Workshop Technology (1) - Engineering Materials - PDF

UNIT 1 Engineering Materials Learning Objectives On completion of this unit a learner will be able to Describe ferrous metals , non-ferrous metals and non-metals Know the properties and uses of ferrous and...

UNIT 1 Engineering Materials Learning Objectives On completion of this unit a learner will be able to Describe ferrous metals , non-ferrous metals and non-metals Know the properties and uses of ferrous and non ferrous metals Know the safety precautions to be followed in a work shop 1.0 Introduction Engineering materials are those which are extensively used in various engineering applications such as used for construction of bridges, machine tools, automobiles, locomotives, ships, space crafts and many more.Steel is extensively used in construction of bridges.Iron is used for various machine tools.Aircrafts have aluminium bodies.Large number of household ,industrial goods,electronics goods are made using plastics like TV cabinets computer bodies & toys. Classification of Engineering Materials Engineering materials are basically classified into two groups namely metals and non-metals, and their sub classification is given below. 2 Automobile Engineering Technician Engineering Materials Metals Non Metals Non Ferrous Ferrous Polymers Ceramics metals metals Wrought iron, Al, Cu, T he rmo Thermo Carbon Steels, Sl, tin, static plastics plastic Alloy steels, Cast Iron. zn PVC Polythene, Phenol Acrylic resins formal dehyde Refractoreis, Abrasives, glass, Cement Classification of Engineering Materials and concrete Mechanical Properties of Metals The mechanical properties that determine the behavior of metals under applied forces. These properties are most important for the designing point of view. 1. Strength : Ability of a material to resist loads without failure. 2. Tensile Strength : Ability of a material in tension to withstand stress without failure. 3. Shear Strength : Ability of a material to withstand transverse loads without fracture. 4. Elasticity : Property of material which enables it to regain its original shape after deformation with in the elastic limit. 5. Stiffness : Property of material which enables it to resist deformation. 6. Plasticity : Ability of material to be deformed permanently without fracture even after removal of force. Paper - I Workshop Technology 3 7. Ductility : Ability of a material to deform plastically without rupture under tensile load. 8. Malleability : Property which enables the metal to withstand deformation by a compressive load without fracture. 9. Brittleness : Property of the material of sudden fracture without any appreciable deformation. 10. Hardness : Property of the material which enables it to resist abrasion, indentation, machining and scratching. 11. Toughness : Ability of material to absorb maximum energy upto fracture takes place. 12. Fatigue : Failure of material under repeated (cyclic) loads or fluctuating loads. 13. Weldability : Ability of a material to be joined by welding 14. Castability : Property of a metal which indicates the ease with which it can be cast into different shapes and sizes from its liquid state. Ferrous Metals The metals which contain iron as base are called ferrous metals. Eg. Cast iron, Alloy steels etc. These are clssified as 1) Pig iron 2) Cast iron 3) Wrought iron 4) Carbon Steel 5) Alloy steel. The properties and uses of common engineering materials. 1.1 Cast Iron Pig iron remelted and there by refined together with definite amount of lime stone,steel scrap and spoiled castings in cupola. It contain 2-4% carbon, a small percentage of silicon, sulphur, phosphorus and manganese. Properties of Cast Iron 1. It has good fluidity 2. It can be easily machined 3. It is brittle in nature 4. It is resistance to deformation 4 Automobile Engineering Technician 5. It is wear resistant. Uses of Cast Iron 1. It is used in making pipes 2. It is used for making machine bodies 3. It is used in making automotive industry parts. 1.2 Mild Steel These are also called low carbon steels having carbon content of 0.15 - 0.3%. Properties of Mild Steel 1. It has low fluidity. 2. It has good tensile strength. 3. It is ductile 4. It can be cold worked easily. Uses 1. It is used for making structures 2. It is used for making nuts and bolts 3. It is used for making machine components. 4. It is used for making boiler plates. 1.3 High Carbon Steels High carbon steels have more than 0.60% carbon i.e. 0.6 - 0.9% carbon. It is generally used for making parts requiring strength, hardness and wear resistance. Properties of High Carbon Steels (1) It has good strength (2) It has high toughness (3) It has increased wear resistance. Paper - I Workshop Technology 5 Uses 1. It is used for making Drop hammers 2. It is used for making Screw drivers 3. It is used for making laminated Springs 4. It is used for making gears. 5. It is used for making piston rings 1.4 Alloy Steels Steel is a metal alloy consisting mostly of iron, in addition to small amount of carbon, depending upon the grade and quality of the steel. Alloy steel is any type of steel to which one or more elements besides carbon have been added to produce a desired physical properties. The most common alloying elements added to steel are Chromium, Nickel, manganese, silicon, Vanadium etc.. Properties of Alloy Steel (1) High Strength (2) High corrosion resistance (3) High wear resistance (4) Good toughness. Uses (1) It is used for making Aeroplane parts (2) It is used for making automobile parts (3) It is used for railway track work (4) It is used for making locomotive parts 1.5 Stainless Steel It contains 18% chromium, 8% nickle, 0.06% to 0.12% carbon. They are called stainless because in the presence of oxygen, they develop a thin adherent film of chromium oxide that protects the metal from corrosion. Properties of Stainless Steel 1. It has high corrosion resistance. 6 Automobile Engineering Technician 2. It has high strength 3. Good toughness 4. It posses non magnetic properties. 5. It can be rolled. Uses 1. It is used for making surgical instruments. 2. It is used for making utensils 3. It is used for making containers for pharmacautical industries. 4. It is used for making springs. Non Ferrous Metals The metal which do not contain iron as base Eg: Al, cu, Lead ,Zn and gold etc. All the non ferrous metals have common set of properties. The melting point of these metals are generally lower than ferrous metals. 1.6 Copper Copper is easily identified from all other metals due to reddish in colour and is extracted from copper pyrates. Properties of Copper : 1. It is relatively soft. 2. It is very malleable and ductile 3. It is very good conductor of heat and electricity. 4. It is very flexible. Uses of Copper 1. It is used for making electrical cables. 2. It is used for making kitchen vessels 3. It is used for making pipes which are used in refrigerators. 4. It is used making for ornaments. Paper - I Workshop Technology 7 1.7 Brass It is basically refers to a yellowish alloy of copper and zinc and it comprises of 65% copper and 35% zinc. There are various classes of brass, depending on the proportion of copper and zinc are available for various uses. The melting point of brass ranges from 800oC - 1000 oC. Properties of Brass 1. It is non corrosive 2. Air, water and some acids do not affect it. 3. It is poor conductor of electricity. Uses 1. It is used for making utensils. 2. It is used for manufacturing ornaments. 3. It is used in hydraulic fittings, pump lining, in making bearing and bushes. 4. It is used in making locks. 1.8 Bronze It is alloy of copper and tin. The composition range is 5-25% tin and 75 to 95% copper. The corrosion resistance of bronzes are superior than brasses. Properties of Bronze 1. It is comparativley hard 2. It is resistance to surface wear 3. It can be casted into wires and sheets 4. It has high strength. Uses 1. It is used in hydraulic fittings, pump linings, 2. It is used in making utensils, bearings, bushes, sheets, rods, wire etc. 1.9 Tin Although it is used in small amounts, tin is an important metal. Tin is used as protective layer on the sheet metal. It is obtained from tin stone. 8 Automobile Engineering Technician Properties of Tin 1. It is white soft metal 2. Good resistance to acid corrosion 3. Low strength 4. It is malleable and ductile. 5. It does not corrode at both dry and wet climates. Uses 1. It is used as a coating on steel containers for preservation of food products 2. It is used in making thin foils and as an alloying element in the manufacture of bearings. 1.10 Zinc It is fourth most utilized industrially after iron, Aluminium and copper. It is used for galvanising the steel sheet or wire as it serves as anode to protect from corrosion attack. Properties of Zinc 1. It is soluble in copper 2. Low melting point and high fluidity. 3. High corrosion resistance 4. It is ductile and malleable. Uses 1. It is used for die casting 2. It is used for production of brass 3. It is used in battery cells for making dry batteries 4. It is used as protective coating in iron and steel against rusting 1.11 Gun Metal Gun metal contains 10%tin, 88% copper and 2% zinc. Zinc is added to clean the metal and increase fluidity. It is not suitable for being worked in th cold state. Paper - I Workshop Technology 9 Properties of Gun Metal 1. It is highly anti corrosive 2. It has good machinability 3. It has good hardenability. Uses 1. It is used for casting guns and cannons. 2. It is used for boiler fitting. 3. It is used for making bearings. 4. It is used for making glands in centrifugal pumps 1.12 White Metal White metal contains copper-tin-antinomy and it contain 88% tin, 8% antimony and 4 % copper. Properties 1. It is a soft metal with low coefficient of friction 2. It has little strength Uses It is the most common bearing metal used into cast iron boxes when the bearing are subjected to high pressure and load. 1.13 Aluminium Aluminium is most abundant metal in the earth crust. It is silvery white in colour. It makes up about 8% by weight of the earth’s solid surface Aluminium is remarkable for its low density and ability to resist corrosion Properties of Aluminium 1. It is a good conductor of heat and electricity. 