Welding and Fabrication Eng. Craft Practice 2, WASSCE (SC), 2017

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.