used for welding brasses,

bronzes and cast iron.


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It is very important to keep in mind that while producing the oxidizing flame the inner cone

should be shortened otherwise back firing will occurs.

The oxidizing flame is used for welding of Mn-steel, brass, bronze, alluminium, nickel etc.

Heat transfer to the work in this process is very poor, about 30%, and may lead to wide HAZ

around the weld. The welding speed is also low.

Reducing or carburizing flame

This flame is produced when the oxygen is kept slightly less than acetylene. It has three distinct

zones. The inner cone is the brightest and is surrounded by a bluish feathery flame. This flame is

advantageous for non-ferrous metals, silver soldering and hard facing. It is also used in creating

surface fusion on steel.

Figure: The three types of oxy-acetylene flames


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ASSIGNMENT-2

Objective: To study about the arc welding process.

Electric arc welding

Arc is a state of plasma. Arc is placed between the electrodes at the zone where the joint is to be

made. The electric source is either AC or DC supply. The arc is developed due to high resistance

encountered by the flowing current. The heat due to arc is so intense that the base metal and the

electrodes melt simultaneously as it is in the range of 27000

to 55000C. The metal of the

electrode drops in the form of fine globules. Also due to the force of the arc both the metals fuse

into each other, thoroughly. On cooling a perfect joint is available.

Safety Precautions in Arc welding Shop

Arc welding

1. Never look at arc with naked eyes2. Always use a shield while welding3. Always wear the safety hand glove, apron and leather shoes4. Ensure proper insulation and check before opening5. Apply eye drop after welding is over to relieve the strain on eyes.

There are following two types of arc welding

AC welding

It uses AC source. Its initial cost is low. It operates quietly. Since there are practically no moving

parts, its maintenance cost is also low. Arc blow is not encountered but it cant be operated in

those places where there is no power supply.

DC welding

It uses DC power supply. The voltage range is around 45 volts. Both the current and voltage may

be changed in this machine. It creates arc blow, besides, it is noisy too.


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Figure: Arc welding setup: (1) switch box (2) secondary terminals (3) welding machine (4)

current reading scale (5) current regulating hand wheel (6) leather apron (7) leather hand gloves(8) protective glasses strap (9) electrode holder (10) hand shield (11) Channel for cable

protection (12) welding cable (13) chipping hammer (14) wire brush (15) earth clamp (16)

welding table (metallic) and (17) job.


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ASSIGNMENT-3

Objective: To study the Tungsten Inert Gas welding (TIG).

Electric arc is struckbetween non consumable tungsten electrode and the work piece andshielding is provided by argon, helium or CO2 or mixture of any two as shown in figure. Filler

rod may or may not be used (as in close fit joints). It is an all position welding technique.

Electrode used in TIG welding are non-consumable type of tungsten electrode which varies in

size from 0.13 to 9.5 mm and are of two main types: (a) Thoriated or (b) Zirconiated tungsten

electrode which gives better electron emission, easy start of arc, cool running, better arc stability

and restart of arc even at 15A. Pure tungsten electrode is seldom used.

Figure: Tungsten Inert Gas (TIG) welding


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Arc initiation by (a) torch started or by (b) high frequency AC power. Both DC and AC are used.

Dc with straight polarity (DCSP) is more common for longer life of electrode. DCRP is used for

welding aluminum, magnesium, nickel, molybdenum and copper where oxides are removed by

blasting action of positive ions of shielding gas striking work piece. In general, AC power source

is best for TIG welding of non ferrous alloys. For ferrous alloy DCSP is better for reducing

volumetric loss from tungsten electrodes.

TIG was originally developed for welding magnesium and its alloy but it is now used for many

alloys, particularly adopted to welding dissimilar metals and for hard facing worn or damage die.

It is used for welding thin metal work piece up to 6 mm thickness. TIG welds are cleaned,

smooth and do not need grinding and finishing. The process is however, slow in operation.


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ASSIGNMENT-4

Objective: To study the Metal Inert Gas welding (MIG)

Arc is established between a continuously fed consumable metal electrode or wire and the work

piece as shown in figure. Arc is shielded by inert gas like argon, helium, carbon dioxide or

mixture of these gases. Electrode wire is fed from a coil rotated with a constant speed motor and

the arc length is maintained constant by using (a) self adjusted arc for semi automatic plants or

(b) self controlled arc in fully automatic MIG plants.

