Fitting Shop PDF

FITTING Even in the most mechanized industry, although majority of the work can be finished with the help of machines, there are certain operations, which have to be carried out manually using hand tools. For example, i) In production shops, when two or more parts are to be assembled ii) Sometimes i...

FITTING Even in the most mechanized industry, although majority of the work can be finished with the help of machines, there are certain operations, which have to be carried out manually using hand tools. For example, i) In production shops, when two or more parts are to be assembled ii) Sometimes it necessary to replace or repair a component, which must fit accurately with another component on re-assembly. The operations required Fitting: Fitting is related for the 'fitting' are usually Bench Work: The term to assembly of parts, after carried out on a work ‘bench work’ refers to the bringing the dimension or bench. The term bench production of components shape to the required size work is also added with by hand on the bench. or form, in order to secure the name fitting. The the necessary fit. person working in the fitting shop is called fitter. Ferrous Metals Iron pig iron, cast iron, wrought iron, carbon steel, Alloy steel, Nickel steel. attracted by magnets steel prone to rusting. Metal Engineering Non-Ferrous Metals Materials Non-Metal Gold, Silver, Copper, Aluminium, Tin, Platinum,Nickel, Bronze etc neither rust nor can be attracted by magnets. Cast iron It is an Iron based material where carbon contain is more than 2%. (2-4%), Silicon (0.4-2.8%), Manganese (0.25-1.25%), Sulfur (0.2%max) and Phosphorous (0.6%max). Types of Cast iron: - Gray cast iron, malleable iron, white cast iron. Steel: It is an Iron based material where Carbon contain is less than 2%. Besides this, it also contains Silicon, Manganese, Sulfur and Phosphorous. One of the differences between Cast iron and steel is the amount of carbon percentage. Based on the carbon content, steel is divided into a) Low Carbon Steels- the carbon content ranges from 0.03-0.35%. Low carbon steels are also called as soft or Mild steel (M.S). b) Medium Carbon Steels-the carbon content ranges from 0.35-0.6%. c) High Carbon Steels-The carbon content ranges from 0.6-1.7% Mild steel (MS) Iron based material; Carbon is 0.15-0.35%. Besides this, it also contains Silicon, Manganese, Sulfur and Phosphorous. Low carbon steels are also called as soft or mild steel. These steels are used for bolts and nuts, structural work, axles, shafts etc. Alloy Steel In alloy steel in addition to carbon and iron, alloying elements such as chromium, Nickel, Vanadium etc. is mixed. Ex: - Stainless-steel, High-Speed steel (H.S.S) or Tool steel. Tool steel is widely used in the manufacturing of cutting tools. FITTING TOOLS: Fitting shop tools are classified as below: Work Holding Devices/ Clamping Tools. Measuring and Marking Tools. Cutting Tools. Striking Tools. Drilling Tools. Threading Tools. Fig. 1 Fig. 2 WORK HOLDING DEVICES/ CLAMPING TOOLS: 1. WORK BENCH: A fitting process can be done at various places, but most of the important operations of fitting are generally carried out on a table called work bench. The work bench is a strong, heavy and rigid table made up of hard wood. (See Fig. 1) 2. BENCH VICE: It is firmly fixed to the work bench with the help of nuts and bolts. It consists of a cast Iron body and cast- steel jaws. Two jaw plates are fitted on both the jaws. The holding surface of the jaw plates is knurled in order to increase the gripping. One jaw is fixed to the body and the second slides on a square threaded screw with the help of a handle. Handle is used to move the movable jaw. (See Fig. 2) Specification: - the width of the jaws determines the size of the vice. 3. V BLOCK: V‐block is rectangular or square block with a V‐groove on one or both sides opposite to each other. V‐block is. used to hold cylindrical or circular work securely. Material- Hardened Steel or Cast Iron. (See Fig. 3) : Fig. 3 Fig. 4 MEASURING TOOLS 1. STEEL RULE: It is used for measuring and marking the required dimensions on the work piece. The scale is graduated in millimeters, centimeters and inches. Least count of normal steel rule is 