2. It is very light in weight. 3. In pure state is very weak and soft. Uses 10 Automobile Engineering Technician Uses 1. It is used for making automobile parts 2. It is used for ornamemtal purpose 3. It is used for making aircraft parts 4. It is used for making bars, tubes&rivets 1.14 Non Metals 1. Wood : Another name given to wood is timber.It is obtained from trees after full growth and made suitable for engineering building process. 2. Plastics : The word plastic is commen term that is used for many materials of a synthetic or semi synthetic nature. Now plastic materials are most widely used for domestic as well as industrial purpose due to its low cost, light weight and it looks decorative. 3. Rubber : Rubber is a polymer which is a word that is derived from the greek meaning “many parts”. Natural rubber is formed in the latex which comes from the rubber trees. It is collected in a cup mounted on each tree. Rubber is used for making tyres, tubes, shock absorbers, rubber cushions, weather stripping around car’s windshield and gaskets. 1.15 Safety Precautions 1. Never wear loose clothing, ties and shirts with long sleeves. 2. Keep the shop floor clean and free from oil and greese. 3. Donot use blunt or dull tool, it slips and causes injury. 4. While using chisels, see that cutting is performed in the direction away from the body. 5. Keep hands away from moving parts. 6. There must be sufficient light and ventilation at work place. 7. Exhaust fans should be provided to remove smokes and fumes. 8. Use proper tools according to the nature of the job. 9. Use of shoes and apron is essential. 10. Never carry tools in pocket. Paper - I Workshop Technology 11 11. Observe all the safety codes while working in the workshop. Summary 1. All engineering materials are mainly clssified into metals and non metals 2. Metals are further classified in to ferrous and non ferrous metals. 3. The metals which contain iron as base are ferrous metals 4. Ferrous metals are classified in to five types i) Pig iron ii) Cast iron iii) Wrought iron iv) Carbon steels v) Alloys steels. 5. The metals which do not contain iron as base are non-ferrous metals 6. All non ferrous metals have common set of properties 7. Steels are classified in to i)low crbon steels ii)medium carbon steels iii)high carbon steels Activity 1. A learner should collect a piece of cast iron and mild steel 2. A learner should collect a piece of copper,silver,aluminium and lead Short Answer Type Questions 1. Classify Engineering materials 2. Write the properties of copper 3. What is the composition of gunmetal 4. What are uses of aluminium 12 Automobile Engineering Technician UNIT 2 Fitting Learning Objectives On completion of this unit a learner will be able to Explain various cutting tools used in fitting shop. Describe various work holding device used in fitting shop. List out various marking and measuring tools used in fitting. Explain about radial drilling machine. 2.0 Introduction Although majority of the work can be finished to fairly good degree of accuracy through various machining operations, but still needs some hand operations to obtain desired finish and fit.These operations are usually carried on bench by fitter. Hence fitting is the process of assembling various parts manufactured in the machine shop. Also a fitter’s task is unavoidable when different parts are to be assembled in position. Hence various tools and equipments are required to perform operations to finish the work to the desired shape and size in assembling the unit. Tools used in fitting: Tools used in fitting is classified into following groups: Paper - I Workshop Technology 13 1. Cutting tools 2. Striking tools 3. Holding tools 4. Marking and measuring tools In addition to the above tools ,the fitter needs other miscellaneous tools such as screw drivers and spanners etc. 2.1 Cutting Tools Cutting tools plays a most important role in removing excess metal from the job to obtain desired finished part. The various cutting tools used in fitting are: 1. Chisels 2. Hacksaws 3. Files 4. Scrapers 5. Drill bits 6. Reamers 7. Taps 8. Dies and sockets 2.1.1 Chisels Cold chisels are used for cutting thin sheets and to remove excess material from large surfaces.In this case the surface finish and accuracy are usually poor. Parts of chisel:It consists of following parts a) Head b) Body or shank c) Point or cutting edge Head : The head is tapered towards top and made tough to with stand hammer blows Body or Shank : The cross section of the shank is made hexagonal or octagonal to have grip while working. 14 Automobile Engineering Technician Point or Cutting Edge : The cutting edge is hardened and tempered and made to specified angle. The hardening followed by tempering makes the chisel to maintain its sharp edge. HEAD SHANK POINT Fig. 2.1 Parts of Chisel The shape of cutting edge is required to specify the chisel. The five most important types of chisels are: 1. Flat chisel 2. Cross cut chisel 3. Half round chisel 4. Diamond point chisel 5. Side chisel Flat Chisel: It is most common chisel used for chipping large surfaces and cutting the sheets. It is also used to part off metal after chain drilling. The length of a flat chisel varies from 100mm to 400mm and the width from 16mm to 32mm. Fig. 2.2 Flat Chisel Cross Cut Chisel: The cross cut chisel or cape chisel is used for cutting grooves and channels and keys ways in shafts and pulleys. Its cutting edge wider than the supporting metal to provide clearance. The length of chisel varies from 100mm to 400mm and width varies from 4mm to 12mm. Paper - I Workshop Technology 15 Fig. 2.3 Cross cut Chisel Half Round Chisel : It is particularly useful for cutting oil ways ,cutting curved grooves in bearings ,bosses and pulleys.They are also used for setting over pilot holes. When a hole is to be drilled a pilot hole is drilled first. Fig. 2.4 Half Round Chisel Diamond Point Chisel.: Its edge is in the form of diamond used for cutting V- grooves, cleaning corners and squaring small holes. Fig. 2.5 Diamond Point Chisel Side Chisel : This is used for chipping and removing the surplus metal in rectangular slots. The shank of the chisel is bent out a little side way and vertically down again. 16 Automobile Engineering Technician Fig. 2.6 Side Chisel 2.1.2 Hack Saw : It is a basic hand cutting tool used for cutting unwanted material. It is used for cutting metals and making recesses priper to filing or chipping. It is also used for cutting slots and contours. Parts of Hack saw : It consists of the following parts. 1. Metal frame 2. Blade 3. Handle. 4. Wing nut 5. Screw The frame is made to hold the blade tightly. They are made in two types. a) The solid frame hack saw in which the length cannot be changed. b) The adjustable frame in which the frame can be adjusted to hold the blades of different lengths. Solid Frame Adjustable Frame Wing Handle Nut Pin Stand Blade (b) Adjustable Frame Hacksaw Fig. 2.7 Hack Saws Hacksaw Blade : It is thin, narrow steel strip made of high carbon steel or low alloy steel or high speed steel. The balde has two pin holes at the ends which fits over two pins which project from the stand that slides in and out of the frame end. Tightening the wing nut at the front end tensions the blade sufficiently to prevent it from flexing when cutting. The blade must be fitted such that teeth pionts away from the handle so that cut takes on the forward stroke. Paper - I Workshop Technology 17 Blade Length Pin Hole Pin Hole 250 to 200 mm Direction of Cut Width Fig. 2.8 Hack Saw Blade 2.1.3 FILES : File is a cutting tool with multiple teeth like cutting edges used for producing smooth surface. The accuracy that can be acheived from 0.2 to 0.05 mm. Wooden Point or Tip Teeth Heel handle Shoulder Feerule Edge Face Length of File Tang Face Handle Heel Tip Edge Shoulder Ferrule Fig. 2.9 Parts of File Parts of the File 1. Tang 2. Tip or point 3. Face or side 4. Edge 5. Heel 6. Shoulder 7. Handle 18 Automobile Engineering Technician 1. Tang : It is the pionted part which fits in to the wooden handle. 2. Tip or point : It is the opposite end of the tang. 3. Face or side : This is the broad part of a file with teeth cut on it. 4. Edge : It is the safe edge of file which has no teeth. 5) Heel : The heel is next to handle of the file with or without teeth. 6) Shoulder : The curved part of the file separating the tang from the body. 7) Handle : The part which is fitted to the handle made of wood.. The files of different cross section or types are needed to suit the various job operations. The most commonly used files are (a) Flat file (b) Hand File (c) Square file (d) Round file (e) Half round file (f) Triangular file (g) Knife edge file (h) Pillar file. (a) Flat File : This is tapered in both width and thickness used for heavy filing. This file is parallel to about two third of length, then tapers in both width and thickness. Fig. 2.10 Flat file (b) Hand File : This is used where flat file is not suitable for filing flat surfaces and has rectangular cross section with parallel edges throughout, but thinkness is tapered towards point. Fig. 2.11 Hand file (c) Square file : This is in square cross section used for filing square and rectangular holes and for finishing the bottom narrow slots. Fig. 2.12 Square file Paper - I Workshop Technology 19 (d) Round File : They are round in cross-section and usually tapered. They are used for filing circular holes, curved surfaces and finishing fillets. Fig. 2.13 Round File (e) Half Round File : This file is tapered double-cut and its cross-section is not a half circle but only one third of a circle. This file is used for round cuts and filing curved surfaces. Fig. 2.14 Half Round File (f) Triangular File : The cross section of file is like equilateral triangle used for filing grooves, slots , holes and sharp corners. Fig. 2.15 Triangular File (g) Knife Edged File : Its shape is like a knife used to file narrow slots, grooves and sharp corners. Its width and thickness are tapered towards point in the form of knife. Fig. 2.16 Knife Edge File 2.1.4 Scrapers : These are used to shaving off thin slices of metal to make a fine and smooth surface which is not possible with a file or chisel. This is made of good quality forged steel and its cutting edge is usually made thin, made from old files. 