.

Figure Metal Inert Gas (MIG) welding

MIG welding employs power source with flat or dropping characteristics mostly DC generator or

AC transformers with rectifier is used. AC is not generally preferred because of unequal/burn off

rates in positive and negative half cycle. DCRP (Direct current reverse polarity) gives deeper

penetration and is used for thicker job. Shielding gases used include argon, helium, carbon


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dioxide or nitrogen and the mixture thereof. Argon or helium is used for welding of Aluminum,

Magnesium, and Copper and Carbon dioxide for mild Steel and nitrogen for copper. Argon +

CO2 are used for welding Mild steel, low alloy steel and stainless steels, whereas as a mixture of

argon, helium and CO2 is used for welding austenitic stainless steel.

MIG, with short circuiting metal transfer mode is popular for welding thin sheets and sections

(less than 6 mm) of carbon steels, low alloy steels, stainless steels, aluminum, magnesium,

copper, nickel and their alloy and also for welding tool steel and die steel.

MIG with globular transfer mode gives deeper penetration and find applications in aircraft,

pressure vessels and ship building industries


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ASSIGNMENT-5

Objective: To study tools and equipments of the welding.

Equipments and Tools

1. Protective equipmentsA.Exhaust fan: For maintaining good ventilation in the welding booth or chamber an

exhaust fan must be installed. The booth is always full of fumes from flux coating.

B.Eye Shield: To protect the eyes from the UV and IR rays, an eye shield is essentialfor a welder. The shield is made of fiber and contains dark colored glasses for looking

at the arc joint. In case of gas welding, goggles are used to protect from high intensity

light and heat rays, which are harmful to naked eyes.

C.Hand gloves: hand gloves are made of leathers and must be put on to protect handsfrom intense heat of the arc. In this way the hand gloves enables to hold the eyes

shield in one hand the electrode holder in other hand.

D.Apron: A leather apron must be worn while welding to protect from splatter.

2. Operating equipmentsA. Oxygen cylinder: Cylinder is made up of steel in capacity range 2.25 to 6.3 mm 3. The

cylinders filled with oxygen at about 150 kg/cm3

at 210C. A safety valve is also

provided on it. The cylinder can be opened or closed by a wheel which operates a

valve. A protector cap is provided on the top of a cylinder to safeguard the valve. The

color of cylinder is black.

B.Acetylene cylinder: Acetylene cylinder is also made up of steel. Gas is filled at apressure of 18-20 kg/cm

3. The capacity of the cylinder is about 10 m

3. Regulator

valve and safety valve are mounted on cylinder. Safety plugs are also provided on thebottom of the cylinder, the acetylene is dissolved in acetone. The color of cylinder is

red or maroon.

C.Regulator: regulator is used to control the flow of gasses from high pressure cylinder.


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D. The torch: Torch is a device used to mix acetylene and oxygen in the correctproportion and the mixture flows to the tip of the torch. There are two types of

torches

Low pressure or injector torches Medium pressure or equal pressure torches

E. Work bench: It provides good support to the work being welded. It is essentiallyfabricated from steel section with top prepared from fire clay bricks. It also forms one

of the electrodes during welding.

F. Cables: A thickly insulated and flexible cable is always preferred. One cable isneeded for metal electrode and the other is used for grounding.

G.Electrode holder: It is clamping device for holding electrode and the holder is usedfor firmly holding the electrode which is done with the aid of a firm holding device

and a quick releasing device for the electrode. It has provisions for holding electrodes

of different sizes.

H.Electrodes: The electrodes are two types Coated electrodes Bare electrodes

Coated electrodes are generally applied in arc welding processes. A metallic core iscoated with some suitable material. The material used for core is mild steel, nickel

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

holding.. Bare electrodes produce the welding of poor quality. These are cheaper than

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

welding.

3. Miscellaneous equipmentsA. Chipping hammerB. Wire brushC.Light ball pin hammerD. Pair of tongs


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E. PliersF. Flexible scale

Figure: Miscellaneous equipments


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Welding joints

There are several types of welding joints as mentioned below

A.Butt joint: In this type of join, the edges of the metal to be joint should be so madethat it gives a little shape of V at the place of joint. Now on welding the V or U

shape structure is filled up giving rise to a strong joint as shown in figure.

