Model engineers workshop pdf download

The operations required for the same are usually carried out on a work bench, hence the term bench work is also added with the name fitting. The bench work and fitting plays an important role in engineering. Although in today's industries most of the work is done by automatic machines which produces the jobs with good accuracy but still it job requires some hand operations called fitting operations. 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. The size of the work bench required is about to cm length, nearly 90 cm width and approximately 76 to 84 cm height. It consists of a cast Iron body and cast iron jaws.

Two jaw plates are fitted on both the jaws. The holding surface of the jaw plates is knurled in order to increase the gipping. Jaw plates are made up of carbon steel and are wear resistant.

One jaw is fixed to the body and the second slides on a square threaded screw with the help of a handle. The jaws are opened upto required length; job is placed in the two jaws and is fully tightened with the help of handle. The screw of the clamp applies the holding pressure. When the handle is rotated there is movement in the screw. These are marked in inches or millimetres.

All the faces are machined true. The edges of steel rule should be protected from rough handling. Calipers These are generally used to measure the inside or outside diameters.

Different types are: i. Outside Caliper: It is used to measure the outside dimensions. Inside Caliper: It is used to measure the inside dimensions. Spring Caliper: Spring is provided to apply the pressure and lock nut is provided to lock any desired position. Hermaphrodite, Jenny or Oddleg 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. Calipers 3. Vernier Caliper: It is used for measuring the outer dimensions of round, flat, square components and also the inner size of the holes and bore. A narrow blade is used to measure the depth of bar slots etc. The reading accuracy in metric system is 0. It is made of stainless steel. 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 planed 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. Angle Plate 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.

Scriber and Surface Gauge It consists of a cast iron bass on the center of which a steel rod is fixed vertically. Scriber is made up of high carbon steel and is hardened from the front edge. It is used for locating the centres of round bars or for marking of the lines. Scriber and Surface Gauge 4. Punches Punches are used for marking purposes. Dot punches are used for marking dotted line and centre punch is used to mark the centre of hole before drilling.

Punches are made up of high carbon steel or high speed steels. One end is sharpened. Hammering is done on the second end while working. For dot punch, angle of the punching end is 60 degree while in centre punch; angle of punching end is 90 degree. Try Square It is used for checking squareness of two surfaces. It consists of a blade made up of steel, which is attached to a base at 90 degree. The base is made up of cast iron or steel. It is also used to mark the right angles and measuring straightness of surfaces.

Never use try square as a hammer. Vernier Height gauge: A Vernier height gauge consists of a heavy base, a graduated beam, a sliding head with Vernier sliding jaws holding the scriber and a fine adjustment clamp.

It is similar to large Vernier calipers in construction, except that it consists of a heavy base which allows the gauge to stand upright instead of a fixed jaw in a Vernier. The movable jaw of Vernier height gauge consists of a projection or extension which is levelled to sharp edge for scribing lines at any required height. The procedure Fig.

The surface to be marked is coated with the paste of chalk or red slide C-Scriber clamp screw D — Scriber E lead and allowed to dry. Then the work is held In a holding device depending upon shape and size.

If it is flat, use surface plate, if it is round use V block and clamp, else use angle plate etc. Lines in horizontal direction are scribed by means of a surface gauge. Lines at right angles can be drawn by turning the work through 90 degree and then using the scriber. If true surface is available, try square can also be used. The centre on the end of a round bar can be located by using an odd leg caliper, surface gauge etc. The circles and arcs on a flat surface are marked by means of a divider.

After the scribing work is over, indentations on the surface are made using dot punch and hammer. Hacksaw Hacksaw is used for cutting of rods, bars, pipes, flats etc. It consists of a frame, which is made from mild steel. The blade is placed inside the frame and is tightened with the help of a flange nut. The blade is made up of high carbon steel or high speed Fig. Hand Hacksaws steel. The teeth of the blades are generally forward cut so in the case, pressure is applied in the forward direction only.

Depending upon the direction of cut, blades are classified as: o Forward cut o Backward cut. 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 i. 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. 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. The various shapes of cross-section available are hand file, flat file, triangular, round; square, half round, knife-edge, pillar, needle and mill file. 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. 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. 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. Triangular file: It has width either parallel throughout or upto 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. 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. 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 upto 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. Knife edge file: It has a width tapered like a knife blade and it is also tapered towards the tip and thickness. It carries double cut teeth on the two broad faces and single cut teeth on the edge.

It is used for finishing sharp corners of grooves and slots h. Diamond file: Its cross-section is like a diamond. It is used for special work. Needle file: These are thin small files having a parallel tang and a thin, narrow and pointed blade made in different shapes of its cross-section to suit the particular need of the work.