20 Automobile Engineering Technician Parts of Scrapers 1. Cutting edge with rounded corners. 2. Blade 3. Tang 4. Wooden handle. Fig. 2.17 Parts of Scrapper 1. Cutting edge with rounded corners : The cutting edge is hardened without tempered to make hard. 2. Blade : The broad part of a scraper 3. Tang : The narrow part which fits into wooden handle. 4. Wooden handle : That fits into tang to have grip while scrapping According cross section, the scrapers are classified into three types. They are (a) Flat Scraper (b) Triangular Scraper (c) Half round scraper. (a) Flat Scraper Fig. 2.18 Flat Scrapper This type of scraper is used for scapping plane surfaces or slots and the cutting edge at the ends of the balde is curved. The corners are rounded to prevent deep scratches on finished surface. It also helps to scrap the metal exactly at the desired spot. (b) Triangular Scraper Fig. 2.19 Triangular Scrapper Paper - I Workshop Technology 21 It has three cutting edges and is made from old triangular files used to scrap round or curved surfaces and to remove sharp corners. (c) Half round Scraper : It is used for finishing curved surfaces and chamfering holes and removing burrs. 2.1.5 Drill Bits A drill is a cutting tool for making through hole in a metal piece and usually it has two cutting edges set an angle with axis. It does not produce accurate hole. There are three types of drills. (a) Flat Drill (b) Straight Fluted Drill (c) Twist Drill (a) Flat Drill : It is a simple drill used for producing holdes in softer materials like wood and plastic. This is made of high carbon steel and has two cutting edges. Fig. 2.20 Flat Drill (b) Straight Fluted Drill : It has two cutting edges and two straight flutes used for drilling brass and non-ferrous metals. Fig. 2.21 Straight Fluted Drill (c) Twist Drill : This is most commonly used cutting tool in workshop. It has two cutting edges and two helical grooves which admits coolant and allows the chips to escape during the drilling. These are made of high speed steel. Neck Body Cutting Shank Edge Flute Land Body Clearance Fig. 2.22 Twist Drill 22 Automobile Engineering Technician 2.1.6 Reamers : A drill does not produce accurate hole and it must be finished by finishing tool called reamer. When an accurate hole with a smoother finish a required a reamer is used. Hence the reamer can only follow the drilled hole and removes very small amount of metal to make it smooth There are two types of reamers (a) Hand Reamers (b) Machine Reamers (a) Hand Reamer : This reamer is turned by hand called hand reamer.The shank has a square tang so that a tap wrench can be used to turn the reamer in to work. These are available with straight or helical flutes. Fig. 2.23 Hand Reamer (b) Machine Reamers : These are used to turn by the machine called machine reamers. Its shank is tapered which fits directly in the internal taper of the machine spindle. These are also available with straight shanks which are held and driven by drill chuck. Fig. 2.24 Machine Reamer 2.1.7 Taps : A tap is a screw like tool which has threads like a bolt and three or four flutes cut across the threads which is used to produce internal threads. The edge of the thread formed by the flutes are the cutting edges. The lower part of the tap is some what tapered so that it can well attack the walls of the drill hole. Paper - I Workshop Technology 23 Hand taps are usually made in sets of three (1) Taper tap (2) Second tap (3) Bottom tap. (1) Taper Tap : In this tap about six threads are tapered and is used to start the thread, so that the threads are formed gradually as the tap is turned into the hole. Fig. 2.25 Taper Tap (2) Second tap : It is tapered back from the edge about three or four threads used after taper tap.It has been used to cut the threads as far as possible Fig. 2.26 Second Tap (3) Bottom Tap : It has full threads for the whole of its length. This is used to finish the work prepared by the other two taps. Fig. 2.27 Bottom Tap 2.1.8 Dies It is a circular disc of harderned tool steel used to make external threads on a round rod or bolts with a die and stock. Die has a hole containing threads and flutes which form cutting edges. These are mainly two types 1. Solid Die 2. Adjustable Die. 1. Solid Die : It is one which has fixed dimension and cannot be adjusted for smaller or large diameter. It is used for recutting damaged threads and may be driven by suitable wrench. 2. Adjustable Die : It can be set to cut larger and smaller diameters. It has a split through one side and a slight adjustment is possible with the help of set screw. 24 Automobile Engineering Technician Fig. 2.28 Two - Plate Die 2.1.9 Sockets It is used for the drills whose taper is larger than spindle hole taper. It is much larger than sleeve. Its taper shunk conforms to the spindle hole taper and fits in to it. 2.2 Striking Tools --- Hammers Hand hammers are also called striking tools used to strike the job. They are made of forged steel of various sizes and shapres to suit various purposes like punching, chipping, marking, bending and riverting. 2.2.1 Parts of Hammer Face Fig. 2.29 Parts of Hand Hammer A hammer consists of four parts namely Face, Peen, Cheek and eye hole. Face : It is the striking portion polished well and is given slight convexity to avoid spoilage of the surface of the metal to be hammered. Peen : It is the other end of the head and is made into different shapes to suit various operations. Cheek : Middle portion of the hammer head. Eye-Hole : It is made oval or elliptical in shape to accommodate the handle.. Paper - I Workshop Technology 25 Depending upon the shape of the peen, hand hammers are classified as 1) Ball peen hammer 2) Cross peen hammer 3) Straight peen hammer. 1. Ball Peen Hammer : It has a flat striking face and ball shaped peen which is hardened and polished. This hammer is chiefly used for chipping and riverting. Fig. 2.30 BallPen Hammer 2. Cross - Peen Hammer : It has wedged shape peen across the eye. It is used for bending, stretching, hammering into shoulders. Fig. 2.31 Cross-Pen Hammer 3. Straight Peen Hammer : This is similar to cross peen hammer except that the peen in this case is parallel to eye. It is used for stretching and peening the metal. Fig. 2.32 Straight Peen Hammer 4. Soft Hammer or Mallet : These are soft hammers used give light blows where the work surface must not be damaged. They are made of either rubber, plastic or wood. 26 Automobile Engineering Technician Fig. 2.33 Soft Hammer 2.3 Holding Devices or Vices In most of the metal cutting operations quite a large number of forces will be involved. So it is necessary that the work must be secured highly so that it does not move when subjected to the cutting forces. Therefore, holding the job is an important aspect of all metal cutting operations. A vice is a work holding device used to grip the job tightly. Different types of vices are used for various purposes. They include a. Bench vice b. Pipe vice c. Hand vice d. Pin vice e. Tool maker’s vice 2.3.1 Bench vice This is most commonly used tool for Sliding Jaw holding the work. It has two jaws one of Face which is fixed to the bench and other slides Body with the aid of square screw and a box nut arrangement.The outer end of screw carries a handle, and a collar prevents the screw from coming out of the unit while rotating.The sliding jaw moves close to the fixed jaw to Handle hold the work and the tightening force is exerted by further rotation of handle.The Fig.2.34 Bench Wise working faces of jaws are serrated to give additional grip. Paper - I Workshop Technology 27 2.3.2 Pipe Vice It is generally used for holding round sections ,tubes and pipes etc.It has two serrated jaws,one is fixed and the is moved by rotation of handle.It is used in lumbing work and it grips the circular objects at four points on its surfaces. Fig. 2.35 Pipe Vice 2.3.3 Hand vice It is used for gripping small objects like screw, rivets, keys when they are inconvenient to hold by the bench vice. It has two legs made of Mild steel which holds two jaws at the top and are hinged together at the bottom.A spring is provided between these legs to keep them away. The work is held between the serrated jaws by means of a wing nut and screw. Fig. 2.36 Hand Vice 2.3.4 Pin vice It is used for holding small parts such as wires ,nails and pins. It consists of three jaw self centering chuck which is operated by turning the handle to hold work. Fig. 2.37 Pin Vice 28 Automobile Engineering Technician 2.3.4 Tool makers vice It is a small vice made of mild steel used for holding small jobs which requires fitting or drilling.It is used by tool and die makers and silver smiths to hold small jobs. Handle Screw Fixed Jaw Movable Jaw Body Fig. 2.38 Tool Maker’s Vice 2.4 Marking Tools 1. Surface Plate 2. V - Block 3. Scribers 4. Angle plate 5. Punches 6. Try - Square 2.4.1 Surface Plate Surface plate is made of grey cast iron of solid design. It is used for testing the flatness of work and also used for marking-out the work. A surface plate has a surface of proved flatness. When used for testing flatness,the top of the plate should be coated with their layer of red lead in oil. The surface to be tested must be cleaned, then place in contact with the plate and moved about. If it is reasonably flat, subsequent examination will show spot of blue or red all over the surface. Fig. 2.39 Surface Plate 2.4.2 V - Block : It is made of hardened steel with V-shaped grooves on the top and botton,and rectangular slots on two sides for the location of clamps. Roundly shaped workpieces which are to be marked or drilled are placed on V-supports. In this way, they are firmly supported in a horizontal position and cannot rotate easily. Paper - I Workshop Technology 29 Fig. 2.40 Surface Plate 2.4.3 Scribers : It is made of tool steel with hardened and tampered points and knurled on the body to provide