Chapter 1 Introduction to Workshop

Safety Regulations Chapter Outline

1.1 Introduction 1.2 General workshop safety rules 1.3 Personal Protective Equipment (PPE) 1.4 Fire Safety

Learning outcome When you complete this chapter you should be able to:

1. Acquire knowledge about safety precautions while working in workshop.

2. Use the protective wear. 3. Classify and be able to understand the safety

equipment : e.g fire extinguisher.

1.1 : INTRODUCTION Before you can use equipment and machines or attempt practical work in a workshop you must understand basic safety rules. These rules will help keep you and others safe in the workshop.

Free access to the workshop areas is restricted to authorised personnel only. No other person may enter the workshop without permission.

Always listen carefully to the workshop supervisor and follow instructions. Safety in a machine shop may be divided into two broad categories:

Those practices that will prevent injury to workers. Those practices that will prevent damage to machines and equipment. Too

often damaged equipment results in personal injuries.

1.2 : GENERAL WORKSHOP SAFETY RULE Any person working in the mechanical workshop must familiarise themselves

with equipments, tools, etc used. Personal Protective Equipment (PPE) is provided and must be used where

necessary. Lab. coats, safety glasses/goggles and safety shoes are to be used as the work dictates.

Report any defective equipment to the workshop supervisor. Do not run in the workshop, you could bump into another pupil and cause an

accident. Always be patient, never rush in the workshop. The gangway through the workshop must be kept clear. Any oil spillage, grease

etc. must be cleaned up immediately. Tools/equipment must be cleaned after use. Any materials, tools or equipment

used must be tidied away. Precision measuring equipment, drills, etc. must be replaced in their appropriate

cabinets after each working day. When carrying tools, sharp edges should be pointed downwards. Tools and equipment must not be removed from the workshop without permission

from the workshop supervisor. In the event of a fire, leave the building immediately and proceed to the assembly

point. All unusual incidents (cuts. burns, direct chemical exposure, etc.) and

emergencies whether personal injury resulted or not, must be reported to the workshop supervisor. The person witnessing the occurrence, the person directly involved and the supervisor workshop may fill out the report. The report must be signed by the person reporting the incident.

Safety rules for MACHINE used in the workshop :

When learning how to use a machine, listen very carefully to all the instructions given by the workshop supervisor. Ask questions, especially if you do not fully understand.

Use the appropriate machine for the work to be done.

When working with machine tools or other equipment with rotating spindles, jewellery, loose clothes etc. are prohibited and long hair must be completely covered.

No machine may be used or work undertaken unless the workshop supervisor is satisfied that the person is capable of doing so safely. If equipment is fitted with guards these must be used. Equipment should never be used if the safety guards have been removed.

1.3 : PERSONAL PROTECTIVE EQUIPMENT (PPE) For the operation of the work, PPE must be worn in the workshop. It is the individuals responsibility to maintain PPE in good condition. PPE is used to increase individual safety while performing potentially hazardous tasks.

Eye Protection Where a potential for flying particles or any damage to the eyes exists, eye protection must be worn by all persons who may be affected. Face shields or goggles must be worn when operating a grinding wheel. Examples of operation requiring the use of eye protection include chipping, impact drilling, welding or grinding.

Hearing protection Damage to hearing can occur from both impact noise and exposure to lower intensity steady state noise over long period of time. Both hand and power tools are capable of producing damage to hearing. It is recommended that hearing protection must be worn if average noise levels exceed 85BA (decibels) over an 8 hour period. Dust Masks Make sure that the appropriate masks are worn in dusty conditions. Foot wear Make sure that appropriate solid covered footwear is worn to protect feet from falling objects. NO slippers are allowed!!! Gloves Wear the appropriate work gloves as needed to protect your hands from injuries caused by handling sharp or jagged objects, wood, or similar hazard-producing materials.

Laboratory coats Lab coats provide additional protection and it is recommended that they must be worn at all times in a workshop. Body protection Loose fitting clothing, neckties, rings, bracelets, or other apparel that may become entangled in moving machinery will not be worn by machine operators.

1.4 : FIRE SAFETY Workshop must be equipped with a fire extinguisher. In selecting the appropriate extinguishers, the type of combustible material must

be considered. Fire extinguishers Class A : Combustible materials such as wood, cloth, paper, rubber and many plastic (RED). Class B : Flammable liquid and gases, oils, greases, tars, oil-base paints, lacquers and some plastics (LIGHT YELLOW). Class C : Involve Class A and/or B materials in the presence of live electrical equipment, motors, switches and wires (BLACK/GREEN). Class D : Combustible materials such as Magnesium, Titanium, Sodium, Potassium, Zirconium, Lithium and any other finely-divided metals which are oxidizable (LIGHT BLUE). Fire prevention precautious : Know the location and the operation of every fire extinguisher in the workshop. Know the location of the nearest fire exit from the building. Know the location of the nearest fire-alarm box and its operating procedure. When using a welding or cutting torch, be sure to direct the sparks away from any

combustible material. Always dispose of oily rags in proper metal containers. Be sure of the proper procedure before lighting a gas furnace. Storage of Flammables Flammable liquids shall be handled and stored away from sources of heat, spark,or open flame.

Chapter 2.0: Introduction to Bench Fitting

Chapter Outline2.1 Introduction to bench fitting2.2 Overall safety in bench fitting2.3 Application of hand tools

a) Fileb) Hacksawc) Fixing tools

2.4 Application of layout tools a) Steel ruleb) Caliperc) Scriberd) Try squaree) Surface gauge

2.5 Application of simple manual machines a) Drillingb) Tapping

Learning outcomeWhen you complete this chapter, you should be able to:

1. Understand common operations in bench fitting workshop

2. Describe various types of hand tools used.3. Explain the application of various hand tools. 4. Understand the safety procedure/practice in bench

fitting workshop

2.1 INTRODUCTION TO BENCH FITTINGBench Fitting is an operation where hand tool are use (which are held by hand to perform the operation and not required any machine).

Hand tools are used to remove small amounts of material, usually from small areas of the workpiece.

Bench fitting usually conducted due to :i. No machine is availableii. The workpiece is too large to go on a machineiii. The shape is too complicated or simply that it would be too expensive to set up a

machine to do work

Since the use of hand tools is physically tiring, it is important that the amount of material to be removed by hand is kept to an absolute minimum and thus that the correct tool is chosen for the task.

Common bench fitting operation1. Marking2. Sawing3. Filing4. Scrapping5. Chipping

6. Drilling7. Threading8. etc

COMMON HAND TOOL1. Hammer2. Hacksaw3. Files4. Vices5. V-block6. C-Clamp7. Try Square8. Scribers9. Punch

10. Scrappers11. Chisels12. Trammel13. Screw driver14. Drills15. Spanner16. Pliers17. Tap

2.2 OVERALL SAFETY IN BENCH FITTING1. Dont used pliers for cutting hardened steel wire2. Never used bent, dented, crack, chipped or worn-out chisel3. Used right tool for job4. Keep tool at their proper place5. Never play with tools6. Dont used pipe or other improvised leverage extensions on handles7. Plastic handles are only for comfort and dont act as insulation8. Always used eye protection equipment9. Ensure that files have handles10. Dont put sharp or pointed tools in your pocket

2.3 APPLICATIONS OF HAND TOOLS

2.3a FileA file is a metalworking and woodworking tool used to cut fine amounts of material from a workpiece. Prior to the industrialization of machining and the development of interchangeable parts, filing is much more important in the construction of mechanisms. component parts were roughly shaped by forging, casting or machining. These components were then individually hand-fit for assembly by careful and deliberate filing.

Files come in a wide variety of sizes, shapes, cuts, and tooth configurations. The cross-section of a file can be flat, round, half-round, triangular, square, knife edge or of a more specialized shape.

File featuresMost files are made from high carbon steel where the Length has been hardened and tempered, but the Tang has been left soft. Files are manufactured in a variety of shapes and sizes. They are known either by their cross-section, the general shape, or by their particular use. Which file you use is dependent on the type of work you are doing and the material you are using. Files are used to square ends, file rounded corners, remove burrs from metal, straighten uneven edges, file holes and slots, smooth rough edges, etc. Files have three distinguishing features, and are classified by these features:

Length (measured without the Tang) Cross-section or Shape Grade of Cut

Figure 2.1 : File features

The Point is sometimes called the Top. The Shoulder can also be called the Heel. Files have cutting teeth on both Faces. In the case of the Hand File, only one of

the Edges has teeth on it and the other is smooth, and called the Safe Edge. The Safe Edge allows you to rub the File up against a surface without wearing any material away.

Always make sure that the Handle is securely attached to the Tang, otherwise you could give yourself a nasty injury.

The Length of the File, (measured in millimeters), is measured from the Shoulder to the Point.

Grade of Cut Files are usually made in two types of cuts :

Single Cut; and

Double Cut

The Single Cut File has a single row of teeth extending across the face at an angle of 65 to 85 for the length of the file. It is often used with light pressure to produce a smooth surface or to put a keen edge on knives, shears and saws.