These are available in sizes from mm to mm of various shapes and cuts. These files are used for filing very thin and delicate work. Methods of filing The following are the two commonly used methods of filing: 1. Cross-filing 2. Draw filing. Cross - filing. Refer Fig. 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. 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.

When particles of metal clog the teeth the file is said to the pinned, a condition that causes scratching of the surface of the work.

Files, therefore, require cleaning by means of a file card or by dislodging the material between the teeth by means of a piece of soft iron, copper, brass, tin plate and so on, sharpened at the end. Hardened steel should never be used Fig. Odd leg caliper 3. Dot punch 9. Ball peen hammer 0. Filling 2. Punching 4. Sawing 5. Filling 6. The given mild steel flat piece is checked for given dimensions. One edge of given is filled to straightness with rough and smooth files and checked with try square.

An adjacent is also filled such that is square to first edge and checked with try square. Wet chalk is applied on one side of the flat and dried for making.

Lines are marked according to given figure, using odd leg caliper and steel rule. The excess materials removed from the remaining two edges with try square level up to half of the marked dots. Finally buts are removed by the filling on the surface of the fitted job.

The perpendicularity of face ends edges is checked perfectly by using try square. Finishing is given by using only with smooth files. Marking is done without parallax error. Knife Edge file 9. Dot punch Steel Rule Sequence of Operations: 1. One edge of given is filled with rough and smooth files and checked with try square for straightness.

An adjacent edge is also filled such that it is square to first edge and checked with try square. Wet chalk is applied on one side of the flat and dried for marking. Using the dot punch, punches are made along the marked lines. It is embedded in molding sand and suitable ramming of molding sand around the pattern is made. The pattern is then withdrawn for generating cavity known as mold in molding sand.

One piece or solid pattern 2. Two piece or split pattern 3. Cope and drag pattern 4. Three-piece or multi- piece pattern 5. Loose piece pattern 6. Match plate pattern 7. Follow board pattern 8.

Gated pattern 9. Sweep pattern Skeleton pattern Segmental or part pattern 1. Single-piece or solid pattern: Solid pattern is made of single piece without joints, partings lines or loose pieces.

It is the simplest form of the pattern. Typical single piece pattern is shown in Fig. Two-piece or split pattern: When solid pattern is difficult for withdrawal from the mold cavity, then solid pattern is split in two parts. Split pattern is made in two pieces which are joined at the parting line by means of dowel pins. The splitting at the parting line is done to facilitate the withdrawal of the pattern. A typical example is shown in Fig. Single Piece Pattern Fig. Molding sands may be of two types namely natural or synthetic.

Natural molding sands contain sufficient binder. Binder In general, the binders can be either inorganic or organic substance. The inorganic group includes clay sodium silicate and port land cement etc. Binders included in the organic group are dextrin, molasses, cereal binders, linseed oil and resins like phenol formaldehyde, urea formaldehyde etc. Organic binders are mostly used for core making. Among all the above binders, the bentonite variety of clay is the most common.

However, this clay alone cannot develop bonds among sand grins without the presence of moisture in molding sand and core sand. Some common used additives for enhancing the properties of molding and core sands are discussed as under.

Coal dust: Coal dust is added mainly for producing a reducing atmosphere during casting. Corn flour: It belongs to the starch family of carbohydrates and is used to increase the collapsibility of the molding and core sand 3. Dextrin: Dextrin belongs to starch family of carbohydrates that behaves also in a manner similar to that of the corn flour.

It increases dry strength of the molds. Sea coal: Sea coal is the fine powdered bituminous coal which positions its place among the pores of the silica sand grains in molding sand and core sand 5. Wood flour: This is a fibrous material mixed with a granular material like sand; its relatively long thin fibers prevent the sand grains from making contact with one another.

The clay and water furnish the bond for green sand. It is fine, soft, light, and porous. 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. Loam sand: Loam is mixture of sand and clay with water to a thin plastic paste. 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. This sand is subjected severest conditions and must possess, therefore, high strength refractoriness. 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. Parting sand: Parting sand without binder and moisture is used to keep the green sand not to stick to the pattern and also to allow the sand on the parting surface the cope and drag to separate without clinging 7.

Core sand: Core sand is used for making cores and it is sometimes also known as oil sand. This is highly rich silica sand mixed with oil binders such as core oil which composed of linseed oil, resin, light mineral oil and other bind materials.

Refractoriness: Refractoriness is defined as the ability of molding sand to withstand high temperatures without breaking down or fusing thus facilitating to get sound casting. It is a highly important characteristic of molding sands. Refractoriness can only be increased to a limited extent 2. Permeability: It is also termed as porosity of the molding sand in order to allow the escape of any air, gases or moisture present or generated in the mould when the molten metal is poured into it.