grip. Scriber is used for making straight lines on metal surface with the aid of steel rule, try square and templates. The bent end is used to scratch line in places where the straight end cannot reach. The ends are sharpened on an oil stone when necessary. Fig. 2.41 Single point Scriber Fig. 2.42 Double point Scriber 2.4.4 Angle plate : This is used in conjunction with the surface plate for supporting work in the perpendicular position. It is madeof grey cast iron has two plane surfaces at right angles to each other. It has various slots in it to enable the work to be held firmly by bolts and clamps. Fig. 2.43 Angle Plate 30 Automobile Engineering Technician 2.4.5 Punches : Punches are used in a bench work for marking out work, locating centres, etc in permanent manner. It is made of tool steel, hardened and tempered. The shank is knurled to provide grip. Punches are two types 1. Prick punch 2. Centre punches. Prick punch is sharply pointed tool used for marking small dots along the layout lines in order to make them last longer. Centre punch has an angle more than abtuse and used to mark the centres of holes to be drilled. Fig. 2.44 Prick Punch Fig. 2.45 Centre Punch 2.4.6 Try Square : It is made of steel and consist of a blade and a stock made in one piece set at right angle to each other. It is used to test trueness of mutually perpendicular surfaces and for making straight lines at right angle to each other. BLADE STOCK Fig. 2.46 Try Square Paper - I Workshop Technology 31 2.5 Miscelleneous Tools In addition to the above tools, the following tools are widely used in fitting. 1) File Card 2) Screw driver 3) Spanner 4) Pliers 1. File Card It is the short wire brush used to remove small chips called pins, and to clean the file. While filing these chips are deposited between the teeth of file which reduces cutting ability and casuing scratches on work piece. Fig. 2.47 File Card 2. Screw Driver Screw driver is used for tightening and loosening the screws. It is made in variety of shapes to suit various job operations. Fig. 2.48 Screw Driver 3. Spanners These are also called wrenches, are used for tightening or loosening nuts and bolts. The following types of spanners are widely used in fitting. a. Single end Spanner b. Double end Spanner c. Adjustable Spanner d. Box Spanner 32 Automobile Engineering Technician Fig. 2.49 Spanner 4. Pliers These are used for holding small jobs which are difficult to held by hand. They are used for bending and cutting the wires. The following types of pliers are most common. 1. Cutting pliers 2. Nose Pliers Fig. 2.50 Cutting Plier Fig. 2.51 Nose plier 2.6 Checking and Measuring Instruments Measuring Instruments : a) Steel rule b) Calipers c) Depth gauge d) Vernier Calipers e) Micrometer f) Gauge block a) Steel Rule It is used for direct measurement of length which do not require great accuracy and also used to transfer the measurements from steel rule to calipers. These are available in 150 mm or 300 mm in length. Fig. 2.52 Steel Rule Paper - I Workshop Technology 33 b. Calipers These are used for measuring and transferring the inside or outside dimensions for components. These are also used for comparing the sizes with existing standards. The following types of calipers are most widely used in workshops 1. Outside Calipers 2. Inside Calipers 1. Outside Calipers It is used for measuring outside dimensions of cylindrical shapes and the thickness of metal pieces. It has two steel legs bent inwards. Fig. 2.53 Outside Calipers 2. Inside Calipers It is used to measure the diameter of holes and width of key ways or recesses. Its legs are bent outwards. Fig. 2.54 Inside Calipers 3) Depth Gauge It is used to measure the bling holes, slots, recesses and height of projections. 34 Automobile Engineering Technician Fig. 2.55 Depth Guage 4. Vernier Calipers These are widely used for precision measurement of length, thickness, depth and inside and outside diameters. With vernier caliper we can achieve accuracy upto 0.02 mm. Fig. 2.56 Vernier Calipers 5. Micrometer Micrometer is a precision tool used to measure external or internal dimensions such as diameters and thickness, with an accuracy upto 0.01 mm. Fig. 2.57 Screw Thread Micrometer Paper - I Workshop Technology 35 Spindle Barrel Thimble (Ext-Rod) Distance Measured Handle Fig. 2.58 Inside Micrometer 6. Gauge Block They are used to check the accuracy of gauges to set comparators, sine bars and to make machine tool setups. Vernier Slide Fine Adjustment Beam Work Vernier Scale Lock Screws Fig. 2.59 Guage Block 7. Dividers These are used for transferring dimensions and scrubing circles and arcs on work surface. These are also used for dividing straight and curved lines. 2.7 Drilling Machines Drilling is a process of making holes in a work piece and is carried out by driving a rotating tool called “drill” into a rigidly held work peice. To accomplish the drilling two things are required i.e. drilling macine and drilling tools. A drilling machine is used for drilling holes. However it can perform operations other than drilling such as reaming, boring, lapping etc. Types of Drilling Machine 1) Portable drilling machine 36 Automobile Engineering Technician 2) Sensitive drilling machine 3) Radial drilling machine 4) Upright drilling machine 5) Gang drilling machine 2.7.1 Sensitive Drilling Machine It isa small drilling machine is mounted on a bench in which feed is hand operated, and the cutting force applied is determined by sense of feel of the operator. The parts of sensitive drilling machine as shown below. It consists of a vertical column, a work table, head supporting the motor and driving mechanism, and a vertical spindle for driving and rotating the drill. The work is mounted on the work table which may be raised or lowered by the clamp to accomodate work pieces of different sizes. The driving mehanism consists of V-belt drive from machine spindle to drill spindle. Three or four speed stepped cone pulley is provided to give various speed ranges. The spindle is designed and mounted in a sleeve such that the spindle rotates and simultaneously moves up and down to provide feed for drill. This is achieved by a rack and pinion mechanism. Fig. 2.60 Sensitive Drilling Machine Paper - I Workshop Technology 37 2.7.2 Radial Drilling Machine Radial drilling machines are used for drilling heavy work pieces, where it is easier to move the drill rather than work and specially for the jobs where high degree of accuracy is required. It consists of base, column, radial arm, drill head and driving mechanism. The arm of radial drilling machine can be swing around the column to any position and angle. A wide range of spindle speeds, together with automatic feed of the spindle, makes the radial drilling machine suitable for drilling large castings. For lowering or raising the radial arm, a separate motor is provided. The work can be firmly champed on the table having T-slots. The table is fixed to the base. The radial arm and the spindle can be adjusted without disturbing the work setting. Fig. 2.61 Radial Drilling Machine 2.8 Drill Fittings The following devices are used for holding the drills. a. Drill Chuck : It is designed to hold straight shank drills of different sizes. The jaws of the chuck are tightened around the drill by means of drill chuck key.. These drill chucks have standard taper shanks. b. Machine spindle : These have morse taper holes. Standard taper drills are directly fitted in the spindle. The drill may be removed by driving the drift.. 38 Automobile Engineering Technician Fig. 2.62 Drill Chuck Fig. 2.63 Machine Spindle c. Sleeve : It is used to hold the taper shank drills whose taper is less than taper hole of the spindle. Taper Shank Taper hole Fig. 2.64 Sleeve Fig. 2.65 Socket d. Socket : It is used for the drilling whose taper is larger than spindle hole taper. It is much longer than sleeve. Its taper shank confirms to the spindle hole taper and fits into it. 2.9 Drilling Operations The following operations are generally performed on drilling machine. a) Drilling b) Reaming c) Boring Paper - I Workshop Technology 39 d) Counter boring e) Counter sinking f) Tapping a) Drilling : It is the process of making cylindrical hole by rotation of cutting tool. b) Reaming : It is the process of making a hole smoothly and accurately by the tool called reamer. c) Boring : It is the operation of enlarging a drilled hole to bring it to required size by using single point cutting tool. d) Counter boring : This operation is used for enlarging only to a certain depth of already drilled hole in order to maintain alignment and true concentricity of the counter bored hole with the previously drilled hole and the tool is provided with a pilot at its bottom. e) Counter Sinking : It is the operation of enlarging the end of a drilled hole to give a conical shape for a short distance. This is done for providing a seat to the counter sunk heads of screws. f) Tapping : It is the operation of cutting internal threads by using a cutting tool called tap. In order to tap the hole, a special tapping chuck must be used. Drilling Reaming Boring Counter Sinking Tapping Fig. 2.66 Drilling Machine Operations 40 Automobile Engineering Technician Summary 1. Fitting is the process of assembling various parts manufactured in the machine shop. 2. In fitting the hand tools are classified as cutting tools, marking tools, striking tools,holding tools, measuring and checking instruments. 3. Chisels are used to cut thin sheets and to remove excess material in the form of layers 4. Hacksaw is abasic hand cutting tool used to remove excess metal from the job 5. Files are used to remove excess metal from the job in the form of pow- der to make it smooth 6. Scrapers are used to remove excess metal in form of thin layers at se- lected spots to make it truly flat surface 7. Drilling is the process of making circular holes on the metal piece by rotating the tool against work piece 8. Reamer is a tool used to finish the already drilled hole on cylindrical holes 9.Tap is acutting tool used to cut internal threads and dies are used to cut external threads on the cylindrical rods and pipes 10. Striking tools are hammers used to strike the work or tool 11. Holding devices are used to hold work tightly to prevent slipping during cutting operations. Activity 1. A learner should collect L-shape M S flat. 2. A learner should collect T-shape MS flat. Short Answer Type Questions 1. What is the use of a file. 2. What is the purpose of chisel. 