Manufacturing Process (INX-101) PDF

Manufacturing Process (INX-101) (i) Manufacturing – Need and concept: The successful creation of men’s material welfare (MMW) depends mainly on: availability of natural resources (NR) exertion of human effort (HE); both physical and mental development and use of...

Manufacturing Process (INX-101) (i) Manufacturing – Need and concept: The successful creation of men’s material welfare (MMW) depends mainly on: availability of natural resources (NR) exertion of human effort (HE); both physical and mental development and use of power tools and machines (Tools), This can be depicted in a simple form, MMW = NR(HE)TOOLS where, NR: refers to air, water, heat and light, plants and animals and solid and liquid minerals TOOLS: refers to power plants, chemical plants, steel plants, machine tools etc. which magnify human capability. This clearly indicates the important roles of the components; NR, HE and TOOLS on achieving MMW and progress of civilization. Production or Manufacturing Definition: This can be simply defined as value addition processes by which raw materials of low utility and value due to its inadequate material properties and poor or irregular size, shape and finish are converted into high utility and valued products with definite dimensions, forms and finish imparting some functional ability. Manufacturing Process: Production Engineering covers two domains: (a) Production or Manufacturing Processes (b) Production Management (a) Manufacturing Processes This refers to science and technology of manufacturing products effectively, efficiently, economically and environment-friendly through -Application of any existing manufacturing process and system -Proper selection of input materials, tools, machines and environments. -Improvement of the existing materials and processes -Development of new materials, systems, processes and techniques All such manufacturing processes, systems, techniques have to be Technologically acceptable Technically feasible Economically viable Eco-friendly Classification of Engineering Manufacturing Processes. All these processes used in manufacturing concern for changing the ingots into usable products may be classified into six major groups: as (1) Primary shaping processes, (2) Secondary machining processes, (3) Metal forming processes, (4) Joining processes, (5) Surface finishing processes and (6) Processes effecting change in properties. Classification of Engineering Manufacturing Processes. Primary shaping processes are manufacturing of a product from an amorphous material. Some processes produces finish products or articles into its usual form whereas others do not, and require further working to finish component to the desired shape and size. Some of the important primary shaping processes is: (1) Casting, (2) Powder metallurgy, (3) Plastic technology, (4) Gas cutting, (5) Bending and (6) Forging. 2. Secondary or Machining Processes The process of removing the undesired or unwanted material from the work piece or job or component to produce a required shape using a cutting tool is known as machining. This can be done by a manual process or by using a machine called machine tool (traditional machines namely lathe, milling machine, drilling, shaper, planner, slotter). Some of the common secondary or machining processes are— (1) Turning, (2) Threading, (3) Knurling, (4) Milling, (5) Drilling, (6) Boring, (7) Planning, (8) Shaping, (9) Slotting, (10) Sawing, (11) Broaching, (12) Hobbing, (13) Grinding, (14) Gear cutting, (15) Thread cutting 3. Metal Forming Processes Forming processes encompasses a wide variety of techniques, which make use of suitable force, pressure or stresses, like compression, tension and shear or their combination to cause a permanent deformation of the raw material to impart required shape. These processes are also known as mechanical working processes and are mainly classified into two major categories i.e., hot working processes and cold working processes. Hot working Processes (1) Forging, (2) Rolling, (3) Hot spinning, (4) Extrusion, (5) Hot drawing and (6) Hot spinning. Cold working processes (1) Cold forging, (2) Cold rolling, (3) Cold heading, (4) Cold drawing, (5) Wire drawing, (6) Stretch forming, (7) Sheet metal working processes such as piercing, punching, lancing, notching, coining, squeezing, deep drawing, bending etc. 4. Joining Processes Many products observed in day-to-day life, are commonly made by putting many parts together may be in subassembly. For example, the ball pen consists of a body, refill, barrel, cap, and refill operating mechanism. All these parts are put together to form the product as a pen. The process of putting the parts together to form the product, which performs the desired function, is called assembly. An assemblage of parts may require some parts to be joined together using various joining processes. (1) Welding (plastic or fusion), (2) Brazing, (3) Soldering, (4) Riveting, (5) Screwing, (6) Press fitting, (7) Sintering, (8) Adhesive bonding, (9) Shrink fitting, (10) Explosive welding, (11) Diffusion welding, 5. Surface Finishing Processes: Surface finishing processes are utilized for imparting intended surface finish on the surface of a job. By imparting a surface finishing process, dimension of part is not changed functionally; either a very negligible amount of material is removed from the certain material is added to the surface of the job. Some of the commonly used surface finishing processes are: (1) Honing, (2) Lapping, (3) Super finishing, (4) Belt grinding, (5) Polishing, (6) Tumbling, (7) Organic finishes, (8) Sanding, (9) deburring, (10) Electroplating, (11) Buffing, (12) Metal spraying, (13) Painting, 6 Processes Effecting Change in Properties Processes effecting change in properties are generally employed to provide certain specific properties to the metal work pieces for making them suitable for particular operations or use. Some important material properties like hardening, softening and grain refinement are needed to jobs and hence are imparted by heat treatment. (1) Annealing, (2) Normalising, (3) Hardening, (4) Case hardening, (5) Flame hardening, (6) Tempering, (7) Shot peeing, (8) Grain refining and (9) Age hardening. 7. Regenerative manufacturing: Production of solid products in layer by layer from raw materials in different form: liquid – e.g., stereo lithography powder – e.g., selective sintering sheet – e.g., LOM (laminated object manufacturing) wire – e.g., FDM. (Fused Deposition Modelling) Out of the aforesaid groups, Regenerative Manufacturing is the latest one which is generally accomplished very rapidly and quite accurately using CAD and CAM for Rapid Prototyping and Tooling. Selection criteria for manufacturing process: 1) Production rate 2) Cost 3) Performance 4) Size 5) Shape Questions: 1. How do you classify the manufacturing processes? 2. Distinguish between ‘primary’ and ‘secondary’ processes? 3. Discuss primary shaping processes. Give also a brief account of the primary shaping processes. 4. Explain the secondary or machining processes. Give also a brief account of these processes. 5. Describe and name the types of joining processes, surface finishing operations and the processes employed for changing the properties of manufactured components. 6. Write a short note on assembly process. 