B.Lap joint: This type of joint is used in joining two overlapping plates so that thecorner of each plate is jointed with the surface of the plate. Common types of lap

joints are single lap, double lap or offset lap joint. Single welded lap joint do not

develop full strength as compare to double welded lap.

C. Corner joint: Here metal pieces are placed perpendicular to each other at one corner.Now the welding is done in the corner. Such joints are made in frames, steel boxes,

etc.

D. T-joint: In this type of joint, the metal pieces are placed in such a manner that theyform the shape of T. In other words the angle between surfaces is kept 90

0as shown

in figure.

E. Edge joint: In this joint two parallel plates are welded edge to edge.F. Plug joint: Plug joint is used in holes instead of rivets and bolts.

Figure: Different types of welding joints


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Advantages of oxy acetylene welding

1. It is easy to learn2. OA equipment can also be used to flame cut large pieces of material.3. Total welding cost is less.4. Wide varieties of electrodes are available.5. The welding equipment is simple, less costly and portable.6. Welding can be carried out in any position with highest weld qualities.

Disadvantages of oxy acetylene welding

1. OA weld lines are much rougher in appearance than other kinds of welds, and requiremore finishing if neatness is required.

2. OA welds have large heat affected zones (areas around the weld line that have had theirmechanical properties adversely affected by the welding process).

3. Welding control is difficult as compare to MIG welding.4. Because of flux coating chances of slag entrapment are more.


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ASSIGNMENT-6

Objective: To make T-filler joint on the given work pieces as per drawing

Raw material: Two pieces of Mild steel (MS) flat 60305 mm

Tools and equipment: File, scale, wire brush, hammer, gas lighter, welding torch, oxygen and

acetylene cylinder with nose pipe and fitting regulator, welding goggles, apron etc.

Procedure:

1. Assemble all the materials needed to make the weld. This includes parts, OA equipment,fixturing, tools, safety mask, gloves and filler rod.

2. Clean the parts to be welded to remove any oil, rust, or other contaminants. Use a wirebrush if needed to remove rust.

3. Assemble and fixture the parts in place-the parts need to be stable for good weld line.Ceramic bricks, vise grip, pliers, and clamps are available in a file cabinet in the weld

room for fixturing.

4. Wear all the protective clothes.5. Select the nozzle you plan to use for welding. Turn on the welding machine to get flame.

Hold the nozzle in one hand to weld it.

60

30

5


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6. Now set the work pieces in correct position as shown in the figure and then welding to becarried out through out the length.

7.

After completing the job, put it in water to get cool and inspect it and replace allequipment


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ASSIGNMENT-7

Objective: To make a double transverse lap joint as per drawing.

Raw material: Two pieces of Mild steel (MS) flat 60405 mm

Tools and equipment: File, scale, wire brush, hammer, gas lighter, welding torch, oxygen and

acetylene cylinder with nose pipe and fitting regulator, welding goggles, apron etc.

Procedure:

1. Assemble all the materials needed to make the weld. This includes parts, AW equipment,fixturing, tools, safety mask, gloves and filler rod.

2. Clean the parts to be welded to remove any oil, rust, or other contaminants. Use a wirebrush if needed to remove rust.

3. Cut the required size of piece from Mild Steel flat.4. Place the two pieces in proper position and the welding table for lap joint.5. Wear all the protective clothes.6. Hold the electrode holder you plan to use welding.7. Turn on the source, and touch the electrode on the sample work piece to get arc and weld

the specimen.

8. After completing the job, remove the slag from the welding joint by chipping hammerand clean with wire brush.


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Precautions:

1. Do not see the produced arc by naked eyes.2. Use goggles at the time of chipping.3. The joint of the cables should not be loose.4. Make proper arc for welding carefully.


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Sheet Metal Shop


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ASSIGNMENT-1

Objective: To study the sheet metal shop.

Brief introduction of sheet metal shop

The sheet metal shop is very important for every engineering concern. It deals with the working

of metal sheets. It requires a through knowledge of projective geometry particularly the

development of surface, because the laying out of pattern and cutting of metal sheets to correct

size and shape entirely depend upon the knowledge of workman. The various operations

performed in a sheet metal shop are cutting, shearing, bending etc.

