PRAGATI ENGINEERING COLLEGE (Approved by AICTE, Permanently Affiliated to JNTUK Kakinada & Accredited by NBA) 1-378, ADB Road, Surampalem – 533 437, Near Peddapuram, E.G.Dist., A.P. Ph: (08852) – 252233, 252234, 252235 Fax: (08852) – 252232 DEPARTMENT OF MECHANICAL ENGINEERING ENGINEERING WORKSHOP Page 1 Certificate This is to certify that this is the bonafide observation of the work done in the Engineering Workshop laboratory by Mr. /Ms. B.tech year semester. H.T.No of branch during the academic year 20 to 20 . Faculty in charge Head of the Department
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PRAGATI ENGINEERING COLLEGE (Approved by AICTE, Permanently Affiliated to JNTUK Kakinada & Accredited by NBA)
To prepare the square cross-section from the given circular cross sectional bar.
MATERIAL REQUIRED:
M.S bar of dimensions .Length=150 mm, Diameter=12mm
TOOLS AND EQUIPMENT REQUIRED:
1. Open Hearth (Forge fire)
2. Round Tong
3. Flat Tong
4. Hand Hammer
5. Sledge Hammer
6. Anvil
7. Flatter
8. Steel rule
PROCEDURE:
1. Take the work piece of required dimensions i.e., Length (L) =150 mm, Diameter (D)=12 mm dia.
2. Hold the work piece with the help of tongs and place it in the hearth (forge fire). 3. Heat the work piece until it get red hot condition i.e., at which it possess high plastic
properties. 4. Hold work piece on one end with the help of round tongs and place it on the anvil. 5. Hammering is done with help of hand hammer due to this top and bottom faces are
flattered. 6. Rotate the work piece 900 and the other two faces are hammered to get the required
square shape. 7. If the temperature falls, repeat the steps 2, 3,4,5,6 until the required shape is obtained.
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1. Hold the work piece tightly with the help of suitable tongs when it is in red-hot condition.
2. The work piece is observed for proper heating. 3. Hammering of the raw material is done in red heat condition only. 4. Watch properly while hammering. 5. Beware of your clothes. Do not expose them to heat. 6. Use gloves and gum boots
RESULT:
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AIM: To prepare the S-HOOK from the given mild steel round rod.
MATERIAL REQUIRED:
M.S round rod of length 182 mm and 6 mm diameter.
TOOLS AND EQUIPMENT REQUIRED:
1. Open Hearth (Forge fire)
2. Flat Tong
3. Swage block
4. Hand Hammer
5. Sledge Hammer
6. Cold Chisel
7. Anvil
8. Flatter
9. Steel rule
PROCEDURE:
1. Take the work piece of required dimensions i.e., MS round bar of cross section 6×6 mm, Length (L) =182 mm.
2. Hold the work piece with the help of tongs and place it in the hearth (forge fire). 3. Heat the work piece until it get red hot condition i.e., at which it possess high plastic
properties. 4. Hold work piece on one end with the help of round tongs and place it on the anvil. 5. Bend the work piece by hammering with the help of hand hammer. 6. Repeat the same procedure for the other end to get the required S-shape.
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PRECAUTIONS: 1. Hold the work piece tightly with the help of suitable tongs when it is in red-hot
condition. 2. The work piece is observed for proper heating. 3. Hammering of the raw material is done in red heat condition only. 4. Watch properly while hammering. 5. Beware of your clothes .Do not exposes them to heat. 6. Use gloves and gum boots
RESULT:
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1. The given piece of wood is fitted to the carpentry vice; planning is done on all the four sides to required dimensions (35*20*300 mm3) with help of the jack plane, steel rule and try square.
2. The planed wooden piece is cut into two halves by handsaw. 3. Then the two pieces are marked as per the drawing of T lap joint with the help of try square,
marking gauge and steel rule. 4. Unwanted material of the two wooden pieces is removed by sawing and chiseling. 5. The above two finished pieces are joined to form the T lap joint.
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1. The wooden pieces should be fitted between jaws of carpentry vice tightly. 2. While planning, uniform pressure should be applied. 3. Chiseling must be done layer by layer so that we get a fine finish.
