Counter-boring is the process of enlarging the end of an existing hole to accommodate the head of socket screw.
Counter-boring is the process of enlarging the end of an existing hole to accommodate the head of socket screw.
Countersinking is an operation of bevelling the end of a drilled hole. The tool used is called a countersink.
For conduit and other thin tubing, sheet metal work etc. use a 0.8 mm pitch.
For soft materials such as bronze, brass, soft steel, cast iron, heavy angles etc. use a 1.8 mm pitch blade.