7. Explain the Economical and technological considerations in manufacturing References: Introduction to Basic Manufacturing Process & Workshop Technology by Rajender Singh A TEXTBOOK OF WORKSHOP TECHNOLOGY : MANUFACTURING PROCESSES (English, J. K. GUPTA, R. S. KHURMI) Elements Of Workshop Technology Vol-1 and Vol-II by Choudhury H SK Chapter 2: Materials properties and their application: Different engineering materials, Properties, Nomenclature, Basics of heat treatment Classification of Materials Classification of Materials Classification of Materials Classification of Materials Classification of Materials: AISI:American Iron and Steel Institute; SAE: Society of Automotive Engineers; ASTM: American Society for Testing and Materials Classification of Materials: Composition of some alloyed medium carbon steels: UNS:The unified numbering system (UNS) is an alloy designation system widely accepted in North America. Classification of Materials: Compositions and Application of some Tool steels Classification of Materials: Stainless Steel: Stainless Steel: Applications of Stainless steels Cast Irons Grey Cast Iron Nodular or Ductile Iron: White Cast Iron: Malleable Cast Iron: Applications of Cast iron Nonferrous Metals Copper: Copper: Copper Alloys: Copper Alloys-Brass Bronze: Beryllium copper Aluminum: Aluminum Alloys Temper Designations Titanium Titanium Titanium Alloys: Nickel: Nickel: Application of Nickel: Magnesium Magnesium Ceramics Materials Refractory Materials Composition of some common refractory materials:  Abrasive Ceramics  The ceramics which are used to cut, grind and polish other softer materials are known as abrasives. Diamonds - natural and synthetic, are used as abrasives, though relatively expensive. Industrial diamonds are hard and thermally conductive. Diamonds unsuitable as gemstone are used as industrial diamond. Common abrasives – SiC, WC, Al2O3 (corundum) and silica sand. Either bonded to a grinding wheel or made into a powder and used with a cloth or paper. Silicon carbide Glass: Glass - inorganic, non-crystalline (amorphous) material. Range - soda-lime silicate glass for soda bottles to the extremely high purity silica glass for optical fibers. Widely used for windows, bottles, glasses for drinking, transfer piping and receptacles for highly corrosive liquids, optical glasses, windows for nuclear applications. The main constituent of glass is silica (SiO2). The most common form of silica used in glass is sand. Sand fusion temp to produce glass - 1700 °C. Adding other chemicals to sand can considerably reduce the fusion temperature. Sodium carbonate (Na2CO3) or soda ash, (75% SiO2 + 25% Na2O) will reduce the fusion temperature to 800 °C. Other chemicals like Calcia (CaO) and magnesia (MgO) are used for stability. Limestone (CaCO3) and dolomite (MgCO3) are used for this purpose as source of CaO and MgO. Key Properties of Glass Glass-ceramic materials should have: Relatively high mechanical strengths Low coefficients of thermal expansion Relatively high temperature capabilities Good dielectric properties Good biological compatibility Thermal shock resistance Compositions and Characteristics of some common Glasses Polymers: Polymers – Chain of H-C molecules. Each repeat unit of H-C is a monomer e.g. ethylene (C2H4), Polyethylene – (–CH2 –CH2)n Polymers: Thermosets – Soften when heated and harden on cooling – totally reversible. Thermoplasts – Do not soften on heating Plastics – moldable into many shape and have sufficient structural rigidity. Are one of the most commonly used class of materials. Are used in clothing, housing, automobiles, aircraft, packaging, electronics, signs, recreation items, and medical implants. Natural plastics – hellac, rubber, asphalt, and cellulose. Elastomers: Elastomer – a polymer with rubber-like elasticity. Each of the monomers that link to form the polymer is usually made of carbon, hydrogen, oxygen and/or silicon. Cross-linking in the monomers provides the flexibility. Glass transition temperature, Tg, is the temperature at which transition from rubbery to rigid state takes place in polymers. Elastomers are amorphous polymers existing above their Tg. Hence, considerable segmental motion exists in them. Their primary uses are in seals, adhesives and molded flexible parts. Characteristics and Applications of some commercial Elastomers:  Advanced Ceramics: Automobile Engine parts Advantages: Operate at high temperatures – high efficiencies; Low frictional losses; Operate without a cooling system; Lower weights than current engines Disadvantages: Ceramic materials are brittle; Difficult to remove internal voids (that weaken structures); Ceramic parts are difficult to form and machine Potential materials: Si3N4 (engine valves, ball bearings), SiC (MESFETS), & ZrO2 (sensors), Possible engine parts: engine block & piston coatings Basic of Heat Treatment: Heat treatment is a heating and cooling process of a metal or an alloy in the solid state with the purpose of changing their properties. It can also be said as a process of heating and cooling of ferrous metals especially various kinds of steels in which some special properties like softness, hardness, tensile-strength, toughness etc, are induced in these metals for achieving the special function objective.  It consists of three main phases namely: (i) heating of the metal (ii) soaking of the metal and (iii) cooling of the metal. The theory of heat treatment is based on the fact that a change takes place in the internal structure of metal by heating and cooling which induces desired properties in it. The rate of cooling is the major controlling factor. Rapid cooling the metal from above the critical range, results in hard structure. Whereas very slow cooling produces the opposite affect i.e. soft structure. In any heat treatment operation, the rate of heating and cooling is important. A hard material is difficult to shape by cutting, forming, etc. During machining in machine shop, one requires machineable properties in job piece hence the properties of the job piece may requires heat treatment such as annealing for inducing softness and machineability property in workpiece. Objectives of Heat Treatment The major objectives of heat treatment are given as under 1. It relieves internal stresses induced during hot or cold working. 2. It changes or refines grain size. 3. It increases resistance to heat and corrosion. 4. It improves mechanical properties such as ductility, strength, hardness, toughness, etc. 5. It helps to improve machinability. 6. It increases wear resistance 7. It removes gases. 8. It improves electrical and magnetic properties. 9. It changes the chemical composition. 10. It helps to improve shock resistance. 11. It improves weldability. CONSTITUENTS OF IRON AND STEEL Fig. (a) shows micro structure of mild steel (0.2-0.3% C). White constituent in this figure is very pure iron or having very low free carbon in iron in form of ferrite and dark patches contain carbon in iron is chemically combined form known as carbide (Cementite). Cementite is very hard and brittle. Pearlite is made up of 87% ferrite and 13% cementite. But with increase of carbon content in steel portion of pearlite increases up to 0.8% C. The structure of steel at 0.8% C is entirely of pearlite. However if carbon content in steel is further increased as free constituent up to 1.5% C, such steel will be called as high carbon steel.  ALLOTROPY (the existence of two or more different physical forms) OF IRON Fig: Allotroic changes during cooling of pure iron ALLOTROPY (the existence of two or more different physical forms) OF IRON (i) First changing occurs at l539°C at which formation of delta iron starts. (ii) Second changing takes place at 1404°C and where delta iron starts changes into gamma iron or austenite (FCC structure). (iii) Third changing occurs at 910°C and where gamma iron (FCC structure) starts changes into beta iron (BCC structure) in form of ferrite, leadaburite and austenite. (iv) Fourth changing takes place at 768°C and where beta iron (BCC structure) starts changes into alpha iron in form of ferrite, pearlite and cementite. TRANSFORMATION DURING HEATING AND COOLING OF STEEL If heat is extracted, the temperature falls unless there is change in state or a change in structure. This change of structure does not occur at a constant temperature. It takes a sufficient time a range of temperature is required for the transformation. This range is known as transformation range. Heat Treatment Lower Critical Temperature: When a plain-carbon steel is heated through a sufficient temperature range, there is a particular temperature at which the internal grain structure begins to change. This temperature, known as the lower critical temperature, is about 700°C and is the same for all plain-carbon steels. Upper Critical Temperature: When the steel is heated still further, the structural changes continue until a second temperature is reached where the change in the internal structure of the steel is complete. This temperature is known as the upper critical temperature and varies for plain-carbon steel according to the % carbon content. The temperature range between the lower and upper critical temperatures is known as the critical range.  IRON-CARBON EQUILIBRIUM DIAGRAM 1. Austenite is a solid solution of free carbon (ferrite) and iron in gamma iron. On heating the steel, after upper critical temperature, the formation of structure completes into austenite which is hard, ductile and non-magnetic. It is formed when steel contains carbon up to 1.8% at 1130°C. On cooling below 723°C, it starts transforming into pearlite and ferrite. 