39) Angle between the top face of cutting point and normal (90 degree) to the work surface at the cutting edge

40) Tool chatter is caused by

41) High carbon steels are machined using tools having

42) If the recommended cutting speed of mild steel is 20 m/min, what is the rotational speed (rpm) required for a 020 mm drill bit.

43) The angle of the prick punch used for witness marks is