Safety precautions in sheet metal shop

1. Be very careful and attentive while working in sheet metal shop as one is involved insharp tools.

2. Avoid putting or filling the cut portion by hand while cutting with snip.3. Use hand leather gloves while handling heavy sheets.4. Do not use tools with blunt cutting edge.5. Do not cut metal heavier than capacity of snip.6. The safest and most efficient method of testing a soldering to the solder being to flow the

correct temperature has been achieved.

7. Keep work area free from obstruction.

Types of sheet metal

1. Mild Steel sheets: It is known as black iron sheet susceptible to rust and corrosion due touncoating protected by painting and is mostly used for water tank, fabrication work, and

agricultural implements.2. Stainless Steel sheets: It has silver-crome appearance. It is an alloy of high grade steel

with chromium, nickel and traces of manganese, phosphorous, etc. It can be easily

welded. It is used in canneries, dairies, food processing plants. It is very costly as

compare to GI sheets.


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3. Galvanized Iron sheets: It is soft steel sheet coated with zinc. Sheets have corrosionresistance due to zinc coating. Welding is not easy. These are used for making AC duct,

roof flashing, boxes buckets, cooler etc.

4. Tin plate: Steel or iron coated with tin is called tin sheets. It is used for making foodcontainer, dairy equipment, and furnace fittings. These are now replaced by stainless

steel, aluminum and other materials.

Tools and equipments

1. Bench Vice: It is a suitable tool for gripping different tools such as a straight edge anvil,etc. It consists of a cast iron steel body; carrying a fixed jaw, a moveable jaw and threaded

screw which is made to pass through the moveable jaw at outer end. It runs through the

fixed nut longitudinally under the moveable jaw. The work is held between jaws and kept

tightened.

Figure: Bench Vice


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2. Measuring and marking ToolsA. Steel rule: Overall dimensions, length and breadth of required piece of steel are

marked with the help of a steel rule. The rule is calibrated.

Figure: Steel rule

B. Scriber: It is used for marking sheet pieces dimensions. It is steel wire of 200 mmlength with one end sharp and hardened to make or draw lines on metal sheet.

Figure: scriber

C.Pliers: It is used for holding small articles which are difficult to be held by hand.

Figure: Pliers


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D. Steel square: It is a L-shaped piece of hardened steel. It is used to make squarecorners. It is also used for checking and marking right angles.

Figure: Steel square

E. Divider: It is used to scribe arcs and circles on metallic sheets and to divide lines, arcsor circle into equal parts.

Figure: Divider

F. Punches: The following punches of tool steel are used in sheet metal shop Prick punch: Used for marking indentation marks for locating the center

position or dividers, having included angle of 300

Centre punch: Used for marking the location of the point and the centre ofholes to be drilled. It tapered point is grounded to 90

0included angle.


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Figure: Punches

3. Cutting ToolsA. Straight Snip: For cutting along straight lines, straight snip is used whose blades are

straight. It is used to cut 22 SWG or lighter. To cut sheets of greater thicker lever

shearing machine is used.

B.Bent snip: Blades are curved back from the cutting edge which allows the metal toslide over top blades.

C.Hollow punch: When circular holes are to be cut in the sheet then the hollow punchis used for thin sheets. The sheet should be placed over the wood of thick block of

lead to avoid chipping of edges of the punch.

D. Chisel: These are generally used in sheet metal shop for cutting sheets, rivet andbolts.

Figure: Various types of snips

4. Striking ToolsA.Hammer: The hammers are used for striking work, bending of sheets, smoothing of

sheets, locking of joints, etc. For these operations the following hammer are generally

used.

Ball peen hammer: Has a round, a slightly curved face and a roundhead.


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Setting hammer: Has a square, flat face and a tapered peen withbeveled end.

Raising hammer: Has a oblong flat face with corners slightly roundedoff.

Riveting hammer: Has a square, slightly curved face with bevelededges to prevent the head of the hammer to marking the metal.

B.Mallet: Mallet is made good gravity wood or plastic is used whenever light force isrequired. Mainly used for smoothing of sheets.