2. Ferrite contains very little or no carbon in iron. It is the name given to pure iron crystals which are soft and ductile. The slow cooling of low carbon steel below the critical temperature produces ferrite structure. Ferrite does not harden when cooled rapidly. It is very soft and highly magnetic. 3. Cementite is a chemical compound of carbon with iron and is known as iron carbide (Fe3C). Cast iron having 6.67% carbon is possessing complete structure of cementite. Free cementite is found in all steel containing more than 0.83% carbon. It increases with increase in carbon % as reflected in Fe-C Equilibrium diagram. It is extremely hard. 4. Pearlite is a eutectoid alloy of ferrite and cementite. It occurs particularly in medium and low carbon steels in the form of mechanical mixture of ferrite and cementite in the ratio of 87:13. Its hardness increases with the proportional of pearlite in ferrous material. Pearlite is relatively strong, hard and ductile, whilst ferrite is weak, soft and ductile. Common Heat Treatment Processes: 1. Normalizing 2. Annealing. 3. Hardening. 4. Tempering 5. Case hardening (a) Carburizing (b) Cyaniding (c) Nitriding Annealing This process is carried out to soften the steel so that it may be machined or so that additional cold-working operations such as pressing and bending can be carried out. The process involves heating the steel to a temperature depending upon its carbon content, Fig. , holding it at this temperature for a period of time depending upon the thickness of the steel, so that the whole mass reaches the correct temperature (known as ‘soaking), and finally allowing the steel to cool as slowly as possible. This slow rate of cooling is achieved by switching off the furnace, allowing the steel in the furnace and the furnace itself to cool at the same slow rate. The result is a steel having large grains in its structure which is soft, ductile, low in strength and easily shaped by machining, pressing and bending. Normalising This heat-treatment process is carried out to give the steel its ‘normal’ structure. For example, a steel which has been forged has a grain structure which has been distorted due to the hot working. Such a steel requires normalising, to return the grains to their normal undistorted structure to be in the best condition for use. The process differs from annealing only in the rate of cooling. The steel is heated to the required temperature, depending again upon the carbon content, Fig. and is allowed to soak. The steel is then removed from the furnace and is allowed to cool in still air. This gives a faster rate of cooling than annealing, resulting in a steel with smaller grains which is stronger but less ductile than an annealed steel. Hardening Hardening is a hardness inducing kind of heat treatment process in which steel is heated to a temperature above the critical point and held at that temperature for a definite time and then quenched rapidly in water, oil or molten salt bath. It is some time said as rapid quenching also. Steel is hardened by heating 20-30°C above the upper critical point for hypo eutectoid steel and 20-30°C above the lower critical point for hyper eutectoid steel and held at this temperature for some time and then quenched in water or oil or molten salt bath. Hardening is carried out by raising the temperature, again depending on the carbon content, Fig., in the same way as for annealing and normalising, and allowing the steel to soak. The difference is again in the rate of cooling. This time the steel is removed from the furnace and is cooled very quickly, or quenched, by immersion in a suitable liquid such as water or oil. Low-carbon steels can be hardened by a method known as case- hardening. The steel is heated to above the upper critical temperature while in contact with a carbon-rich material. Carbon is absorbed into the surface of the steel, raising the carbon content at the surface to around 0.9%, a process known as carburising. The steel can then be hardened as a 0.9% steel as previously described. Case Hardening Case hardening is a process that is used to harden the outer layer of case hardening steel while maintaining a soft inner metal core. The case hardening process uses case hardening compounds for the carbon addition. Steel case hardening depth depends upon the application of case hardening depth. Case hardening steel is normally used to increase the object life. This is particularly significant for the manufacture of machine parts, carbon steel forgings, and carbon steel pinions. Case hardening is also utilized for other applications. Case hardening is also called surface hardening. Case hardening has been in use for many centuries, and was frequently used for producing horseshoes and different kinds of cooking utensils that were subjected to substantial wear and tear. Case Hardening Cyaniding: A process in which an iron-base alloy is heated in contact with a cyanide salt so that the surface absorbs carbon and nitrogen. Cyaniding is followed by quenching and tempering to produce a case with a desired combination of hardness and toughness. Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. These processes are most commonly used on low-carbon, low-alloy steels. They are also used on medium and high-carbon steels, titanium, aluminium and molybdenum. Tempering: This heat-treatment process is carried out after a steel has been hardened. Steel in a hard state is brittle and if used could easily break. Tempering removes some of the hardness, making the steel less brittle and more tough. This is done by reheating the hardened steel to a temperature between 200°C and 450°C, to bring about the desired structural change. The steel can then be quenched or cooled slowly, since it is the temperature to which the steel is raised which brings about the necessary structural change, not the rate of cooling. In general, the higher the temperature to which the hardened steel is raised the tougher the steel will be, with a corresponding reduction in hardness and brittleness SPHEROIDIZATION It is lowest temperature range of annealing process in which iron base alloys are heated 20 to 40°C below the lower critical temperature, held therefore a considerable period of time e.g. for 2.5 cm diameter piece the time recommended is four-hours. It is then allowed to cool very slowly at room temperature in the furnace itself. Objectives: 1. To reduce tensile strength 2. To increase ductility 3. To ease machining 4. To impart structure for subsequent hardening process CARPENTRY Carpentry may be defined as the process of making wooden components. It starts from a marketable form of wood and ends with a finished product. It deals with building work, furniture , cabinet making etc. Joinery, i.e. preparation of joints is one of the important operations in all wood-works. It deals with specific work of a carpenter like making different types of joints to form a finished product. Working with wood for various applications. A student have to study commonly used carpentry joints such as Cross lap joint, Tee joint, Dovetail joint, Mortise & tenon joint etc. WOOD CLASSIFICATIONS The classification of wood divides them into hard and soft, referring to a botanical difference rather than to any definite degree of hardness. The two groups differ in cell structure, appearance and general properties. Hardwood trees have broad, flat leaves that falloff after maturity. The Softwood trees have needle or scale-like leaves which they retain all year; they are the evergreens. Most hardwoods are stronger and less likely to dent than the softwoods; they also hold nails and screws more securely. There are some, such as poplar and aspen that are actually softer than some of the so-called softwoods. Difference between Hard Wood and Soft Wood  Classification of Wood Hard wood Soft wood Shisham, Deodar, Sal, Chid, Teak, Kail, Kiker, Fir wood and Mango, Haldu Walnut pine oak Seasoning of Wood: The process of removal of moisture content from wood so as to make it useful for construction and other uses is called drying of wood or seasoning of wood. This reduces the chances of decay, improves load bearing properties, reduces weight, and exhibits more favourable properties like thermal & electrical insulation, glue adhesive capacity & easy preservative treatment etc. Natural seasoning Artificial kiln seasoning Kiln drying of lumber is perhaps the most effective and The traditional method of seasoning timber economical