The Double Cut File has two rows of teeth which cross each other. For general work, the angle of the first row is 40 to 45, and the angle of the second row can be anywhere between 30 and 87. First set of teeth is know as the overcut, second is known as upcut and upcut is finer then overcut. This type of file usually used with heavier pressure than the single cut and removes material faster from the workpiece.

Figure 2.2 : Single cut file and double cut file

Files are also classified by the coarseness of the teeth. The bigger the teeth the rougher the feel of the File, and the quicker the File will remove material when you are using it.

There are four main levels of coarseness that you may come across in the metalwork room and they are :

1. Rough file (8 teeth per cm)2. Coarse middle file (10 teeth per cm)3. Bastard file (12 teeth per cm)4. Second cut file (16 teeth per cm)5. Smooth file (20 - 24 teeth per cm)6. Dead file (40 or more teeth per cm)

Type of files

Figure 2.3 : Types of file

Care of file 1. Store the files in wooden rack and must not contact each other2. If not using for long time applied lubricant for preventing from rust. When it

going to used, lubricant have to be wash out3. Applied chalk to the file before use prevent chip stick on file surface (holes

between teeth)4. Clean files before and after used -- file cleaner or file brush5. If the file have been used for filling hard material never used it for filling soft

material

2.2b HACKSAW Used for cutting metal rods, bars, pipes etc.

Job piece held in a vice and hacksaw move forward and backward

Cutting operation occur in forward stroke (required pressure) and in return stroke, no cutting action takes place

Hacksaw blade are made from high carbon steel and high speed steel

A hacksaw is a fine-tooth saw with a blade in a frame, used for cutting materials such as metal or bone.

Hacksaw features

Hand-held hacksaws consist of a metal arch with a handle, usually a pistol grip, with pins for attaching a narrow disposable blade. A screw or other mechanism is used to put the thin blade under tension. The blade can be mounted with the teeth facing toward or away from the handle, resulting in cutting action on either the push or pull stroke. On the push stroke, the arch will flex slightly, decreasing the tension on the blade.

Figure 2.4 : Hacksaw features

Frame : There are two types of Hacksaw Frame, a fixed and an adjustable. The fixed frame can only take one length of Blade, but is more rigid that the adjustable type, which can take Blades of different lengths ( typically handles 25 mm and 30 mm blades, some can accept blades ranging from 20 mm to 40 mm).

Blade & teeth : Blades are available in standardized lengths, usually 25 mm or 30 mm for a standard hand hacksaw. The blade chosen is based on the thickness of the material being cut, with a minimum of three teeth in the material.

Hacksaw blade are made from Low Tungsten Steel or Carbon Steel, however the more expensive blades are made from High Speed Steel.

Different hacksaw blades have different number of teeth ranging from 14 to 32 teeth per 25 mm. Blades having lesser number of teeth per cm are used for cutting soft materials like aluminum, brass and bronze. Blades having larger number of teeth per cm are used for cutting hard materials like steel and cast iron.

Table 2.1. Selection of hacksaw blade

Teeth per 25mm

Use

14 Soft thick materials. Aluminium, Copper, Mild Steel

18 General use. Soft materials in thin sections. Hard materials in thick sections.

24 Thin section hard materials.

32 Very thin materials such as thin tubing and sheet metal.

No of teeth per 25 mmMaterial

thickness (mm) Hard materials Soft materialsUp to 3 32 323 to 6 24 246 to 13 24 1813 to 25 18 14

Thin stock calls for finer teeth; thicker metal requires fewer teeth per 25 mm.

Handle :There are three types of Hacksaw Handle used. The most commonly used handles are the File Handle and the Pistol Grip Handle.

Figure 2.5 : Types of hacksaw handleSawing Procedure

i. The hacksaw blade is fixed in the hacksaw frame through.ii. When fitting a new blade to a hacksaw, point the teeth forward, (away from the

handle). iii. Tighten the wing nut and then as a general rule tighten three turns. It is important

to have the correct tension on the blade, if it is too loose then the blade will buckle and not cut straight, and if it is too tight damage to the blade ends or the frame may result.

Figure 2.6 : Types of hacksaw a) Adjustable frame [pistol grip], b) Fixed frame, c) Tubular adjustable frame

1. Groove 2. Pistol 3. Pin 4. Pin 5. Thumb rest6. Lock screw

Care of hacksaw1. Choose the correct blade for the material being cut. 2. Secure the blade with the teeth pointing forward. 3. Keep the blade rigid and the frame properly aligned. 4. Cut using strong, steady strokes directed away from you. 5. Use the entire length of the blade in each cutting stroke. 6. Keep saw blades clean, and use light machine oil on the blade to keep it from overheating and breaking.

7. Cut harder materials more slowly than soft materials. 8. Clamp thin, flat pieces that require edge cutting.

2.2c FIXING TOOLS i] Vice A vice is a mechanical screw apparatus used for holding or clamping a work piece to allow work to be performed on it with tools such as saws, drills, screwdrivers, etc. Vises usually have one fixed jaw and another, parallel, jaw which is moved towards or away from the fixed jaw by the screw.

There are three types of vice :

Bench vice

Drilling vice

Hand vice

Bench vice

Figure 2.7 : Bench viceBecause the bench vise is fitted on the bench, generally it is not possible to change the height of the vice or the vice itself. Thus, care is needed when fitting a vice on the bench so that it is at a suitable and convenient height. The height of the top of the bench vice should be at level with the elbow of the worker. For this purpose, the height of an average man is selected as height of elbow of individual varies.

Fixed jaw Moveable jaw

Handle

Spindle with buttress thread

Figure 2.8 : A vice must be mounted so that when you are standing next to it, the top surface of its jaws is level with your bent elbow.

Figure 2.9 : If the bench top is too low, the vice can be raised with a hardwood block.

Drilling viceIt is used to hold the job on the drilling machine for drilling holes in the workpiece.

Drilling vice generally consists of different parts like handle, fixed jaw, screw, moveable jaw, nut, washer, etc but its base is provided with slots through which it is fitted on the drilling machine.

Figure 2.10 : a) Machine vice with swivel base b) Parallel jaw machine vice1. Moveable jaw 2. Fixed handle 3. Body fixed on base

4. Swivel base

Hand viceIt is a very small machine which is used for gripping very small jobs.

Figure 2.11 : Hand vice

Figure 2.12 : Holding of flat, small workpieces in the hand vice

Care of viceWhile using a vice, the following precautions should always be ensured :

1. Always set the workpiece in the centre of the jaw.

Figure 2.132. If it is necessary to hold the job on one side of the jaws, then use a piece of steel

or wood on the other side to keep jaws parallel and free from excessive strain.

3. Length of the handle of the vice must be sufficient to tighten the job. Never use a hammer to tighten the workpiece.

4. Clean the vice and its moving parts regularly before use for smooth working.5. Fixed the vice rigidly to the work bench with the help of nuts and bolts.

2.2c FIXING TOOLS ii] ClampIt is used to hold different jobs together to perform fitting operations like assembly and marking. A c clamp is a form of a clamp used to hold metal or wood items. As the name implies, they are shaped in the letter C which offers a good grip to the metal and wooden items.

Many people also refer this clamp to be a G clamp as the screw part beneath the revolving rod gives it a shape of the letter G. These tools are considered as the most recognizable clamps and are available in sizes varying from 1 inch to 8 inches. Every size denotes the maximum opening width of the tool. Although, there are larger sizes available as well however, the smaller ones are most commonly used.

Figure 2.14 : Types of C-clamp

2.2c FIXING TOOLS

iii] V block Basic function of V block is to mark and drill. The bar length is placed longitudinally in the V groove and the screw of U-clamp is tightened. It grips the rod firmly with its axis parallel to the axis of the V groove. It is used in conjuction with a U-clamp for holding round bars for marking, centre drilling, for holding in the centre of a lathe and for drilling holes.

Figure 2.15 : V block

Figure 2.16 : V blocks hold round stock securely

2.4 APPLICATION OF LAYOUT TOOLS

i. Steel ruleii. Caliper

iii. Scriberiv. Try squarev. Surface gauge

vi. Surface flat

i] Steel rule The most basic of the graduated measuring devices is the rule (made of steel, and

often called a steel rule), used to measure linear dimensions.

Rules are available in various lengths. Metric rule lengths include 150, 300, 600, and 1000 mm, with graduations of 1 or 0.5 mm.

Steel rules may be flexible or non flexible, but the thinner the rule, the more accurately it measures, because the division marks are closer to the work.

Figure 2.17 : Steel rule

Beside measuring the length, a steel rule can also be used to assess the flatness of a surface.

Procedure to measure the flatness of a surface :

1. Place the rule on edge across the surface then hold the work and the rule up to the light (Figure 2.18)

2. If the surface is flat, no light will be able to penetrate between the edge of the rule and the work piece.

Figure 2.18 : Measuring flatness of a material by using a steel rule

There are two important aspects to keep in mind when using a steel rule :1) The first is that the rule should be placed so that the graduations are as close to the

work as possible (Figure 2.19). This will eliminate parallax and other errors which might result because of the thickness of the rule.For example, where possible, the rule should be placed at 90 to the work so that the graduations actually touch the work surface.

