Observation

Most of the candidates could not provide the correct responses to these questions. The required responses are given below.

• Identifying the parts labelled P,Q and R

P – Sprue hole
Q – Cavity/Facing sand.
R -  Vent holes                           

• Stating the function of the parts labelled Pand R

Sprue hole (P) is the passage for the molten metal into the cavity.
Vent holes (R) serve as passages for gases to escape.
(b)        Stating one effect each of the following:
(i)  using a pinned file
-  It will prevent effective cutting.
(ii) too great a cutting speed

• It will cause overheating.

(iii) too long a rivet tail

• The rivet tail will bend and prevent proper head formation

(iv) drill bit ground off-centre
It produces an oversized hole.