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Mechanical workshop practice 2 by sudarshan.bollapu

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THIS MATERIAL USED FOR FIRST YEAR B.TECH.,MECHANICAL-STUDENTS

THIS MATERIAL USED FOR FIRST YEAR B.TECH.,MECHANICAL-STUDENTS

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  • 1. 2013Workshop Practice-II B.SUDARSHAN M.Tech., (Ph.D.) 1/1/2013-2014
  • 2. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL1 CUTM Centurion University of Technology and Management Mechanical work shop practice-2(BLME1214) CYCLE OF EXPERIMENTS  FOUNDRY 1. Pattern making –using wood turning lathe 2. Preparation of sand mould including gating system 3. Casting a product  WELDING 1. Preparation of lap joint, butt joint(any one) 2. Preparation of t-joint 3. Fabrication of stool and hand grinding process  PLUMBING 1. Basic pipefittings 2. Sanitary fittings 3. Pipe lay out installation with water meter  BLACK SMITHY 1. Converting round rod into square 2. Converting round rod into square s-hook 3. Converting round rod into L-bend. Total experiments (3+3+3+3) =12 Centurion University of Technology and Management –Department of Mechanical Engineering pg. 1
  • 3. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL2 CUTM Centurion University of Technology and Management –Department of Mechanical Engineering pg. 2
  • 4. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL3 CUTM Instructions to the students: 1. Enter the lab with proper dress- code (blue apron and shoes) 2. Maintain a 200 pages white long note book and divide it into four parts with the Titles of the trades namely foundry, plumbing, black smithy and Welding. 3. Draw the figures of tools and equipment’s proportionately using pencil only on the left side of the page. 4. Write the related theory part only on the right side of the page. 5. For every experiment, draw the related figure and write the individual procedure in the observation book and take signature by the concerned technician. Write the date and Experiment number in the observation book. And take signature of staff member on index page of lab manual. 6. Only after taking signature in the observation book, write the record. Both will be checked. Marks are allotted for your regularity. Performance of the students will be assessed for every session of workshop being conducted. 7. The records should be written up to date without delay. They should be signed by the concerned faculty. 8. Medical kits provided in the First – Aid Box. The students can utilize the available Medicines if at all there is any necessity. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 3
  • 5. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL4 CUTM Welding INTRODUCTION: 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 metals joined. In the beginning, welding was mainly used for repairing all kinds of worn or damaged parts. Now, it is extensively used in manufacturing industry, construction industry (construction of ships, tanks, locomotives and automobiles) and maintenance work, replacing riveting and bolting, to a greater extent. The various welding processes are: 1. Electric arc welding, 2. Gas welding 3. Thermal welding 4. Electrical Resistance welding and 5. Friction welding However, only electric arc welding process is discussed in the subject point of view. 3.2 ELECTRIC ARC WELDING: Arc welding is the welding process, in which heat is generated by an electric arc struck between an electrode and the work piece. Electric arc is luminous electrical discharge between two electrodes through ionized gas. Fig: Arc welding setup Centurion University of Technology and Management –Department of Mechanical Engineering pg. 4
  • 6. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL5 CUTM Any arc welding method is based on an electric circuit consisting of the following parts: a. Power supply (AC or DC); b. Welding electrode; c. Work piece; d. Welding leads: (Electric cables) connecting the electrode and work piece to the power supply Electric arc tween the electrode and work piece closes the electric circuit. The arc temperature may reach 10000°F (5500°C), which is sufficient for fusion the work piece edges and joining them. When a long joint is required the arc is moved along the joint line. The front edge of the weld pool melts the welded surfaces when the rear edge of the weld pool solidifies forming the joint. Transformers The transformers type of welding machine produces A.C current and is considered to be the least expensive. It takes power directly from power supply line and transforms it to the voltage required for welding. Transformers are available in single phase and three phases in the market. Motor generators These are D.C generators sets, in which electric motor and alternator are mounted on the same shaft to produce D.C power as pert the requirement for welding. These are designed to produce D.C current in either straight or reversed polarity. The polarity selected for welding depends upon the kind of electrode used and the material to be welded. Rectifiers These are essentially transformers, containing an electrical device which changes A.C into D.C by virtue of which the operator can use both types of power (A.C or D.C, but only one at a time).In addition to the welding machine, certain accessories are needed for carrying out the welding work. Welding cables Two welding cables are required, one from machine to the electrode holder and the other, from the machine to the ground clamp. Flexible cables are usually preferred because of the case of using and coiling the cables. Cables are specified by their current carrying capacity, say 300 A, 400 A, etc. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 5
  • 7. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL6 CUTM Electrodes Filler rods are used in arc welding are called electrodes. These are made of metallic wire called core wire, having approximately the same composition as the metal to be welded. These are coated uniformly with a protective coating called flux. While fluxing an electrode; about 20mm of length is left at one end for holding it with the electrode holder. It helps in transmitting full current from electrode holder to the front end of the electrode coating. Flux acts as an insulator of electricity. Figure. Shows the various parts of an electrode. Figure: Parts of an electrode In general, electrodes are classified into five main groups; mild steel, carbon steel, special alloy steel, cast iron and non‐ferrous. The greatest range of arc welding is done with electrodes in the mild steel group. Various constituents like titanium oxide, potassium oxide, cellulose, iron or manganese, Ferro silicates, carbonates, gums, clays, asbestos, etc., are used as coatings on electrodes. While welding, the coating or flux vaporizes and provides a gaseous shield to prevent atmospheric attack. The size of electrode is measured and designated by the diameter of the core wire in SWG and length, apart from the brand and code names; indicating the purpose for which there are most suitable. Electrodes may be classified on the basis of thickness of the coated flux. As 1. Dust coated or light coated 2. Semi or medium coated and 3. Heavily coated or shielded Electrodes are also classified on the basis of materials, as 1. Metallic and 2. Non‐metallic or carbon Centurion University of Technology and Management –Department of Mechanical Engineering pg. 6
  • 8. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL7 CUTM Metallic arc electrodes are further sub‐divided into 1. Ferrous metal arc electrode (mild steel, low/medium/high carbon steel, cast iron, stainless steel, etc.) 2. Non‐ferrous metal arc electrodes (copper, brass, bronze, aluminum, etc.).In case of non‐ metallic arc electrodes, mainly carbon and graphite are used to make the electrodes. WELDING TOOLS: Electrode holder The electrode holder is connected to the end of the welding cable and holds the electrode. It should be light, strong and easy to handle and should not become hot while in operation. Figure shows one type of electrode holder. The jaws of the holder are insulated, offering protection from electric shock. Figure: Electrode holder Figure: Ground clamp Ground clamp: The end of the ground cable and is clamped to the work or welding table to complete the electric circuit. It should be strong and durable and give a low resistance connection. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 7
  • 9. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL8 CUTM Wire brush and chipping hammer: A wire brush is used for cleaning and preparing the work for welding. A chipping hammer is used for removing slag formation on welds. One end of the head is sharpened like a cold chisel and the other, to a blunt, round point. It is generally made of tool steel. Molten metal dispersed around the welding heads, in the form of small drops, is known as spatter. When a flux coated electrode is used in welding process, then a layer of flux material is formed over the welding bead which contains the impurities of weld material. This layer is known as slag. Removing the spatter and slag formed on and around the welding beads on the metal surface is known as chipping. Figure: Wire brush Figure: Chipping hammer Welding table and cabin: It is made of steel plate and pipes. It is used for positioning the parts to be welded properly. Welding cabin is made up by any suitable thermal resistance material, which can isolate the surrounding by the heat and light emitted during the welding process. A suitable draught should also be provided for exhausting the gas produced during welding. Face shield: A face shield is used to protect the eyes and face from the rays of the arc and from spatter or flying particles of hot metal. It is available either in hand or helmet type. The hand type is Centurion University of Technology and Management –Department of Mechanical Engineering pg. 8
  • 10. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL9 CUTM convenient to use wherever the work can be done with one hand. The helmet type though not comfortable to wear, leaves both hands free for the work. Shields are made of light weight nonreflecting fiber and fitted with dark glasses to filter out the harmful rays of the arc. In some designs, a cover glass is fitted in front of the dark lens to protect it from spatter. Hand gloves: These are used to protect the hands from electric shocks and hot spatters Hand held type, Helmet type Figure: Hand gloves Figure: Face shield Centurion University of Technology and Management –Department of Mechanical Engineering pg. 9
  • 11. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL10 CUTM Figure 1 BALLPEEN HAMMER Figure 2 FLATBIT TONG Figure 3 FACE SCREEN Figure 4 Flat File Figure 5 Chipping hammer Figure 6STEEL RULE Figure7 Trysquar Figure 8 Scriber Figure9 Benchvice Figure10 Hacksaw TECHNIQUES OF WELDING: Centurion University of Technology and Management –Department of Mechanical Engineering pg. 10
  • 12. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL11 CUTM Preparation of work: Before welding, the work pieces must be thoroughly cleaned of rust, scale and other foreign material. The piece for metal generally welded without beveling the edges, however, thick work piece should be beveled or veed out to ensure adequate penetration and fusion of all parts of the weld. But, in either case, the parts to be welded must be separated slightly to allow better penetration of the weld. Before commencing the welding process, the following must be considered a) Ensure that the welding cables are connected to proper power source. b) Set the electrode, as per the thickness of the plate to be welded. c) Set the welding current, as per the size of the electrode to be used. Table Electrode current vs. electrode size vs. plate thickness. Plate thickness, (mm) Electrode size, (mm), Electrode current range, (amp) Plate thickness, mm Electrode size, mm Electrode current range, amp 1.6 1.6 40‐60 2.5 2.5 50‐80 4.0 3.2 90‐130 6.0 4.0 120‐170 8.0 5.0 180‐270 25.0 6.0 300‐400 NOTE: While making butt welds in thin metal, it is a better practice to tack weld the pieces intervals to hold them properly while welding. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 11
