Question 2
(a) State two safety precautions each to be observed when using the following machines:
(i) drilling machine;
(ii) grinding machine;
(b) State one use each of the following tools:
(i) scriber;
(ii) trammel.
(c) Explain the process of bending a sheet of metal.
Observation
Questions 2 (a) and (b) did not pose any difficulty to the candidates but it was reported that candidates were not able to explain the process of bending a sheet of metal. The required responses are as given below.
2(a) (i) Drilling Machine
- Stop the machine before removing chips/swarf.
- Hold the work properly in a vice.
- Bolt the vice when necessary to prevent it from spinning round.
- Use all protective guards on the machine.
- Never be tempted to hold small workpiece with hand.
- Do not wear loose dress.
- Remove chuck key before starting the machine.
- Do not remove chips/swarf with bare hand, use brush.
- Avoid distraction when drilling.
- Hold drill bit firmly in the chuck.
- Do not apply too much pressure while feeding.
- Do not use volatile or corrosive coolant.
- Wear goggles to prevent chips and other flying particles from entering the eye.
(ii) Grinding Machine
- Use eye guard and goggles to protect the eyes while grinding.
- Small workpiece should be properly held in a hand vice.
- Check grinding wheels for possible cracks and concentricity before use.
- Remove chips by suction when dry grinding.
- Maintain correct gap between tool rest and wheel.
(b)
(i)Scriber: used for marking/scratching/drawing lines on metal surface.
(ii)Trammel: used for scribing/drawing/bisecting/marking large arcs or circles.
OR
It is used to transfer measurement from rule to work.
(c) The process of bending a sheet of metal involves;
- marking out the point to bend;
- holding the work in vice/folding bar/folding machine;
- bending to the right shape using appropriate tool/machine.