DEPARTMENT OF MANUFACTURING & MATERIALS
WORKSHOP TECHNOLOGY MME 1103
BENCHWORK
MANUFACTURING AND MATERIALS DEPARTMENT
MME1103 Workshop Technology Manual Benchwork
1 1. Objective To identify various types of hand tools and its usage 2. Required Apparatus Bench vise, marking out table, hand hammer, files, center punch, ruler, steel file brush, scriber, high vernier caliper, hacksaw, angle plate, dividers 3. Required Materials Cast Iron 4. Introduction The workbench is the craftsman’s head quarters, where operations involving the use of hand tools such as sawing, filing, chiseling and marking out are appropriately carried out. In this section, students will be introduced to the basic complement of hand tools commonly used in all branches of mechanical technology such as bench vise, files, hacksaw and center punch, and scriber.
4.1 Bench Vise The bench vise is used to help grip the workpiece for filing, hacksawing, chiseling and bending light metal. The bench vice mainly consist of a fixed jaw, movable jaw and jaw plates (Figure 1). Most bench vises have hardened insert jaws that are sharply serrated and will dig into finished workpieces enough to mar them beyond repair. Hence, soft jaws made of copper, other soft metals or wood are often slip over the vise jaws to protect the workpiece’s finished surface.
Figure 1: Bench Vise (Workshop Manual) Bench vise should be mounted correctly on the workbench where the top of the vise jaws should be at elbow height. Inappropriately mounted bench vises causes poor workpiece to be produced.
MANUFACTURING AND MATERIALS DEPARTMENT MME1103 Workshop Technology Manual Benchwork
2 4.2 Filing Filing involves the small scale removal of material from a surface, corner, or hole, including the removal of burrs (Kalpakjian and Schmid, 2001). Files are usually made of hardened steel and are available in a variety of cross sections such as flat, round, half round, square and triangle (Figure 3).They are commonly manufactured in four different cuts: single, double, curved tooth and rasp. Each cut design has its own purpose. For instance, rasp files are frequently used with wood while curved tooth files are used with soft materials
such as aluminium, brass, plastic, or lead. Files also vary in their coarseness; rough, coarse, bastard, second cut, smooth and dead smooth (Kibbe et.al., 2002).
Figure 2: Basic components of a file (Workshop Manual) Figure 3: Various file cross sections (Workshop Manual)
MANUFACTURING AND MATERIALS DEPARTMENT MME1103 Workshop Technology Manual Benchwork
3 In order to produce a flat surface, work should be held firmly in the vise with the minimum amount of projecting and with the surface to be filed to be truly horizontal. The right hand pushes and presses while the left hand only presses with the same amount of pressure. Pressure should only be applied during forward stroke only. The Figure 4 below illustrates the proper technique of hand filing. Success in filing flat is dependant on hand control to keep the file horizontal throughout its stroke and an equal distribution of pressure. In order to test the surface of work during filing, a straightedge can be placed on it. If rays of light can be seen between the two surfaces of the workpiece and the straightedge, then the surface of the workpiece is not flat.
Figure 4: Hand movement during filing (Workshop Manual)
Care should be taken while filing to avoid dulling and breakage of its teeth. Teeth on files will break if the tools lie on top of each other and if too much pressure is applied while filing. Dulling of teeth is caused by the filing of hard materials or by filing too fast. A good rule of thumb is the harder the material, the slower the strokes should be; the softer the material, the coarser the file should be.
4.3 Sawing The hacksaw is one of the more frequently used hand tools. It consists of the frame, the handle and the saw blade (Figure 5). The spacing of the teeth on a hand hacksaw blade is called the pitch. Standard pitches are 14, 18, 24 and 32 teeth per inch, with the 18pitch blade used as a general-purpose blade. The hardness and thickness of a workpiece determine to a great extent which pitch blade to use (Kibbe et.al., 2002). Generally, a coarse tooth blade should be use on soft materials and a fine tooth blade on harder materials. There are a few points that should be noted in order to obtain maximum performance from a blade:•
Make long steady strokes using the full length of the blade
MANUFACTURING AND MATERIALS DEPARTMENT MME1103 Workshop Technology Manual Benchwork
5 4.6 Scriber The scriber is a round steel piece of about 150mm to 300mm long and 3mm to 5mm in diameter. Its one end is sharp and pointed and the other end is also sharp but bent. The bent end is used to scratch lines in places where the straight end cannot reach.
Figure: Scriber Figure 7: Scriber (Workshop Manual) 5. Project Methodology
1. Use “L” square and appropriate file to obtain flat surface (180°) 2. Select another side of the work piece and file as previous step to obtain a flat 90˚ surface MANUFACTURING AND MATERIALS DEPARTMENT MME1103 Workshop Technology Manual Benchwork
6 3. Use engineering square to check the surfaces, if rays of light cannot be viewed between the work piece and the engineering square, i.e. the surface is already flat. Make sure that the workpiece is filed to the correct dimension.
4. Select the flat surface as the reference surface for marking process 5. Mark the workpiece using high vernier caliper and plate angle on the marking table. 6. Create the rounded curve using divider based on given dimension. 7. In order to make the cross section point line more visible, use the center punch. This to ensure the measurement is consistently correct. 8. Begin the removing process by cutting the unused material using hacksaw only. 9. Smooth the edges of the workpiece through filing. 10. Perform the drilling work for counterbore according to the steps described below:a. Center drill b. Drill size Ø5.5 mm c. Counterbore M10x5.5 mm with a depth of 5 mm 11. Do the drilling work for through hole accordingly as below:a. Center drill
b. Drill bit size Ø6 mm c. Drill bit size Ø8 mm d. Drill bit size Ø10 mm
MANUFACTURING AND MATERIALS DEPARTMENT MME1103 Workshop Technology Manual Benchwork
7 Questions 1. List the tools used to produce the project. 2. Draw the end product of the project. 3. Name type of drilling tool used. 4. Write the function of Engineering “L” square.