Figure: Special types of hammers and hollowing block

5. Supporting ToolsA. Stakes: Stakes are used to support sheets in bending, seaming, forming, riveting,

punching etc. Some commonly used stakes are

Hand stake: It is handy stake with a flat face, two straight edges oneconcave edge and other convex edge and is used for pressing the inner

sides of straight joint.

Half round stake: It is used for pressing round seam joint on inner side.


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Taper stake: It is used for rounding of tapering jobs such as conicaljobs.

Grooving stake: It is made up of forged steel and is used to makegrooves of different sizes. Grooves are made to impart strength.

Figure: Different types of stakes used for bending sheet metals

B.Anvil: It is made of cast steel mounted on CI stand or provided with a handle. The topworking or cutting face is made of tough steel. Square and round holes are provided

for bending operation.

Specification of sheet metal

The sheets are specified by standard gauge numbers. Each gauge designates a definite thickness.

The gauge number can be identified by Standard Wire Gauge or SWG.


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The following table shows gauge numbers and their corresponding thickness of sheet. The larger

is the gauge number, the lesser is the thickness and vice versa.

Table: Gauge numbers and corresponding thickness

SWG 10 12 14 16 18 20 22 24 26 30

Thickness (mm) 3.2 2.6 2.0 1.6 1.2 0.9 0.7 0.6 0.4 0.3

Sheet Metal Joints

1. Lap joint2. Seam joint3. Locked seam joint4. Hem joint5. Wired edge joint6. Cup or circular joint7. Flanged joint8. Angular joint9. Cap joint

Figure: Some of the common types of sheet metal joints


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Sheet Metal Operations

1. Measuring and Marking2. Laying out3. Hand cutting and shearing4. Hand forming5. Nibbling6. Circle cutting7. Piercing and blanking8. Edge forming and wiring9. Joint making10.Bending11.DrawingA. Measuring and Marking: The required size of the component may be smaller than the

standard size is available in market. So, a standard size is to be cut. A little allowance for

cutting is to be added to the required overall sizes so that the cut pieces are not under

size.

The procedure of marking various lines are:

1. Marking a straight line2. Marking circles and arc3. Marking irregular curves4. Marking indentation marks

B. Laying out: Laying out means the operation of scribbling the development of the surfaceof component on the sheet or sheet blank, together with the added allowance for

overlapping, bending, hammering, etc. which when cut out of the blank and folded and

joined will give the required components.

C. Hand cutting and Shearing: The sheet metal is cut by chisel and hammer manually. Theterm shearing is stand for cutting the sheet metal by two parallel cutting edges moving in

opposite direction. This can be done either manually by using hand shear or snips or by


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means of machine called shears. The operation is known as machine shearing or

mechanical shearing.

D. Hand forming: The term metal forming stands for shaping and/or bending of sheet metalin three dimensions in order to give it desire shape and size of the final product. For

these, the metal is either is required to be starched or shrunk in all direction or may need

a combination of both.

E. Nibbling: Nibbling is a process of continuous cutting along a contour, which may be astraight line or irregular profile. The machine used in this operation is known as nibblers,

which are portable size shearing machine.

F. Circle cutting: It is the operation of cutting circular blank or curved contour with thehelp of a circle cutting machine. It is also a continuous cutting operation.

G. Piercing and Blanking: Piercing is basically a hole punching operation while blanking isan operation of cutting out a blank. In both the cases blank will be produced, but in the

former cases obtaining a blank is not the objective. It is hole of a desire size which is the

objective and the blank produced may not be used further. However, in the latter

operation the production of a blank of the desired size is the main objective which is a

useful part for further processing.

H. Edge forming and Wiring: The edges of sheet metal product are form to ensure safetyof hands, while handling these products and to provide stiffness to the products in order

that they will retain shape during handling i.e., will not get buckled by simple hand or

finger pressure during handling.

I. Joint making: For joining large size parts, especially when they are to be fastened toother metallic or large non-metallic bodies, screwed fasteners can be used. Sheet metal

parts can also be joined by riveting, welding, brazing and adhesives.

J. Bending: It may be done over stakes, blocks of wood or edge of a bench top.1. A line is marked with scriber where the metal is to be bent. In order to make

right angled bend the sheet is placed on the bench so that the line is even with

the edges of the bench. Now bend is made by striking metal with a mallet.