1mm. These are made up of stainless steel and are available in many sizes ranging from 20 cm- 30cm. The edges of steel rule should be protected from rough handling. (See Fig. 5)  Fig. 5 2. CALIPERS: These are generally used to measure the inside or outside diameters. Material- Tool steel. (See Fig. 4) Different types are: I. OUTSIDE CALIPER: It is used to measure the outside dimensions. II. INSIDE CALIPER: It is used to measure the inside dimensions. III. ODD LEG CALIPER: One leg is bent at the tip inwardly and the other has a straight pointed end. It is used to scribe lines parallel to the straight edges. MARKING TOOL: 1. SURFACE PLATE: It is used for testing the flatness, trueness of the surfaces. It is made up of cast iron or graphite. Its upper face is planned to form a very smooth surface. It is also used in scribing work. While not in use, it should be covered with a wooden cover. Fig. 6 It is made up of cast iron in different sizes; it has two planed surfaces at right angles to each other and has various slots in each surface to hold the work by means of bolts and clamps. Never do hammering on the angle plate to fasten (lighten) the nuts and bolts. (Fig. 6) 2. SCRIBER AND SURFACE GAUGE: Scriber is made up of high carbon steel and is hardened from the front edge. It is used for locating the centers of round bars or for marking of the lines. (Fig. 7) Fig. 7 3. PUNCH: 4. TRY SQUARE: Punches are used for marking purposes. Prick It is used for checking squareness of two surfaces. punches are used for marking dotted line and centre It consists of a blade made up of steel, which is punch is used to mark the centre of hole before attached to a base at 90 degrees. The base is made drilling. Punches are made up of high carbon steel up of cast iron or steel. It is also used to mark the or high speed steels. One end is sharpened. right angles and measuring straightness of surfaces. Hammering is done on the other end while working. Never use try square as a hammer. ( See Fig. 9) ( See Fig. 8) Fig. 8 Fig. 9 (a)In center punch; angle of punching end is 90 degrees. (b)In Prick punch, angle of the punching Depending upon the pitch of the teeth (Distance end is 60 degrees between the two consecutive teeth) blades is CUTTING TOOLS classified as: 1. HACKSAW : Coarse (8-14 teeth per Inch) Depending upon the direction of cut, blades are Medium (16-20 teeth per inc) classified as Fine (24-32 teeth per inc) 1.Forward cut 2. Backward cut. Fig. 10 The hacksaw is used for cutting metal by hand. The hacksaw blade has a number of teeth ranging from 8 to 32 per centimeter. Lesser number of teeth is used for cutting materials like Aluminium, brass and bronze and large number of teeth is used for cutting hard materials like steel, C.I etc. Hack saw blades are fitted either in a solid frame or adjustable frame to accommodate different lengths of blade. It is made of high-speed steel. The hacksaw blades are specified byits material, length, width, thickness and pitch of the teeth. The common dimensions are length 250-300 mm, width 13 mm-16 mm, thickness 0.6 to 0.8 mm, pitch 1 to 1.8 mm. The blades are fixed with teeth facing forward and the teeth are staggered, which are known as ‘set of teeth’. These make slots wider than blade thickness, preventing the blade from jamming 2. FILES Files are multi points cutting tools. It is used to remove the material by rubbing it on the metals. Files are available in a number of sizes, shapes and degree of coarseness. CLASSIFICATION OF FILES: ON THE BASIS OF LENGTH: 4”, 6”, 8”, 12” ON THE BASIS OF GRADE: Rough (R) (20 teeth per inch) Bastard (B) (30 teeth per inch) Second cut (Sc) (40 teeth per inch) Smooth file (S) (50 teeth per inch) Dead smooth (DS) (100 teeth per inch) Rough and bastard files are the big cut files. When the material removal is more, these files are used. These files have bigger cut but the surface produced is rough. Dead smooth and smooth files have smaller teeth and used for finishing work. Second cut file has degree of finish in between bastard and smooth file. ON THE BASIS OF NUMBER OF CUTS:  Single cut files. Double cut files In single cut files the teeth are cut in parallel rows at an angle of 60 degree to the face. Another row of teeth is added