3. Define scrappers. 4. Differentiate tap and die. Paper - I Workshop Technology 41 5. What are srtiking tools. 6. Define drilling and reaming. 7. What is the importance of holding devices. 8. Name different types of drilling machines. Long Answer Type Questions 1. Define file and explain about any four files with sketch. 2. Explain about bench vice with naet sketch. 3. Define chisel and Explain about any two. OJT Type Question 1. Prepare U,V,L& T Shapes from a given MS Flat 42 Automobile Engineering Technician UNIT 3 Sheet Metal Work Learning Objectives On completion of this unit, a learner will be able to List out metals used for sheet metal work. List and explain various tools used in sheet metal work. Explain various sheet metal operations. List and explain various sheet metal joints commonly used. Explain various fastening methods. 3.0 Introduction Sheet metal work is generally regarded as the working of metal from 16 SWG down to 30 SWG with hand tools and simple machines into various forms by cutting ,forming into shapes and joining. Each guage designates a definite thickness.Higher the gauge number and lesser the thickness. The common examples of sheet metal work are pipes, boxes, funnels, photoframes, buckets, and cans etc. In sheet metal work the knowledge of geometry, mensuration and properties of metal are most important for preparation of specific object. Paper - I Workshop Technology 43 3.1 Metals used in Sheet Metal Work The following metals are used in sheet metal work. 1. Black iron 2. Galvanised iron 3. Copper 4. Aluminium 5. Tin 6. Stainless Steel 1. Black Iron :It has a bluish black appearance. It is cheapest metal and rusts rapidly. Its use is limited to fabrication of articles for general use and are to be painted with enamel for protecting them from rust. It is used for making tanks, stoves, pipes etc. 2. Galvanised Iron : Zinc coated iron is called galvanised iron. This is soft sheet is popularly known as G.I. sheet. The zinc coating resists rust, improves the appearance of the metal and permits it to be soldered with ease. It is used for making buckets, pans, cabinets, gutters etc. 3. Copper : Copper resist rust and have better appearance, but the cost is very high. It is used for ornamental work and making kitchen wear. 4. Aluminium : It is not used in pure form as it is very soft, but it is used with a small amount of copper, silicon, manganese etc. It is anti corrosive and has good appearance, relatively cheap and light in weight. It is used in making a number of articles like household appliances, refrigerator trays, light fixtures, windows, in the construction of aero plane parts etc., 5. Tin : Steel sheets are coated with pure tin and have bright silvery appearance. This is used for nearly all solder work as it is easiest metal to join by soldering. The thickness of the tin plates are denoted by special marks not by gauge numbers. It is used for making buckets, pans, cans, etc. 6. Stainless Steel : Resists rust and has pleasing appearance. But the cost is high. This is alloy of steel with nickle, chromium and traces of other elements. It is used in canneries, food processing plants and chemical plants, kitchen wares etc. 44 Automobile Engineering Technician 3.1.1 Sheet Metal Hand Tools A large number of hand tools used by sheet metal workers. Some of the important tools used are given below. 1. Measuring tools (a) Steel rule (b) Folding rule (c) Circumference rule (d) Vernier Calipers (e) Micrometer (f) Sheet metal guage 2. Straight edge 3. Scriber 4. Divider 5. Trammel point 6. Chisel 7. Punches 8. Hammers 9. Snips or Shears 10. Pliers 11. Stakes 12. Groovers 13. Rivetsets 14. Soldering Iron 3.1.2. Measuring Tools (a) Steel Rule : It is used for measuring and layouting small works with an accuracy upto 0.5 mm. Paper - I Workshop Technology 45 Fig. 3.1 Steel rule (b) Folding Rule : It is used for measuring and laying out larger work pieces accuracy upto 0.5 mm Fig. 3.2 Folding rule (c) Circumference Rule : It is used to find out directly the circumference of a cylinder. One of the edge is marked with diameters and the values of circumference corresponding to each diameter is marked in the other edge. Fig. 3.3 Circumference Rule (d) Vernier Caliper : It is used for measuring dimensions upto 0.02 mm. Fig. 3.4 Vernier Caliper 46 Automobile Engineering Technician (e) Micro Meter : This is used to measure the thickness of the metal sheet accurately upto 0.01 mm. Fig. 3.5 Micrometer (f) Sheet Metal Guage : This is used to measure the thickness of the sheet. Fig. 3.6 Sheet Metal Guage (2) Straight Edge : It is a steel bar has one long edge is bevelled and comes in variety of lengths. It is used for drawing long straight lines. Straight Edge Work Scriber Fig. 3.7 Straight Edge (3) Scriber : It is a steel wire and its one end is sharply pointed and hardened to mark layout lines on the sheet metal. Paper - I Workshop Technology 47 Fig. 3.8 Single point Scriber Fig. 3.9 Double point Scriber (4) Divider : Dividers are used to draw circle or arcs on sheet metal and to divide the lines into two equal parts. Fig. 3.10 Divider (5) Trammel Point : These are used to describe large circles and arcs beyond the limits of dividers. Fig. 3.11 Trammel point (6) Chisels : These are used to cut sheets, rivets, bolts and for chipping operations. Fig. 3.12 Chisels 48 Automobile Engineering Technician (7) Punches : There are various types of punches used for making small indentation for locating centres in a more permanent manner. There are two most common types of punches are used 1) Prick punch, used for making small dots 2) Centre punch, used for making location of points and centre of holes to be drilled. Fig 3.13 Punches (8) Hammers : Hammers are used for forming shapes by hollowing, stretching or throwing off. The commonly used hammers are given below. (a) Ball peen Hammer : It is a general purpose hammer (b) Rivet Hammer : This is used for spreading rivets. Fig 3.14 River Hammer (c) Setting Hammer : A flat face is used for flattering seams without damage to the sheet metal. Fig 3.15 Setting Hammer Paper - I Workshop Technology 49 (d) Raising Hammer : This hammer is used for denting the metal down to shape. Fig. 3.16 Raising hammer (e) Mallet : Mallets are used where ever light blows are required. These may be made of either fiber, plastic, wood or rubber. Fig. 3.17 Mallet (9) Snips or Shears : These are heavy scissors used for making straight or circular cuts. It is used only to cut 20 guage or thinner metals. The most common types of snips are a) Straight snips, used for straight cuts, b) Bent snips, used to make curved cuts. Fig. 3.18 Straight Snips (10 ) Pliers : There are two pliers which are used in sheet metal work. They are flat nose plier and round nose plier. Flat nose pliers are used for forming and holding work while round nose pliers are used for holding and forming in to various shapes. Fig. 3.19 Pliers 50 Automobile Engineering Technician (11) Stakes : These are sheet metal worker’s anvil used for bending seaming, forming using hammer or a mallet. They are actually work supporting tools while working. They are made in different shapes and sizes to suit the requirements of the work. The double seaming stake is used to make double seam. The break horn state is used for riveting, forming round and square surfaces, bending straight edges and making corners. The bevel edged stake is used to form corners and edges. Hatched stake is used to make straight and sharp bends. Honk Head Shanks Fig. 3.20 Stakes (12) Groovers : These are used for grooving and flattening a seam. These are available in many shapes. Fig. 3.21 Groovers 13) Rivet Set : Rivetset has a deep hole in the bottom to draw a rivet through metal and a cup shaped hole to form the finished head of a rivet. Outlet on side Burrs Outlet Deep hole Shallow concav Fig.3.22 Sections of Rivet Sets Paper - I Workshop Technology 51 (14) Soldering Iron : It is used to join two pieces of sheet metal by soft soldering (al alloy of tin and lead). Soft solder is transferred to the joint by means of soldering iron. (a) Straight Iron (b) Hatchet Iron Fig. 3.23 Types of Soldering Irons 3.2 Sheet Metal Operations The major types of sheet metal operations are given below. (1) Shearing (2) Bending (3) Drawing (4) Squeezing (1) Shearing Shearing is the process of cutting across a sheet or strip. The various shearing operations include (a) Cutting off (b) Parting (c) Blanking (d) Punching (e) Piercing (e) Slitting (g) Trimming a. Cutting Off : It is the operation of shearing the piece from sheet metal with a cut along a single line. b. Parting : This means that the strip is removed between the two pieces to part them. c. Blanking : It is the operation of cutting the flat sheet to the required shape and size using punch and die. 52 Automobile Engineering Technician d. Punching : It is the operation of making only circular holes in a sheet metal. e. Piercing : It is the operation of making a hole of any shape in a sheet metal by punch and die. f. Slitting : It is the operation of cutting the sheet metal in a line along the length. g. Trimming : It is the operation of finishing the edges of a part by removing excess metal around it. 2. Bending : It is the folding operation by using suitable tools. It may be done over stakes. The common forms of bending the sheet metal is single bend and double bend etc. 3. Drawing :It is the process of producing thin walled hallow or vessel shaped parts from the sheet metal. Again this process can be divided into two types. a) Deep drawing and shallow drawing..In deep drawing, the height of the component is greater than the diameter or width. In shallow drawing the height of the component is less than the diameter or width. Fig. 3.24 (4) Squeezing : It is the quick and widely used method. The operation involves severe cold deformation and it requires a greater amount of pressure to deform the metal at cold state. The most commonly used squeezing operation are sizing, coining, hobbing, riveting. (a) Sizing : This operation is used for surfacing or flattening. A special die is needed for every job. (b) Coining : This is a process of making impressions or raising of images by a plastic flow by using a punch and die. Paper - I Workshop Technology 53 (c) Hobbing : It is the process of producing cavities into surface of material by pressing with a special punch called hub. (d) Riveting : It is the process of fastening the two metal sheets by inserting metal pin in to the sheets and spreading out by hammering to form the rivet head. 3.3 Sheet Metal Joints 3.3.1 Hem and Seam Joints (1) Hem Joint : Hem is an edge or border made by folding. It strengthens the edges and eliminate the sharp edges. Hems are three types a) Single hem b) Double hem c) Wired edged hem (a) Single Hem : It is made by single folding of the edge of sheet metal. Fig. 3.25 Single Hem (b) Double Hem : It is made by folding the edge over twice to make it smooth. It provides much greater strength than single hem. Fig. 3.26 Single Hem c) Wired Edged Hem : It consists of holding a piece of sheet metal around a wire of given diameter. 