  • 13. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL12 CUTM Striking an arc: The following are the stages and methods of striking an arc and running a bead a) Select an electrode of suitable kind and size for the work and set the welding current at a proper value. b) Fasten the ground clamp to either the work or welding table. c) Start or strike the arc by either of the following methods Strike and withdraw: In this method the arc is started by moving the end of the electrode onto the work with a slow sweeping motion, similar to striking a match. Touch and with draw: In this method, the arc is started by keeping the electrode perpendicular to the work and touching or bouncing it lightly on the work. This method is preferred as it facilitates restarting the momentarily broken arc quickly. If the electrode sticks to the work, quickly bend it back and forth, pulling at the same time. Make sure to keep the shield in front of the face, when the electrode is freed from sticking. d) As soon as the arc is struck, move the electrode along, slowly from left to right, keeping at 15º to25º from vertical and in the direction of welding. Strike and withdraw Touch and withdraw Figure: striking an arc Centurion University of Technology and Management –Department of Mechanical Engineering pg. 12
  • 14. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL13 CUTM Weaving: A steady, uniform motion of the electrode produces a satisfactory bead. However, a slight weaving or oscillating motion is preferred, as this keeps the metal molten a little longer and allows the gas to escape, bringing the slag to the surface. Weaving also produces a wider bead with better penetration. 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 Fig: Brazing Advantages • Dissimilar metals which cannot be welded can be joined by brazing • Very thin metals can be joined • Metals with different thickness can 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 Centurion University of Technology and Management –Department of Mechanical Engineering pg. 13
  • 15. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL14 CUTM Disadvantages • Brazed joints have lesser strength compared to welding • Joint preparation cost is more • Can be used for thin sheet metal sections 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 TYPES OF JOINTS: Welds are made at the junction of the various pieces that make up the weld ment. The junctions of parts, or joints, are defined as the location where two or more numbers are to be joined. Parts being joined to produce the weld ment may be in the form of rolled plate, sheet, pipes, castings, forgings, or billets. The five basic types of joints are listed below. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 14
  • 16. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL15 CUTM Figure: Types of welding joints. A butt joint Is used to join two members aligned in the same plane this joint is frequently used in plate, sheet metal, and pipe work. A joint of this type may be either square or grooved. Corner and tee joints are used to join two members located at right angles to each other In cross section, the corner joint forms an L‐shape, and the tee joint has the shape of the letter T. Various joint designs of both types have uses in many types of metal structures. A lap joint, As the name implies, is made by lapping one piece of metal over another view. This is one of the strongest types of joints available; however, for maximum joint efficiency, you should overlap the metals a minimum of three times the thickness of the thinnest member you are joining. Lap joints are commonly used with torch brazing and spot welding applications. WELDING POSITIONS Depending upon the location of the welding joints, appropriate position of the electrode and hand movement is selected. The figure shows different welding positions. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 15
  • 17. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL16 CUTM Figure: Welding positions Flat position welding: In this position, the welding is performed from the upper side of the joint, and the face of the weld Is approximately horizontal. Flat welding is the preferred term; however, the same position is sometimes called down hand. Horizontal position welding: In this position, welding is performed on the upper side of an approximately horizontal surface and against an approximately vertical surface. Vertical position welding: In this position, the axis of the weld is approximately vertical as shown in figure. Overhead position welding: In this welding position, the welding is performed from the underside of a joint. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 16
  • 18. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL17 CUTM ADVANTAGES & DISADVANTAGES OF ARC WELDING Advantages: 1. Welding process is simple. 2. Equipment is portable and the cost is fairly low. 3. All the engineering metals can be welded because of the availability of a wide variety of electrodes. Disadvantages: 1. Mechanized welding is not possible because of limited length of the electrode. 2. Number of electrodes may have to be used while welding long joints. 3. A defect (slag inclusion or insufficient penetration) may occur at the place where welding is restarted with a fresh electrode. SAFE PRACTICE: Always weld in a well-ventilated place. Fumes given off from welding are unpleasant and in some Cases may be injurious, particularly from galvanized or zinc coated parts. 1. Do not weld around combustible or inflammable materials, where sparks may cause a fire. 2. Never weld containers, which have been used for storing gasoline, oil or similar materials, without first having them thoroughly cleaned. 3. Check the welding machine to make sure that it is properly grounded and that all leads properly Insulated. 4. Never look at the arc with the naked eye. The arc can burn your eyes severely. Always use a face shield while welding. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 17
  • 19. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL18 CUTM 5. Prevent welding cables from coming in contact with hot metal, water, oil, or grease. Avoid dragging the cables around sharp corners. 6. Ensure proper insulation of the cables and check for openings. 7. Always wear the safety hand gloves, apron and leather shoes. 8. Always turn off the machine when leaving the work. 9. Apply eye drops after welding is over for the day, to relieve the strain on the eyes. 10. While welding, stand on dry footing and keep the body insulated from the electrode, any other parts of the electrode holder and the work. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 18
  • 20. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL19 CUTM Exercise 1 Single V ‐ Butt joint Aim: To make a single v‐butt joint, using the given mild steel pieces of and by arc welding. Material used: Two mild steel pieces of 100X40X6 mm. Equipment required: A.C. Transformer with all welding accessories like Electrode holder, cables. Tool Required: 1. Steel rule 2. Scriber 3. Flat file 4. Try square 5. Flat Tong 6. Chipping hammer 7. Ball peen hammer 8. Wire brush 9. Welding screen Sequence of Operations: 1. Marking 2. Filing 3. Welding 4. Finishing Sketch Figure: Single‐V butt joint Operations to be carried out: 1. Cleaning the work pieces 2. Tack welding 3. Full welding 4. Cooling 5. Chipping 6. Finishing Procedure: 1. Take the two mild steel pieces of given dimensions and clean the surfaces thoroughly from rust, dust particles, oil and grease. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 19
  • 21. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL20 CUTM 2. Remove the sharp corners and burrs by filing or grinding. 3. One edge of each piece is beveled, to an angle 30°. 4. The two pieces are positioned on the welding table such that, they are separated slightly for better penetration of the weld. 5. The electrode is fitted in to the electrode holder and the welding current is set to a proper value. 6. The ground clamp is fastened to the welding table. The machine is switched ON 7. Wearing the apron, hand gloves, using the face shield, the arc is struck and the work pieces are tack welded At the ends and holding the two pieces together; first run of the weld is done to fill the root gap. 8. Second run of the welding is done with proper weaving and with uniform movement. During the process of welding, the electrode is kept at angle of 15° to 25° from vertical and in the direction of welding. 9. The slag formation on the weld is removed by chipping hammer. 10. Filing is done to remove spatters around the weld. Safety Precautions: 1. Use welding screen leather apron and leather hand gloves while welding 2. Use flat tong and hand gloves for handling of work pieces during and after welding. Result: The single v‐butt joint is thus made, using the tools and equipment as mentioned above. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 20
  • 22. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL21 CUTM Exercise 2 Double ‐Lap joint Aim: To make a double lap joint, using the given mild steel pieces and by arc welding. Material used: Two mild steel pieces of 100X40X6 mm. Equipment required: A.C. Transformer with all welding accessories like Electrode holder, cables. Tool Required: 1. Steel rule 2. Scriber 3. Flat file 4. Try square 5. Flat Tong 6. Chipping hammer 7. Ball peen hammer 8. Wire brush 9. Welding screen Sequence of Operations: 1. Marking 2. Filing 3. Welding 4. Finishing Sketch Figure: Double lap joint Operations to be carried out 1. Cleaning the work pieces 2. Tack welding 3. Full welding 4. Cooling 5. Chipping 6. Finishing Centurion University of Technology and Management –Department of Mechanical Engineering pg. 21
  • 23. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL22 CUTM Procedure: 1. Take the two mild steel pieces of given dimensions and clean the surfaces thoroughly from rust, dust particles, oil and grease. 2. Remove the sharp corners and burrs by filing or grinding and prepare the work pieces. 3. The work pieces are positioned on the welding table, to form a lap joint with the required overlapping. 4. The electrode is fitted in to the electrode holder and the welding current is set to a proper value. 5. The ground clamp is fastened to the welding table. 6. Wearing the apron, hand gloves, using the face shield and holding the over lapped pieces the arc is struck and the work pieces are tack‐welded at the ends of both the sides 7. The alignment of the lap joint is checked and the tack‐welded pieces are reset, if required. 8. Welding is then carried out throughout the length of the lap joint, on both the sides. 9. Remove the slag, spatters and clean the joint. Safety Precautions: 1. Use welding screen leather apron and leather hand gloves while welding 2. Use flat tong and hand gloves for handling of work pieces during and after welding. Result: The double lap joint is thus made, using the tools and equipment as mentioned above. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 22
  • 24. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL23 CUTM Exercise 3 T‐ joint Aim To make a T‐ joint, using the given mild steel pieces and by arc welding. Material used Two mild steel pieces of 100X40X6 mm. Equipment required: A.C. Transformer with all welding accessories like Electrode holder, cables. Tool Required: 1. Steel rule 2. Scriber 3. Flat file 4. Try square 5. Flat Tong 6. Chipping hammer 7. Ball peen hammer 8. Wire brush 9. Welding screen Sequence of Operations: 1. Marking 2. Filing 3. Welding 4. Finishing Sketch: Figure: T‐joint Operations to be carried out 1. Cleaning the work pieces 2. Tack welding 3. Full welding 4. Cooling Centurion University of Technology and Management –Department of Mechanical Engineering pg. 23
  • 25. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL24 CUTM 5. Chipping 6. Finishing Sequence of Operations: 1. Marking 2. Filing 3. Welding 4. Finishing Procedure 1. Take the two mild steel pieces of given dimensions and clean the surfaces thoroughly from rust, dust particles, oil and grease. 2. Remove the sharp corners and burrs by filing or grinding and prepare the work pieces. 3. The work pieces are positioned on the welding table such that, the T shape is formed. 4. The electrode is fitted in to the electrode holder and the welding current is set to a proper value. 5. The ground clamp is fastened to the welding table. 6. Wearing the apron, hand gloves, using the face shield and holding the pieces the arc is struck and the work pieces are tack‐welded at both the ends. 7. The alignment of the T joint is checked and the tack‐welded pieces are reset, if required. 8. Welding is then carried out throughout the length of the T joint as shown in the figure. 9. Remove the slag, spatters and clean the joint. Safety Precautions: 1. Use welding screen leather apron and leather hand gloves while welding 2. Use flat tong and hand gloves for handling of work pieces during and after welding. Result: The Tee joint is thus made, using the tools and equipment as mentioned above. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 24