All these gaseous generated during pouring and solidification process must escape otherwise the casting becomes defective 3. Green strength: The green sand after water has been mixed into it, must have sufficient strength and toughness to permit the making and handling of the mould. For this, the sand grains must be adhesive, i.

Dry strength: As soon as the molten metal is poured into the mould, the moisture in the sand layer adjacent to the hot metal gets evaporated and this dry sand layer must have sufficient strength to its shape in order to avoid erosion of mould wall during the flow of molten metal 6. Flowability or plasticity: It is the ability of the sand to get compacted and behave like a fluid.

It will flow uniformly to all portions of pattern when rammed and distribute the ramming pressure evenly all around in all directions 7. Adhesiveness: It is property of molding sand to get stick or adhere with foreign material such sticking of molding sand with inner wall of molding box 8. Collapsibility: After the molten metal in the mould gets solidified, the sand mould must be collapsible so that free contraction of the metal occurs and this would naturally avoid the tearing or cracking of the contracting metal.

It is generally used for cleaning the sand for removing foreign material such as nails, shot metal, splinters of wood etc. Even power operated riddles are available for riddling large volume of sand. Shovel: It consists of a steel pan fitted with a long wooden handle. It is used in mixing, tempering and conditioning the foundry sand by Fig.

Showel hand. It is also used for moving and transforming the molding sand to the container and molding box or flask.

Sprue Pin Fig. Rammers 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. Sprue pin: 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. Trowels: These are used for finishing flat surfaces and comers inside a mould. Common shapes of trowels are shown as under. They are made of iron with a wooden handle.

Lifter: A lifter is a finishing tool used for repairing the mould and finishing the mould sand. Lifter is also used for removing loose sand from mould. Lifter Strike off bar: It is a flat bar, made of wood or iron to strike off the excess sand from the top of a box after ramming. Vent wire: It is a thin 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 used to make small Fig.

Slicks: 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 Fig.

Slicks 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. Swab Gate cutter: Gate cutter Fig. Gate Cutter 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.

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. Sprue Pin: It is a tapered wooden pin, used to make a hole in the cope through which the molten metal is poured into the mould.

It is frame or box of wood or metal. It is made of two parts cope and drag as shown in figure. Raw material required: Moulding sand, Parting sand, facing sand, baking sand, single piece solid pattern, bottom board, moulding boxes etc.

Tools Required: 1. Molding board 2. Drag and cope boxes 3. Molding sand 4. Parting sand 5. Rammer 6. Strike-off bar 7. Bellows 8. Riser and sprue pins 9. Gate cutter Vent rod Draw spike Wire Brush Sequence of operations: 1.

Sand preparation 2. Placing the pattern at the centre of the moulding flask 4. Ramming the drag 5. Placing runner and riser 6. Ramming the cope 7. Removal of the pattern, runner, riser 8. Gate cutting Procedure: Mould Making 1. First a bottom board is placed either on the molding platform or on the floor, making the surface even. The drag molding flask is kept upside down on the bottom board along with the drag part of the pattern at the centre of the flask on the board.

Dry facing sand is sprinkled over the board and pattern to provide a non-sticky layer. Freshly prepared molding sand of requisite quality is now poured into the drag and on the pattern to a thickness of 30 to 50 mm.

Rest of the drag flask is completely filled with the backup sand and uniformly rammed to compact the sand. After the ramming is over, the excess sand in the flask is completely scraped using a flat bar to the level of the flask edges. Now with a vent wire which is a wire of 1 to 2 mm diameter with a pointed end, vent holes are in the drag to the full depth of the flask as well as to the pattern to facilitate the removal of gases during casting solidification.

This completes the preparation of the drag. Now finished drag flask is rolled over to the bottom board exposing the pattern. Using a slick, the edges of sand around the pattern is repaired The cope flask on the top of the drag is located aligning again with the help of the pins of the drag box.

Sprue of the gating system for making the sprue passage is located at a small distance of about 50 mm from the pattern. The sprue base, runners and in-gates are also located as shown risers are also placed. Freshly prepared facing sand is poured around the pattern. The moulding sand is then poured in the cope box. The sand is adequately rammed, excess sand is scraped and vent holes are made all over in the cope as in the drag.

The sprue and the riser are carefully withdrawn from the flask Later the pouring basin is cut near the top of the sprue.