54 Automobile Engineering Technician Sheet Hammer Wire Fig. 3.27 Wired Hem (2)Seam Joint : It is the joint formed by two edges of sheet metal. The process of joining the edges are called seaming. Different kinds of seams are given below. a) Lap seam b) Groove seam c) Single seam d) Double seam e) Dovetail seam f) Flanged Seam a) Lap Seam : It is a simple type of seam which consists of lapping the edgeof one sheet over the other and the joint is made by soldering or riveting. Fig. 3.28 Lap Seam (b) Grooved Seam : It is made by hooking two single hems together Fig. 3.29 Grooved Seam (c) Single Seam : Single seam is used to join a bottom to vertical bodies of various shapes. Paper - I Workshop Technology 55 Fig. 3.30 Single Seam (d) Double Seam : It is similar to single seam with the difference that its formed edges bent upwards against the body. Fig. 3.31 Double Seam (e) Flanged Seam : It is used to join the bottom of a container to its body. Fig. 3.32 Flanged Seam (f) Dovetail Seam : It is used to join sections such as one pipe to another pipe or a sheet to pipe It consists of narrow strips of metal which are formed by slitting the end of pipe. Fig. 3.33 Dovetail Seam 56 Automobile Engineering Technician 3.3.2 Fastening Methods The following fastening methods are widely adopted in sheet metal work. (a) Riveting (b) Soldering (c) Brazing (d) Welding. (a) Riveting : It is a permanent fastening method by using rivet. Rivet consists of head, shank and tail are generally made of same metal as the parts that are being joined. The required holes must be either punched or drilled before riveting. Hammer Blow Hammer Blow a) Drawing Rivet Set b) Shaping Rivet Set c) Forming Rivet Fig. 3.34 Rivet Sets (b) Soldering : It is the process of joining two or more metal pieces by means of an alloy. This alloy is called solder made of lead and tin. The melting point of solder is less than the metal to be joined. For soldering, the base metal is heated by soldering iron which also melts solders and flux. the flux (zinc chloride paste) is used to dissolve the oxide film on the surface and also prevents oxidation during soldering. The molten solder fills the space between mating surfaces. It solidifies and forms a strong joint. Solder Solder Iron Fig. 3.35 Solder Paper - I Workshop Technology 57 c) Brazing : It is similar to soldering, but it gives much stronger joint. The major difference is that use of a harder filler material called spelter and its melting point is higher than solder., but lower than the metal being joined. In brazing operation the two metal pieces are to be joined must be cleaned. Flux (Borax) is applied on the joint and heated to a temperature just above the melting point of the spelter. The liquid spelter is distributed between the surfaces by capillary action. After solidification it forms strong joint. d) Sport Welding : The spot welding is used for joining the sheets by application of heat and pressure at specific locations called spots. In this, the sheets to be joined together are held between two electrodes at required located sports. Normally a high amperage current and low voltage is passed through electrodes causing local heating at that spots. The pressure applied on the electrodes squeezes the sheet metal at various locations thus joining the two sheets together to form a joint. 1,2 Electrodes 3. Movable Arm 4. Fixed Arm 5. Frame Spot Weld Tra nsformer Fig. 3.36 Sport Welding Summary 1. Sheet metal work is the process of making useful articles for household as well as industrial. 2. Commonly used sheet metals are black iron, galvonised iron, copper, aluminium, stainless steel etc. 3. Tools used in sheet metals are measuring tools and operational tools. 4. Most common sheet metal operations are shearing, bending, drawing, squeezing etc. 5. Important fastening methods in sheet metal are riveting, soldering, brazing and spot welding. 58 Automobile Engineering Technician Activity 1. A learner should collect funnel madeof sheet metal. 2. A learner should collect a square tray 3. A learner should collect riveted joint sheet metal piece. 4. A learner should collect soldered joint sheet metal piece. Short Answer Type Questions 1. Name different tools used in sheet metal work. 2. Define Seam in sheet metal work. 3. What is the purpose of mallet ? Long Answer Type Questions 1. Explain about any four important sheet metal operations. 2. Explain different sheet metal joints with sketches. 3. Explain brazing and soldering. OJT / Related Questions 1. Prepare a rectangular tray from a given G.I. sheet 2. Prepare a funnel of given dimensions from G.I. Sheet metals. 3. Join the given two sheet metal pieces by soldering. 4. Join the given sheet metal pieces by riveting.  UNIT 4 Carpentary Learning Objectives On completion of this unit a learner will be able to Explain various hand tools used in carpentry Know the importance of holding devices Explain about various carpentry joints Know the different carpentry processes 4.0 Introduction Carpentry deals with the processing of wood to obtain desired shapes and sizes. Strictly speaking carpentry deals with all works of a carpentry such as roofs, floors, partitions etc of a buildings. While joining deals with the making of doors, windows, cupboards, dressers stairs and all interior fitments for a building. Timber is the basic material used for any type of wood work. It is available in a wide choice of weights, strengths, colours and textures. Wood having good machining characteristics. 60 Automobile Engineering Technician 4.1 Markings and Measuring Tools Marking is one of the most important features of wood work and the job accuracy depends upon marking and measuring. These tools are used in wood work for marking, measuring and checking the work at various stages. Measuring Tools The following tools are commonly used in wood work. 1. Steel rule 2. Wooden folding rule 3. Steel tape (1) Steel Rule : It is simplest and direct measuring instrument. Various sizes and designs are available for measuring and setting out dimensions. This is graduated on both sides as millimeter and centimeter. (2) Wooden Folding Rule : This is graduated both in centimeters and inches. The most commonly used wooden rule is form fold wood rule. It is made of pieces of each 150mm length. (3) Steel Tape : This is used to measure longer dimensions. They are available in different lengths ranging from 0.6 m to 2.5 m. (a) Steel Rule (b) Four-Fold Rule (c) Steel Tape Fig. 4.1 Measuring Tools Paper - I Workshop Technology 61 Marking Tools The following tools are used for marking in wood working. (1) Straight Edge (2) Try square (3) Marking guage (4) Divider (5) Marking knife (1) Straight Edge : The straight edge is a machined flat piece having truely straight and parallel edges. One of the longitudinal edge is generally made bevelled. It is used for testing trueness of surface and straightness of edges. Straight Edge Work Scriber Bevelled Edge Fig. 4.2 Straight Edge (2) Try Square : This is used for marking and testing angles of 90o. It consists of a steel blade, rivetted to a hard woodstock which has a protective brass plate on the working surface. Fig. 4.3 Try square 62 Automobile Engineering Technician (3) Mitre Square : It is used for marking and testing 45o. It consists of a steel blade fitted in a wooden or metal stock at an inclination of 45o with horizontal. Fig. 4.4 Mitre Square (4) Marking Knife : All the dimensional lines marked with pencil are cut with marking knife. It has a chisel edge at one end and sharp point at other end. It is made of steel. Fig. 4.5 Marking Knife (5) Marking Guage : It is commonly used when absolute accuracy is required. It has a stem with a sharp point pin at one end. It is used to cut line along the grains and parallel to an edge. The distance can be adjusted by sliding the stock. Fig. 4.6 Marking Guage (6) Divider : It has two pointed legs and hardened to prevent wear. It is used for transferring dimensions and scribing curves or circles. Paper - I Workshop Technology 63 Fig. 4.7 Divider 4.2 Cutting Tools Cutting tools are used to cut the wood to approximate size. The following cutting tools are used in carpentry. (a) Saw or Hand Saw : The saw is most commonly used cutting tool in wood working section. All saws used in wood work essentially consists of two main parts - the blade which carries the cutting teeth and the handle used for holding during the cutting operations to apply pressure. The classification of saws is according to their teeth and the direction of grains of the wood to be cut. Fig. 4.8 Hand Saw The following types of saws are used in wood working. (b) Rip Saw : Rip saw is used to cut the wood along the grains. The cutting action starts from near the tip and gradually the whole length. Fig. 4.9 Rip Saw 64 