method available. was to stack it in air and let the heat of the atmosphere and the natural air movement Drying rates in a kiln can be carefully controlled and defect losses reduced to a minimum. Length of drying time is also around the stacked timber remove the greatly reduced and is predictable so that dry lumber moisture. The process has undergone a inventories can often be reduced. Where staining is a number of refinements over the years that problem, kiln drying is often the only reasonable method that can be used unless chemical dips are employed. have made it more efficient and reduced the quantity of wood that was damaged by drying Kilns are usually divided into two classes: too quickly near the ends in air seasoning. Progressive The basic principle is to stack the timber so Compartment Both methods rely on the controlled environment to dry out the timber and require the following that plenty of air can circulate around each factors: piece. The timber is stacked with wide spaces between each piece horizontally, and with Forced air circulation by using large fans, blowers, etc. strips of wood between each layer ensuring that there is a vertical separation too. Heat of some form provided by piped steam. Humidity control provided by steam jets. Air can then circulate around and through the stack, to slowly remove moisture. In some cases, weights can be placed on top of the Amount and Duration of Air, Heat and Humidity depends upon: stacks to prevent warping of the timber as it Species dries. Size Quantity The process of sawing wooden logs into useful sizes and shapes (boards, planks squares and other planes section and sizes etc.) for market or commercial requirements is known as conversion. Defects Due to Conversion and Seasoning Defects due to conversion and seasoning of timber involve shakes, warping, bowing, twist, diamonding, casehardening and honey combing. Warping is a kind of variation from a true or plain surface and may include a one or combination of cup, bow, crook and twist. Warping board which is tangentially sawn may invariably warp. This takes the form of a hollowing or cupping across the face of the board and when wide flat boards are required this will act as a serious drawback. Wind or twist defect occurs when thin boards are cut from a log having curved longitudinal grain. This tendency is for the board distort spirally. Diamonding in timber is the tendency of square cut pieces to become diamond shaped when cut from certain areas of the log. This happens when the piece has been cut with growth rings running diagonally, causing the unequal shrinkage between summer and spring growth to pull it out of shape. TOOLS USED IN CARPENTRY TOOLS USED IN CARPENTRY TOOLS USED IN CARPENTRY TOOLS USED IN CARPENTRY Wood Joints  CARPENTRY MACHINES Wood working machines are Different machines are needed employed for large production to save time and labor in work. These possess the following carpentry work for various quick advantages over the hand tools. wood working operations 1. The carpentry machines help to especially for turning and sawing reduce fatigue of carpenter. purposes. 2. The carpentry machines are used The general wood working for production work. machines are wood working 3. The carpentry machines save Lathe, time and are used for accuracy circular saw and work. band saw. 4. They are used for variable job variety and more designs are possible.  Wood Working Lathe It consists of a cast iron bed, a headstock, tailstock, tool rest, live and dead centers and drawing mechanisms. The long wooden cylindrical jobs are held and rotated between the two centers. The tool is then fed against the job and the round symmetrical shape on the jobs is produced. Scrapping tool and turning gauge are generally used as a turning tool on a woodworking lathe. Wood working Lathe  Circular Saw: It is also called as table or bench saw which is used to perform various operations such as grooving, rebating, chamfering etc. It consists of a cast iron table, a circular cutting blade, cut off guides, main motor, saw guide, elevating hand wheel, tilting hand wheel etc. The work is held on the table and moved against the circular saw to perform the quick and automatic sawing operation and other operation on wood as said above. The principal parts include the frame, arbor, table, blade, guides for taking cuts, guards and fencing. Band Saw Band saw is shown in Fig. which generally used to cut the heavy logs to required lengths, cutting fine straight line and curved work. It consists of a heavy cast bed, which acts as a support for the whole machine, a column, two wheel pulleys, one at the top and other at the bottom, an endless saw blade band, a smooth steel table and guide assembly. It is manufactured in many sizes ranging from little bench saw to a larger band saw mill. COMMON SAFETY IN CARPENTRY SHOP 1. Before starting any wood working machine, it should be ensured that all the safety guards are in proper places and secured well. 2. While working on a circular saw, one should not stand in a line with the plane of the rotating blade and always keep your fingers always away from the reach of blade. 3 The wooden pieces should not be fed to the sawing machines faster than the cutting speed of the machine. 4. While working on wood lathes, the job should be properly held. 5. One should not use defective or damaged carpentry tools while carrying out carpentry work. 6. Nails, screws should be properly kept in a box for proper house keeping. 7. Sufficient safety precautions are to be taken for preventing fire in the carpentry shop. 8. No carpentry tools should be thrown for saving time in handling. Fitting: Introduction, Tools used in fitting, measuring and marking tools, the process of making sawing, Filling, Tapping and die, Introduction to drills. Fitting is a manufacturing process which refers to Assembling of parts together and removing metals to secure necessary fit. This operations include measuring & marking, sawing, chipping, filing etc.  TOOLS USED IN FITTING SHOP Tools used in bench and fitting shop are classified as under. 1. Marking tools 2. Measuring devices 3. Measuring instruments 4. Supporting tools 5. Holding tools 6. Striking tools 7. Cutting tools 8. Tightening tools, and 9. Miscellaneous tools TOOLS USED IN FITTING TOOLS USED IN FITTING TOOLS USED IN FITTING TOOLS USED IN FITTING TOOLS USED IN FITTING Marking Tools Steel rule, prick punch, circumference rule, centre punch, straight edge, try square, flat steel square, bevel square, scriber, vernier protractor, semi-circular protractor, combination set and surface divider, gauge. trammel, 2. Measuring Devices Fillet and radius gauge, Line measuring and end measuring screw pitch gauge, devices surface plate, (i) Linear measurements try square, (A) Non-precision instruments dial gauge, 1. Steel rule feeler gauge, 2. Calipers plate gauge and 3. Dividers wire gauge. 4. Telescopic gauge 5. Depth gauge Line measuring and end measuring devices (B) Precision instruments (ii) Angular measurements 1. Micrometers A) Non-precision instruments 2. Vernier calipers 1. Protector 3. Vernier depth gauges 2. Engineers square 4. Vernier height gauges 3. Adjustable bevel 5. Slip gauges 4. Combination set (C) Comparators (D) Coordinate measuring machines Line measuring and end measuring devices (B) Precision instruments 4. Supporting Tools 1. Bevel protector These are vee-block, marking table, surface 5. Angle gauges plate, and angle plate. 6. Sine bar 5. Holding Tools 7. Clinometers These are vices and clamps. Various types of vices are used for different purposes. They 8. Autocollimators include hand vice, bench vice, leg vice, pipe 9. Sprit level vice, and pin vice. The clamps are also of different types such as c or g clamp, plane slot, (iii) Surface measurement goose neck, double end finger, u-clamp, 1. Straight edge parallel jaw, and clamping block. 