61) If the major diameter of an ISO metric thread is 6 mm and the pitch is 1 mm the recommended tap drill diameter is

62) If the recommended cutting speed of mild steel is 20 m/min, what is the rotational speed (rpm) required for a Dia=20 mm drill bit?

63) Tool will rub against the work surfaces and the cutting force increases when

64) The rake angle required for machining cast iron is

65) Helix angle in twist drill determines the