Automobile Engineering Technician (b) Crosscut Saws : It is used for cutting the wood across the grains. The action of the teeth is that of a series of knives which sever the fibre and force out the waste wood in the form of saw dust. Fig. 4.10 Cross-cut saw (c) Panel Saw : It has a fixer blade and is used for fine work, mostly on the bench. This is often used for ripping as well as cross cutting. The teeth have slightly more hook than those of a cross cut saw. (d) Tenon Saw : This saw is mostly used for cross-cutting when a fine and more accurate finishing is required. The blade is very thin and reinforce with a rigid steel back. Fig. 4.11 Panel Saw (e) Dovetail Saw : It is a smaller version of tenon saw, this saw is used where the greatest accuracy is needed and fine shallow cuts are to be needed. Fig. 4.12 Dovetail Saw (f) Bow-Saw : It has a narrow blade which is held in tension by twisting the string with a small wooden lever. These saws are used for cutting quick curves Paper - I Workshop Technology 65 and the handles can revolve in their sockets. The blades can be adjusted to any desired position when in use. Fig. 4.13 Bow Saw (g) Key Hole Saw : It is smallest saw. It has a tapered blade fixed into the handle by screws. It is used for cutting key holes and is very useful for internal and intricate work. Fig. 4.14 Key hole Saw Chisels : A fairly large number of chisels are used in wood work for cutting in different manners to produce desired shapes and cavities. The chisel consists of these parts irrespective of their size and use. The common types of chisels are used in carpentry work are the following. Handle Handle Brass Tang Shoulder Neck Blade Cutting Edge Fig. 4.15 Chisel 66 Automobile Engineering Technician (i) Firmer Chisel : This chisel is capable of doing heavy work and is used for joining and shaping the wood with or without mallet. The blade is made of rectangular section with bevel edge. (ii) Paring Chisel : These chisel have a long blades used to cut the deep corners with hand pressure. These are mostly used for pattern making. (iii) Mortise Chisel : It is used for taking heavy and deep cuts resulting in more stock removal as in case of making mortises. (iv) Socket Chisel : It is provided with socket instead of tang. The wooden handle is inserted into this socket. This prevents splitting of handle while removing heavy stock. (i) Firmer Chisel (ii) Pairing Chisel (iii) Mortise Chisel Blade Socket Handle (iv) Socket Chisel Fig. 4.16 Types of Chisels Planes Planes are used in producing flat and smooth surfaces by cutting thin layers of wood. The plane consists of these parts - Body, cutting blade, handle, knob and other controls. The common types of planes used in carpentry are (a) Jack Plane : It consists of a wooden body or stock in which blade or cutter is fastened at an angle 45o to the sole. The plane iron and cap iron are assembled and inserted in a mouth of plane along with the wedge. The back iron supports the cutting edge and also breaks the shavings so that curl away from the blade. The blade can be set for taking deeper or shallower cuts. Paper - I Workshop Technology 67 Fig. 4.17 Wooden Jack Plane (b) Trying Plane : These are used to make a true flat surfaces which are formed by jack plane. It is longer than jack plane. Fig. 4.18 Trying Plane (c) Smoothing Plane : It is nothing but a smaller wooden jack plane without handle. In operation its stock itself is held in both hands. It is used for better finish and smoothness to the surface already plane by a jack plane. Fig. 4.19 Smoothing Plane (d) Rebate Plane : It is small in size and is used to cut the recess along the edge of a work piece. In rebate plane the edges of cutting iron is in line with the side of plane. 68 Automobile Engineering Technician Fig. 4.20 Rebate Plane (e) Plough Plane : It is used for making deep grooves of standard size. A deep guage is fixed on the body, and is operated by thumb screw. It allows the plane to make a groove of constant depth. Fig. 4.21 Plough Plane (f) Router Plane : These planes are used for finishing the grooves to a constant depth which are formed by chisel or saw. Fig. 4.22 Plough Plane Boring Tools Boring tools are necessary to make holes in wood. The various types of boring tools used are as follows (1) Bradawl : It is used for boring small holes for inserting the screws and nails. It has chisel like point and it is operated by hand. Paper - I Workshop Technology 69 (a) Bradawl (b) Gimlet Fig. 4.23 (2) Gimlet : It is hand operated tool used for making small holes for screws. It has a spiral flutes with screw like point. (3) Brace : It is a boring tool used for making holes. It holds and rotates various types of bits for producing holes and is operated by hand.The most commonly used braces are ratchet brace and wheel brace. These are used for making larger holes of different sizes. Head Crank Sweep Handle Cam Ring Ratchet Chuck Jaws Fig. 4.24 Ratchet Braces (4) Auger bit : It is used for producing long deep holes of diameter ranging from 6 to 40 m. It is steel bar , an eye at top to which the handle is fitted. The bottom end is provided with a screw point. 70 Automobile Engineering Technician Fig. 4.25 Auger Striking Tools Striking tools are called hammers used to drive in nails and to operate chisels. The most common striking tools used in carpentry are hammers and mallets. (a) Warrington hammer:It is used for bench work and light work. It is made of cast steel with tempered face and peen. The wooden handle fits in the eye and steel widge is driven in to form a rigid joint. (b) Claw Hammer: It is dual purpose hammer and face is used to drive in nails, and claw at the other end for pulling out nails. (c) Mallet : It is used for operating the chisel and gauges. it is made of hard wood and is provided with handle. (a) Warrington Hammer (b) Claw hammer (c) Mallet Fig. 4.26 Striking Tools 4.3 Holding Devices To enable the wood worker to cut the wood accurately, it must be held steady. There are number of devices to hold the job (a) Bench vice : it is made of steel. It has the jaws, one is fixed to the side of the table while the other is kept movable by means of a screw and handle. Paper - I Workshop Technology 71 The job tab is held between the two jaws. The faces of jaws are lined with hard wood to prevent damage of work surface. Fig. 4.27 Bench Vice (b) Bench Stop : It is simply a block of wood projecting above the top surface of the bench. This is used to prevent the wood from moving forward when being planed. (c) Bench hold Fast : It consists of a cast iron pillar, steel arm and screw with a handle. It is used for securing the work to the bench. The pillar drops into a hole bored in the bench and the screw operates the arm to hold work on the table. Fig. 4.28 Bench Hook Fig. 4.29 Bench Holdfast (d) Bench hook : It is used to support work while planning or cutting. It is made of wood and can be placed conveniently on the work table. (e) Sash Cramp : This is used for holding wide work such as frames or tops. It consists of a steel bar fitted with two jaws one of which is movable by a screw and other is fixed into one of the spaced holes by a fastening pin. 72 Automobile Engineering Technician Fig. 4.30 Sash Cramp (g) G-Clamp : It is used to hold small works and it consists of frame with a fixed jaw at one end and movable jaw is operated by a screw and a thumb nut at the other end. It is also used to hold small parts for gluing. Fig. 4.31 G-Clamp 4.4 Miscellaneous Tools (1) Rasp or File : It is used for finishing the wood surface. It has sharp cutting teeth and it is used for finishing small curved surfaces. (a) Rasp (b) File Fig. 4.32 Rasp and File (2) Scraper : It has a fine edge which cuts fine shavings and removes plane marks. (3) Glass paper : Where a surface is having very small imperfections that the no other cutting tool will do, then glass paper is used. It consists of small particles of glass struck tosheet of paper. Its sharp edges cuts the wood. (4) Ratchet Screw Driver : It is very useful for turning screws through a few degrees in. Paper - I Workshop Technology 73 (a) Cabinet Screw Driver (b) Ratchet Screw Driver Fig. 4.42 Types of Screw Driver (5) Screw Driver : These are used for screwing or unscrewing for the screws used in wood work. 4.5 Carpentary Processes 1. Marking : It is one of the most important operation of wood work and the success of completing a job depends on accurate and orderly marking. These dimensions can be measured from an existing model and can be set out from the drawing prepared for the purpose. The dimensions are marked with respect to the finished edge or finished face of a work. 2. Sawing : Sawing is one of the basic cutting operation carried out in a carpentry shop. To start the cut, the thumb of left hand is placed against the blade. This steadies the blade and enabling it to start in the right place. One or two short movements are given first, taking care that the saw works in the right direction. And then full, easy strokes are applied to cut the wood in a forward direction only. A point to note in all sawing work that the cut is made on one side of the line already marked and that is on waste side Fig. 4.33 Sawing 3. Planing : It is the operation of tuning up a piece of wood by a planner. The work for planning is supported by the bench stop in the vice. The pressure is applied during forward stroke and released on the returned stroke. It is important to move plane in straight line to avoid rounding at the ends and to 74 Automobile Engineering Technician obtain smooth surface. Planing is done along the grains. The surface planed are tested for flatness in all directions using a try square. (a) Surface Planning (b) Edge Planning Fig. 4.34 Planning 4. Chiselling : It is the process of cutting excess wood with chisel to obtain desired shape. In chiselling hard pressure is applied to remove thin layers. Mallet is used when cuts are made across the grains. (a) Horizontal Paring (b) Vertical Paring Fig. 4.35 Chiselling 5. Boring : It is the process of making holes in wood. The work is secured to suitable vice and the hole position is marked with punch. The hole is provided by turning and feeding the bit into work. 6. Rebating : It is the process of cutting a recess along the edge of wood by a rebate plane. While rebating, the plane must be kept pressed into the side of the wood. 7. Polishing : It is the process of producing a smooth reflecting surface with only the minimum removal of material. To obtain such a finish it is necessary to incorporate a suitable abrasive within the polishing composition. 