RESULT:
PRAGATI ENGINEERING COLLEGE (Approved by AICTE, Permanently Affiliated to JNTUK Kakinada & Accredited by NBA)
1. The given piece of wood is fitted to the carpentry vice, planning is done on all the four sides to required dimensions (35*20*300 mm3) with help of the jack plane, steel rule and try square.
2. The planed wooden piece is cut into two halves by handsaw. 3. Then the two pieces are marked as per the drawing of T joint with the help of try square,
marking gauge and steel rule. 4. Unwanted material of the two wooden pieces is removed by sawing and chiseling. 5. The above two finished pieces are joined to form the T joint.
PRAGATI ENGINEERING COLLEGE (Approved by AICTE, Permanently Affiliated to JNTUK Kakinada & Accredited by NBA)
1. The wooden pieces should be fitted between jaws of carpentry vice tightly. 2. While planning, uniform pressure should be applied. 3. Chiseling must be done layer by layer so that we get a fine finish.
RESULT:
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Machine tools are capable of producing work at a faster rate, but, there are occasions when components are processed at the bench. Sometimes, it becomes necessary to replace or repair a component which must fit accurately with another component on re-assembly. This involves certain amount of hand fitting. The accuracy of work done depends upon the experience and skill of the fitter.
The term,” Bench work” refers to the production of components by hand on the bench, whereas fitting deals with the assembly of mating parts, through removal of metal, to obtain the required fit.
Both the bench work and fitting requires the use of number of simple hand tools and considerable manual effort. The operations in the above works consist of filing, chipping, scrapping, sawing, drilling, tapping, etc.
FITTING TOOLS
HOLDING TOOLS
Bench vice
Fig.2. 1 Bench vice
The bench vice is a work-holding device (Fig.2.1).It is the most commonly used vice
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in a fitting shop. It is fixed to the bench with bolts and nuts. The vice body consists of two main parts, fixed jaw and a movable jaw. When the vice handle is turned in a clockwise direction, the sliding jaw forces the work against the fixed jaw. The greater the pressure applied to the handle, the tighter is work held. Jaws caps made of soft material are used to protect finished surface, gripped in the vice. The size of the vice is specified by the length of the jaws. The vice body is made of cast iron which is strong in compression, weak in tension and so fractures under shocks and therefore should never be hammered.
V -block with clamp
The v-block is a rectangular or square block with V-groove on one or both sides,
opposite to each other. The angle of the ‘V’ is usually 900.V-block with a clamp is used to
hold cylindrical work securely, during layout of measurements, for measuring operation
or for drilling (Fig.2.2.).For this the bar is placed longitudinally in the V-groove and the
screw of V-clamp is tightened. This grips the rod firmly, with its axis parallel to the axis of
the V-groove.
Fig.2. 2 V-Block with clamp Fig. 2. 3 C-Clamp C-clamp
This is used to hold work against an angle plate or V-block or any other surface, when gripping is required(Fig.2.3).Its fixed jaw is shaped like English alphabet, ”C” and the movable jaw is round in shape and directly fitted to the threaded screw at the end. The working principle of this clamp is the same as that of the bench vice.
MARKING AND MEASURING TOOLS
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The surface plate (Fig.2.4) is machined to fine limits and is used for testing the flatness of the work piece .It is also used for marking out small works and is more precise than the marking table. The degree of fineness of the finish depends upon whether it is designed for bench work in a fitting shop or for using in an inspection room. The surface plate is made of cast iron, hardened steel or granite stone. It is specified by length’ width’ height’ grade. Handles are provided on two opposite sides, to carry it while shifting from one place to another.
The angle plate is made of cast iron. It has two surfaces, machined at right angle to each other (Fig.2.5).Plates and components, which are to be marked out, may be held against the upright face of the angle plate, to facilitate the marking. Slots are provided on the angle plate to clamp the work in position.