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2. In order to make curve bend, the edges of the wooden block is planed to havedesired curvature the wooden block is placed even with the edges of the

bench. Now strike the metal with a mallet, bent the sheet over the curved

edges of the block.

K. Drawing: The walled hollow shapes are produced in sheet metal through the drawingoperation. The operation is carried out with the help of die and a punch on a suitable

press. If the drawn length of the component is less than its width or diameter it is called

shallow drawing. When the drawn length is more than the width, the operation is known

as deep drawing.

ASSIGNMENT-2


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Aim: To make a cylinder from the given sheet metal as per drawing.

Apparatus

1. Metal sheet, 2. Mallet, 3. Steel rule, 4. Scriber, 5. Straight Snip, 6. Stakes, 7. Flattener.Material required

Galvanized iron (GI) sheet with available SWG is required.

Procedure

1. The given sheet metal is checked for its dimensions using steel rule.2. Then the sheet is leveled on the leveling plate using a mallet.3. Any suitable dimensions are chosen according to the figure shown below for cylinder

diameter and height.

4. Remove the unwanted material using straight snip.5. Then the folding is done in such a way that to get the cylinder shape.6. Both the closing edges are joined together by the seaming process.

ASSIGNMENT-3

D

H H

D + material required for folding


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Aim: To make a cylindrical container from the given sheet metal using development of surface

method

Apparatus

1. Metal sheet, 2. Mallet, 3. Steel rule, 4. Scriber, 5. Straight Snip, 6. Stakes, 7. Flattener, 8.Plain paper

Material required


Procedure

1. The given sheet metal is checked for its dimensions using steel rule.2. Then the sheet is leveled on the leveling plate using a mallet.3. Any suitable dimensions are chosen according to the figure shown below for cylinder

diameter (D) and height (H) and mark out development of the sheet by the parallel line

development as per dimensions.

4. Remove the unwanted material using straight snip.5. Then the folding is done in such a way that to get the cylinder shape.6. Both the closing edges are joined together by the seaming process.7. Finally, the bottom of the cylinder is closed with round portion of the sheet metal of

diameter (D) and using suitable joint to join with the cylinder.

ASSIGNMENT-4

D

H

D + material required for folding

H

D


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Aim: To make a cone from the given sheet metal using development of surface method.

Apparatus

1. Metal sheet, 2. Mallet, 3. Steel rule, 4. Scriber, 5. Snips, 6. Stakes, 7. Flattener, 8. Divider,9. Protractor, 10. Ball peen hammer, 11. Plain paper, 12. Groover.

Material required


Procedure

1. The given sheet metal is checked for its dimensions using steel rule.2. The required shape is first produced in paper which is used for producing the exact size

on the sheet metal.3. The slanting angle of the sector is calculated by using the formula 3600(R/L) where, R is

a base circle radius and L is the slant height.4. The required shape is cut from the paper.5. Then the exact shape of the paper cut is placed on the GI sheet, so that the same size can

be produced on the sheet metal using the scriber.6. Then the sheet is folded using the funnel stake to make a cone shape.7. Then edges of the folded portion are joined together by seaming process using a groover.

ASSIGNMENT-5

100

R=50

10

10

=3600(R/L)

= 3600(50/112)

= 1610

10

L

1125010022=+=L


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Aim: To make an open end square box as per drawing.

Raw material: GI sheet 21 SWG 140100 mm

Tools required: Snip 12, scriber 6, scale 12, mallet, V-block, hatched stake, etc.Procedure

(a) Make, i.e. draw the development of the given job on the sheet with all allowances marked on

it.

(b) After the approval of development, trace it on metal sheet using scriber with allowances.

(c) Cut the sheet using shear.

(d) Mark the six notches as shown in development attached on adjacent page using shear.

(e) Bent the allowances at 90" on proper side using stake and mallet.

(f)Bent the sheet at marked places to get four sides of the box.

(g) Prepare the seam to lock the sides

(h) Prepare single hem on top sides.

(i) Bent the bottom sides at 90' outwards.

(j) Cut out metal sheet for base of the box using development, shear and scriber.

(k)Bent the outer allowances at 90" and then further by 60".