2. Surface gauge 6. Strking Tools 3. Surface table These are various types of hammers such as ball peen hammer; straight peen hammer; 4. Optical flat cross-peen hammer; double face hammer; 5. Profilo-meter soft face hammer  7. Cutting Tools Files. There are different types of files 8. Tightening Tools such as flat, square, round, triangular, These are pliers and wrenches, knife, pillar, needle and mill. which are sub classified as under. Scrapers. These are flat, hook, Pliers. These are namely ordinary, triangular, half round types. needle nose, and special type. Chisels. There are different types of Wrench. These are open single chisels used in fitting work such as flat ended, open double ended, closed chisel, cross cut chisel, diamond point ended adjustable, ring spanner, chisel, half round chisel, cow mouth offset socket, t- socket, box chisel and side cutting chisel. wrench, pipe wrench and allen The other cutting tools are drills, wrench. reamers, taps, snips, hacksaws (hand hacksaw and power hacksaw) etc. 9. Miscellaneous Tools These are die, drifts, counter sink tools, counter boring tools, spot facing bit and drill press. Some of above mentioned important tools are discussed as under.  1. Measuring Tools 1.1 Steel rule 1.2 Circumference Rule 1.3 Straight Edges: They are mostly used for scribing long straight lines. Measuring Tools: 1.4 Flat Steel Squrae It is a piece of flat hardened steel with graduations on either end. It is commonly used for marking lines in the perpendicular direction to any base line. 1.5 Scribers Fig. shows the various types of scribers, which are sometimes called the metal worker’s pencil. These are made up of high carbon steel and are hardened from the front edge. Scriber is used for scratching lines on the sheet metal during the process of laying out a job. Measuring Tool: 1.6 Bever Protractor The bevel protector (Fig.) is an instrument used for testing and measuring angles within the limits of five minutes accuracy. 1.7 Divider It is used for marking and drawing circle and arcs on sheet metal. 1.8 Trammel Trammel is used for marking and drawing large circles or arcs, which are beyond the scope of dividers. 19.2.1.9 Prick Punch The prick punch, which is used for indentation marks. It is used to make small punch marks on layout lines in order to make them last longer. The angle of prick punch is generally ground to 30° or 40° whereas for centre punch it is kept 60 °or 90°. Measuring Tool: 1.10 Centre Punch Which is used for locating centre for indentation mark for drilling purposes. 1.11 Surface Gauge or Scribing Block The surface gauge which is a principal marking tool used generally in the fitting and the machine shops. It is made in various forms and sizes. 2.2 Measuring Devices There are some general purpose measuring devices such as fillet and radius gauge, screw pitch gauge, surface plate and try square which are described as under. 2.2.1 Fillet and Radius Gauge This instrument is highly useful for measuring and checking the inside and outside radii of fillets and other round surfaces. The fillet and radius gauges are made in thin strong strips curved to different radii at end. 2.2.2 Screw Pitch Gauge The screw pitch gauge, which is a highly fool-proof, very effective and fairly accurate instrument used to identify or check the pitch of the threads cut on different threaded items. Measuring Tool: 2.2.3 Surface Plate The surface plate, which is a cast iron plate having generally a square top well planed and square with adjacent machined faces. Its specific use is in testing the trueness of a finished surface, testing a try square, providing adequate bearing surface for V-block and angle plates, etc. in scribing work. 2.3.4 Slip Gauges Slip gauges are also called as precision gauges blocks. They are made of rectangular blocks using alloy steel, which are being hardened before finishing them to size of high degree of accuracy. They are basically used for precise measurement for verifying measuring tools such as micrometers, comparators, and various limit gauges. The distance between two opposite faces determines the size of the gauge. They are made in higher grades of accuracy Measuring Tool: 2.3.13 Inspection Gauges Inspection gauges are commonly employed to avoid costly and lengthy process of testing the component dimensions. These gauges are basically used for checking the size, shape and relative positions of various parts. These are of fixed type measuring devices and are classified as standard and limit The double end kind of limit gauge has the GO portion at one end and the NO GO portion at the other end. GO portion must pass into or over an acceptable piece but the NO GO portion should not pass. Measuring Tool: Plug Gauges These are used for checking cylindrical, tapered, threaded, splined and square holes portions of manufacture components. 2.4 Holding Tools Holding tools used in fitting shop comprises of basically vices and clamps. The clamps are C or G clamp, plane slot, goose neck, double end finger, u-clamp, parallel jaw, and clamping block. 2.4.1 Vices The vices are hand vice, bench vice, machine vices, carpenter vice, shaper vice, leg vice, pipe vice, and pin vice. Measuring Tool: 2.4.1.2 Machine vice These types of vices are commonly used in fitting shop for holding a variety of jobs. They are used for precision work on the machine table like shaping, milling, drilling and grinding. They are generally made of grey cast iron. 2.4.1.3 Universal swivel base machine vice It is commonly used in fitting shop for holding a variety of jobs. The jobs after holding in jaws can be adjusted at any angle either horizontally or vertically with the help of swelling head. Measuring Tool: 2.4.1.4 Toolmaker’s vice It is commonly used by tool maker, watch maker, die maker and goldsmith for holding a variety of small parts for carrying some operation. 2.4.1.5 Hand vice Hand vice which is utilized for holding keys, small drills, screws, rivets, and other similar objects which are very small to be easily held in the bench vice. This is made in various shapes and sizes. Measuring Tool: 2.4.2 Clamping Divices There are two types of clamps namely C clamp and tool maker clamp. A C- clamp is used for gripping the work during construction or assembly work. Whereas tool maker clamp is used for gripping or holding smaller jobs. 2.5 Cutting Tools 2.5.1 Files The widely used hand cutting tool in workshops is the file. It is a hardened piece of high grade steel with slanting rows of teeth. It is used to cut, smooth, or fit metal parts. It is used file or cut softer metals. 2.5.1.1 Size of a File Size of a file is specified by its length. It is the distance from the point to the heel, without the tang. Files for fine work are usually from 100 to 200 mm and those for heavier work from 200 to 450 mm in length. 2.5.1.2 Classification of Files (A) Type of Cut (i) Single (ii) Double and (iii) Rasp (B) Grade of Cut Files are cut with teeth of different grades. Those in general are (i) Smooth (ii) Second cut (iii) Bastered (iv) Rough (C) Shape of File Common shapes of files are having different cross sections, which cover most requirements. Files Classifications 2.5.1.4 Hand files: Hand files are commonly used for finishing surface work. Both faces of the file are double cut. Either both edges are single cut or one is uncut to provide a safe edge. 2.5.1.5 Flat files: Flat files are generally used for filing flat surfaces in fitting shop. 2.5.1.6 Triangular files: Triangular files are commonly used for filing corners between 60° and 90°. They are double cut on all faces. 2.5.1.7 Square files: Square files are commonly used for filing in corners in jobs. They are double cut on all sides and tapers. 2.5.1.8 Round files: Round files are generally used for opening out holes and rounding inside corners. Rough, bastard, second cut and smooth files under 15 cm in length are single cut. 2.5.1.9 Half round files: These files comprises of flat and half round sides. The flat side of half round file is used for general work and the half round side for filing concave surfaces. 2.5.1.10 Knife-edge files: These files are commonly used for cleaning out acute- angled corners. They are extremely delicate and are used for fine work such as pierced designed in thin metal. 2.5.1.11 Pillar files: These files are used for finishing narrow slots. Both faces are double cut and either bothnedges are single cut or one is uncut to provide a safe edge of the file. 2.5.1.12 Needle files: Needle files are generally used for filling keys tooth wheels of clocks and other curved surfaces. 