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This is used for scribing lines for layout work and checking parallel surfaces
(Fig.2.6).Referring the figure, it may be noted that its spindle can be quickly adjusted to any angle, by an adjusting screw. In some designs, the base of the block will have a “V” shaped groove, to enable the block to rest on round bars if require, to set-off the dimensions from the bar to the surface of the components. Try-square
It is a measuring and marking tool for 90 degrees angle. In practice, it is used for checking the squareness of many types of small works, when extreme accuracy is not required (Fig.2.7).The blade of the try-square is made of hardened steel and the beam, of cast iron or steel. The size of the try-square is specified by the length of the blade. Combination set
It is a combination of measuring tools used for measuring linear dimensions, angular dimensions and for checking flatness of surfaces. It consists of a rule, square head, centre head, protractor and spirit level (Fig.2.8).This may be used as a rule, a square, a depth gauge, for marking meters (450), for locating the centre on the end of a round bar and for measuring and marking angles. The rule is made of tempered steel with grooves. The combination set is specified by the length of its rule.
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A scriber is a slender steel tool, used to scribe or mark lines on metalwork pieces (Fig.2.9).It is made of hardened and tempered high carbon steel. The tip of the scriber is generally ground at 120 to 150. It is generally available in lengths, ranging from 125mm to 250mm.It has two pointed ends. The bent end is used for marking lines where the straight end cannot reach.
Fig.2. 9 Scriber
Odd-leg calliper
This is also called ‘Jenny Calliper’ or Hermaphrodite’. This is used for marking parallel lines from a edge and also for locating the centre of round bars (Fig.2.10.).As shown in figure, it has one leg pointed like a divider and the other leg bent like a calliper. It is specified by the length of the leg up to the hinge point.
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It is basically similar to the callipers except that its legs are kept straight and pointed at the measuring edge. This is used for marking circles, arcs, laying out perpendicular lines, bisecting lines, etc.(Fig.2.11).It is made of case hardened mild steel or hardened and tempered low carbon steel. Its size is specified by the length of the legs. Punches
These are used for making indentations on the scribed lines, to make them visible clearly. These are made of high carbon steel’s punch is specified by its length and diameter, say as 150,12.5mm.It consists of a cylindrical knurled body, which is plain for some length at the top of it. At the other end, it is ground to a point the tapered point of the punch is hardened over a length of 20 to 30 mm.
Fig.2. 12 Punches
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Dot punch This is used to lightly indent along the layout lines, to locate centre of hole sand to
provide a small centre mark for divider point, etc. For this purpose, the punch is ground to a conical point having 60 degrees included angle (Fig.2.12a.). Centre punch
This is similar to the dot punch, except that it is ground to a conical point having 90 degrees included angle (Fig.2.12b).It is used to mark the location of the holes to be drilled.
CUTTING TOOLS: Hacksaw
The hacksaw is used for cutting metal by hand. it consists of a frame ,which holds a thin blade, firmly in position .Hacksaw blade is specified by the number of teeth per centimetre. Hack saw blades have a number of teeth ranging from 5 to 15 per centimetre .blades having lesser number of teeth per cm are used for cutting soft materials like aluminium, brass and bronze. Blades having large no of teeth per centimetre are used for cutting hard materials like steel and cast iron.
Hacksaw blades are classified as: (i) all hard and (ii) Flexible types. The all hard
blades are made of H.S.S, hardened and tempered throughout to retain their cutting edges longer .these are used to cut hard metals .these blades are hard and brittle and can break easily by twisting and forcing them into the work while sawing .flexible blades are made of H.S.S or low alloy steel but only the teeth are hardened and the rest of the blade is soft and flexible. These are suitable for use by un-skilled or semi–skilled persons.
Fig.2. 13 hacksaw frames with blades
The teeth of the hacksaw blade are staggered , as shown in fig.2.14 and are known as
a ‘set of teeth ‘.these are slots wider than the blade thickness ,preventing the blade from jamming.
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Chisels Chisels are used for removing surplus metal or for cutting thin sheets(fig.2.15). These
tools are made from 0.9% to 1.0% carbon steel of octagonal or hexagonal section. Chisels are annealed, hardened and tempered to produce a tough shank and a hard cutting edge. Annealing relieves the internal stresses in the metal .the cutting angle of the chisel for general purpose is about 600.