  • 26. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL25 CUTM Exercise 4: Fabrication of Stool and Hand Grinding Practice Aim: To Fabrication of Stool and Hand Grinding Practice using the given mild steel pieces and by arc welding. Material used Six mild steel pieces of 6X253 mm, 1X354mm and4X584mm Equipment required: A.C. Transformer with all welding accessories like Electrode holder, cables. Tool Required: 1. Steel rule 2. Scriber 3. Flat file 4. Try square 5. Flat Tong 6. Chipping hammer 7. Ball peen hammer 8. Wire brush 9. Welding screen Sequence of Operations: 1. Marking 2. Filing 3. Welding 4. Finishing Sketch: Procedure: 1. Take the elven mild steel pieces of given dimensions and clean the surfaces thoroughly from rust, dust particles, oil and grease. 2. Remove the sharp corners and burrs by filing or grinding and prepare the work pieces. 3. The work pieces are positioned on the welding table such that, the L shape is formed. 4. The electrode is fitted in to the electrode holder and the welding current is set to a proper value. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 25
  • 27. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL26 CUTM 5. The ground clamp is fastened to the welding table. 6. Wearing the apron, hand gloves, using the face shield and holding the pieces the arc is struck and the work pieces are tack‐welded at both the ends. 7. The alignment of the L joint is checked and the tack‐welded pieces are reset, if required. 8. Welding is then carried out throughout the length of the T joint as shown in the figure. 9. Remove the slag, spatters and clean the joint. Safety Precautions: 1. Use welding screen leather apron and leather hand gloves while welding 2. Use flat tong and hand gloves for handling of work pieces during and after welding. Result: The fabrication of stool thus made, using the tools and equipment as mentioned above. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 26
  • 28. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL27 CUTM PLUMBING INTRODUCTION: Plumbing deals with the laying of a pipeline. A craftsman may be perfectly proficient with the hammer, saw and other tools, but the faces difficulties with leaking pipes and overflowing toilets. Many people rush to a plumber on seeking a tripping pipe, but a person with a little knowledge of the sanitary system can control this problem easily, saving time and, one with help of few tools. Domestic plumbing: The domestic plumbing employs for house hold appliance such as fresh water supply, waste water treatment supply, rainwater drain, gas supply, air conditioning, firefighting systems, garden waters and irrigation. Industrial plumbing: The industrial plumbing is mainly used in industrial equipment such as a petroleum plant, a power plant, etc. the fittings like gauges, indicators, regulators, valve etc. are added in pipelines Plumbing tools: The tools used by a plumber can be classified as follows 1. Pipe wrench 4. Pipe vice 2. Hacksaw 5. Dies 3. plumb bob 6. Pipe cutter 7. Files and Rasps Pipe wrench A pipe wrench is used for holding and turning the pipes, rods and machine parts. Wrenches are classified as follows.1.Fixed wrenches 2. Adjustable wrenches Centurion University of Technology and Management –Department of Mechanical Engineering pg. 27
  • 29. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL28 CUTM Pipe vice: A pipe vice is fitted on the work bench. This has a set of jaws to grip the pipe and prevent it from turning while cutting, threading and fitting of bends, couplings etc. The yoke vice is commonly used in plumbing used in plumbing practice Pipe cutter: The pipe cutter mainly consists of three wheels which are hardened with sharp cutting edges along their periphery. Of these three wheels, one can be adjusted to any desired distance to accommodate different size of pipes. After adjusting the cutter on a pipe, it is around the pipe, so that the cutter wheels cut the pipe along a circle as shown in fig. Hacksaw: A hacksaw is used for cutting metal rods, bars, pipes, etc. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 28
  • 30. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL29 CUTM Threading dies and taps: It is used for cutting external thread on pipes. Threads are produced in various shape and sizes which are used for fitting inside a handle. Files and rasps: The file surface is covered with sharp edged teeth and its used for removing metal by rubbing. A rasp is used for finishing the surface of the work piece Plumb bob: It is used for check the vertical line and made up of steel or brass. Pipe fittings: Centurion University of Technology and Management –Department of Mechanical Engineering pg. 29
  • 31. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL30 CUTM Fig: Pipe Fittings Pipe fittings are made up of wrought iron. The size of pipe fitting is designated by the size of the pipe on which it fits. Some of the common pipe fittings are shown in fig. Coupling: It is a short a cylindrical sleeve with internal threads throughout. A couplings is used for joining two pipes in a straight and bend where at least one pipe can be turned. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 30
  • 32. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL31 CUTM Union: A union is used for joining two pieces of pipes, where either can be turned. It consists of three parts, two parts joint can be screwed, in to two pipe ends, and the third on for tightening called center part. Nipple: A nipple is a short piece of pipe with external threads at both ends. It is used to make up the required length of a pipe line. Elbow: An elbow is to make an angle between adjacent pipes. Tee: A tee is a fitting that has one side outlet at a right angle to the run. It is used for a single outlet branch pipe. Reducer: It is used to connect two different sized of pipes Plug: It is used to screw on to a threaded opening, for closing it temporarily Valves Valves are used for regulating the flow of fluid through a pipe. The commonly used valves in plumbing’s are 1. Gate valve 2. Globe valve 3. Plug valve 4. Check valve 5. Air relief valve Fig: Types of pipe joints Centurion University of Technology and Management –Department of Mechanical Engineering pg. 31
  • 33. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL32 CUTM Bell and spigot joints A connection between two sections of pipe i.e. the straight spigot end of one section is inserted into the flared out end of the adjoining section. The joint is sealed by a sealing component Flanged joints: A flanged joint helps to connect and disconnect two pipes as per the need. A similar example is as shown in fig. Bolted joints: The use of bolted joint is advantageous in the following circumstances Centurion University of Technology and Management –Department of Mechanical Engineering pg. 32
  • 34. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL33 CUTM 1. The component that cannot be serviced in line. 2. The components being joined that are not capable of being welded. 3. Quick field assembly is required. 4. The component or pipe section that needs to be frequently removed for surface Threaded joints: Threads are cutted in a pipe, flange coupling to connect them with each other and these joints are called threaded joints. Flexible joints The flexible joints are generally used to connect between a washbasin and an angle valve. Swing joints Swing joints are special purpose joints mainly used for industrial oriented purposes wherea long bend is required Welded and brazed joints: Welded and brazed joints are the most commonly used joints for joining pipe components. Expansion joints: Expansions joints are specially designed in pipeline where a small extension of pipe is required Centurion University of Technology and Management –Department of Mechanical Engineering pg. 33
  • 35. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL34 CUTM Single line diagram: Single line diagram are most commonly used in plumbing diagram. All power plants and bottling plant pipes are made by the single line piping diagram. Double line diagram: It is used for catalogs and other applications where the visual appearance is more important. Sewage plumbing system: The sewage plumbing system is shown in figure. Here the waste line from the bath tub, sink, toilet, bathroom, shower etc. is connected to a single outlet pipe using pipe pitting’s, directly to sewage. An emergency cleaning out let is provided to clean the sludge if any block occurs in the pipe line. A vent is provide for the harmful gas to lead out and to avoid air lock Centurion University of Technology and Management –Department of Mechanical Engineering pg. 34
  • 36. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL35 CUTM Connect two lavatories in series: Figure shows the connection of two lavatories in series. Here with a single pipe using cross bends and elbows, the lavatory is coupled with the outlet drain. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 35
  • 37. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL36 CUTM Ex.no: Plumping of one tap water distribution system Aim: To construct the one tape water distribution system by using plumbing components. Fittings required 1. PVC pipes 2. Tank fitting (GI) 3. Union (GI) 4. MTA (PVC) 5. Gate valve 6. Elbow 7. Reducer (GI) 8. Bend (PVC) 9. FTA (PVC) 10. TAP (PVC) Procedure: 1. The given PVC pipes are measured out to the required size. 2. The suitable die is selected. 3. Gate valve is connected between the two MTA. 4.1” x ¾” reducer connected between 1” pipe and ¾” pipe. 5.1” (GI) bend is connected between the two pipes. 6.¾”x1/2” reducer connected between ¾” pipe and ½”. 7.½” bend connected between ¾” and ½” pipe. 8. At the end of the pipe ½” MTA tap is connected. Result: Thus the plumbing of one tap water distribution system was constructed Centurion University of Technology and Management –Department of Mechanical Engineering pg. 36
  • 38. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL37 CUTM FOUNDRY INTRODUCTION: There are large number of tools and equipment’s used in foundry shop for carrying out different operations such as sand preparation, molding, melting, pouring and casting. They can be broadly classified as hand tools, sand conditioning tool, flasks, power operated equipments, metal melting equipments and fettling and finishing equipments. Different kinds of hand tools are used by molder in mold making operations. Sand conditioning tools are basically used for preparing the various types of molding sands and core sand. Flasks are commonly used for preparing sand moulds and keeping molten metal and also for handling the same from place to place. Power operated equipments are used for mechanizing processes in foundries. They include various types of molding machines, power riddles, sand mixers and conveyors, grinders etc. Metal melting equipment includes various types of melting furnaces such as cupola, pit furnace, crucible furnaces etc. Fettling and finishing equipments are also used in foundry work for cleaning and finishing the casting. General tools and equipment used in foundry are discussed as under. HAND TOOLS USED IN FOUNDRY SHOP The common hand tools used in foundry shop are fairly numerous. A brief description of the following foundry tools (Fig.) used frequently by molder is given as under. Hand riddle: Hand riddle is shown in Fig. It consists of a screen of standard circular wire mesh equipped with circular wooden Frame. It is generally used for cleaning the sand for removing foreign material such as nails, shot metal, splinters of wood etc. from it. Even power operated riddles are available for riddling large volume of sand. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 37