(1) Place the four sided hollow box on the base and prepare double seam using the allowances

provided for it.

(m) Check for any sharp edges and dents.

(n) We get the required box.

Result

(a) The box of sheet metal has been prepared having given dimensions.

(b) Precautions and Sources of Errors.

(c) Take the proper allowances, low value of allowances may lead to poor locks of metal while

high value of allowances leads to metal wastage.

(d) Any bleeding caused by cut from metal should be immediately treated.


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(e) Precaution should be taken while hammering to avoid dent formation on the metal surface.


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Soldering Shop

ASSIGNMENT-1


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Objective: To study the soldering and de-soldering process

Soldering: Soldering is the process of joining similar or dissimilar metals by means of a

fusible filler metal or alloy called solder applied in the molten stage.

The molting temperature of the soft solder is about 3500

C to 3700

C and that of the hard solder is

about 6000

C to 9000

C. But the melting temperature of the solder is always lower than the

melting temperature of joining metals.

It is the process of joining electrical parts together to form an electrical connection using a

molten mixture of lead and tin (solder) with a soldering iron.

Soldering process:First the joining surfaces are cleaned thoroughly. The joining portions of

the metals are positioned to get the required type of joint. The flux is then applied over thejoining portions. The soldering portion of surface is heated to a temperature just above the

melting temperature of solder.

When the solder carrying the electric power supply is touched on the heated surface, the solder

melts and flows into the cavities of the joining surfaces completely and gets solidified. Hence the

required soldering is done.

Soldering accessories:

1. Soldering iron: A soldering iron supplies sufficient heat to melt solder by heat transfer,when the iron tip is applied to a connection to be soldered. Soldering irons are available

in different temperature ranges.

2. Solder: Solder is one of the most widely used alloys in soldering process. It is an alloy oflow melting metals like tin, lead, cadmium, bismuth, silver etc. The most commonly used

alloy combination is 63% tin and 37% lead. The solders are available in diameters of

0.038-0.318 cm.

3. Soldering flux: Soldering flux is a resin, specially designed to flow over the job andprevents contact with the atmosphere. Metals, particularly copper when heated, tend to

oxidizing and prevent the alloying or good electrical bond between the copper and the

solder. Applying flux can stop this oxidization process.


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Figure: Soldering Iron

Types of soldering iron:

1. Temperature-controlled soldering iron: It uses thermostatic control which maintains itstemperature at a fixed level.

Figure: Temperature-controlled Soldering Iron

2. Soldering iron with soldering gun: It runs at 100 W, is not suitable for microelectronicsand components.


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Figure: Soldering with soldering gun

3. Gas-powered soldering iron: It uses butane instead of electrical supply and can be usedwhere electrical supply is not available.

Safety precautions while soldering:

Dos Donts

1. All parts of the board must be cleanedincluding the work table.

1. Dont use the table, which is already used

for soldering and not cleaned. It may lead to

short circuit.

2. Clean the hot soldering tip with a dampsponge frequently

2. Do not over heat the tip

3. Apply sufficient solder 3. Do not use excess solder. It may lead toshort circuit with near by components

4. Use an iron stand for safety 4. Do not pull the iron on the table, use asoldering iron stand

5. The mains where the iron is connectedshould be earthed properly

5. Do not move the soldering iron until the

solder has cooled

6. Always wore protective clothing likegloves, apron, boots, etc.


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Checking the continuity for electronic circuit

A continuity tester is used for checking circuit board tracks, wires and connections for

continuity. With the use of tester, we can confirm whether the electricity can flow through a

cord, wire and metallic track. Electricity needs a continuous path or circuit in order to flow. To

ensure this, the continuity tester is used.

Figure: Circuit diagram for a continuity tester

Components:The following are the components of a continuity tester:

9 V battery Red LED 390 resistor Crocodile clips

While checking the continuity, the LED lights brightly, dimly or not at all, according to the

resistance of the item. When the tester is not in use the 9 V batteries should be unclipped or the

crocodile clips are attached to a piece of plastic to prevent them touching. An ON/OFF switch

can be added in the red wire from the battery clip.

Working procedure: The continuity tester sends electricity from an internal battery

through one side of the item and down the wires. If the LED gets electrical current, the other side

lights up confirming that the path is good.