Fig.2. 14 set of teeth Fig.2. 15 flat chisel Combination pliers
This is made of high carbon steel by proper hardened and tempering and is used for cutting as well as for gripping the work (Fig.2.16).It has small cutting edges in both the jaws, which make it able to cut small diameter wires. The serrations in the jaws offer the facility for gripping, it is named as combination plier. Its handles are well insulated, which makes it suitable for electrical working.
Fig.2. 16 Combination plier Nose plier
It is similar to combination plier but its gripping jaws have extra length in tapered form which makes it suitable for gripping small objects and also gripping in narrow spaces (Fig.2.17).
Fig.2. 17 Nose plier
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Bench drilling machine Holes are drilled for fastening parts with rivets, bolts or for producing internal
threads. Bench drilling machine is the most versatile machine used in a fitting shop for the purpose (fig.2.18).twist drills, made of tool or high speed steel are used with the drilling machine for drilling holes.
It is the most useful of all pieces of drilling equipment .it is readily portable and convenient for use. Generally, it is used for drilling holes in small pieces held in a vice (fig. 2.19).the capacity of the portable drill is designated by the maximum diameter of the hole it can drill in steel.
FINISHING TOOLS Files
Filing is one of the methods of removing small amounts of material from the surface of a metal part. A file is a hardened steel tool, having slant parallel rows of cutting edges or teeth on its surfaces. On the faces, the teeth are usually diagonal to the edge. On end of the file is shaped to fit into a wooden handle. Fig 2.20 shows the parts of a hand file. The hand file is parallel in width and tampering slightly in thickness, towards the tip. It is provided with double cut teeth on the faces, single cut on one edge and no teeth on the other edge, which is known as the safe edge.
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Files are classified according to their shape, cutting teeth and pitch or grade of the teeth. Figure 2.21 shows the various types of files based on their shape. Types of files and their description and uses are given below.
Fig.2. 21 Types of files
Further, single cut and double cut files are shown in fig.2.22.single cut files are rows of teeth running in one direction, across their faces and double cut files have a second row of teeth, cut diagonally to the first row.
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Rectangular in section, tapered in thickness but parallel in width. The faces have double cut teeth and one of the edges, single cut. The other edge does not have any teeth and hence called as safe edge file. It is used for filing a surface, at right angle to an already finished surface. Flat file
Rectangular in section and tapered for 1/3rd length in width and thickness. The faces have double cut teeth and the edges, single cut. Used for general purpose filing. Square file
Square in section and tapered for 1/3rd length on all faces. All the faces have double cut teeth. Used for filing corners and slots and also o cut keyways. Triangular file
Equilateral triangular in section and tapered for 1/3rd length on all faces .All the faces have double cut teeth. Used for filing internal corners. Half round file
It has one flat face, connected by a curved face and tapered for 1/3rd length. The curved face is not exactly semi-circular but only a part of circle. The flat face has double cut teeth and the curved face, single cut. Used for filing concave surfaces and internal corners. Round file
Circular cross-section and tapered for 1/3rd length. It has double cut teeth.Used for filing concave surfaces and circular openings.
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Swiss or needle file It is normally 150mm long, with cut teeth. Used for filing corners, grooves,narrow
slots, etc., in intricate work. File card
It is a metal brush, used for cleaning the files, to free them from filings, clogged in-between the teeth (Fig.2.23).
MISCELLANEOUS TOOLS Ball-peen hammer
Hammers are named, depending upon their shape and material and specified by their weight. A ball-peen hammer has a flat face, which is used for general work and a ball end, particularly used for riveting (Fig.2.24).
It is similar to ball-peen hammer, except the shape of the peen(Fig.2.25).This is used for chipping, riveting, bending and stretching metals and hammering inside the curves and shoulders. Straight-peen hammer
This is similar to cross-peen hammer, but its peen is in –line with the hammer handle (Fig.2.26).It is used for swaging, riveting in restricted places and stretching metals.
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A screw driver is designed to turn screws (Fig.2.27a).The blade is bade of steel and is available in different lengths and diameters. The grinding of the tip to the correct shape is important .A Phillips (star) screw driver is specially designed to fit the head of Phillips screws. The end of the blade is fluted instead of flattened (Fig.2.27b).The size of a screw driver is specified by the length of the metal part from handle to the tip.