Figure 2.19

2) Secondly, a habit to avoid is measuring a work piece from the beginning of the rule the very end markings of a steel rule may have been damaged.Read the measurement at the graduation that coincides with the distance to be measured.

However, when you use the rule in this way, remember to subtract the initial numbered amount from the total reading.

Figure 2.20

ii] Caliper The calipers are opened (either by being pulled open against a friction screw or

having an adjustment knob unwound) until the jaws of the caliper are a gentle push-fit over the work.

This manual calipers do not have a scale to read the measurement. Therefore, the calipers are then transferred to steel rule and a reading made of the distance between the manual calipers jaws. With care, this process can be highly accurate.

Three types of spring calipers : Inside Outside Hermaphrodite

Figure 2.21 : Inside Caliper

Figure 2.22 : Outside Caliper

Figure 2.23 : Hermaphrodite Caliper

iii] Scriber A scriber is a piece of hardened steel rod having a needle like a point on one or

both sides. It is used in metalworking to mark lines on workpiece, prior to machining.

The process of using a scriber is called scribing and is just part of the process of marking out.

It is used instead of pencil or pen, because the marks are hard to see, easily erased, and inaccurate due to their wide mark; scribe lines are thin and semi-permanent.

For proper use, the end of scriber must be kept sharp. If the end of the scriber gets blunt, it can be sharpened with an oil stone.

Figure 2.24 : Types of scriber

Using the Scribera.Sharpness. Make sure the point of the scriber is sharp. To sharpen, rotate the scriber between the thumb and forefinger while moving the point back-and forth on an oilstone.

b.Work Surface . Clean work surfaces of all dirt and oil.

c.Steel Rule . Place a steel rule or straight edge on the work beside the line to be scribed.

d.Holding the Scriber . Use the fingertips of one hand to hold the rule in position and hold the scriber in the other hand as you would a pencil.

e. Scribing the Line . Scribe the line by drawing the scriber along the edge of the rule, at a 45 degree angle and tipped outward slightly in the direction it is being moved.

Figure 2.25 : Scribing the line

Care of scriber1. Place a soft wood over the point of scriber when not in use. 2. Coat scriber with rust prevention compound before storage. 3. Do not store scribers in drawer with other tools. This practice can cause damage

to scribers and injury to personnel. 4. Rack properly and store in a suitable box. Do not use scribers for purposes other

than those intended.

iv] Try squareIt is used for scribing straight lines at right angles to each other, for testing trueness of a surface and for testing mutually perpendicular surface.Try squares are made from hardened alloy steel blades. More accurate try squares have properly ground and leveled edges with a fine finish. Both inner and outer surfaces of the blade are kept true at right angles to the corresponding surfaces of the stock.

Figure 2.26 : Try square

v] Surface gauge It is also called scribing block. A surface gauge is used for layout work.

It consists of a heavy flat cast iron black fitted with a vertical steel rod.

Surface gauge is used for locating the centre of round bars held in V block by drawing straight lines and by tilting the job through different angles.

Figure 2.27 : Surface gauge is also used to the diameter of round bars

Figure 2.28 : Surface gauge is used to scribe layout lines

The spindle may be adjusted to any position with respect to the base and tightened in place with the spindle nut.

The scriber can be positioned at any height and in any desired direction on the spindle by adjusting the scriber.

Figure 2.29: Surface gauge

Normally, surface gauge is used in conjunction with either a surface plate or a marking table which is needed to set the surface gauge to the correct dimension (Figure 2.30).

Figure 2.30

2.5 APPLICATION OF SIMPLE MANUAL MACHINESi. Drilling

ii. Tapping

i] Drilling Drilling is an operation of producing circular holes o different sizes with the help

of drills.

It cuts by applying pressure and rotation to the workpiece, which forms chips at the cutting edge.

Twist drills are generally used drills for drilling holes in workpieces.

Figure 2.31 : Twist drill

Figure 2.32 : A drill bit enters the workpiece axially and cuts a hole with a diameter equal to that of the tool

ii] Tapping

This tool is used for cutting internal threads in cylindrical holes.

A tap cuts a thread on the inside surface of a hole, creating a female surface which functions like a nut.

Figure 2.33 : Tap

Figure 2.34 : Parts of a tap

Two types of taps :1) Hand operated taps2) Machine operated taps

Hand operated taps

Figure 2.35 : Hand operated taps

By using a set of taps : starting tap, intermediate tap and finishing tap.

Different tap set are required for cutting different threads of different diameter.

Figure 2.36 : Hand tap

Figure 2.37 : Set of taps

Starting tap (a.k.a taper tap) : * The number of tapered threads typically ranges from 8 to 10. * A very gradual cutting action that is less aggressive than that of the plug tap.* Most often used when the material to be tapped is difficult to work (e.g., alloy steel) or the tap is of a very small diameter and thus prone to breakage.

Intermediate tap (a.k.a plug tap or second tap) : * The number of tapered threads typically ranges from 3 to 5.* It has tapered cutting edges, which assist in aligning and starting the tap into an untapped hole. Finishing tap (a.k.a bottoming tap) : * It has a continuous cutting edge with almost no taper between 1 and 1.5 threads. * This feature enables a bottoming tap to cut threads to the bottom of a blind hole.* A bottoming tap is usually used to cut threads in a hole that has already been partially threaded using one of the more tapered types of tap.

Wrench is a tool for holding the tap during the hand tapping process.

Figure 2.38 : A tap and T-wrench.

Procedure (using wrench-hand operated taps):1. A hole must be drilled to the tapping size for the thread. 2. After drilling a hole of the required size, the taper or fixed in the wrench and

screwed into the hole. 3. When starting the cutting, the tap must be perpendicular in all planes to the work. 4. Excessive force must not be used, as this will result in breaking the tap. 5. Cutting fluid should be used to improve the surface finish of threads..6. Start the cutting action keeping in mind that the tap is turned continuously but

after every half turn, it should be reversed slightly to clear the threads.7. Therefore, threads must be cleared as often as is necessary to prevent the flutes

from clogging.8. Proceed until the taper tap is through the hole.9. Repeat the above operations with the intermediate and finishing tap to finish the

hole.

Figure 2.39 : Using Tap Wrench to create a thread for a screw

Machine operated taps

* By using lathe, radial drilling machine, vertical milling machine, etc.* Machine tapping is faster and generally more accurate because human error is eliminated.

Figure 2.40 : Machine operated taps

Care of tap

1. Care must be taken not to damage the cutting edges. A chipped tap must never be used.

2. When not in use, taps should be kept clean and stored in a rack (Figure 2.34).

Figure 2.41

References

Books :1. B.J.Black, Workshop processes, practices and materials, 2nd Edition, Arnold,

1997.2. F.W.Turner, O.E.Perrigo, H.P.Fairfield, Machine Shop Work3. S.K. Yadav, Workshop Practice : Principles and Applications, IBS Buku Sdn

Bhd.

Website : 1. http://www.wikipedia.com2. http://home.howstuffworks.com3. http://homerepair,about.com4. http://www.practicalstudent.com5. http://autospeed.co.nz 6. http://www.technologystudent.com 7. http://www.tpub.com8. http://books.google.com.my 9. http://chestofbooks.com 10. http://www.mechlook.com11. http://www-mdp.eng.cam.ac.uk12. http://www.cdxetextbook.com 13. http://www.custompartnet.com

Chapter 3 Measuring instrument, gauges

and marking out tools Chapter Outline 3.1 Introduction 3.2 Errors In Measurement 3.3 Vernier Scale

3.3.1 Vernier Caliper 3.3.2 Vernier Height Gauge 3.3.3 Vernier Depth Gauge 3.4 Micrometers

3.4.1 External Micrometer 3.4.2 Internal Micrometer 3.4.3 Depth Micrometer

3.5 Gauges Learning outcome When you complete this chapter you should be able to:

1. Describe common measuring instruments, gauges and marking out tools in mechanical workshop

2. Select suitable measuring instruments, gauges and marking out tools in engineering application.

3. Use accurately common measuring instruments, gauges and marking out tools in engineering application.

3.1 INTRODUCTION There are three reasons why we need measurement.

1. To make things, whether the things we make are of our own designs or somebody elses.

2. To control the way other people make things. This applies to ordering an engagement ring, fencing a yard or producing a million spark plugs.

3. For scientific description. It would be impossible to give definite information to someone about aircraft design, electron mobility, etc without measurements.

In some application, not only measurements are required but precise measurement is necessary especially where parts are to be fit together. To achieve any degree of precision, the measuring equipment used must be precisely manufactured with reference to the same standard of length. Having produced the measuring equipment to a high degree of accuracy, it must be used correctly. 3.2 ERRORS IN MEASUREMENT Any measurement made with a measuring device is approximate. If you measure the same object two different times, the two measurements may not be exactly the same. The difference between two measurements is called variation in the measurement. Another word for this variation - or uncertainty in measurement is "error". This "error" is not the same as a "mistake." It does not mean that you got the wrong answer. The error in measurement is a mathematical way to show the uncertainty in the measurement. It is the difference between the result of the measurement and the true value of what you were measuring Errors can be minimized, by choosing an appropriate method of measurement, but they cannot be eliminated. Causes of error : 1) Reading value Digital : Record all the digits shown.