2.5.2 Scrapers Scrapers are made up of old files and the cutting edge of scraper is hardened and tempered. They are mainly used to scrap metal surfaces by rubbing the work surface. They also produce a bearing surface, which has been filed or machined earlier. The scrapers are hand cutting tools used for removing metal from surfaces in form of thin slices or flakes to produce smooth and fine surfaces. The following types of scrappers according to shape are commonly classified as (i) Flat (ii) Hook (iii) Triangular (iv) Half round 2.5.3 Chisel Chisel is one of the most important tools of the sheet metal, fitting and forging shop. It is widely used for cutting and chipping the work piece. It is made of high carbon steel or tool steel. It is in the form of a rod having cutting edge at one end, hexagonal or octagonal body and striking head at the other end. The size of a chisel is described by its length and width of edge. When the cutting edge becomes blunt, it is again sharpened by grinding. For cutting the job or work piece with the chisel, it is placed vertically on the job or work piece and hammering is carried out upon its head. But for chipping, the chisel is inclined at 40°-70° with the job orwork piece. The angle of the cutting edge of the chisel is 35°-70°according to the metals to be cut. 2.5.4 Drill Drill is a common tool widely for making holes in a metal piece in fitting shop. It is generally held in chuck of bench drilling machine 2.5.5 Reamer The drill does not always produce the correct hole some time with good finish. Thus a correct hole is produced with good finish of a pre drilled hole using a reamer. 2.5.6 TAPS Taps are used for cutting or producing internal threads of either left or right hand kind in nuts or pre-drilled holes. Taps are threaded externally. The threads being cut by grinding to give a high class finish. Taps are made up of alloy steel or hardened steel. To provide cutting edges, grooves known as flutes are ground along the threaded portion of the tap so that the thread is divided into rows of teeth. 2.5.8 Hand hacksaw Hand hacksaws are made in two types namely a fixed frame and adjustable frame oriented The former possesses solid frame in which the length cannot be changed and where as the latter comprises the adjustable frame which has a back that can be lengthened or shortened to hold blades of different sizes. The hand hacksaws are commonly used for sawing all soft metal. However a power operated hacksaw can also be used for cutting raw materials in sizes in case of continuous cutting generally occurring frequently in fitting or in machine shops. Measuring Tool: 2.6 Sriking Tools Various types of hammers such as Ball peen hammer, straight peen hammer, cross-peen hammer, double face hammer and soft face hammer 2.7 Tightening Tools: The tightening tools include pliers, screw driver and wrenches Pliers are namely ordinary needle nose and special type. These are commonly used by fitter and electrician for holding a variety of jobs. Screw driver is a screw tightening tool. It is generally used by hand for tightening the screws. It is also of various types depending upon the kind of work. Wrenches are commonly known as spanners. These generally come in sets and are commonly identified by numbers. These are of various types and few general types involve open single ended, open double ended, closed ended adjustable, ring spanner, offset socket, t-socket, box wrench, pipe wrench and Allen wrench. OPERATIONS PERFORMED IN FITTING WORK The operations commonly performed in bench and fitting work may be classified as under. 1. Marking 2. Chipping 3. Filing 4. Scrapping 5. Sawing 6. Drilling 7. Reaming 8. Tapping 9. Grinding and 10. Polishing SAFE WORK PRACTICES IN FITTING WELDING PRACTICE: 1.1 Introduction 1.2 Various welding processes with brief introduction 1.2.1 Electric Arc welding, Arc welding procedure, List of equipment for electric arc welding, 1.2.3 Gas welding process and equipment 1.3 Soldering and Brazing process. Overview of processes Welding 1. Process in which two (or more) parts are coalesced at their contacting surfaces by application of:  Heat and pressure 2. Some welding processes use a filler material added to facilitate coalescence  Principle of welding Assembly two parts together by creating a fusion and/or deformation in the interaction area, which is further based on the physics laws such as fusion and solid state deformation. Principle of welding Fusion welding (FW) Heat materials to melt the materials of compositions and melting points. Due to the high-temperature phase transitions inherent to these processes, a heat-affected zone is created in the material Principle of welding Solid State welding (SSW) On the interface between two materials there is no melting that happens but the interface of materials is reconfigured to form many structure. 1.1. Welding is the process of joining similar metals by the application of heat, with or without application of pressure or filler metal, in such a way that the joint is equivalent in composition and characteristics of the metal joined Welding Application: Welding is used for making permanent joints. It is used in the manufacture: Automobile bodies, Aircraft frames, railway wagons, Machine frames, structural works, tanks, furniture, boilers, General repair work and ship building etc. Two Categories of Welding Processes 1. Fusion welding - coalescence is accomplished by melting the two parts to be joined, in some cases adding filler metal to the joint Examples: arc welding, oxyfuel gas welding, resistance spot welding 2. Solid state welding - heat and/or pressure are used to achieve coalescence, but no melting of base metals occurs and no filler metal is added Examples: forge welding, diffusion welding, friction welding  The general function of welding 1. Provides a permanent joint 2. One of the most economical ways to join parts in terms of material usage and fabrication costs Mechanical fastening usually requires additional hardware (e.g., screws) and geometric alterations of the assembled parts (e.g., holes) 3. Not restricted to a factory environment Welding can be accomplished "in the field" Limitations and Drawbacks of Welding 1. Most welding operations are performed manually and are expensive in terms of labor cost. 2. Most welding processes utilize high energy and are inherently dangerous. 3. Welded joints do not allow for convenient disassembly. 4. Welded joints can have quality defects that are difficult to detect.  Welding Fusion Welding (FW) Solid State Welding (SSW) Arc Welding (AW)  Principle of the process Structure and configuration Process modeling Defects Design For Manufacturing (DFM) Process variation  1.2 Classification of Welding Processes (i) Arc welding (iv)Thermit Welding Carbon arc Metal arc (v)Solid State Welding Friction Metal inert gas Tungsten Ultrasonic inert gas Diffusion Plasma arc Submerged arc Explosive (vi)Newer Welding Electro-slag Electron-beam (ii). Gas Welding Laser Oxy-acetylene Air-acetylene Oxy-hydrogen (vii)Related Process Oxy-acetylene cutting (iii). Resistance Welding Arc cutting Hard facing Butt Spot Brazing Seam Projection Percussion Soldering Arc Welding It is a fusion welding processes How an arc is formed? which uses an electric arc to produce The arc is like a flame of intense the heat required for melting the heat that is generated as the metal. electrical current passes through The welder creates an electric arc a highly resistant air gap. that melts the base metals and filler metal (consumable) together so that they all fuse into one solid piece of metal Arc Welding: It is a fusion welding processes which uses an electric arc to produce the heat required for melting the metal. The welder creates an electric arc that melts the base metals and filler metal (consumable) together so that they all fuse into one solid piece of metal Also known as “stick welding” Uses an arc between a covered electrode and a workpiece Shielding is obtained from decomposition of the electrode cover Pressure is not used Filler metal is obtained from the electrode Principle of Arc Welding: Process of Arc Welding: A suitable gap is kept between the – Intense heat at the arc melts the work and electrode tip of the electrode A high current is passed through – Tiny drops of metal enter the arc the circuit. stream and are deposited on the The electric energy is converted parent metal into heat energy, producing a – As molten metal is deposited, a temperature of 3000°C to 4000°C. slag forms over the bead which This heat melts the edges to be serves as an insulation against air welded and molten pool is formed. contaminants during cooling On solidification the welding joint – After a weld ‘pass’ is allowed the is obtained cool, the oxide layer is removed by a chipping hammer and then cleaned with a wire brush before the next pass. Procedure of Arc Welding: Prepare the base materials: An electric arc is generated remove paint and rust between