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Diploma (Mechanical)
Workshop Practice For 1
st
Semester
Expt: 1. Practice correctly safety procedures in the workshop.
1. Always listen carefully to the teacher and follow instructions.
2. Do not run in the workshop, you could ‘bump’ into another pupil and cause
an accident.
3. Know where the emergency stop buttons are positioned in the workshop. If
you see an accident at the other side of the workshop you can use the
emergency stop button to turn off all electrical power to machines.
4. Always wear an apron as it will protect your clothes and hold lose clothing
such as ties in place.
5. Wear good strong shoes. training shoes are not suitable.
6. When attempting practical work all stools should be put away.
7. Bags should not be brought into a workshop as people can trip over them.
8. When learning how to use a machine, listen very carefully to all the
instructions given by the teacher. Ask questions, especially if you do not
fully understand.
9. Do not use a machine if you have not been shown how to operate it safely
by the teacher.
10. Always be patient, never rush in the workshop.
11. Always use a guard when working on a machine.
12. Keep hands away from moving/rotating machinery.
13. Use hand tools carefully, keeping both hands behind the cutting edge.
14. Report any damage to machines/equipment as this could cause an
accident.
AIM: To study the tools used in Fitting Shop
Tools are mainly classified as i) Holding tools – to hold the work firmly when several operations are being carried out. Ex: Bench vice, leg vice, clamp, tongs etc., ii) Striking tools – to impart the required energy to the tool to cut the material. Ex: Hammer, mallet. iii) Cutting tools – used to cut the material. They have sharp cutting edges for the removal of material. Ex: Chisel, hack was jack plane, drill, shear, file taps. iv) Marking tools – used to mark the work surface so that the final dimensions can be clearly laid out the work piece. Ex: Divider, punch, scriber. v) Measuring tools – used to measure dimensions/angles on the work piece so that the given size of the model can be measured and marked. Ex: Scale, calipers, bevel protractor. In the next paragraphs the description of each of the above classified tools has been given. Effort has been made to cover most of them.
1. Holding Tool Bench vice :- is a work holding device, fixed to the working bench, ridgidly. It has a fixed end with a jaw bolted on to the table. A moveable end with a jaw is connected through a screw rod. The screw rod has a handle on one end. By actuating (rotating the handle) the moveable jaw can be moved towards the fixed jaw or away from it. Between the gap of the jaws, the workpeice is held rigidly. (fig.13 a shows this) Leg vice : It is a work holding device fixed to the working bench rigidly. It contains fixed and moveable jaws connected to two long leg like members. A screw rod connects the two legs. A spring holds the legs in tension. A handle provided on to the screw rod is used to actuate the moveable jaw portion. The gap between the jaws can be increased or decreases to facilitate gripping of the workpiece. It is used for heavy duty work. Anvil : It is used to keep the work piece and apply necessary pressure using a hammer. It consists of a rigid base with a top flat surface and a pointed beak on one side. It is also consists of a small square hole to keep the work piece while imparting necessary pressure. Using the beak portion of the anvil the shee metal can be bent into an arc of a circle and necessary bending action can be imparted to the sheet. Carpenter’s vice : consists of fixed and moveable jaws. The face of the jaws are provided with wooden surface backed by metal surface. By using handle the moveable jaw can be moved to an fro and facilitate clamping of wood. C-clamp : is a work holding device, in the form of a C. It is handy and portable one. The gap between the ends of the C can be adjusted using a screw rod and handle.