  • 39. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL38 CUTM Shovel: Shovel is shown in Fig. It consists of a steel pan fitted with a long wooden handle. It is used in mixing, tempering and conditioning the foundry sand by hand. It is also used for moving and transforming the molding sand to the container and molding box or flask. It should always be kept clean. Rammers: Rammers are shown in Fig. These are required for striking the molding sand mass in the molding box to pack or compact it uniformly all around the pattern. The common forms of rammers used in ramming are hand rammer, peen rammer, floor rammer and pneumatic rammer which are briefly described as (i) Hand rammer: It is generally made of wood or metal. It is small and one end of which carries a wedge type construction, called peen and the other end possesses a solid cylindrical shape known as butt. It is used for ramming the sand in bench molding work. (ii) Peen rammer: It has a wedge-shaped construction formed at the bottom of a metallic rod. It is generally used in packing the molding sand in pockets and comers. (iii) Floor rammer It consists of a long steel bar carrying a peen at one end and a flat portion on the other. It is a heavier and larger in comparison to hand rammer. Its specific use is in floor molding for ramming the sand for larger molds. Due to its large length, the molder can operate it in standing position. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 38
  • 40. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL39 CUTM (iv) Pneumatic rammers They save considerable time and labor and are used for making large molds. Sprue pinSprue pin is shown in Fig. It is a tapered rod of wood or iron which is placed or pushed in cope to join mold cavity while the molding sand in the cope is being rammed. Later its withdrawal from cope produce a vertical hole in molding sand, called sprue through which the molten metal is poured into the mould using gating system. It helps to make a passage for pouring molten metal in mold through Gating system Sprue pin Sprue pin is shown in It is a tapered rod of wood or iron which is placed or pushed in cope to join mold cavity while the molding sand in the cope is being rammed. Later its withdrawal from cope produce a vertical hole in molding sand, called sprue through which the molten metal is poured into the mould using gating system. It helps to make a passage for pouring molten metal in mold through gating system Strike off bar: Strike off bar is a flat bar having straight edge and is made of wood or iron. It is used to strike off or remove the excess sand from the top of a molding box after completion of ramming thereby making its surface plane and smooth. It’s one edge is made beveled and the other end is kept perfectly smooth and plane. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 39
  • 41. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL40 CUTM Mallet Mallet is similar to a wooden hammer and is generally as used in carpentry or sheet metal shops. In molding shop, it is used for driving the draw spike into the pattern and then rapping it for separation from the mould surfaces so that pattern can be easily withdrawn leaving the mold cavity without damaging the mold surfaces. Draw spike Draw spike is shown Fig. It is a tapered steel rod having a loop or ring at its one end and a sharp point at the other. It may have screw threads on the end to engage metal pattern for it withdrawal from the mold. It is used for driven into pattern which is embedded in the molding sand and raps the pattern to get separated from the pattern and finally draws out it from the mold cavity. Vent rod Vent rod is shown in Fig. It is a thin spiked steel rod or wire carrying a pointed edge at one end and a wooden handle or a bent loop at the other. After ramming and striking off the excess sand it is utilized to pierce series of small holes in the molding sand in the cope portion. The series of pierced small holes are called vents holes which allow the exit or escape of steam and gases during pouring mold and solidifying of the molten metal for getting a sound casting. Lifters Lifters are shown in Fig. They are also known as cleaners or finishing tool which are made of thin sections of steel of various length and width with one end bent at right angle. They are used for cleaning, repairing and finishing the bottom and sides’ of deep and narrow openings in mold cavity after withdrawal of pattern. They are also used for removing loose sand from mold cavity. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 40
  • 42. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL41 CUTM Trowels Trowels are shown in Fig. They are utilized for finishing flat surfaces and joints and partings lines of the mold. They consist of metal blade made of iron and are equipped with a wooden handle. The common metal blade shapes of trowels may be pointed or contoured or rectangular oriented. The trowels are basically employed for smoothing or slicking the surfaces of molds. They may also be used to cut in-gates and repair the mold surfaces. Slicks Slicks are shown in Fig. They are also recognized as small double ended mold finishing tool which are generally used for repairing and finishing the mold surfaces and their edges after withdrawal of the pattern. The commonly used slicks are of the types of heart and leaf, square and heart, spoon and bead and heart and spoon. The, nomenclatures of the slicks are largely due to their shapes. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 41
  • 43. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL42 CUTM Smoothers Smothers are shown in Fig. According to their use and shape they are given different names. They are also known as finishing tools which are commonly used for repairing and finishing flat and round surfaces, round or square corners and edges of molds Swab Swab is shown in Fig. It is a small hemp fiber brush used for moistening the edges of sand mould, which are in contact with the pattern surface before withdrawing the pattern. It is used for sweeping away the molding sand from the mold surface and pattern. It is also used for coating the liquid blacking on the mold faces in dry sand molds. Spirit level Spirit level is used by molder to check whether the sand bed or molding box is horizontal or not. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 42
  • 44. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL43 CUTM Gate cutter Gate cutter (Fig.) is a small shaped piece of sheet metal commonly used to cut runners and feeding gates for connecting sprue hole with the mold cavity. Gaggers Gaggers are pieces of wires or rods bent at one or both ends which are used for reinforcing the downward projecting sand mass in the cope are known as gaggers. They support hanging Bodies of sand. They possess a length varying from 2 to 50 cm. A gagger is always used in cope area and it may reach up to 6 mm away from the pattern. It should be coated with clay wash so that the sand adheres to it. Its surface should be rough in order to have a good grip with the molding sand. It is made up of steel reinforcing bar. Spray-gun Spray gun is mainly used to spray coating of facing materials etc. on a mold or core surface. Nails and wire pieces They are basically used to reinforce thin projections of sand in the mold or cores. Wire pieces, spring and nails they are commonly used to reinforce thin projections of sand in molds or cores. They are also used to fasten cores in molds and reinforce sand in front of an in-gate. Bellows Bellows gun is shown in Fig. It is hand operated leather made device equipped with compressed air jet to blow or pump air when operated. It is used to blow away the loose or unwanted sand from the surfaces of mold cavities. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 43
  • 45. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL44 CUTM Clamps, cotters and wedges They are made of steel and are used for clamping the molding boxes firmly together during pouring. FLASKS The common flasks are also called as containers which are used in foundry shop as mold boxes, crucibles and ladles. 1. Moulding Boxes Mold boxes are also known as molding flasks. Boxes used in sand molding are of two types: (a) Open molding boxes. Open molding boxes are shown in Fig. They are made with the hinge at one corner and a lock on the opposite corner. They are also known as snap molding boxes which are generally used for making sand molds. A snap molding is made of wood and is hinged at one corner. It has special applications in bench molding in green sand work for small nonferrous castings. The mold is first made in the snap flask and then it is removed and replaced by a steel jacket. Thus, a number of molds can be prepared using the same set of boxes. (b) Closed molding boxes. Closed molding boxes are shown in Fig. which may be made of wood, cast-iron or steel and consist of two or more parts. The lower part is called the drag, the upper part the cope and all the intermediate parts, if used, cheeks. All the parts are individually equipped with suitable means for clamping arrangements during pouring. Wooden Boxes are generally used in green-sand molding. Dry sand moulds always require metallic boxes because they are heated for drying. Large and heavy boxes are made from cast iron or steel and carry handles and grips as they are Centurion University of Technology and Management –Department of Mechanical Engineering pg. 44
  • 46. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL45 CUTM manipulated by cranes or hoists, etc. Closed metallic molding boxes may be called as a closed rectangular molding box or a closed round molding box 2. Crucible Crucibles are made from graphite or steel shell lined with suitable refractory material like fire clay. They are commonly named as metal melting pots. The raw material or charge is broken into small pieces and placed in them. They are then placed in pit furnaces which are coke-fired. In oil- fired tilting furnaces, they form an integral part of the furnace itself and the charge is put into them while they are in position. After melting of metals in crucibles, they are taken out and received in crucible handle. Pouring of molten is generally done directly by them instead of transferring the molten metal to ladles. But in the case of an oil fired furnace, the molten metal is first received in a ladle and then poured into the molds 3. Ladle It is similar in shape to the crucible which is also made from graphite or steel shell lined with suitable refractory material like fire clay. It is commonly used to receive molten metal from the Centurion University of Technology and Management –Department of Mechanical Engineering pg. 45
  • 47. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL46 CUTM melting furnace and pour the same into the mold cavity. Its size is designated by its capacity. Small hand shank ladles are used by a single foundry personal and are provided with only one handle. It may be available in different capacities up to 20 kg. Medium and large size ladles are provided with handles on both sides to be handled by two foundry personals. They are available in various sizes with their capacity varying from 30 kg to 150 kg. Extremely large sizes, with capacities ranging from 250 kg to 1000 kg, are found in crane ladles. Geared crane ladles can hold even more than 1000 kg of molten metal. POWER OPERATED EQUIPMENTS Power operated foundry equipments generally used in foundries are different types of molding machines and sand slingers, core making, core baking equipment, power riddles, mechanical conveyors, sand mixers, material handling equipment and sand aerators etc. Few commonly used types of such equipments are discussed as under. Moulding Machines Molding machine acts as a device by means of a large number of co-related parts and mechanisms, transmits and directs various forces and motions in required directions so as to help the preparation of a sand mould. The major functions of molding machines involves ramming of molding sand, rolling over or inverting the mould, rapping the pattern and withdrawing the pattern from the mould. Most of the molding machines perform a combination of two or more of functions. However, ramming of sand is the basic function of most of these machines. Use of molding machine is advisable when large number of repetitive castings is to be produced as hand molding may be tedious, time consuming, laborious and expensive comparatively. Classification of Moulding Machines: 1. Squeezer machine 2. Jolt machine 3. Jolt-squeezer machine 4. Slinging machines 5. Pattern draw machines 6. Roll-over machine Centurion University of Technology and Management –Department of Mechanical Engineering pg. 46