an electrode and the Choose the right welding process parent metal Choose the right filler material The electrode carries the electric current to form the arc, produces a Assess and comply with safety gas to control the atmosphere and requirements provides filler metal for the weld Use proper welding techniques bead and be sure to protect the molten Electric current may be AC or DC. puddle from contaminants in the air Inspect the weld Electric Power for Welding DC Arc Welding: Current used may be D.C. machines are made up to the – 1. AC capacity range of 600 amperes. – 2. DC 45 to 95 volts For most purposes, DC is preferred. D.C. can be given in two ways: (a) Straight polarity AC Arc Welding (b) Reverse polarity Instead of 220 V at 50 A, for The polarity will affect the weld size example, the power supplied by the and application transformer is around 17–45 V at currents up to 600 A. Comparison of A.C. and D.C. arc Arc Welding Equipments: welding Direct Current (from Generator) 1. Less efficiency 2. Power consumption more 3. Cost of equipment is more 4. Low voltage – safer operation 5. Suitable for both ferrous non ferrous metals 6. Preferred for welding thin sections 7. Positive terminal connected to the work 8. Negative terminal connected to the electrode  Types of Electrodes Coated Electrodes: 1. Bare electrodes The electrode is coated in a metal 2. Coated electrodes mixture called flux, which gives off gases as it decomposes to prevent 1. Weld contamination The choice of electrode for SMAW depends on a number of factors, 2.Introduces deoxidizers to purify the including weld 1. The weld material 3.Causes weld-protecting slag to form 2. Welding position and 4. Improves the arc stability, and 3. The desired weld properties. 5.Provides alloying elements to improve the weld quality. 6. Electrode coatings can consist of a number of different compounds, including rutile, calcium fluoride, cellulose, and iron powder. Role of common constituents added in flux of SMAW electrode is given below. SMAW Types of Electrodes: Arc Welding Power Supplies: Electrodes can be divided into three The current for arc welder can be supplied by line groups— current or by an alternator/generator. 1. Fast-fill electrodes, – The amount of heat is determined by the current flow (amps) Fast-fill electrodes are designed to melt – The ease of starting and harshness of the arc is quickly so that the welding speed can be determined by the electrical potential (volts). maximized Amperage Output: 2. Fast-freeze electrodes, fast-freeze The maximum output of the power supply electrodes supply filler metal that solidifies determines the thickness of metal that can quickly, making welding in a variety of be welded before joint beveling is required. positions possible by preventing the weld pool from shifting significantly before 185 to 225 amps is a common size. solidifying. and For an individual weld, the optimum 3. Intermediate electrodes go by the name output "fill-freeze"or "fast-follow" electrodes. amperage is determined by – thickness of the metal – type of joint and – type of electrode Advantages of arc welding: Disadvantages: 1. Simple welding equipment Not clean enough for reactive 2. Portable metals such as aluminium and 3. Inexpensive power source titanium. 4. Relatively inexpensive equipment The deposition rate is limited because the electrode covering tends 5. Welders use standard domestic to overheat and fall off. current. 6. Process is fast and reliable The electrode length is ~ 35 mm and requires electrode changing 7. Short learning curve lower the overall production rate. 8. Equipment can be used for multiple functions 9. Electric arc is about 5,000 oC 10. Used for maintenance, repair, and field construction  Welding Fusion Welding (FW) Solid State Welding (SSW) Arc Welding (AW) Consumable electrodes Non-consumable electrodes Two Basic Types of Arc Welding (Based on Electrodes) 1. Consumable electrodes  consumed during welding process  added to weld joint as filler metal  in the form of rods or spools of wire 2. Non-consumable electrodes  not consumed during welding process but does get gradually eroded  filler metal must be added separately if it is added GAS Welding :Gas welding is a welding process that melts and joins metals by heating them with a flame caused by a reaction of fuel gas and oxygen. Sound weld is obtained by selecting The most commonly used method proper size of flame, filler material and is Oxyacetylene welding, due to its method of moving torch high flame temperature. The temperature generated during the The flux may be used to deoxidize process is 33000c and cleanse the weld metal. When the metal is fused, oxygen from The flux melts, solidifies and forms the atmosphere and the torch combines a slag skin on the resultant weld with molten metal and forms oxides, metal. results defective weld Fluxes are added to the welded metal to remove oxides Common fluxes used are made of sodium, potassium. Lithium and borax. Flux can be applied as paste, powder,liquid.solid coating or gas. Gas Metal Arc Welding (GMAW)  Gas Metal Arc Welding (GMAW) In the GMAW process, an arc is established between a continuous wire electrode (which is always being consumed) and the base metal. Under the correct conditions, the wire is fed at a constant rate to the arc, matching the rate at which the arc melts it. The filler metal is the thin wire that’s fed automatically into the pool where it melts. Since molten metal is sensitive to oxygen in the air, good shielding with oxygen-free gases is required. This shielding gas provides a stable, inert environment to protect the weld pool as it solidifies. Consequently, GMAW is commonly known as MIG (metal inert gas) welding. Since fluxes are not used (like SMAW), the welds produced are sound, free of contaminants, and as corrosion-resistant as the parent metal. The filler material is usually the same composition (or alloy) as the base metal. Gas Tungsten Arc Welding (GTAW)  Gas Metal Arc Welding (GMAW) GMAW is extremely fast and economical. This process is easily used for welding on thin-gauge metal as well as on heavy plate. It is most commonly performed on steel (and its alloys), aluminum and magnesium, but can be used with other metals as well. It also requires a lower level of operator skill than the other two methods of electric arc welding discussed in these notes. The high welding rate and reduced post-weld cleanup are making GMAW the fastest growing welding process.  TIG vs. MIG Welding - What's the Difference? MIG welding, or Metal Inert Gas TIG welding, also known as welding, combines two pieces of metal Tungsten Inert Gas welding, uses together with a consumable wire nonconsumable tungsten, along connected to an electrode current. A with an inert gas, to weld two work wire passes through the welding gun at pieces together. The tungsten the same time as the inert gas. The electrode provides the electricity, inert gas protects the electrode from but not the filler, for the welding contaminants. process. While it can use filler, it A range of material thicknesses can be sometimes creates a weld where welded from thin gauge sheet metal one part melts into another. right up to heavier structural plates. TIG welding on the other hand is more commonly used for your thinner gauge materials. Items that are made with this process are things like kitchen sinks and tool boxes. The biggest benefit is that you can get your power down really low and not blow through the metal. Gas Metal Arc Welding (GMAW) GAS WELDING EQUIPMENT 1. Gas Cylinders Pressure Oxygen – 125 kg/cm2 Acetylene – 16 kg/cm2 2. Regulators Working pressure of oxygen 1 kg/cm2 Working pressure of acetylene 0.15 kg/cm2 Working pressure varies depends upon the thickness of the work pieces welded. 