Figure 3.1

Non digital : Record all the figures that are known for certain

Figure 3.2

2) Parallex Error The error that occurs when the pointer on a scale is not observed along a line normal to the scale

Figure 3.3

3) Rounding off If the last figure is between 5 and 9 inclusive round up If the last figure is between 0 and 4 inclusive round down

Should not be done after each step of a calculation (it causes rounding errors) Should only be done at the end of a calculation

4) Errors in procedure The accuracy of a final result also depends on the procedure used. Ways to improve accuracy in measurement : 1. Make the measurement with an instrument that has the highest level of precision. The smaller the unit, or fraction of a unit, on the measuring device, the more precisely the device can measure. The precision of a measuring instrument is determined by the smallest unit to which it can measure.

2. Know your tools! Apply correct techniques when using the measuring instrument and reading the value measured. Avoid the error called "parallax" -- always take readings by looking straight down (or ahead) at the measuring device. Looking at the measuring device from a left or right angle will give an incorrect value.

3. Repeat the same measure several times to get a good average value.

4. Measure under controlled conditions. If the object you are measuring could change size depending upon climatic conditions (swell or shrink), be sure to measure it under the same conditions each time. This may apply to your measuring instruments as well. 3.3 VERNIER SCALE 3.3.1 VERNIER CALIPER The vernier caliper is a precision instrument that can be used to measure internal, external, step and depth measurement. It is used to take measurements that are accurate to within 0.001 of an inch or 0.02 of a millimeter, depending whether the vernier is metric or imperial. Vernier Caliper are important in tool room die making, model making and similar applications. They provide long measurement ranges (6 to 80 inch) and are economical.

A vernier caliper has an L-shaped design with a movable arm. The movable arm can be slid out to allow an object to fit between the arms, and a measurement can be taken.

Vernier calipers have two scales. The main scale is fixed, while the vernier, the secondary scale, slides along the main scale as the movable arm is shifted. Measurements are taken by looking for the mark on the main scale which is just to the left of the zero on the vernier caliper for the first

measurement, and then looking to see which mark on the vernier caliper comes most closely into alignment with a mark on the main scale. This yields a secondary measurement.

Features Parts of a vernier caliper:

1. External jaws: used to measure external diameter or width of an object 2. Inside jaws: used to measure internal diameter of an object 3. Depth probe: used to measure depths of an object or a hole 4. Matric scale: gives measurements of up to one decimal place(in cm). 5. Imperial scale: gives measurements in fraction(in inch) 6. Vernier scale gives measurements up to two decimal places(in cm and inch) 7. Locking screw(Retainer): used to block movable part to allow the easy transferring a measurement

Figure 3.4 : Vernier caliper

Measuring with Vernier Caliper Example 1

Example 2

Exercise

DIAL CALIPER Accomplish with a dial for the least count readout. Normally dial caliper is accurate to 20 m per 150 mm (0.001 in. per 6 in.) of travel.

In this instrument, a small gear rack drives a pointer on a circular dial. Typically, the pointer rotates once every inch, tenth of an inch, or 1 millimeter, allowing for a direct reading without the need to read a vernier scale (although one still needs to add the basic inches or tens of millimeters value read from the slide of the caliper).

Figure 3.5 : Dial caliper

DIGITAL CALIPER Another extension of vernier caliper scale reading is used in the electronic digital caliper. These battery operated devices not only count the distance travelled by the moveable jaw and display the count on a digital readout, but they also provide parts for computer cables, so that the data can easily be used in statistical process control.

Because the digital display makes the instrument even easier to read, electronic digital caliper is very useful for less experienced users. It also use a floating zero which allows users to make any point within the scale ranges the references, setting it to zero. Some digital calipers can be switched between metric and inch units.

Figure 3.6 : Digital caliper

3.3.2 VERNIER HEIGHT GAUGE This is also a sort of vernier caliper, equipped with a special base block and other attachments which make the instrument suitable for height measurements. It follows the principle of a vernier caliper and also follows the same procedure for linear measurement. The vernier height gauge is mainly used in the inspection of parts and layout work. With a scribing attachment in place of measuring jaw, this can be used to scribe lines at certain distance above surface.The vernier height gage may be used to measure or mark work off vertical distances to + or - .001 inch (.02 mm) accuracy.

Figure 3.7 : Vernier height gauge features The vernier height gauge consists of a vertical graduated beam or columnon which the main scale is engraved. The vernier scale can move up and down over the beam. The bracket carries the vernier scale which slides vertically to match the main scale. The bracket also carries a rectangular clamp used for clamping a sciber blade. The whole arrangement is designed and assembled in such a way that when the tip of the sciber blade rests on the surface plate, the zero of the main scale and vernier scale coincides. The scriber tip is used to scribed horizontal lines for preset height dimensions.

The height gauges can also be provided with dial gauges or electronic readout instead of a vernier. The dial height gauge reads to 20 m (0.001 in). Electronic height gauge is even more precise which reads to 10 m (0.0001 in)

Figure 3.8 : Electronic and dial height gauge

3.3.3 VERNIER DEPTH GAUGE A depth gauge is a precision measuring instrument, designed specifically to measure the depth of holes, recesses, cavities and distances from a plane surface to a projection. In other word, a depth gauge is a variation of the ruler. The depth gauge consists of a rulerusually a narrow one to measure the depth of holes, counter bores, etc. There is a base through which the ruler can slide up and down, and a locking screw on the cover to clamp the ruler in place.

Figure 3.9 : Vernier depth gauge

Locking screw

ruler

base

Depth gauges comes in various configurations, depending on the specific application. Depth gauge types include digital tire thread depth gauges, digital depth gauges, single hook type digital depth gauges, needle digital depth gauges, double hooks digital depth gauges, digital depth gauges with adjustable base, vernier depth gauges, and dial depth gauges.

The digital version is capable to output measurements to a wide variety of peripherals and data collection devices. These simple, inexpensive tools are typically about 150mm long, and they can even measure up to longer range, such as 1000mm.

Figure 3.10 : Digital depth gauge

Caution

1) All depth gauges should be calibrated at least once a year, depending on how frequent it is used. If a gauge had an impact, it should be tested before use. If a gauge is not calibrated, it can be checked against an accurately marked shot line.

2) When the display keeps flashing or does not appear, take off the battery cover as the arrow shows and replace the battery with a new one (SR44, 1.55V). Note that the positive pole of the battery must be facing out. If the battery bought from the market does not work properly, it might be power lost due to long shelf life.

3.4 MICROMETER A micrometer allows a measurement of the size of a body. It is one of the most accurate mechanical devices in common use.

Three most common types of micrometer; the names are based on their application:

External micrometer, used to measure the diameter of holes. Internal micrometer (aka micrometer caliper), typically used to measure wires, spheres,

shafts and blocks. Depth micrometer, measures depths of slots and steps.

Figure 3.11 : a) External micrometer b) Internal micrometer c) Depth micrometer

The micrometer is a precision measuring instrument, used by engineers. Each revolution of the rachet moves the spindle face 0.5mm towards the anvil face. The object to be measured is placed between the anvil face and the spindle face. The rachet is turned clockwise until the object is trapped between these two surfaces and the rachet makes a clicking noise. This means that the rachet cannot be tightened anymore and the measurement can be read.

Reading an inch-system micrometer

The spindle of an inch-system micrometer has 40 threads per inch, so that one turn moves the spindle axially 0.025 inch (1 40 = 0.025), equal to the distance between two graduations on the frame. The 25 graduations on the thimble allow the 0.025 inch to be further divided, so that turning the thimble through one division moves the spindle axially 0.001 inch (0.025 25 = 0.001). To read a micrometer, count the number of whole divisions that are visible on the scale of the frame, multiply this number by 25 (the number of thousandths of an inch that each division represents) and add to the product the number of that division on the thimble which coincides with the axial zero line on the frame. The result will be the diameter expressed in thousandths of an inch.

Figure 3.12 : Micrometer thimble showing 0.276 inch where 0.2000 + 0.075 + 0.001

Example :

- The spindle has 40 threads per inch. - Distance between two graduations on the sleeve = 1/40 = 0.025 - 25 graduations on the thimble allow the 0.025 inch to be further divided

(0.025 25 = 0.001).

Sleeve read (full) = 0.3 Sleeve read (sub-division) = 1 * 0.025 = 0.025 Thimble read = 1* 0.001 = 0.001 Total Measurement = 0.326 inch

Sleeve = 0.025 inch Thimble = 0.001 inch

Reading a metric micrometer

The spindle of an ordinary metric micrometer has 2 threads per millimeter, and thus one complete revolution moves the spindle through a distance of 0.5 millimeter. The longitudinal line on the frame is graduated with 1 millimeter divisions and 0.5 millimeter subdivisions. The thimble has 50 graduations, each being 0.01 millimeter (one-hundredth of a millimeter). To read a metric micrometer, note the number of millimeter divisions visible on the scale of the sleeve, and add the total to the particular division on the thimble which coincides with the axial line on the sleeve.