  • 48. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL47 CUTM MOLD AND CORE MAKING: A suitable and workable material possessing high refractoriness in nature can be used for mould making. Thus, the mold making material can be metallic or non-metallic. For metallic category, the common materials are cast iron, mild steel and alloy steels. In the non-metallic group molding sands, plaster of Paris, graphite, silicon carbide and ceramics are included. But, out of all, the molding sand is the most common utilized non-metallic molding material because of its certain inherent properties namely refractoriness, chemical and thermal stability at higher temperature, high permeability and workability along with good strength. Moreover, it is also highly cheap and easily available. MOLDING SAND The general sources of receiving molding sands are the beds of sea, rivers, lakes, granular elements of rocks, and deserts. The common sources of molding sands available in India are as follows: 1. Batala sand (Punjab) 2. Ganges sand (Uttar Pradesh) 3 .Oyaria sand (Bihar) 4. Damodar and Barakar sands (Bengal- Bihar Border) 5 .Londha sand (Bombay) 6 .Gigatamannu sand (Andhra Pradesh) and 7 .Avadi and Veeriyambakam sand (Madras) Molding sands may be of two types namely natural or synthetic. Natural molding sands contain sufficient binder. Whereas synthetic molding sands are prepared artificially using basic sand molding constituents (silica sand in 88-92%, binder 6-12%, water or moisture content 3-6%) and other additives in proper proportion by weight with perfect mixing and mulling in suitable equipments. Properties of molding sand: The essential requirement of a good molding sand it should produce sound castings which are free from defects. For producing sound castings, molding sand or mold should possess the following properties Centurion University of Technology and Management –Department of Mechanical Engineering pg. 47
  • 49. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL48 CUTM 1. Porosity or permeability: When molten metal is poured into a mold, gases and steam be formed. The sand mold should have sufficient porosity to allow the gases and steam to pass through it. If they are not removed, casting defects such as blow holes will be formed 2. Plasticity: It is the property of the molding sand by virtue of which, it flows to all the corners around pattern in the mold 3. Cohesiveness: It is the property of the molding sand by which the sand particles stick to each other. Coarse- grained sand particles give better cohesiveness than spherical grained sand particles 4. Adhesiveness: Sticking of the sand particles to another body is known as adhesiveness. The molding sand sticks to the sides of the cope and drag parts of the molding box. 5. Refractoriness: It is the property of the molding sand, to resist high temperature, without undergoing any changes. 6. Collapsibility: It is the property of the molding sand by which the mould should disintegrate with minimum force after the casting has solidified KINDS OF MOULDING SAND Molding sands can also be classified according to their use into number of varieties which are described below. Green sand Green sand is also known as tempered or natural sand which is a just prepared mixture of silica sand with 18 to 30 percent clay, having moisture content from 6 to 8%. The clay and water furnish the bond for green sand. It is fine, soft, light, and porous. Green sand is damp, when squeezed in the hand and it retains the shape and the impression to give to it under pressure. Molds prepared by this sand are not requiring backing and hence are known as green sand molds. This sand is easily available and it possesses low cost. It is commonly employed for production of ferrous and non-ferrous castings. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 48
  • 50. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL49 CUTM Dry sand Green sand that has been dried or baked in suitable oven after the making mold and cores, is called dry sand. It possesses more strength, rigidity and thermal stability. It is mainly suitable for larger castings. Mold prepared in this sand are known as dry sand molds. Loam sand Loam is mixture of sand and clay with water to a thin plastic paste. Loam sand possesses high clay as much as 30-50% and 18% water. Patterns are not used for loam molding and shape is given to mold by sweeps. This is particularly employed for loam molding used for large grey iron castings. Facing sand Facing sand is just prepared and forms the face of the mould. It is directly next to the surface of the pattern and it comes into contact molten metal when the mould is poured. Initial coating around the pattern and hence for mold surface is given by this sand.. It is made of silica sand and clay, without the use of used sand. Different forms of carbon are used to prevent the metal burning into the sand. A facing sand mixture for green sand of cast iron may consist of 25% fresh and specially prepared and 5% sea coal. They are sometimes mixed with 6-15 times as much fine molding sand to make facings. The layer of facing sand in a mold usually ranges from 22-28 mm. From 10 to 15% of the whole amount of molding sand is the facing sand. Backing sand Backing sand or floor sand is used to back up the facing sand and is used to fill the whole volume of the molding flask. Used molding sand is mainly employed for this purpose. The backing sand is sometimes called black sand because that old, repeatedly used molding sand is black in color due to addition of coal dust and burning on coming in contact with the molten metal. System sand In mechanized foundries where machine molding is employed. A so-called system sand is used to fill the whole molding flask. In mechanical sand preparation and handling units, no facings and is used. The used sand is cleaned and re-activated by the addition of water and special additives. This is known as system sand. Since the whole mold is made of this system sand, the properties such as strength, permeability and refractoriness of the molding sand must be higher than those of backing sand. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 49
  • 51. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL50 CUTM Fig .Schematic illustration of the sequence of operations for sand casting Source: Steel founders society of America Melting and Pouring of Metals The next important step in the making of casting is the melting of metal. A melting process must be capable of providing molten metal not only at the proper temperature but also in the desired quantity, with an acceptable quality, and within a reasonable cost. In order to transfer the metal from the furnace into the molds, some type of pouring device, or ladle, must be used. The primary considerations are to maintain the metal at the proper temperature for pouring and to ensure that only quality metal will get into the molds. The operations involved in melting of metal in oil fired furnace/induction furnace and pouring of liquid metal into the mold cavity will be shown during the demonstration. Removal and Finishing of Castings After complete solidification, the castings are removed from the mold. Most castings require some Cleaning and finishing operations, such as removal of cores, removal of gates and risers, removal of fins and flash, cleaning of surfaces, etc. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 50
  • 52. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL51 CUTM PATTERN MAKING For producing a mould or impression of desired shape in Moulding sand or other materials, one needs to have a wooden or metallic pattern similar to the shape of the mould. The art and science of preparing the pattern is called pattern making. Patterns: A pattern is a replica of the desired casting, which when packed in a suitable material, produces a cavity called the mould. This cavity filled with molten metal, produces the desired casting after solidification Pattern Materials Some of the common materials used for pattern making are wood, metal, plaster, wax and plastic. Wood Wood is the most common material used for pattern making as it satisfies most of the essential requirements which are considered for a good pattern. It is light in weight and easily available at low cost, may be easily shaped into different forms as obtained good surface finish easily. The most common woods used for pattern are Deodar, Teak, Shishum and Mahogany. Metal It is used for pattern when a large number of casting with a closer dimensional accuracy is desired. The pattern of metal has a much longer life than wooden pattern as it does not change its shape when subjected to moist conditions. A metal pattern is itself cast from a wooden pattern called “Master Pattern”. Cast-iron, aluminium and its alloys, brass and white metal are commonly used as a pattern metals. Plaster Plaster of Paris (gypsum cement) is also used for making patterns and core-boxes. It can be easily worked and casted into desired shape. It has a high compressive strength (up to 300 kg/ cm2). Its specific use is in making small patterns and core-boxes involving intricate shapes and closer dimensional control. Wax Patterns which are generally used in investment casting process are made by wax. The wax patterns are made by pouring the heated wax into a split die or metal mould. The die is kept cool by circulating the water around it. After complete cooling, the die parts are separated and wax in shape of pattern is taken out. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 51
  • 53. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL52 CUTM Plastic At present, plastics are finding their place as a pattern materials due to their specific characteristics such as high strength and resistance to wear, lightness in weight, fine surface finish and low solid shrinkage etc. Types of patterns: Wood or metal are used in foundry practice. These are difficulty of Moulding on account of design or typical shape of casting. The most common types of pattern are listed and described below: (a) Solid or Single Piece Pattern (b) Split Pattern (c) Gated Pattern (d) Loose Piece Pattern (e) Sweep Pattern (f) Match Plate Pattern (g) Multipiece Pattern Solid or Single Piece Pattern This type of pattern is the simplest of all the patterns. It is made without joints, partings or loose pieces For Moulding with two patterns, one or two Moulding boxes may be used. Moulding operation with this pattern takes more times as the moulder has to cut his own runners, risers and feeding gates. This type of patterns are usually used for simple and large sizes of casting. Split Pattern Whenever the design of casting offers difficulty in making of mould and withdrawal of pattern with a single piece pattern, split or two-piece pattern is most suitable. This type of pattern eliminates this difficulty and can be used to form the mould of intricate design or unusual shape of casting. Split patterns are made in two parts so that one is placed in cope and other in drag with the dowel pins holding the two together (Figure The surface formed at the line of separation of the two parts, usually at the center line of the pattern, is called parting line. Gated Pattern Workshop Technology In mass production, a number of castings are prepared in a single multi cavity mould by joining a group of patterns. In such type of multi cavity mould, gates or runners for the molten metal are formed by connecting parts between the individual patterns as shown in Figure These are made of wood or metal and specially used for mass productions of small castings. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 52
