The point angle of twist drill for general purpose is

Lip clearance angle

The relief angle given behind the cutting lips is called Lip Clearance angle

9.75 mm

Counter-boring

Counter-boring is the process of enlarging the end of an existing hole to accommodate the head of socket screw.

Counter-sinking

Countersinking is an operation of bevelling the end of a drilled hole. The tool used is called a countersink.