Figure 3.13 : Micrometer thimble showing 5.78 mm where 5.00 + 0.5 + 0.28 = 5.78 mm

Example :

The accuracy of micrometers is checked by using them to measure gauge blocks, rods, or

similar standards whose lengths are precisely and accurately known.

3.4.1 EXTERNAL MICROMETER

Figure 3.14 : External micrometer features

Frame

The C-shaped body that holds the anvil and barrel in constant relation to each other. It is thick because it needs to minimize flexion, expansion, and contraction, which would distort the measurement.

Anvil The shiny part that the spindle moves toward, and that the sample rests against.

Sleeve / barrel / stock The stationary round part with the linear scale on it. Sometimes vernier markings.

Lock nut / lock-ring / thimble lock The knurled part (or lever) that one can tighten to hold the spindle stationary, such as when momentarily holding a measurement.

Screw (not seen) The heart of the micrometer, as explained under "Operating principles". It is inside the barrel.

Spindle The shiny cylindrical part that the thimble causes to move toward the anvil.

Thimble The part that one's thumb turns. Graduated markings.

Ratchet stop Device on end of handle that limits applied pressure by slipping at a calibrated torque.

3.4.2 INTERNAL MICROMETER The normal procedure for using inside micrometers is to set them across diameters or between inside surfaces, remove them, and then read the dimension. For this reason, the thimble on an inside micrometer is much stiffer than the one on a micrometer caliper. Thus, it holds the dimension better. It is good practice to verify the reading of an inside micrometer by measuring it with a micrometer caliper.

Figure 3.15 : Internal micrometer

3.4.3 DEPTH MICROMETER

The depth micrometer is used to measure the precise depths of holes, grooves, and recesses by using interchangeable rods to accommodate different depth measurements. The ratchet is turned clockwise until the spindle face touches the bottom of the blind hole. The scales are read in exactly the same way as the scales of a normal micrometer.

Figure 3.16 : Depth micrometer

Care of micrometer

1. Coat metal parts of all micrometers with a light coat of oil to prevent rust. 2. Store micrometers in a separate container provided by manufacturer. 3. Keep graduations and markings on all micrometers clean and legible. 4. Do not drop any micrometer. Small nicks or scratcthes can cause inaccurate

measurements.

3.5 GAUGES In engineering, a gauge or gage, is used to make measurements.

1. Bore gauge 2. Center gauge 3. Dial indicator 4. Feeler gauge 5. Block gauge 6. Pressure gauge 7. Radius gauge 8. Ring gauge 9. Thread pitch gauge

Types of

gauge Purpose Picture

Bore gauge A device used for measuring holes.

Center gauge (a.k.a fishtail gauge)

It is a tool used in machining to check the angle of tool bits used to cut screw threads

The center gauge helps ensure that the tool bit is the correct dimensions to cut these threads.

Dial indicator (a.k.a dial test indicator, dial gauge or probe indicator)

To check the variation in tolerance during the inspection process of a machined parts.

Used in industrial.

Feeler gauge

Used to measure gap widths.

Mostly used in engineering to measure the clearance between two parts.

They consist of a number of small lengths of steel of different thicknesses with measurements marked on each piece.

In a metric set of feeler gauges the thickness ranges from 0.05 mm to approximately 1 mm in varying steps.

When using the thinner gauges care should be taken to pull the gauge through a gap rather than push, as by pushing, the gauge will tend to bend and wrinkle or possibly if a sideway movement is used the gauge will tear.

Block gauge Used as a reference for the setting of measuring equipment used in machine shops, such as micrometers, calipers, and dial indicators

Pressure gauge (a.k.a vacuum gauge)

Used for pressure measurement of a gas or liquid. E.g. : used to measure the pressure difference between a system and the surrounding atmosphere.

Radius gauge (a.k.a fillet gauge)

Used to measure the radius [internal and external] of an object.

The gauges are a set of thin blades with a convex (external) and concave (internal) radius of the same size on each blade.

The size of the radius is marked on each blade.

It requires a bright light behind the object to be measured.

The gauge is placed against the edge to be checked and any light leakage between the blade and edge indicates a mismatch that requires correction.

Inside radius

Outside radius

Ring gauge

Used for checking the external diameter of a cylindrical object.

Thread pitch gauge (treading gauge, pitch gauge, screw gauge)

Used to measure the screw pitch threads.

It is a series of thin marked blades which have different pitched teeth. Each set of screw pitch gauges has the thread form stamped on it.

Thread pitch gauges also come in the standard thread forms of metric, Whitworth, BSF, UNF, and UNC which allows both the pitch of the thread to be gauged and the form or shape of the thread, to be checked.

References

1. http://www.knockhardy.org.uk 2. http://www.me.iitb.ac.in 3. http://www.regentsprep.org 4. http://www.splashmaritime.com.au 5. http://www.technologystudent.com 6. http://www.tresnainstrument.com 7. http://www.wikihow.com 8. http://www.wisegeek.com 9. Anand K Bewoor, Vinay A. Kulkarni. Metrology & measurement. McGraw Hill.

Chapter 4 Industrial materials used in

workshop and identification

Chapter Outline 4.1 Steel and its alloys 4.2 Cast Iron 4.3 Copper and its alloys 4.4 Aluminum and its alloys 4.5 Bearing Metals Learning outcome When you complete this chapter you should be able to:

1) Acquire knowledge on basic engineering materials in real world industry.

2) Differentiate types of engineering materials, basic characteristics and its application.

3) Application of engineering materials especially in workshop practice.

4.0 : INTRODUCTION Generally, engineering materials can be divided into two categories; metal and non-metal. The major characteristics of metallic materials are their crystallinity, conductivity to heat and electricity and relatively high strength and toughness.

In workshop practices, all materials we use are metallic material. Metal mainly comprises as ferrous and nonferrous. It means classification of metal based on ferrous (iron) content or non ferrous content. There are five types of metal covered in this topic such as :

4.1 Steel and its alloys 4.2 Cast Iron 4.3 Copper and its alloys 4.4 Aluminum and its alloys 4.5 Bearing Metals Table below show classification of engineering material based on manufacturing engineering references book by Serope Kalpakjian.

Figure 4.1 : Enginering materials

4.1 : STEEL AND ITS ALLOYS Steel mainly consist of iron that contains carbon ranging by weight between 0.022% and 2.14% It often includes other alloying ingredients: -

Manganese Chromium Nickel Molybdenum

Steel can be grouped into the following categories:

(1) PLAIN CARBON STEELS Contain carbon as the principal alloying element; with only small amounts of other elements (about 0.5% manganese is normal). Designation scheme : American Iron and Steel Institute (AISI) & the Society of Automotive Engineers (SAE) First digit indicates the family to which the steel belongs : 1- Carbon steels; 2- Nickel steels; 3- Nickel-chromium steels; 4- Molybdenum steels; 5- Chromium steels;

Steel

Plain carbon steels

Low alloy steels

Stainless steels

Low carbon steels

Medium carbon steels

High carbon steels

Tool steels

6- Chromium-vanadium steels; 7- Tungsten-chromium steels; 9- Silicon-manganese steels. Second digit indicate % of major alloying elements (1 means 1%). Last two digits (3rd and 4th number) indicate amount of carbon in steel (10 means 0.10% C). Example : Plain carbon steels are specified by a four-digit number system: 10XX

where , 10 indicates that the steel is plain carbon, and XX indicates the percent of carbon in hundredths of percentage points. For example, 1020 steel contains 0.20% C.

The plain carbon steels can be classified into three groups according to their carbon content: TYPES OF

PLAIN CARBON

STEEL

CARBON CONTENT

APPLICATION PROPERTIES/ CHARACTERISTICS

Low carbon steels

Contain less than 0.25% C

Automobile sheet metal parts

Plate steel for fabrication

Tin can Nails Bolt and nut

Relatively soft and

weak, but possess high ductility and toughness

Good formability, Good weldability

Low cost Rated at 55-60%

machinability

Easy to form in which high strength is not

required.

Medium carbon steel

Range in carbon between 0.25% and 0.60%

Machinery components and engine parts

i.e : crankshafts, gears and connecting rods.

Applications requiring higher strength than low carbon steel

Machinability is 60-70%

Good toughness and ductility

Fair formability

High carbon steel

Carbon in amounts greater than 0.60% but less than 1.4%

Springs, cutlery Cutting tools &

blades

Hardest, strongest Least ductile of the

carbon steel High wear resistance

Increasing carbon content :

Strengthens and hardens the steel Ductility is reduced. Can be heat treated - improved properties of steel (hard and strong)

(2) LOW ALLOY STEELS Low alloy steels are iron-carbon alloys that contain additional alloying elements in amounts totaling less than about 5% by weight. Owing to these additions, low alloy steels have mechanical properties that are superior to those of the plain carbon steels for given applications. Superior properties usually mean;

Higher strength Higher hardness High hot hardness High wear resistance Higher toughness

Heat treatment is often required to achieve these improved properties.

The effects of the principal alloying ingredients as follows:

ALLOYING ELEMENTS EFFECTS OTHERS

Chromium (Cr)

Improves : Strength, Hardness, Wear resistance Hot hardness.