  • 54. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL53 CUTM Loose Piece Pattern As per requirement, some solid or single piece type of patterns are made as assemblies of loose component pieces. Loose pieces are arranged in such a way that it can be removed from the mould easily as shown in Figure. Usually, this type of pattern requires much maintenance and are slower to mould. Sweep Pattern Large sizes of symmetrical moulds are generally prepared by means of sweep patterns. It consists of a base, a wooden sweep board and a vertical spindle. The outer end of sweep board carries a shape corresponding to the shape of desired casting. Usually, sweep patterns are employed for Moulding part carrying circular sections. The sweep board is attached with the vertical spindle. After holding the spindle in vertical position, the Moulding sand is rammed in place. Multipiece Pattern Sometimes, it is necessary to prepare a pattern in more than two parts in order to facilitate an easy Moulding and withdrawal of pattern This type of pattern is known as Multipiece pattern. This type of pattern is used for casting having a more complicated design. For the preparation of mould this type of pattern requires generally three Moulding boxes. Pattern Making Allowances Usually, the pattern is always made larger than the desired size of the casting on account of allowance which should be allowed for machining, shrinkage, distortion and rapping etc. For a pattern, the following allowances are provided: Machining Allowance The extra amount of metal provided on the surfaces of casting to be machined is called as a machining allowance. The amount of this allowance depends upon the method of casting used, metal of casting, method of machining. Size and shape of casting etc. Ferrous types of metals require more allowance comparative to non-ferrous metals. Shrinkage Allowance Metals used for casting usually shrink and contract due to solidification and cooling. It is compensated by providing adequate amount of allowance in the pattern which is called as shrinkage allowance. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 53
  • 55. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL54 CUTM Distortion Allowance Casting of irregular shape and design tend to distort during cooling period. Distortion of casting will take place due to uneven metal thickness, shrinkage and rate of cooling. To eliminate this defect, distortion in opposite direction is provided in the pattern so that this effect of distortion may be neutralized. Rapping Allowance When a pattern is withdrawn from a mould, rapping is used in the pattern. As a result of this rapping, the cavity in the mould is slightly increased. Therefore, a negative allowance is to be provided in the pattern to compensate the same. Draft Allowance To facilitate easy and early with drawl of pattern from the mould without injuring the vertical surfaces and edges of mould, patterns are given a slight taper on all vertical surfaces. This slight taper inward on the vertical surfaces of a pattern is known as the draft or draft allowance. Draft allowance may be expressed either in degrees or in terms of millimeter per meter on a side. Its amount varies from 10 mm to 25 mm per meter on external surfaces and from 40 mm to 70 mm per meter on internal surfaces. WOODEN PATTERN AND WOODEN CORE BOX MAKING TOOLS 1. Measuring and Layout Tools 1. Wooden or steel scale or rule 2. Dividers 3. Calipers 4. Try square 5. Caliper rule 6. Flexible rule 7. Marking gauge 8. T-bevel 9. Combination square 2. Sawing Tools 1. Compass saw 2. Rip saw 3. Coping saw 4. Dovetail saw 5. Back saw 6. Panel saw 7. Miter saw Centurion University of Technology and Management –Department of Mechanical Engineering pg. 54
  • 56. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL55 CUTM 3. Planning Tools 1. Jack plane 2. Circular plane 3. Router plane 4. Rabbet plane 5. Block plane 6. Bench plane 7. Core box plane 4. Boring Tools 1. Hand operated drills 2. Machine operated drills 3. Twist drill 4. Countersunk 5. Brace 6. Auger bit 7. Bit gauge 5. Clamping Tools 1. Bench vice 2. C-clamp 3. Bar clamp 4. Hand screw 5. Pattern maker’s vice 6. Pinch dog 6. Miscellaneous Tools 1. Screw Driver 2. Various types of hammers 3. Chisel 4. Rasp 5. File 6. Nail set 7. Screw driver 8. Bradawl 9. Brad pusher 10. Cornering tool Colour Coding for Patterns Representation of different types of surfaces by means of different colours is known as colour coding. By accepted colour code on pattern, we can judge the casting surfaces either to be machined or not. Parts of pattern as a core print or seat for loose piece are also justified by it. A widely accepted colour code for common practice is given below:  Black color -Surfaces to be left unmachined  Red color - Surfaces to be machined  Yellow colour -Core prints  Red strips on Yellow base Seats for loose pieces  Black strips on Yellow base Stop offs  No colour or Clear Parting surface Centurion University of Technology and Management –Department of Mechanical Engineering pg. 55
  • 57. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL56 CUTM WOODEN PATTERN AND WOODEN CORE BOX MAKING MACHINES Modern wooden pattern and wooden core making shop requires various wood working machines for quick and mass production of patterns and core boxes. Some of the commonly machines used in making patterns and core boxes of various kinds of wood are discussed as under. 1. Wood Turning Lathe. Patterns for cylindrical castings are made by this lathe. 2. Abrasive Disc Machine. It is used for shaping or finishing flat surfaces on small pieces of wood. 3. Abrasive Belt Machine. It makes use of an endless abrasive belt. It is used in shaping the patterns. 4. Circular Saw. It is used for ripping, cross cutting, beveling and grooving. 5. Band Saw. It is designed to cut wood by means of an endless metal saw band. 6. Jig or Scroll Saw. It is used for making intricate irregular cuts on small work. 7. Jointer. The jointer planes the wood by the action of the revolving cutter head. 8. Drill Press. It is used for drilling, boring, mortising, shaping etc. 9. Grinder. It is used for shaping and sharpening the tools. 10. Wood Trimmer. It is used for mitering the moldings accurately. 11. Wood Shaper. It is used for imparting the different shapes to the wood. 12. Wood Planer. Its purpose is similar to jointer but it is specially designed for planning larger size. 13. Tennoner. These are used for sawing (accurate shape and size). 14. Mortiser. It is used to facilitate the cutting of mortise and tenon. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 56
  • 58. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL57 CUTM Exercise-1 Pattern making –using wood turning lathe Aim: To shaping a wood black into a round and cylindrical object such as table leg by using wood turning lathe. Job: a soft wood having length of 550mm and the diameter of 45mm jobaaaa Tools and equipment required: 1. Wood turning lathe 2. Gouge tool 3. Skew chisel tool 4. Parting tool 5. Round nose scrapping tool 6. Steel rule and outside caliper Centurion University of Technology and Management –Department of Mechanical Engineering pg. 57
  • 59. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL58 CUTM Theory: A wood turning lathe machine consists of a cast iron bed, a head stock, a tailstock, a tool rest, live and dead centers, a speed control device, a main motor, a cone pulley system and spindle. The wooden piece to be turned is held between two centers (live and dead centers).the live center is attached to the spindle of the head stock. The work piece is rotated through the spindle by a motor using a cone pulley system .the dead center is attached to the tailstock through bearing and it provides support to the work piece. As the work piece revolves between these two centers, it is cut with a chisel or gouge shaped turning. The tool can be either held on a tool post of the machine or it can be held in hand by the operator. The tool is moved along the work piece to carry out turning or grooving action Procedure: 1. Job is mounted between the centers on wood turning lathe 2. Job is rotated and gouge tool is used for removing material from the job so as to obtain a diameter of 41mm. 3. Tool is changed and skew chisel used to produce a smooth surface. Diameter is maintained at 40mm. 4. Tool is again changed and parting tool is used to obtain the V-grooves on the surface. 5. Tool is again changed and a scrapping tool is used to obtain a round groove on the surface. 6. Tool is again changed and a parting tool is to be found out and marked with a punch before mounting the work piece on the correct length Result: the shape and length leg is obtain as shown in figure. Precautions: 1. The correct centers the work piece is to be found out and marked with a punch before mounting the work piece on the machine. 2. Depth of cut should as small as possible to avoid any vibration of the job. 3. Grooves to cut a correct places. 4. Machine is to be stooped while using calipers for measurements. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 58
  • 60. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL59 CUTM Exercise-2 MAKING A SAND MOLD Aim: To prepare a sand mold, using the given double piece pattern for a connecting rod Tools required: Molding board, drag and cope boxes, molding sand, parting sand, rammer, strike-off bar, bellows. Riser and sprue pins, gate cutter, vent rod, and draw spike. Procedure: Steps Involved In Making a Sand Mold: 1. place the pattern on the molding board, with its flat side on the board 2. place the drag over the board after giving a clay wash inside 3. sprinkle the parting sand on the pattern 4. Pour loose sand, preferably through a riddle over the pattern, until it is covered to a depth of 4 to 5 cm. 5. pack the molding sand around the pattern and is the corners of flask, with the fingers 6. ram the molding sand in the drag flask uniformly using rammers 7. Strike off the excess sand from the top surface of the drag with the help of strike-off bar. 8. Turn the drag upside down 9. Blow-off the loose sand particles with the bellows and smoothen the upper surface. 10. Place the cope part of the pattern on the top of the drag in position. 11. Locate riser pin on the highest point of the pattern. 12. Place the sprue pin at about 5-6cm. from the pattern on other side the riser pin 13. Sprinkle the upper surface with parting sand 14. Repeat steps 3-7 appropriately 15. Make holes with the vent rod from the surface of the flasks to the pattern 16. Remove the sprue and riser pins by carefully drawing them out. Make a funnel shaped cavity at the top of sprue hole, called the pouring basin 17. Lift off the cope flask and place it a side on its edge. 18. Insert the draw pin into the pattern, wet the edges around the pattern loosen the pattern by rapping. Then draw the pattern straight up. 19. Adjust and repair the mould by adding bits of sands, if necessary. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 59
  • 61. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL60 CUTM 20. Cut gate into the drag from the sprue to the mold, blow-off any loose sand particles in the mold Safety Precautions: 1. Do not let sand too wet. Water is an enemy of molten metals 2. Never sand or look over the mold drawing the poring or immediately after poring because of the metal might sprut out of the hole. 3. While working with the molten metal wear protective clothing such as face shield or safety. Goggles, asbestos or leather gloves, which are tight at the wrist, protective aprons that will protect from heat as well as molten particles of metal. 4. Provide adequate ventilation to remove smoke and fumes. 5. Do not shake-out a casting too hastily, which may result in second and third degree burns. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 60
  • 62. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL61 CUTM Result: The sand mold for a solid flange is thus made, which is ready for pouring the molten metal Centurion University of Technology and Management –Department of Mechanical Engineering pg. 61