4.6 Carpentary Joints Terms joinery involves connecting of different wooden parts together by means of properly made joints. In order to achieve good results, the joint made Paper - I Workshop Technology 75 in wood work are usually secured firmly by means of suitable fastners such as glues, dwels, screws, bolts and buts etc. 1. Halving Joint : The purpose of this joint is to reuse the corners and inter sections of the framing and at the same time keep all the face flush that in the same plane. These joints are used in construction of frames. Marking and cutting of any joint must be accurate, so that it can shed together with the final extreme surface level. (a)Dovetail Halving joint (b)T- Joint Fig. 4.36 ‘T’ Halving Joint 2. Mortise and Tenon Joint : It is strongest joint and is used for the construction of doors windows and frames. The tenon (tongue) fits into a mortise (mouth). 3. Mitre Joint : It is formed by cutting the ends at an angle. The two ends are joined by nails or screws. This joint is used in photo frames. Fig. 4.37 Mortise & Tenon Joint 4. Dovetail Joint :This is strongest joint used for construction of boxes and cup boards. 76 Automobile Engineering Technician Fig. 4.38 Mitre Joint Fig. 4.39 Dovetail Joint 5. Butt Joint : The fastening of boards edges to edges is frequently necessary to give a wider board. eg. Drawing board. In butt joint two true edges are joined with glue. If it is properly done this joint is very strong. Fig. 4.40 Butt Joint 4.7 Wood Working Machines Wood working machine plays a vital role in the modern wood work particularly where large scale production of wooden articles is carried out. Modern development in wood working machinery with regard to the greater safety for the operator, easy operation and greater accuracy. These developments led to higher output. The commonly used wood working machines are as follows. 1. Wood Turning Lathe : It is one of the important and oldest machine used in carpentry shop. This is employed primarily for turning jobs in making cylindrical parts. It resembles the engine lathe most frequently used in the machine shop and consists of a cast iron bed, head stock, tail stock, tool rest, live and dead centres and speed control device. In practice the work piece is either clamped between two centres or on the face plate. Long jobs are held between the centres and turned with the help of Paper - I Workshop Technology 77 goauge, chisel, parting tools. Generally the lathe is supplied together with a number of accessories for making it useful for a variety of jobs. Fig. 4.41 Wood Turning Lathe 2. Circular Saw : It can be used for ripping, cross cutting, bevelling and grooving. This saw has flat table upon a which the work rests while being cut, a circular cutting blade, cut-off guide and a ripping fence that acts as a guide while sawing along the grain of the wood. The circular saw usually has provisions for tilting the table upto 45o to enable the machine to cut at different angles required during mitering and levelling. Fig. 4.42 Circular Saw and Its Use 3. Band Saw : It means that an endless metal saw band that travels over the rims of two or more rotating wheels. Other parts of band saw are frame, table ,saw guide, saw tensioning arrangement. It is most useful for making curved or irregular cuts in wood. The band saw is available in two models vertical and horizontal. In horizontal band saw, two wheels are arranged side by side and the table is mounted underneath. In the vertical band saw the wheels are arranged one over the above in a vertical plane below the table, angular cuts are obtained by tilting the saw table. 78 Automobile Engineering Technician Fig. 4.43 Band Saw 4. Wood Planner : It is used for planning large work pieces and capable of producing true surface with enough accuracy at a faster rate. It consist of table over which the work is fed against a revolving cylindrical cutter head carrying 2-3 knifes. The cutter is mounted on a over head raft and the table can raised or lowered to attain desired thickness. Fig. 4.44 Principle of Wood Planer 5. Sanding Machine : The sanding machine are used for producing smooth surface after planning the wood. It seems a surface suitable for painting. The action of sanding machine is some as the sand paper producing the smooth Paper - I Workshop Technology 79 surface. In sanding an abrasive is rubbed over the surface of wood to wear down hills by friction and thus present a smooth, uniform surface. Work Piece Stop Guard Table Wheel Belt Tool or workres Fig. 4.55 Belt Sander Fig. 4.56 Summary 1. Carpentry is the processing of wood to obtain desired shape and size 2. In carpentry hand tools are classified in to five types ie marking tools , cutting tools ,boring tools ,striking tools and holding devices. 3. The wood working operations includes marking, sawing, planing, chiseling, boring and rebating. 4. The successful construction of wood depends on satisfactory joining.The most common carpentry joints are halving joint,mortise joint tenon joint,mitre joint,dovetail joint,and butt joint. 5. Wood working machines are primarily intended to increase the productivity with higher accuracy which includes wood turning lathe,band saw,circular saw, sanding machine. Activity 1. A learner should collect T-halving joint. 2. A learner should collect plain tenon joint. 3. A learner should collect dovetailbridge and bridge cornerjoint. Short Answer Type Questions 1. Name different cutting tools used in carpentry. 2. What is the use of pincer. 3. Name different types of planes. 80 Automobile Engineering Technician 4. Listout carpentry joints. Long Answer Type Questions 1. Explain about any four carpentry processes. 2. Explain about wood turning lathe with neat sketch. OJT Questions 1. Make saw practicing. 2. Make Plane practicing. 3. Make boring practice. 4. Prepare a corner , T , butt joints etc., from a given wooden piece.  UNIT 5 Forging and Welding Learning Objectives On completion of this unit, a learner will be able to Know different types of hand tools, and their usage. Describe important smithy operations. Explain various machine forging operations. Know the safety precautions to be followed while doing welding. Get the knowledge about arc welding and gas welding procedure and proper handling of equipment used for the purpose 5.0 Introduction Forging is the process of deforming the metal into different shapes by heating up to plastic state and by hammering or pressing at red hot condition. The process is usually carried out above re-crystalization temperature. Therefore this process is called hot working process. The term usually preferred to the production of heavy parts and in large scale. 5.1 Hand Tools used in Forging The following hand tools are used in forging. 82 Automobile Engineering Technician 1) Anvil 2) Swage block 3) Tongs 4) Hammer 5) Chisel 6) Hardie Tools 7) Swages 8) Fullers 9) Flatters 10) Set Hammers 11) Punches 12) Drifts 1. Anvil : The anvil forms a good support for black smith’s work when hammering. Its body is made of mild steel. These are made in different forms to provide the means for other forging operations. The usual form of anvil has a round hole called pitchel hole for bending rods and a square hole called hardie hole for holding square shanks of various tools such as swages, fullers, hardies, chisels. Round Hole Working Face Hardie Hole Step Cutting Face Horn Beak Body Fig. 5.1 Anvil 2) Swage Block : It has different sizes and shapes of slots like half round, square and rectangular along its four sides. It is made of cast iron. This is used as a support in punching holes and forming different shapes. Fig. 5.2 Swage Block Paper - I Workshop Technology 83 3. Tongs : Blacksmith requires tongs to handle the job while forging. These are used to hold the job in position and turning over during forging. The commonly used tongs are (a) Closed mouth (b) Open mouth (c) Round hollow tong (d) Square tong (a) Closed Mouth : This is used for holding thin sections. (b) Open Mouth : This is suitable for holding heavier stock, (c) Round Hollow Tong : This is used for holding round, hexagonal, and octagonal shapes. (d) Square Tong : This is used for holding square work. (a) Open Mouth (b) Closed Mouth (c) Round Hollow Tong (d) Square Fig. 5.3 Types of Tongs 4. Hammers : These are two kinds. a) The Sledge hammers are used by smith’s helper used for heavy blows weighs from 4 kg to 10 kg. b) Hand hammer are used by smith himself used for light blows Fig. 5.4 Sledge Hammers Fig. 5.5 Hand Hammers 84 Automobile Engineering Technician 5. Chisels : These are used for cutting metals and for necking prior to breaking. They may be hot or cold depending on whether the metal to be cut is hot or cold. The hot chisel is used for cutting the metal when hot and its edge is at an angle of 30o. The cold chisel is used to cut cold materials. (a) Hot Chisel (b) Cold Chisel Fig. 5.6 Types of Chisels 6. Hardie Tools : It is a cutting tool with square shank to fit in the square hole of the anvil. It is used in combination with hot or cold chisel. Fig. 5.7 Hardie Tools 7. Swages : Swages are used for reducing and finishing the round, square, and hexagonal shapes. A set of swages are designed for round shapes and square shapes Fig. 5.8 Swages Paper - I Workshop Technology 85 8. Fullers : These are used in pair for necking down a piece of work. The bottom fuller has square shank to fit in the hardie hole and top one is provided with handle. Fig. 5.9 Fullers and Their Use 9. Flatters : These are used to obtain smooth and finished flat surfaces which have already been shaped by fullers and swages. Fig. 5.10 Flatter 10. Set Hammers : It is really a form of