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While using of a continuity tester, first disconnect the item being tested from the power source.

Make sure switches on the device are ON.

Attach the crocodile clip to one side of the item. Now touch the tip of the tester to the other side.

If there is continuity, the LED will light up. Connect a crocodile clip on each side of the

suspected fault.

Assembling Electronic Components on PCB

PCB (Printed Circuit Board): A printed circuit board is the base plate over which all electronic

components are mounted with soldered condition. The interconnection between two components

is made by the metallic tracks.

Figure: Sample for PCB diagramFabrication and assembling electronic components on PCB: There are many types of PCBs out

of which the single-sided PCB is taken for our discussion. The single-sided PCB fabrication

consists of the following steps:

PCB pattern designing Pattern transformation on to PCB Developing PCB Cleaning of PCB Finishing and assembly components

PCB pattern designing: The design factors should be considered for all components,

converted into PCB tracks of appropriate shape and size. While designing the PCB, the following

factors should be considered.


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Component position on the board The grounding system should be properly connected for good ground conduction.

There should not be any conductive loop.

To withstand a possible short circuit in a system. Jumpers should be avoidable.

After these design considerations with the help of self adhesive pads and lines, the master pattern

of PCB is made on a thick sheet with a reverse carbon placed underneath to take the mirror

image on the reverse side of sheet.

Pattern transformation onto PCB:Before doing the pattern transformation onto the PCB,

the copper side of the PCB should be thoroughly cleaned with the help of alcoholic spirit or

petrol, and must be made free from dust and contaminants.

Base laminate is a board of insulating material, which is given a coating of a conducting material

that is copper and alluminium. For a simple circuit, the phenolic board is preferred.

Developing PCB: This process removes all the excessive copper from the base laminate.

After this, only the printed pattern is left behind. A solution of 750

C hot tap water and ferric

chloride is used to remove the excess copper. The above said solution is thoroughly stirred and to

speed up the process, a few drops of HCl may be added.

The board, with its copper side facing upwards, is placed in the above prepared solution. It takes

nearly one hour to complete the process.

Cleaning of PCB:After the developing process, the board should be washed under running

water and should be dried. Now we can see the printed pattern very clearly. If any unwanted

lines are thereby means or using petrol or alcohol the paint or inkline is removed from the PCB.

Finishing and assembling the components:For finishing the board should be fully dried.

Now using high speed drilling, the holes are drilled according to the component size and shape.

After preparing PCB, we have to assemble the electronic components to make the circuit work.

The components are soldered in the correct position and the circuit is tested with a continuity

tester. Now the circuit is ready to us


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Steps followed in soldering:

1. Selection of the bit: According to the work, it should be small in size and can give goodcontact with the surface.

2. Cleaning the bit and surface to be soldered: Clean the bit frequently with a wire brush oremery paper or a special sponge pad. Surface should be cleaned completely and flux

should be applied.

3. Tinning the soldering iron bit: Coat the soldering iron on the surface of the tip whichalso looks bright silver color. Replace the tip if it is old or corroded.

4. Applying flux: Flux may be applied to the surface to be soldered.5. Applying solder: With the use of proper soldering bit, solder should be applied. The

quantity depends on the size of the surface to be soldered.

Figure: Shapes of soldering bits


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Procedure of soldering:

1. Clean the bit and switch on the supply. When hot, tin the soldering irons tip with a smallamount of solder. A clean, well-tinned tip can do the job properly. Wipe the terminal ofcomponents.

2. Bend the components leads to fit the holes on the boards. Do not bend over.3. Heat the joint by placing the soldering irons tip against the component leads and circuit

pad and touch the solder to the lead pad. Only after the flow of solder, remove the lead

and hold the tip in place for one second and remove it without moving the part or board

and let the joint cool.

4. Trim the excess component lead with the side cutter, no need to trim the short leads.5. Inspect the joints, bends and leads, and pad smoothly together and have a bright finish.6. After finishing all soldering, clean the board to remove any flux residue.

Figure: Steps in soldering

Desoldering:When an electronic component is to be removed from a circuit, Desoldering is

needed.

Procedure of desoldering:

1. Hold the terminal which is to be unsoldered by nose pliers.2. Place the tip of the soldering iron on the joint until the solder is melted and remove the

terminal

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