  • 63. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL62 CUTM MOLD MAKING & CASTING Aim: 1. To prepare a pattern for given object for lost form casting. 2. To prepare a molasses sand mold from the prepared pattern. 3. To melt and pour iron metal into the mold. Equipment and Materials Pattern, core box, molding flasks, molding tools, sand Muller, riddle, sand, molasses, Bentonite, core baking oven, thermocole, melting furnace, fluxes, pouring ladle, pyrometer, hacksaw, file. Procedure Core making (i) Prepare the core sand (ii) Assemble (clamp) the core-box after applying some parting sand (iii) Fill the core box cavity with core sand and ram it (iv) Make vent holes or insert reinforcing wire as desired (v) Tap the mold box on all sides to loosen the core from the box, unclamp the core box and carefully transfer the core on to a baking plate or stand. (vi) Keep the core in the baking oven and bake it for desired length of the time at a predetermined temperature. After baking take the core out of the oven and allow it to coolant room temperature. Mold Making (i) Place the drag part of the pattern with parting surface down on ground or molding board at the center of the drag (flask). (ii) Riddle molding sand to a depth of about 2 cm in the drag and pack this sand carefully around the pattern with fingers. (iii) Heap more molding sand in the drag and ram with rammer carefully. (iv) Strike off the excess sand using strike bar. (v) Make vent holes to within 1 cm of the pattern surface in the drag. (vi) Turn this complete drag and place the cope portion (flask) over it. (vii) Place the cope half of the pattern over the drag pattern matching the guide pins and apply parting sand over the parting surface. Also place the sprue pin and riser pin in proper positions. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 62
  • 64. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL63 CUTM (viii) Complete the cope half by repeating steps (ii) to (v). (ix) Remove the sprue and riser pins and make a pouring basin. Separate the cope and drag halves, and place them with their parting faces up. (x) Moisten sand at the copes of the pattern and remove pattern halves carefully using draw spikes. (xi) Cut gate and runner in the drag. Repair and clean the cavities in the two mold halves. (xii) Place the core in position, assembled the two mold halves assemble and clamp them together. Melting and Pouring (i) Melt the metal in the furnace. Use appropriate fluxes at proper stages and measure metal Temperature from time to time. (ii) Pour the molten metal into the pouring ladle at a higher temperature (say 100oC higher) than the pouring temperature. As soon as the desired pouring temperature is reached, pour the liquid metal into the mold in a steady stream with ladle close to the pouring basin ofthe mold. Do not allow any dross or slag to go in. (iii) Allow sufficient time for the metal to solidify in the mold. Break the mold carefully and remove the casting. (iv) Cut-off the riser and gating system from the casting and clean it for any sand etc. (v) Inspect the casting visually and record any surface and dimensional defects observed. Fig: Sand Casting Diagram Centurion University of Technology and Management –Department of Mechanical Engineering pg. 63
  • 65. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL64 CUTM FORGING Introduction: Forging is an oldest shaping process used for the producing small articles for which accuracy in size is not so important. The parts are shaped by heating them in an open fire or hearth by the blacksmith and shaping them through applying compressive forces using hammers. Thus forging is defined as the plastic deformation of metals at elevated temperatures into a predetermined size or shape using compressive forces exerted through some means of hand hammers, small power hammers, die, press or upsetting machine. It consists essentially of changing or altering the shape and section of metal by hammering at a temperature of about980°C, at which the metal is entirely plastic and can be easily deformed or shaped under pressure. Hand forging process is also known as black-smithy work which is commonly employed for production of small articles using hammers on heated jobs. It is a manual controlled process even though some machinery such as power hammers can also be sometimes used. Black-smithy is, therefore, a process by which metal may be heated and shaped to its requirements by the use of blacksmith tools either by hand or power hammer. In smithy small parts are shaped by heating them in an open fire or hearth. Shaping is done under hand control using hand tools. This work is done in a smithy shop. In smith forging or hand forging open face dies are used and the hammering on the heated metal is done by hand to get the desired shape by judgment. Forging by machine involves the use of forging dies and is generally employed for mass production of accurate articles. In drop forging, closed impression dies are used and there is drastic flow of metal in the dies due to repeated blow or impact which compels the plastic metal to conform to the shape of the dies. The final shape of the product from raw materials achieved in a number of steps. There are some advantages, disadvantages and applications of forging operations which are given as under. Advantages of forging Some common advantages of forging are given as under. 1. Forged parts possess high ductility and offers great resistance to impact and fatigue loads. 2. Forging refines the structure of the metal. 3. It results in considerable saving in time, labor and material as compared to the production of similar item by cutting from a solid stock and then shaping it. 4. Forging distorts the previously created unidirectional fiber as created by rolling and increases the strength by setting the direction of grains. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 64
  • 66. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL65 CUTM 5. Because of intense working, flaws are rarely found, so have good reliability. 6. The reasonable degree of accuracy may be obtained in forging operation. 7. The forged parts can be easily welded. Disadvantages of forging Few dis-advantages of forging are given as under. 1. Rapid oxidation in forging of metal surface at high temperature results in scaling which wears the dies. 2. The close tolerances in forging operations are difficult to maintain. 3. Forging is limited to simple shapes and has limitation for parts having undercuts etc. 4. Some materials are not readily worked by forging. 5. The initial cost of forging dies and the cost of their maintenance is high. 6. The metals gets cracked or distorted if worked below a specified temperature limit. 7. The maintenance cost of forging dies is also very high. Applications of forging Almost all metals and alloys can be forged. The low and medium carbon steels are readily hot forged without difficulty, but the high-carbon and alloy steels are more difficult to forge and require greater care. Forging is generally carried out on carbon alloy steels, wrought iron, copper-base alloys, aluminium alloys, and magnesium alloys. Stainless steels, nickel based super-alloys, and titanium are forged especially for aerospace uses. Producing of crank shaft of alloy steel is a good example which is produced by forging. Forging processes are among the most important manufacturing techniques utilized widely in manufacturing of small tools, rail-road equipments, automobiles and trucks and components of aero plane industries. These processes are also extensively used in the manufacturing ofthe parts of tractors, shipbuilding, cycle industries, railroad components, agricultural machinery etc. FORGABLE MATERIALS Two-phase and multi-phase materials are deformable if they meet certain minimum requirements. The requirement of wrought metals is satisfied by all pure metals with sufficient number of slip planes and also by most of the solid solution alloys of the same metal. Wrought alloys must possess a minimum ductility that the desired shape should possess. To be a forgeable metal, it should possess the required ductility. Ductility refers to the capacity of a material to undergo deformation under tension without rupture. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 65
  • 67. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL66 CUTM Forgeable metals are purchased as hot-rolled bars or billets with round or rectangular cross the sections. Forgeable materials should possess the required ductility and proper strength. Some forgeable metals are given as under in order of increasing forging difficulty. 1. Aluminium alloys 2. Magnesium alloys 3. Copper alloys. 4. Carbon and low alloy steels 5. Martensitic stainless steels 6. Austenitic stainless steels 7. Nickel alloys 8. Titanium alloys 9. Columbium alloys 10. Tantalum alloys 11. Molybdenum alloys 12. Tungsten alloys HEATING DEVICES Forgeable metals are heated either in hearth or in a furnace. The hearths are widely used for heating the metals for carrying out hand forging operations. Furnaces are also commonly used for heating metals for heavy forging. The forging job is always heated to the correct forging temperature in a hearth (Fig. 1) or in a furnace (Fig.2) located near the forging arrangements. Gas, oil or electric-resistance furnaces or induction heating classified as open or closed hearths can be used. Gas and oil are economical, easily controlled and mostly used as fuels. The formation of scale, due to the heating process especially on steel creates problems in forging. A non-oxidizing atmosphere should, therefore, be maintained for surface protection. Special gas-fired furnaces have been developed to reduce scaling to minimum. Electric heating is the most modern answer to tackle scaling and it heats the stock more uniformly also. In some cases, coal and anthracite, charcoal containing no sulphur and practically no ash are the chief solid fuels used in forging furnaces. Forge furnaces are built raise temperatures up to 1350°C in their working chambers Centurion University of Technology and Management –Department of Mechanical Engineering pg. 66
  • 68. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL67 CUTM Box or batch type furnaces These furnaces are the least expensive furnaces widely used in forging shops for heating small and medium size stock. There is a great variety of design of box-type furnaces, each differing in their location of their charging doors, firing devices and method, employed for. Charging their products. These furnaces are usually constructed of a rectangular steel frame, lined with insulating and refractory bricks. One or more burners for gas or oil can be provided on the sides. The job-pieces are placed side by side in the furnace using a slot through a suitable tong. It is therefore sometimes called slot type furnace. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 67
  • 69. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL68 CUTM Rotary-hearth furnaces These are set to rotate slowly so that the stock is red to the correct temperature during one Rotation. These can be operated by gas or oil fuels. Continuous or conveyor furnaces These furnaces are of several types and are preferred for larger stock. They have an air or oil-operated cylinder to push stock end-to-end through a narrow furnace. The pieces are charged at one end, conveyed through the furnace and moved at other end at the correct temperature for the forging work. Induction furnaces These furnaces are very popular because induction greatly decreases scale formation and can often be operated by one person. The furnace requires less maintenance than oil or gas- fired furnaces. In induction furnaces the stocks are passed through induction coils in the furnaces. Delivery to forging machine operator can be effected by slides or automatic handling equipment. Resistance furnaces These furnaces are faster than induction furnaces, and can be automated easily. In resistance Heating furnace, the stock is connected to the circuit of a step-down transformer. Fixtures are also equipped along with furnace for holding different length, shape, and diameter of stock. However, the fixtures are often quite simple and can be adjusted to handle a family of parts. Fuels used in forging shop The fuels used in forging shop are classified as solid, liquid and gaseous fuels which are discussed as under. Solid fuels Wood, coal, anthracite, peat, charcoal, coke, pulverized fuel etc. Liquid fuels Crude oil, petroleum, kerosene, tar oil etc. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 68