Effective alloying ingredients for increasing hardenability

Cr improves corrosion resistance.

Manganese (Mn)

Improves Strength Hardness of steel

when the steel is heat treated, hardenability is improved with increased manganese.

Molybdenum (Mo)

Increases Toughness

improves hardenability and forms carbides for wear resistance.

Hot hardness Nickel (Ni)

improves Strength Toughness

Increases hardenability but not as much as some of the other alloying elements

It improves corrosion resistance

Vanadium (V)

Enhances strength toughness of steel

Forms carbides that increase wear resistance.

(3) STAINLESS STEELS A group of highly alloyed steels. Differ from carbon steel by the amount of chromium present.

Called stainless because in the presence of oxygen (air), they develop a thin, hard, adherent film of chromium oxide that protect the metal from corrosion. Also the protective film builds up when the surface is scratched.

Designed to provide high corrosion resistance. Stainless steel does not stain, corrode, or rust as easily as ordinary steel, but it is not stain-proof. It is also called corrosion-resistant steel, particularly in the aviation industry. Stainless steel is used where both the properties of steel and resistance to corrosion are required. The principal alloying element in stainless steel are as follow:

ALLOYING ELEMENTS EFFECTS

Chromium, (usually above 15%)

Contain sufficient chromium to form a passive film of chromium oxide, which prevents further surface corrosion and blocks corrosion from spreading into the metal's internal structure.

Nickel Increase corrosion protection.

Carbon

Used to strengthen and harden the metal; However, increasing the carbon content has the effect of reducing corrosion protection Why? Because chromium carbide forms to reduce the amount of free Cr available in the alloy.

Common used of stainless steel is kitchen cutlery, watch strap, piping and fitting.

Figure 4.2 : Applications of stainless steel (4) TOOL STEELS Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures (red-hardness). A class of high-carbon alloy steels used to forming, machining or cutting other materials. It has an excess carbides (carbon alloys) which make them hard and wear resistant.

Its characteristics:

high strength impact toughness wear resistance

Commonly has two types:

High speed steel(HSS) - The most highly alloyed tool and die steels. - Two basic types of HSS, the molybdenum type (M-series) contain about 10%

molybdenum with other materials or the tungsten type (T-series) contain 12-18% tungsten with other alloying elements. It can be coated with titanium nitride and titanium carbide for improving wear resistance.

Die steel

- Are designed for use at elevated temperatures. It has high toughness and high resistance to wear and cracking. Alloying elements are tungsten, molybdenum, chromium and vanadium.

4.2 : CAST IRON Cast iron is a family of ferrous alloys composed of iron, carbon (ranging from 2% - 4.5%) and silicon (about 3.5%) Mainly act as casting raw material in metal casting industry. There are several types of cast iron :

TYPES OF CAST IRON

DESCRIPTIONS ATTRACTIVE PROPERTIES

TYPICAL PRODUCT

Grey Cast Iron

* The structure causes the surface of the metal to have a grey color when fractured; hence the name gray cast iron. * Grey cast iron accounts for the largest tonnage among the cast irons.

Composition In the range 2.5% to 4% carbon and 1% to 3% silicon.

* Good vibration damping, which is desirable in engines and other machinery * Internal lubricating qualities, which makes the cast metal machinable. * Ductility of grey cast iron is very low; it is a relatively brittle material.

* Automotive engine blocks and heads * Motor housings * Machine tool bases

Ductile Iron

* Composition of grey iron in which the molten metal is chemically treated before pouring to cause the formation of graphite spheroids rather than flakes.

* Stronger and more ductile iron * Ductile and shock resistant

* Machinery components requiring high strength and good wear resistance

White Cast Iron * Has less carbon and silicon than gray cast * Hard and brittle

* Railway brake shoes

iron * Formed by more rapid cooling of the molten metal after pouring * When fractured, the surface has a white crystalline appearance that gives the iron its name.

* Excellent wear resistance * Good strength

Malleable Iron

* When castings of white cast iron are heat treated to separate the carbon out of solution and form graphite

* Ductility (up to 20% elongation)

* Strength

* Shock resistant

* Pipe fittings & flanges * Certain machine components * Railroad equipment parts.

4.3 : COPPER AND ITS ALLOYS Copper first produced in about 4000 B.C.

Properties of copper :

Reddish-pink color, Low electrical resistivity - one of the lowest of all elements. An excellent thermal conductor. Noble metals (gold and silver are also noble

metals), so it is corrosion resistant. Low strength and hardness of copper. Easily process by various forming, machining,

casting and joining technique. Applications : Widely used as an electrical conductor. To improve strength, copper is frequently alloyed. Bronze is an alloy of copper and tin (typically, about 90% Cu and 10% Sn). Brass is another familiar copper alloy, composed of copper and zinc (typically

around 65% Cu and 35% Zn). The highest strength alloy of copper is beryllium - copper (only about 2% Be). Be -

Cu alloys are used for springs.

4.4 : ALUMINUM AND ITS ALLOYS Among the commercial metals, aluminum is second only to iron in production and consumption. Aluminum and its alloy are the most important in nonferrous metallic materials following a few based characteristic.

Attractive Properties

High strength to weight ratio allows the design and construction of strong lightweight structures. Advantages for portable equipment, vehicles and aircraft application (82% of a Boeing 747 and 70% of a Boeing 777) its structural made from aluminum.

Resistance to corrosion in atmospheric environment, in fresh and salt waters and in many chemicals solution. Resistance to corrosion is excellent due to the formation of a hard thin oxide surface film.

Aluminum has no toxic-suitable for processing, handling, storing and packaging of foods and beverage (aluminum can & foil).

High electrical and heat conductivity, especially when light weight is important. Very ductile metal easy to form

Pure aluminum is relatively low in strength, but it can be alloyed and heat treated to compete with some of the steels, especially when weight is taken into consideration high strength but light weight

4.5 : BEARING METALS Also known as babbit metal, was invented in 1839 by Isaac Babbit (USA). Most commonly used in as a thin surface layer in a complex, multi-metal structure, but its original use was as a cast-in place bulk bearing material. Babbitt metal is soft and easily damaged, which suggests that it might be unsuitable for a bearing surface. However, its structure is made up of small hard crystals dispersed in a softer metal, which makes it a metal matrix composite. As the bearing wears, the softer metal erodes somewhat, which creates paths for lubricant between the hard high spots that provide the actual bearing surface. When tin is used as the softer metal, friction causes the tin to melt and function as a lubricant, which protects the bearing from wear when other lubricants are absent.

Figure 4.3 : Bearing metals

Chapter 5 Introduction to Welding

Chapter Outline 5.1 Overall safety in welding 5.2 Filler, Flux, Electrode and shielding gases 5.3 Gas welding

5.3.1 Oxy-acetylene gas welding 5.4 Arc welding

5.4.1 SMAW 5.4.2 MIG 5.4.3 TIG

5.5 Spot welding Learning outcome When you complete this chapter you should be able to:

1. Acquire basic knowledge on arc welding and gas welding and its operating.

2. Differentiate between arc welding, gas welding and its application.

3. Justify which welding operation is relevant to certain task.

4. Acknowledge safety procedure when handling with this equipment

5.1 : OVERALL SAFETY IN WELDING

Figure 1 : Oxy-gas welding station (keep cylinders and hoses away from the flame)

1. Because of the heat sources, such as open flames, arcs, sparks, and hot metal used in

welding and related operations, fire and explosion hazards are always present in the work area.

2. Welding processes should be carried out away from all combustible materials, including flammable fluids, vapors, gases, fuel, wood and textiles.

3. Protection of the operators eyes, face, and body against sparks, spatter, and infrared and ultraviolet radiation is essential.

4. Several types of safety equipment and protective clothing are available and should be used.

5. Welding and related methods and machinery that use electricity as a source of energy also present hazards.

6. Proper installation and maintenance of equipment and training of personnel are essential.

7. Proper ventilation systems must be installed and maintained. 8. Never look at the arc with the naked eye. 9. Stand on dry footing when welding. 10. Keep area around welder clean.

INTRODUCTION This chapter covers permanent joining technique using welding process such as gas welding, arc welding and spot welding.

Welding is a materials joining process in which two or more parts are coalescence at their contacting surfaces by a suitable application of heat and/or pressure. Oxyfuel-gas and arc welding are among the most commonly used joining operations. Gas welding uses chemical energy; to supply the necessary heat, arc welding use electrical energy instead. In all of these processes, heat is used to bring the joint being welded to a liquid state. Shielding gases are used to protect the molten-weld pool and the weld area against oxidation. Filler rods may or may not be used in oxyfuel-gas and arc welding to fill the weld area. The selection of a welding process for a particular operation depends on the workpiece material, on its thickness and size, on its shape complexity, on the type of joint, on the strength required, and on the change in product appearance caused by welding. A variety of welding equipment is availablemuch of which is now robotics and computer controlled with programmable features. Discontinuities can develop in the weld zone (such as porosity, inclusions, incomplete welds, tears, surface damage, and cracks). Residual stresses and relieving them also are important considerations in welding. The weldability of metals and alloys depends greatly on their composition, the type of welding operation and process parameters employed, and on the control of welding parameters. General guidelines are available to help in the initial selection of suitable and economical welding methods for a particular application. Applications of welding : Manufacture of automobile bodies, furniture, machine frames, general repair work and ship building. The weld joint is where two or more metal parts are joined by welding. The five basic types of weld joints are shown in figure below :

Figure 2 : Basic types of weld joints

Butt joint : The parts lie in the same plane and are joined at their edges. Corner joint : The parts in a corner joint form a right angle and are joined at the

corner of the angle. Lap joint : Consist of two overlapping parts.