The length is slightly tapered at the end. They come in 3 sets i) Starting tap has more taper at the end, has coarse threads. ii) Intermediate tap has less taper and finer threads. iii) Final tap has much less taper at the end with finer threads. They are used in sequence to cut internal threads. A tap wrench is used to hold the taps and by using hand the necessary rotation of the tap can be given. Drill bits : These are cutting tools used for creating circular holes in the work piece. A drill but consists of a shank. Which is plan cylindrical one and a flute end which consist of helical grooves with cutting edges. The tip of the helical portion ends in the form of a crone,which will provide the necessary cutting action to the tool. The twist grill or drill bit as it is popularly called as has to be used in a drilling machine to get the necessary rotating action. By applying pressure on to the work piece through the drill bit while it is being rotated the hole of required size can be created. Jack plane : is used in carpentry work. Consists of a rectangular box with slot at the centre to fix a flat shaped cutting blade with adjustable screws. Thin materials of wood can be removed by this. Smooth even surface can be created on the work piece by using this. Wood saw : is used to cut wood. Straight vertical or slant cuts can be made. Cross cut saw is used for faster and larger jobs. Tenon saw is used for light jobs. Shears : find use in sheet metal work. Resembles a shear (scissors). Cutting edges. They are also referred to as snips (hand operated).
4. Marking tools Divider : consists of two pointed legs hinged at one end. The divider is used to mark or lay off distances on the piece. Centre punch & dot punch : are small cylindrical hardened steel pieces with a point at one end. It is used to punch reference marks on the work piece. They are used to mark the layout lines with a dot and also locate the centre of the hold to be drilled. Try Square : is used for checking perpendicularity of adjacent surfaces. It is also used to mark perpendicular adjacent faces with workpiece. It is used in carpentry and fitters’. It is used for checking the squreness of adjacent faces of the work. It consists of a blade of hardend steel and a beam of steel. It is specified by the length of the blade. Bevel square : This tool is similar to the try squre except the angle between the blade and the stock can be adjusted for a given angle so that the given angles can be marked easily.
Surface plate : It is flat horizontal hardened steel plate used to hold work piece along with an angle plate. V-block, scriber etc. to mark the work piece. It helps to mark the surface accuretly. It is used for checking the flatness of the work piece. It is used to mark the work piece. It is made of cast iron or hardended steel or granite stone. It is specified by the length, breadth, height and grade. Scriber block : It consists of a square shaped steel base with a vertical rod attached to it. A small bush with a projection and wing nut can be slid in the rod, up or down. To the bush a long scribing pin is attached. It can be swiveled and held at an angle with respect to vertical axis. This length and the angle of the scriber can be changed. The pin has a pointed end, which is used to mark the work piece. Marking gauge: It is used in carpentry to facilitate marking on the wooden surface. It consists of sharp pointer at one end for marking and a square faced adjustable thin wooden block that can be slid on a square wooden bar. It is provided with a clamp for arresting the square long faced block. Angle plate: it is plate made of cast iron. It has two adjacent surfaces machined at right angles to each other. The work piece to be marked is held against the vertical face of the angle plate and then using a scribing block the surface is marked. The angle plate is used along with a surface plate. Spring calipers : They are used to check the inside and outside diameter of the work piece, with the help of a scale. They are referred to as inside and outside calipers. Spring odd leg calipers : it is used for marking parallel lines from a finished edge. It can also be used to locate the centre of a round bar.
5. Measuring Tool: Vernier caliper : it is a measuring tool used to measure both outside and inside dimensions of the work piece. The least value measurable by the Vernier caliper is specified by the term “Least Count of the caliper”. Least count (L.C) = value of 1 main scale division – value of vernier scale division. Outside micrometer : it is used for measuring outside dimensions accurately to 2nd^ decimal place. It consists of a liner main scale and a circular vernier scale. Wire guage : It is used to check the thickness of the sheet metal and it also act as a measuring tool. It consists of a circular disc with number of slots along its circumference. The thickness of each of the slots is designated by a integer number and it corresponds to a particular thickness in mm. The sheet metal is passed through any of the slot that exactly matches and the thickness can be read out in SWG or mm. Higher the number of the guage thinner is the gauge thickness of the sheet.