  • 70. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL69 CUTM Gaseous fuels Natural gas and some artificially produced gases are used generate heat. A good fuel should have always possesses the following essential characteristic which are given as under. 1. The fuel should be able to generate the required heat. 2. It should have complete combustion. 3. It should be highly efficient. 4. It should not produce excess smoke and flying ash. 5. It should be easy to fire, cheap and easily available. CONTROL OF HEATING DEVICES For good control of heating devices such as hearth or forging furnace, the following points are should always be considered. 1. The nozzle pointing into the center of the hearth is called the tuyre and is used to direct a stream of air into the burning coke. The air is supplied by centrifugal blower. 2. As the hottest part of the fire is close to the tuyre opening, therefore, the tuyre is provided with a water jacket to prevent it from burning away. 3. The hood provided at the top of hearth collects smoke, fumes etc., and directs them away from the workplace through the chimney in form of exhaust. 4. The fuel for the fire may be either black-smiting coal or coke. To light the fire, either use paper and sticks or preferably a gas poker. 5. Impurities will collect as clinker and must be removed from the bottom of the fire when the fire cools. 6. The blowers are used to control the air supply using forced draught. Regulators control the draught and the temperature of the fire. 7. Blower delivers to forge adequate supply of air at proper pressure which is very necessary for the combustion of fuel. 8. A centrifugal blower driven by an electric motor is an efficient means of air supply in forging hearth. 9. Fire tools such as rake, poker and slice are generally used to control or manage the fire and theses tools are kept nearby the side of the hearth. Rake is used to take heated work piece out of the fire. Poker is a steel rod which is used to poke (stir) fire in the hearth. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 69
  • 71. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL70 CUTM 10. The place of the metal to be heated should be placed just above the compact Centre of a sufficiently large fire with additional fuel above to reduce the heat loss and atmospheric oxidation. COMMON HAND FORGING TOOLS For carrying out forging operations manually, certain common hand forging tools are employed. These are also called blacksmith’s tools, for a blacksmith is one who works on the forging of metals in their hot state. The main hand forging tools are as under. 1. Tongs 2. Flatter 3. Swage 4. Fuller 5. Punch 6. Rivet header 7. Hot chisel 8. Hammers 9. Anvil 10. Swage block 11. Drift 12. Set-hammer 14. Brass scale 15. Brass 16. Black smith’s gauge 17. Heading tool Some of the hand forging tool are depicted in Fig.1- 2 and their applications are described as under. Tongs The tongs are generally used for holding work while doing a forging operation. Various kinds of tongs are shown in Fig. 1. Flat tongs are used for mainly for holding work of rectangular section. 2. Straight-lip fluted tongs are commonly used for holding square, circular and hexagonal bar stock. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 70
  • 72. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL71 CUTM 3. Rivet or ring tongs are widely used for holding bolts, rivets and other work of circular section. 4. Gad tongs are used for holding general pick-up work, either straight or tapered. Flatter Flatter is shown in Fig. It is commonly used in forging shop to give smoothness and accuracy to articles which have already been shaped by fullers and swages. Swage Swage (Fig.) is used for forging work which has to be reduced or finished to round, square or hexagonal form. It is made with half grooves of dimensions to suit the work being reduced. It consists of two parts, the top part having a handle and the bottom part having a square shank which fits in the hard die hole on the anvil face. Fuller Fuller (Fig.) is used in forging shop for necking down a forgeable job. It is made in top and bottom tools as in the case of swages. Fuller is made in various shapes and sizes according to needs, the size denoting the width of the fuller edge Punch Punch (Fig.) is used in forging shop for making holes in metal part when it is at forging heat Centurion University of Technology and Management –Department of Mechanical Engineering pg. 71
  • 73. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL72 CUTM Rivet header Rivet header (Fig.) is used in forging shop for producing rivets heads on parts. Chisels Chisels are used for cutting metals and for nicking prior to breaking. They may be hot or cold depending on whether the metal to be cut is hot or cold. A hot chisel generally used in forging shop is shown in Fig. The main difference between the two is in the edge. The edge of a cold chisel is hardened and tempered with an angle of about 60°, whilst the edge of a hot chisel is 30° and the hardening is not necessary. The edge is made slightly rounded for better cutting action Hand hammers There are two major kinds of hammers are used in hand forging: (1) the hand hammer used by the smith himself and (2) the sledge hammer used by the striker. Hand hammers (Fig) may further be classified as (a) ball peen hammer, (b) straight peen hammer, and(c) cross peen hammer. Sledge hammers (Fig.) may further be classified as (a) Double face hammer, (b) Centurion University of Technology and Management –Department of Mechanical Engineering pg. 72
  • 74. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL73 CUTM straight peen hammer, and (c) cross peen hammer. Hammer heads are made of cast steel and, their ends are hardened and tempered. The striking face is made slightly convex. The weight of a hand hammer varies from about 0.5 to 2 kg whereas the weight of sledge hammer varies from 4 to 10 kg. Set hammer A set hammer generally used in forging shop is shown in Fig. It is used for finishing corners in shouldered work where the flatter would be inconvenient. It is also used for drawing out the gorging job. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 73
  • 75. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL74 CUTM Anvil An anvil is a most commonly tool used in forging shop which is shown in Fig. It acts as a support for blacksmith’s work during hammering. The body of the anvil is made of mild steel with a tool steel face welded on the body, but the beak or horn used for bending curves is not steel faced. The round hole in the anvil called pritchel hole is generally used for bending rods of small diameter, and as a die for hot punching operations. The square or hardies hole is used for holding square shanks of various fittings. Anvils in forging shop may vary up to about 100 to 150 kg and they should always stand with the top face about 0.75 mt. from the floor. This height may be attained by resting the anvil on a wooden or cast iron base in the forging shop. Swage block Swage block generally used in forging shop is shown in Fig. It is mainly used for heading, bending, squaring, sizing, and forming operations on forging jobs. It is 0.25 mt. or even more wide. It may be used either flat or edgewise in its stand. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 74
  • 76. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL75 CUTM Drift Drift generally used in forging shop is shown in Fig. It is a tapered rod made of tool steel. Holes are opened out by driving through a larger tapered punch called a drift. Hardie Hardie is a type of chisel used in forging shop. It is shown in Fig. Its taper head is fixed into the hardie hole of the anvil, the cutting edge being upward. The part to be cut is kept over the cutting edge of the fixed hardie on anvil and another chisel is placed over the job and the cutting is performed by hammering. Shovel Shovel generally used in forging shop is shown in Fig. It is used to place coal or coke in the furnace. It is also used to set coal pieces in furnace and remove ash from furnace. Poker Poker is employed for removing clinker from the furnace and to loose the compact coal pieces in the furnace. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 75
  • 77. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL76 CUTM Rake Rake is used to put coal pieces on tuyres. Beak Iron Beak iron generally used in forging shop is shown in Fig. It is also known as small anvil made of forged steel. Its upper front end consists of horn and upper back end comprises of flat tail. Its taper shank is inserted into the hardie hole of the anvil. It is commonly used as anvil for small forge work. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 76
  • 78. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL77 CUTM Exercise-1 SQUARE ROD Aim: To make a square rod from a given round rod by using hand forging operation Tools required: 1. Smith’s forge 2. Anvil 3. Ball peen hammers 4. Flatter 5. Round bit tongs and pick-up tongs Sequence of operation: 1. One half of the rod is heated to red hot condition in the Smith’s forge. 2. Holding the round rod bit tongs, the red is placed on the anvil face, the rod is then hammered. 3. The rod is hammered such that the round rod is converted in the square rod. 4. Following above steps the round rod is converted to square rod up to given specified length. ALL THE DIMENSIONS ARE IN MM Centurion University of Technology and Management –Department of Mechanical Engineering pg. 77
  • 79. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL78 CUTM Precautions: 1. Hold the hot work downward close to the ground, while transfer ring from the hearth to anvil. 2. Use correct size and type of tongs to fit the work. 3. Care should be exercised in the use of hammer. 4. Wear face shield when hammering hot metal. 5. Wear gloves when handling hot metal. 6. Wear steel-toed shoes 7. Ensure that hammers are fitted with tight and welded handles Result: the square rod is thus made from given round rod, following the hand operations, as mentioned above Centurion University of Technology and Management –Department of Mechanical Engineering pg. 78
  • 80. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL79 CUTM Exercise-2 S-HOOK Aim: To make S-hook from a given round rod by using hand forging operation Tools required: 1. Smith’s forge 2. Anvil 3. Ball peen hammers 4. Flatter 5. Round bit tongs and pick-up tongs All dimensions are in mm Sequence of operation: 1. One end of the bar is heated to red hot condition in the smithy’s forge for the required length. 2. Using the pickup tongs, the rod is taken from forge, and holding it with the half round tongs, the heated end is forged into a tapered pointed end 3. The length of the rod require for S-hook is estimated and the excess portion is cut-off using a cold chisel. 4. One half of the rod towards the pointed end is heated end is heated in the forge to red hot condition and then bent into circular shape as shown 5. The other end of the rod is then heated and forged into a tapered end. Centurion University of Technology and Management –Department of Mechanical Engineering pg. 79
  • 81. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL80 CUTM 6. The straight portion of the rod is finally heated and bent into a circular shape as required. 7. Using the flatter, the S-hook made as above, is kept on the anvil, and flattened so that, the shape of the hook is proper. Result: the S-hook is thus made from the given round rod by following stages mentioned above Centurion University of Technology and Management –Department of Mechanical Engineering pg. 80
  • 82. MECHANICAL WORK SHOP PRACTICE LAB MANNUAL81 CUTM Exercise-3 L-BEND Aim: To make L-bend from a given round rod by using hand forging operation Tools required: 1. Smith’s forge 2. Anvil 3. Ball peen hammers 4. Flatter 5. Round bit tongs and pick-up tongs Sequence of operation: 1. One end of the bar is heated to red hot condition in the smithy’s forge for the required length. 2. Using the pickup tongs, the rod is taken from forge, and holding it with the half round tongs, the heated end is forged into a tapered pointed end 3. The length of the rod require for L - bend is estimated and the excess portion is cut-off using a cold chisel. 4. One half of the rod towards the pointed end is heated end is heated in the forge to red hot condition and then bent into circular shape as shown 5. The other end of the rod is then heated and forged into a tapered end 6. The straight portion of the rod is finally heated and bent into a circular shape as required. 7. Using the flatter, the L-bend made as above, is kept on the anvil, and flattened so that, the shape of the hook is proper. Result: the L-bend is thus made from the given round rod by following stages mentioned above Centurion University of Technology and Management –Department of Mechanical Engineering pg. 81

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