Tee joint : One part if perpendicular to the other in the approximate shape of the

letter T. Edge joint : A joint between the edges of two or more parallel or mainly parallel

members. 5.2 : FILLER, FLUX, ELECTRODE AND SHIELDING GASES 5.2.1 Filler When welding two pieces of metal together, we often have to leave a space

between the joint. The material that is added to fill this space during the welding process is known

as the filler material (or filler metal). Filler metals are used to supply additional metal to the weld zone during welding. Filler metal that does not conduct an electric current during the welding process

and often used for gas welding. They are available as filler rods or filler wire and may be bare or coated with flux.

i) Coated Filler Metal Rods of this type of filler metal consists the coating of flux material.

ii) Bare Filler Metal No coating of flux. Typically, filler metal is in the form of rod, 90 mm long and diameter ranging

from 1.6 mm to 9.5 mm. Different types of welding rods are used for welding of different metals. Some

examples are given below. Metal to be welded (a) Iron rich steels (b) Stainless steel (c) Copper (d) Aluminium and its alloy

Composition of welding rod (a) More C Si, Mn less P and S (b) Should have Cr and V. (c) Copper rods with phorphorus. (d) Rods of same metal containing some silicon.

Filler metal composition should be same as that of the material to be welded. Sometimes additional alloying elements are added to them to improve mechanical properties of weldment.

5.2.2 Flux Flux is a substance which is nearly inert at room temperature, but which becomes

strongly reducing at elevated temperatures, preventing the formation of metal oxides.

The role of flux is typically dual: dissolving of the oxides on the metal surface, which facilitates wetting by molten metal, and acting as an oxygen barrier by coating the hot surface, preventing its oxidation.

Before performing any welding process, the base metal must be cleaned form impurities such as oxide because this will weaken the weldment. Flux is used to convert the oxides and nitrides to slag that can be removed from welding zone easily.

Fluxes come in the form of a paste, powder, or liquid. Typical flux : SiO2, TiO2, FeO, MgO, Al2O3

Flux can be supplied through coating of electrode or coating on filler metal or separately.

Different fluxes are used for welding of different metals. For the welding of copper and its alloy sodium nitrate, sodium carbonates are used as flux. For welding of aluminum or its alloy chloride of sodium, potassium, lithium or barium are used.

Figure 3 : Flux used in shielded metal arc welding: (a) overall process; (b) welding area enlarged

5.2.3 Electrode Electrode is a metal rod which conducts a current from the electrode holder to the

base metal. Used in electric arc welding. Two types of electrode :Consumable ; Non consumable

A) Consumable electrode Consumable electrodes not only used as a conductor for the electrical current, but

it provides the source of the filler metal in arc welding. These electrodes are available in two principal forms of wire and rods (also called

sticks). These electrodes are available in two principal forms: rods (also called sticks) and

wire. Welding rods are typically 225 to 450 mm (918 in.) long and 9.5 mm (3/8 in.)

or less in diameter. The problem with consumable welding rods, at least in production welding

operations, is that they must be changed periodically, reducing arc time of the welder

Consumable weld wire has the advantage that it can be continuously fed into the weld pool from spools containing long lengths of wire, thus avoiding the frequent interruptions that occur when using welding sticks.

In both rod and wire forms, the electrode is consumed by the arc during the welding process and added to the weld joint as metal.

Figure 4 : Shielded metal arc welding process (consumable electrode)

Figure 5 : Various welding electrodes and an electrode holder

Consumable electrodes can further be classified into two categories :

i) Coated electrode The most popular arc welding electrodes. No additional filler metal and flux are required with them. Purposes of electrodes coating : It forms a gas shield to prevent impurities in

the atmosphere from getting into the weld and form separable slag from metal impurities.

ii) Bare electrode Rarely used (only in MIG) Simple rods made of filler metal with no coating over them. Flux is required additionally.

B) Nonconsumable electrode Only used as a conductor for the electrical current. Electrode is made of tungsten which resist melting by the arc. A nonconsumable electrode is gradually depleted during the welding process. For arc welding processes that utilize nonconsumable electrodes, any filler metal

used in the operation must be supplied by means of a separate wire that is fed into the weld pool.

5.2.4 Shielding gases Form a protective envelope around the weld area prevent oxidation Shielding gases fall into two categories :

i) Inert shielding gases Example : Argon, helium

ii) Semi-inert shielding gases Carbon dioxide, oxygen, nitrogen, and hydrogen. Most of these gases, in large quantities, would damage the weld, but when

used in small, controlled quantities, can improve weld characteristics.

No flux is required Used in MIG and TIG

5.3 : GAS WELDING 5.3.1 Oxy-acetylene gas welding Oxyfuel-gas welding (OFW) is a general term used to describe any welding process that uses a fuel gas combined with oxygen to produce a flame. This flame is the source of the heat that is used to melt the metals at the joint. Fuel gases (such as hydrogen and methylacetylene propadiene) can be used in oxyfuel-gas welding. But, the most common fuel gas welding process uses acetylene (C2H2). This process is known as oxyacetylene-gas welding (OAW) and is used typically for structural sheet-metal fabrication, automotive bodies and various repair work.

The apparatus used in gas welding consists basically of an oxygen source and a fuel gas source (usually cylinders), two pressure regulators and two flexible hoses (one of each for each cylinder), and a torch. The cylinders are often carried in a special wheeled trolley.

Figure 6 : Apparatus in oxyfuel gas welding

Advantages : 1. Simple, portable and cheap

Disadvantages

1. Low welding speed 2. Not recommended for welding reactive metals such as titanium and zirconium

Flame types In oxy-acetylene welding, flame is the most important tool. All the welding equipment simply serves to maintain and control the flame. The correct type of flame is essential for the production of satisfactory welds. The flame must be of the proper size, shape and condition in order to operate with maximum efficiency. The proportion of acetylene and oxygen in the gas mixture is an important factor in oxyfuel-gas welding. Three basic types of oxyacetylene flames used in oxyfuel gas welding : (a) neutral flame

(b) oxidizing flame (c) carburizing or reducing flame

a) Neutral flame The neutral flame as shown in figure below is produced when the ratio of oxygen to acetylene, in the mixture leaving the torch, is almost exactly one-to-one. Its termed "neutral because it will usually have no chemical effect on the metal being welded. It will not oxidize the weld metal and it will not cause an increase in the carbon content of the weld metal. The neutral flame is commonly used for the welding of:

(i) Mild Steel (ii) Stainless steel (iii) Cast iron (iv) Copper (v) Aluminum

b) Oxidizing flame The oxidizing flame results from burning a mixture which contains more oxygen than required for a neutral flame. It will oxidize or burn some of the metal being welded. To have this flame set carburizing flame first convert it to neutral flame and then reduce the supply of acetylene to get oxidizing flame. Its inner cone is relatively shorter and excess oxygen turns the flame to light blue color. It burns with a harsh sound. An oxidizing flame tends to be hotter than the neutral flame. This is because of excess oxygen and which causes the temperature to rise as high as 6300F. The oxidizing flame is commonly used for the welding metals that are not oxidized readily such as :

(i) Copper base metals (brass, bronze) (ii) Zinc base metals (iii) A few types of ferrous metals, such as manganese steel and cast iron

c) Carburizing flame The carburizing (or reducing) flame, is created when the proportion of acetylene in the mixture is higher than that required to produce the neutral flame. A carburizing flame has an approximate temperature of 5500F (3038C). A reducing flame can be recognized by acetylene feather which exists between the inner cone and the outer envelope. The outer flame envelope is longer than that of the neutral flame and is usually much brighter in color. Larger the excess of acetylene larger will be its length. The carburizing flame is commonly used for the welding of aluminum and nickel alloys. Metals that tend to absorb carbon should not be welded with reducing flame. For example, iron and steel, it produces very hard, brittle substance known as iron carbide. This chemical change makes the metal unfit for many applications in which the weld may need to be bent or stretched.

Figure 7 : (a), (b), (c) shows the three basic types of flames. (d) The principle of the

oxyfuel-gas welding operation.

Figure 8 : Comparison between all three flames:

Welding practice procedure and equipment The basic steps can be summarized as follows:

1. Prepare the edges to be joined and establish and maintain their proper position by using clamps and fixtures.

2. Open the acetylene valve and ignite the gas at the tip of the torch. Open the oxygen valve and adjust the flame for that particular operation.

3. Hold the torch at about 45 from the plane of the workpiece with the inner flame near the workpiece and the filler rod at about 30 to 40.