8. What is sawing? The process of cutting the work piece into two by metal removal using a saw is referred to as sawing. 9. What is filling? Filling is a cutting operation on metals which involve the removal of metal in small quantities by hand or by machine using a file. 10. List different types of files They are classified as: 1. General purpose files – rough, coarse & bastard or 2. as single cut & double cut files or 3. based on shaop Flat file Square file Round file 11. (a) What is the angle of cut in a file? What is the purpose of grooves/cuts on the file? The file surface consists of grooves cut at the angle. The directions of the grooves from the handle is from right to left down wards called as overcut and from left to right down wards called upcut when the file is held vertical with the handle upwards. If the file contains both upcut and overcut grooves then it is referred to as double cut files. The angle of these grooves depend on the type of metals filled. 11. (b) What angle is used for filling the following materials? The normal angle of cut used are: 45 – 60 o^ Bronze 30 – 85 o^ Brass 50 – 60 o^ Al, Steel These grooves are sharper and provide greater chip clearances for easy filling. 12. What are the specifications of a file? Files are specified by their lengths (10 0 - 250mm) or (100-315mm). Shapes – round, flat Cuts – double cut or single cut.
13. When do you prefer single cut and doublt cut files? Single cut files are preferred for softer metals. Double cut files are preferred for harder metals. 14. List the different types of hammers. Hammers are classified as Ball pen hammer, square face-round face Hammer with rubber caps on the face. 15. What is plate? What is sheet? When the thickness of the metal is greater than 5mm then it is referred to as place but when the thickness is less than 5mm then it is refereed to as sheet. 16. How is the size of a try square specified? The size of the try square is specified by the length of the blade. 17. Why is the hacksaw blade teeth are staggered? Teeth of hacksaw blade is staggered to ensure that the metal powder removed from the cutting process does not clog and prevent further cutting of the metal. This also ensures that the width of cut greater than the thickness of the blade. 18. How hacksaw blade is specified? The blade is specified by its length 250 or 300mm. Width 12 or 16mm Thickness 0.65 or 0.8mm and Number of teeth per inch (20 per inch etc). 19. What is surface plate? It is a heavy metal plate with very smooth surface used to hold the work surface. It is used to mark dimensions using various tools and check the flatness of the work piece. 20. What is twist drill? A twist drill is a cutting tool used to cut holes in the work piece. The drill is fitted to a drilling machine. The rotary motion of the drill is used to create a hole.
30. How are files classified? Files may be classified based on the coarseness as Rough, Bustard, Smooth, Dead & smooth and Super smooth in the decreasing order of coarseness. Fitting Model Aim : To prepare a model as per the given sketch. Material given : Mild steel plate of L = 52mm, B=50mm, T=5mm 2 nos. Tools used : Steel scale, try square, Ball peen hammer, Centre punch, Divider, hacksaw with frame, Flat Chisel, Flat file rough and smooth, Leg vice. Procedure:
- Fix the first M.S.piece to the leg vice and file the adjacent edges using rough file.
- Make the edges perpendicular to each other by filling. Check the same using a Try square.
- Repeat the same for the other piece and make the adjacent edges perpendicular each other.
- Now apply a thin layer of wet chalk on the surface of the two pieces and allow it to dry.
- Mark the layout of the given shape on the two pieces (one forms the male part and the other female part) – using scale, scriber pin etc., with the help of a surface plate.
- using centre punch, mark punch marks to get permanent marks on the pieces.
- Shaded portion is to be removed.
- Using hacksaw or chisel, remove AA portion and BB portion.
- Now using hacksaw cut off portion corresponding to V-shape.
- Using small circular file remove the excess material and slowly finish it. Maintain the dimensions by checking the same at regular intervals (by matching both the pieces).
- Match the two surfaces.
- Measure the critical dimensions.
- Compare it with the given dimensions and prepare a deviation table.
- Comment on the deviation in the dimensions and the matching of the two portions of the model. Portion Dimensions in mm Male portion Female portion^ Deviation Drawing Model Drawing Model Radius F Radius M Edges E