3. Pressure Gauges 4. Hoses 5. Welding torch 6. Check valve 7. Non return valve TYPES OF FLAMES: Oxygen is turned on, flame immediately changes into a long white inner area (Feather) surrounded by a transparent blue envelope is called Carburizing flame (30000c). Addition of little more oxygen give a bright whitish cone surrounded by the transparent blue envelope is called Neutral flame (It has a balance of fuel gas and oxygen) (32000c) Used for welding steels, aluminium, copper and cast iron If more oxygen is added, the cone becomes darker and more pointed, while the envelope becomes shorter and more fierce is called Oxidizing flame Has the highest temperature about 34000c Used for welding brass and brazing operation Types of Flame: Types of Gas Welding: 1. Leftward Welding 2. Rightward Welding Gas welding Apparatus 1. Oxygen cylinder 2. Acetylene cylinder 3. Pressure gauges 4. Valves 5. Hose pipes 6. Torch 7. Welding tip 8. Pressure regulators 9. Lighter 10. Goggles Gas welding torch Gas Welding Gas Welding - Advantages Gas Welding – Disadvantages Simple equipment Limited power density Portable Very low welding speed Inexpensive High total heat input per unit Easy for maintenance and repair length Large heat affected zone Severe distortion Not recommended for welding reactive metals such as titanium and zirconium. Welding Joints: Brazing and Soldering Brazing: It is a low temperature joining process. It is performed at temperatures above 840º F and it generally affords strengths comparable to those of the metal which it joins. It is low temperature in that it is done below the melting point of the base metal. It is achieved by diffusion without fusion (melting) of the base Brazing can be classified as Torch brazing Dip brazing Furnace brazing Induction brazing Brazing: Disadvantages Advantages: Brazed joints have lesser strength Dissimilar metals which canot be compared to welding welded can be joined by brazing Joint preparation cost is more Very thin metals can be joined Can be used for thin sheet metal Metals with different thickness can sections be joined easily In brazing thermal stresses are not produced in the work piece. Hence there is no distortion Using this process, carbides tips are brazed on the steel tool holders Soldering: It is a low temperature joining process. It is performed at temperatures below 840ºF for joining. Soldering is used for, Sealing, as in automotive radiators or tin cans Electrical Connections Joining thermally sensitive components Joining dissimilar metals  Soldering Brazing Soldering uses the filler metal system having Brazing uses comparatively higher melting low melting point (183-2750 C generally than point (450-12000C) filler metals (alloys of Al, 4500C) called solder (alloy of lead and tin) Cu and Ni). In general, brazed joints offer greater strength Less strength than brazed joint than solder joints. Higher resistance to thermal load than Lower resistance to thermal load than soldered joint primarily due to difference in soldered joint melting temperature of solder and braze metal. Therefore, solder joints are preferred mainly for low temperature applications. Soldering is mostly used for joining electronic components where they are normally not exposed to severe temperature and loading conditions during service. Brazing is commonly used for joining of tubes, pipes, wires cable, and tipped tool.  Smithy Shop Introduction, Types of forging, Equipment used in the smithy shop, Smithy tools, Black smith’s hearth, Hand forging operations. Smithy Forging: Black" in "blacksmithy" refers to “Forging is defined as the the black fire scale, a layer of controlled plastic deformation of oxides that forms on the surface of metal into predetermined shapes the metal during heating. by pressure or impact blows, or The word "smith" derives from an combination of both.” old word, "smite" (to hit). “Forgeability is the relative ability of a material to deform under a compressive load without rupture.” Grain Structure Parts have good strength High toughness Forgings require additional heat treating HEATING DEVICES Types of Furnaces: Box / Batch Type Furnace: This type of furnace is used for heating small and medium size stock because they are least expensive. These furnaces are usually constructed of a rectangular steel frame lined with insulating and refractory bricks. Rotary Hearth Furnace: These are doughnut shaped and are set to rotate so that the stock is heated to the correct temperature during one rotation. These are heated by gas or oil. Types of Furnaces: Box / Batch Type Furnace: This type of furnace is used for heating small and medium size stock because they are least expensive. These furnaces are usually constructed of a rectangular steel frame lined with insulating and refractory bricks. Rotary Hearth Furnace: These are doughnut shaped and are set to rotate so that the stock is heated to the correct temperature during one rotation. These are heated by gas or oil. Types of Furnaces: Continuous/ Conveyor Furnace: They are generally used to heat one end of the larger workpiece. They had an air or oil operated cylinder to push stock end to end through a narrow furnace. Induction Furnace: In induction furnace the stocks are passed through induction coils in the furnace. An induction furnace greatly reduces scale formation due to oxidation. Resistance Furnace: These furnaces are faster than induction furnace and are often automated. In this furnace the stock is connected into the circuit of step down transformer and is heated due to resistance in circuit. HAND TOOLS USED IN FORGING SHOP: ANVIL- It is soft and is used for cutting; its purpose is to prevent damaging the steel face of the anvil by conducting such operations there and so as not to damage the cutting edge of the chisel, though many smiths shun this practice as it will damage the anvil over time. HAND TOOLS USED IN FORGING SHOP: SWAGE BLOCK: A swage block (or swager block) is a large, heavy blockof cast iron or steel used in smithing, with variously-sized holes in its face and usually with forms on the sides. The through-holes are of various shapes and sizes and are used to hold, support or back up a hot bar of metal for further shaping. Hammers: Tongs: CHISEL: SWAGES FULLERS Flatter HARDY OR ANVIL CUTTER PUNCHES DRIFTS: Forging Process TYPES OF OPEN DIE FORGING Hand forging: Hand forging is done by hammering the piece of metal, when it is heated to the proper temperature, on an anvil. Power forging – Power Hammer: All power hammers employ the same general principle of operation, a falling weight striking the blow, with the entire energy being absorbed by the work. – Power Press: It is a machine tool which changes the shape of workpiece by using pressure rather than blow in previous case. 2. Impression Die Forging TYPES OF IMPRESSION DIE FORGING Drop Forging: It is done with help of three types of drop hammers. They are gravity hammer, air lift hammer and power drop or steam hammer. Press Forging: It is done in presses rather than with hammers. The action is relatively slow squeezing instead of delivering heavy blows Machine Forging: It consists of applying lengthwise pressure to a hot bar held between grooved dies to enlarge some section, usually the end. A. Drop forging B. Press forging C. Machine/ Upset forging Forging Process 3. Flashless /Closed Forging Advantages of Forging Processes Following are some of the major advantages of forging processes. (1) It improves the structure as well as mechanical properties of the metallic parts. (2) Forging facilitates orientation of grains in a desired direction to improve the mechanical properties. (3) Forged parts are consistent in shape with the minimum presence of voids and porosities. (4) Forging can produce parts with high strength to weight ratio. (5) Forging processes are very economical for moderate to high volume productions. Smith Forging Operations 1. Upsetting 6. Bending 2. Cogging/Drawing 7. Punching Down/Drawing out 8. Drifting 3. Setting Down 9. Flattening 4. Fullering 10.Swaging 5. Edging 11.Welding Upsetting Cogging/Drawing Down/Drawing out Setting down Fullering Edging: Bending Punching Drifting Flattening Forging Defects Unfilled Section: In this some section of the die cavity are not completely filled by the flowing metal. Cold Shut: This appears as a small cracks at the corners of the forging. Scale Pits: This is seen as irregular depurations on the surface of the forging. Die Shift: This is caused by the miss alignment of the die halve, making the two halve of the forging to be improper shape. Flakes: These are basically internal ruptures caused by the improper cooling of the large forging. Improper Grain Flow: This is caused by the improper design of the die, which makes the flow of the metal not flowing the final interred direction. Remedies: 1. Shallow cracks and cavities can be removed by chipping process. 2. Surface cracks and decarburized areas are removed by grinding on special machine. 3. Die design should be properly made taking care of all relevant aspects. 4. Destroyed forgings are straightened in presses, if possible. 5. Mechanical properties can be improved by suitable heat treatment process.