Fig.2. 27 Screw Drivers
FITTING OPERATIONS: CHIPPING
Riveting the metal with a chisel is called and is normally used where machining is not possible (Fig.2.28).While chipping, safety goggles must be put on, to protect eyes from the flying chips. To ensure safety of others, a chip guard is placed in position. Care should be taken to see that the chisel is free from mushroom head. NOTE: For better results, the angle of chipping must be the same throughout the operation.
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There are several methods of filing, each with a specific purpose (Fig.2.29).With reference to the figure, the following may be noted: 1. Holding the file For heavy work and to remove more metal, a higher pressure is used.
For light and fine work, a light pressure is applied. 2. Filing internal curves A part of half round file only makes contact as shown, during
filing operation. Movement of the file is indicated by arrows. 3. Cross filing is carried out across two diagonals, to produce medium surface finish. NOTE: The possibility of the surface becoming curved is drastically reduced due to
continuous changing of directions. 4. Draw filing A smooth file with a flat face is used for this purpose and to produce fine
grained structure. NOTE: Draw filing is preferred for the edges of long and narrow work pieces. For this, the file is placed at right angle to the work and held in both the hands across its body, as close as possible. During work, the file is pushed backward and forward, along the edge being filed. Pinning of files This is caused by soft metals, clogging the file teeth and scratching the surface of the work. The pins are removed with a file card. Pinning may be prevented by rubbing chalk into the teeth before filing. Checking flatness and squareness To check flatness, try-square is used .No light should be seen between the bottom edge of the square and the top surface of the work piece, when both are held against light. Similarly, the flatness across thickness of plate is tested as shown.
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It is an operation by which high spots left on the surface of a job after filing or other
machining operations, are removed by using a tool known as scraper. Scraping is aimed at removing only a little amount of metal, to get perfect flat surface. Scraping operation is carried out by holding the scraper in the both hands and then removing it too and fro (fig.2.30).
Fig.2. 30 Scraping
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Fig.2. 31 Methods of measuring and marking MARKING AND MEASURING
Accurate marking is the first step and the methods and instruments used are common in all fitting works. Measurements are taken either from a finished edge or from the centre line. Scriber lines on non ferrous materials and oxide coated steels are readily visible but bright steel needs coating with copper sulphate solution or engineers glue (Prussian blue), for the visibility of the line. Measuring and testing are continuous processes throughout the manufacturing, drawings.
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The following are the measuring methods in the order of increasing accuracy. a. Direct measurement from a rule b. Calipers set to a rule c. Calipers set to a plug gauge d. Vernier calipers e. Micrometer f. Dial indicator PRINCIPLES OF SAWING
Hack saw blades are specified by length and number of teeth in a standard length along the cutting edge. The correct choice of pitch should ensure that at least 3 teeth are in contact with the section to be sawn (fig.2.32).
Hacksaw blade should be inserted in the frame, with the teeth pointing forward, as the saw cuts on forward stroke only. The blade should be tightening such that the blade produces a musical twang when struck lightly with the finger. Only little downward pressure is needed in sawing, as teeth are designed to pull themselves into the work. About 40 strokes per minute is the correct sawing speed.
Fig. 2.32 Selection of blade pitch
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1. Prepare the development of the Open scoop as per the dimensions given. ( l= 104mm, b1=50mm, b2=70mm ,h1=14mm, h2=24mm.
2. Choose a G.I sheet size to accommodate the development. 3. Clean the sheet and mark the development using steel rule, scriber and divider. 4. Remove the unwanted material by using a curved snip. 5. Fold the edges on the required sides by using a suitable stake. 6. Bend the sheet at required markings to get the shape using suitable stake and mallet. 7. The Open scoop of required dimensions is obtained.
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1. Cutting should be done along the marked lines carefully. 2. Selection of stake is important for the required shape. 3. Excessive hammering of mallet during edge folding and finishing should be avoided. 4. Since the sheet metal has sharp edges it should be handled carefully to avoid injuries.