The cope is separated from the drag any loose sand on the cope and drag interface is blown off with the help of the bellows. Now the cope and the drag pattern halves are withdrawn by using the draw spikes and rapping the pattern all around to slightly enlarge the mould cavity so that the walls are not spoiled by the withdrawing pattern.

The runners and gates are to be removed or to be cut in the mould carefully without spoiling the mould. Any excess or loose sand is applied in the runners and mould cavity is blown away using the bellows. Now the facing paste is applied all over the mould cavity and the runners which would give the finished casting a good surface finish.

A dry sand core is prepared using a core box. After suitable baking, it is placed in the mould cavity. The cope is placed back on the drag taking care of the alignment of the two by means of the pins. The mould is ready for pouring molten metal. The liquid metal is allowed to cool and become solid which is the casting desired. Aim: To prepare a sand mold, using the given Split-piece pattern. Raw Material required: Moulding sand, Parting sand, facing sand, baking sand, pattern, bottom board, moulding boxes.

Placing the split pattern at the centre of the moulding flask 4. Placing the pattern at the centre of the moulding flask Cope box 6. Placing runner and riser 7. Ramming the cope 8. Removal of the pattern, runner, riser 9. Freshly prepared molding sand of requisite quality is now poured into the drag and on the split-pattern to a thickness of 30 to 50 mm. Using a slick, the edges of sand around the pattern is repaired and cope half of the pattern is placed over the drag pattern, aligning it with the help of dowel pins Dry parting sand is sprinkled all over the drag surface and on the pattern The sprue base, runners and ingates are also located as shown risers are also placed.

Result: The required mould cavity is prepared using the given Split Pattern. Step :1 Place Drag part of the pattern on mould board and filled with mould sand Step Turn drag box upside down and Place cope box over drag box Step place cope part of the pattern ,riser, Sprue, runner in position and filled with mould sand.

Many products, which fulfill the household needs, decoration work and various engineering articles, are produced fromsheet metals. Common examples of sheet metal work are hoopers, canisters, guards, covers, pipes, hoods, funnels, bends, boxes etc. Such articles are found less expensive, lighter in weight and in some cases sheet metal products replace the use of castings or forgings. The size of the sheet is specified by its length, width and thickness in mm.

The commonly used gauge numbers and the equivalent thickness in mm are given below SWG 16 17 18 19 20 22 24 27 30 No. Thickness 1. Black Iron Sheet It is the cheapest among ail. It has a bluish-black appearance and is uncoated sheet. Being uncoated, it corrodes rapidly. It is prepared by rolling to the desired thickness, then annealed by pleasing in a furnace and then set aside to cool gradually. The use of this metal is limited to articles that are to be painted or enameled such as stovepipes, tanks, pans etc.

Galvanized Iron It is soft steel coated with molten zinc. This coating resist rust, improves appearances, improves solderability, and improves water resistance. It is popularly known as G. Articles such as pans, buckets, furnaces, cabinet etc. Stainless Steel It is an alloy of steel with nickel, chromium and traces of other metals.

It has good corrosive resistance. The cost of stainless steel is very high but tougher than Gl sheets. It is used in kitchenware, food handling equipment, chemical plants etc. Copper It is a reddish colored metal and is extremely malleable and ductile.

Copper sheets have good corrosion resistance as well as good appearances but costs are high as compared to Gl and stainless steel.

Because of high thermal conductivity, it is used for the radiator of automobiles, domestic heating appliances etc. Aluminium Aluminium cannot be used in its pure form, but is used in alloy form. Common additions are copper, silicon, manganese and iron. It has many qualities like high ratio of strength to weight, corrosion resistant qualities, and ease in fabrication and whitish in color.

It is used in manufacturing of a number of products such as refrigerator trays, household appliances, lighting fixtures, window work, construction of airplanes and in many electrical and transportation industries. Tin Plates It is an iron sheet coated with the tin to protect it against rust. This metal has a very bright silvery appearance and is used principally in making food containers, cans and pans. Lead It is a very soft, malleable, low melting point and possesses high resistance to acid corrosion.

It is having low mechanical strength so it is used to provide lining to the highly corrosive acid tanks. The mini-lathe is a useful tool in the model engineer's workshop. With more choice than ever of more compact machines, a mini-lathe is able to accommodate a wide range of engineering requirements, projects and techniques, as well as being suitable for the novice engineer and for those with limited workshop. Simple workshop projects. Metal Lathe for Home Machinists.

The mini-lathe is a useful tool in the model engineer's workshop. With more choice than ever of more compact machines, a mini-lathe is able to accommodate a wide range of engineering requirements, projects and techniques, as well as being suitable for the novice engineer and for those with limited workshop. Simple workshop projects. Metal Lathe for Home Machinists.