4. Touch the filler rod to the joint and control its movement along the joint length by observing the rate of melting and filling of the joint.

Figure 9 : (a) General view of and (b) cross-section of a torch used in oxyacetylene welding. (c) Basic equipment used in oxyfuel-gas welding.

5.4 : ARC WELDING In arc welding, developed in the mid-1800s, the heat required is obtained from electrical energy. The process involves either a consumable or a nonconsumable electrode. An arc is produced between the tip of the electrode and the workpiece to be welded, by using an AC or a DC power supply. Power supply A welding power supply is a device that provides an electric current to perform arc welding operation. Welding usually requires high current (over 80 amperes) and it can need above 12,000 amps in spot welding. Low current can also be used; welding two razor blades together at 5 amps with gas tungsten arc welding is a good example. A welding power supply can be as simple as a car battery and as sophisticated as a modern machine based on silicon controlled rectifier technology with additional logic to assist in the welding process.

Figure 10 : A constant current welding power supply capable of AC and DC

Arc welding (AW) is a fusion-welding process in which coalescence of the metals is achieved by the heat from an electric arc between an electrode and the work. To initiate the arc in an AW process, the electrode is brought into contact with the

work and is then quickly separated from it by a short distance. The electric energy from the arc thus formed produces temperatures of 5500C (10,000F) or higher, sufficiently hot to melt any metal.

A pool of molten metal, consisting of base metal(s) and filler metal (if one is used) is formed near the tip of the electrode. In most arc-welding processes, filler metal is added during the operation to increase the volume and strength of the weld joint. As the electrode is moved along the joint, the molten weld pool solidifies in its wake.

Types of arc gas welding : (i) Shielded metal arc welding (SMAW) (ii) Gas metal arc welding, GMAW (@ metal inert gas welding, MIG) (iii)Gas tungsten arc welding, GTAW (@ tungsten inert gas welding, TIG)

Figure 11 : Basic equipment in arc welding

5.4.1 : Shielded metal arc welding (SMAW) A process that use a coated consumable electrode to lay the weld. SMAW is by far the most widely used arc welding process. Applications : Shipbuilding, repair work, pipelines, construction.

Principle : 1. During operation, the bare metal end of the welding stick (opposite the welding tip)

is clamped in an electrode holder that is connected to the power source. 2. The holder has an insulated handle so that it can be held and manipulated by a

human welder. 3. The heat of the welding process melts the coating to provide a protective atmosphere

and slag for the welding operation. It also helps to stabilize the arc and regulate the rate at which the electrode melts.

4. An electric arc is produced between the end of a coated metal electrode and the steel components to be welded.

5. As the electrode melts, the (flux) coating disintegrates, giving off shielding gases that protect the weld area from atmospheric gases and provides molten slag which covers the filler metal as it travels from the electrode to the weld pool. The slag floats to the surface and protects the weld from contamination as it solidifies. Once hardened, the slag must be chipped away to reveal the finished weld.

6. This process may be performed manually. Advantages : 1. Equipment is portable, cheap & easy to use most widely used of AW process 2. Can be used on carbon steels, low alloy steels, stainless steels, cast irons, copper,

nickel, aluminum

Disadvantages 1. Low productivity 2. Operator dependant 3. Electrode must periodically be changed

Figure 12 : SMAW

5.4.2 : Gas metal arc welding, GMAW (@ metal inert gas welding, MIG)

Also known as MIG welding Most widely used arc welding process for aluminum alloys. A process in which a continuous and consumable wire electrode and a shielding

gas are fed through a welding gun. Applications : Used in fabrication operations in factories for welding a variety of

ferrous and non-ferrous metals, automated welding using robots. Principle :

1. A continuous wire (known as consumable electrode) is fed into the welding gun. 2. The wire melts and combines with the base metal to form the weld. 3. The molten metal is protected from the atmosphere by a gas shield which is fed

through a conduit to the tip of the welding gun. 4. Gases used for shielding : Argon, Helium, Carbon Dioxide (CO2) inert gas 5. The inert gas shield eliminates slag and allows cleaner and stronger weld. 6. This process may be automated.

Advantages : 1. Continuous weld may be produced. 2. High level of operators skill is not required. 3. Slag removal is not required.

Disadvantages :

1. Expensive and non-portable equipment is required. 2. Outdoor applications are limited because of effect of wind, dispersing the

shielding gas. 3. GMAW guns can be bulky and difficult-to-reach small areas or corners.

Figure 13 : MIG 5.4.3 : Gas tungsten arc welding, GTAW (@ tungsten inert gas welding, TIG)

Also known as TIG welding A process that use a nonconsumable electrode [tungsten, Tm = 3410C] to

produce a weld. The weld area is protected from atmospheric contamination by a shielding gas (argon, helium) and a filler metal that is fed manually is usually used.

Applications : Used extensively in the manufacture of space vehicles, when joining pipes for offshore applications, applied to thin materials, frequently employed to weld small-diameter and thin-wall tubing such as those used in the bicycle industry

Principle : 1. The torch holding the tungsten electrode is connected to a shielding gas cylinder

as well as one terminal of the power source. This will allow the welding current from the power source to enter the electrode.

2. The workpiece is connected to the other terminal of the power source through a different cable.

3. The shielding gas goes through the torch body and is directed by a nozzle toward the weld pool to protect it from the air.

4. Protection from the air is much better in TIG than in SMAW because an inert gas such as argon or helium is usually used as the shielding gas and because the shielding gas is directed toward the weld pool.

5. When a filler metal is used, it is added to the weld pool from a separate rod or wire, being melted by the heat of the arc.

6. This process may be performed manually or by machine and automated methods.

Figure 14 : TIG

Advantages : 1. High quality weld 2. Little or no postweld cleaning 3. Can be used to weld reactive metals, such as titanium, zirconium, aluminum and

magnesium.

Disadvantages : 1. Slow process

5.5 : SPOT WELDING Used to join two sheet of metal by lap joint form a small nugget at the

interface. Thickness of workpiece = up to 3 mm (1/8 inch). Applications : In mass production of automobiles, appliances, metal furniture.

Principle : 1. Pressure are applied to workpiece. 2. Current [1000A to 100,000A] is passed through the joint for certain period of

time, so that just enough heat generated to melt the joint. 3. A current stop but the pressure is maintained for certain time until solidification

complete.

Figure 15: Spot welding

Advantages : 1. Very little skill required to operate 2. High production rate 3. Heating involve a small portion (less distortion) 4. Possible to weld dissimilar metal with different thickness

Disadvantages

1. Complex equipment (expensive) 2. Limited to lap joint only

References : http://www.asminternational.org https://eis.hu.edu.jo http://www.ignou.ac.in

Chapter 6 Introduction to Metal

Casting Chapter Outline 6.1 Overall safety in metal casting 6.2 Melting practice 6.3 Sand casting

6.3.1 Process cycle 6.3.2 Elements of gating system 6.3.3 Molding material 6.3.4 Pattern 6.3.5 Core

6.4 Die casting 6.5 Basic design rule in casting 6.6 Cleaning and casting defects Learning outcome When you complete this chapter you should be able to:

1. Have a basic understanding on casting terminology and processes

2. Have acquired knowledge on casting defects and design rules

6.1 : Overall safety in metal casting

1. Aprons, gloves and leggings should be leather as this offers the most protection is a spillage of molten metal occurs.

2. Wear protective clothing and devices like safety glasses and full face shields. 3. Cloths made of natural fibers like cotton are to be preferred over synthetics

that can melt and stick to the skin. 4. Strong, leather shoes should be worn at all times in the workshop as they offer

the best protection for feet. Do not distract anybody during a pour. 5. Do not look into the furnace without appropriate eye safety gear for

splattering and infrared radiation. 6. Always operate in a well-ventilated area. Fumes and dusts from combustion

and other foundry chemicals, processes and metals can be toxic. 7. Spilled molten metal can travel for a great distance. Operate in a clear work

area.

6.2 : Melting Practices Furnaces are charged with melting stock consisting of liquid and/or solid metal, alloying elements and various other materials such as flux and slag forming constituents. Furnace choice is based on the type of metals that are to be melted. Factors for furnace selection

1. Economic consideration (less cost during operation) 2. Composition and melting point of the metal/alloy 3. Capability to control furnace atmosphere 4. Capacity 5. Environmental consideration (environment pollution) 6. Maintenance (less) 7. Safety (high)

Metals or alloys in casting process are melted and prepared in a furnace which may be of:

1. Electric arc 2. Induction 3. Crucible 4. Cupola

When the metal is heat up in the furnace, this molten metal is poured into the assembled mold either via a ladle or directly from the furnace. When the metal has cooled, the mold and the core materials are removed and the casting is cleaned. Certain castings may require welding, heat treatment or painting.

1. Electric arc furnace : The furnace is charged with ingots, scrap, alloy metals and fluxing agents. An arc is produced between three electrodes and the metal charge, melting the metal. A slag with fluxed covers the surfave of the molten metal to prevent oxidation, to refine the metal and to protect the furnace roof from excessive heat. When ready, the electrodes are raised and the furnace tilt