in opposite direction in case of double cut files. Material removal is more in case of double cut files. ON THE BASIS OF SHAPE AND SIZE: The length of the files varies from 4” to 14”. The various shapes of cross-section available are hand file, flat file, triangular, round; square, half round, knife-edge, pillar, needle and mill file. 1. FLAT FILE: This file has parallel edges for about two-thirds of the length and then it tapers in width and thickness. The faces are double cut while the edges are single cut. 2. HAND FILE: For a hand file the width is constant throughout, but the thickness tapers as given in flat file. Both faces are double cut and one edge is single cut. The remaining edge is kept uncut in order to use for filing a right-angled corner on one side only. 3. SQUARE FILE: It has a square cross-section. It is parallel for two-thirds of its length and then tapers towards the tip. It is double cut on all sides. It is used for filing square corners and slots. 4. ROUND FILE: It has round cross-section. It carries single cut teeth all round its surface. It is normally made tapered towards the tip and is frequently known as rat-tail file. Parallel round files having same diameter throughout the length are also available. The round files are used for opening out holes, producing round comers, round-ended slots etc. 5. HALF-ROUND FILE: Its cross-section is not a true half circle but is only about one-third of a circle. The width of the file is either parallel throughout or up to middle and then tapered towards the tip. The flat side of this file is always a double cut and curved side has single cut. It is used for filing curved surfaces. 6.TRIANGULAR FILE: It has width either parallel throughout or up to middle and then tapered towards the tip. Its section is triangular (equilateral) and the three faces are double cut and the edges single cut. It is used for filing square shoulders or comers and for sharpening wood working saws. METHODS OF FILING: The following are the two commonly used methods of filing: 1. Cross-filing 2. Draw filing. 1. CROSS-FILLING: This method is used for efficient removal of maximum amount of metal in the shortest possible time. It may be noted that the file must remain horizontal throughout the stroke (long, slow and steady) with pressure only applied on the forward motion 2. DRAW FILING: This method is used to remove file marks and for finishing operations. Here, the file is gripped as close to the work as possible between two hands. In this filing method, a fine cut file with a flat face should be used. Experiment No 1: To make T-Fitting from the given two M.S Plate as instructed. SQUARE (T) - FITTING EXPERIMENTNO:01 DATE: Aim: - To make T-Fitting from the given two M.S Plate a specified in the diagram Tools required: - 1. Benchvice 7. Dot punch and Centrepunch 2. Steelrule 8. Surfaceplate 3. Trysquare 9. Venire heightgauge 4. Ball peenhammer 10. Rough and smooth flatfiles 5. Scriber 11. Flat chisel and triangularfile 6. Hack saw withblade Materials required: - Mild steel (M.S) plate of size (75 x 50 x 5)x2Nos. Sequence of Operations: - 1. Filing 2. Checking flatness and squareness 3. Marking andmeasuring 4. Punching 5. Sawing 6. Chipping 7. Finish Procedure: - 1. The burrs in the pieces are removed and the dimensions are checked with a steelrule. 2. The pieces are clamped one after the other and the outer mating edges are filed by using rough and smoothfiles. 3. The flatness, straightness and square ness i.e. right angle between adjacent sides are checked with help ofTry-square. 4. Chalk is then applied on the surfaces of the twopieces. 5. The given dimensions of the T-fitting are marked with help of vernier height gaugecarefully. 6. Using the dot punch, dots are punched along the above scribedlines. 7. Using the hack saw, the unwanted portions areremoved. 8. Using the flat chisel, the unwanted material in the piece Y isremoved. 9. The cut edges are filed by the half roundfile. 10. The corners of the stepped surfaces are filed by using a square or triangular file to get the sharpcorners. 11. The pieces (X and Y) are fitted together and the mating is checked for the correctness of thefit. Result: - T-fit is made as per the required dimension.