A countersink is a cutting tool which puts a conical hole into an object. A common use is to allow the head of a countersunk bolt or screw, when placed in the hole, to sit flush with or below the surface. Countersinks may also be used to remove burrs left from drilling or tapping operations.

What is the purpose of countersinks?

Countersinks are mainly used for countersinking drill holes, countersinking screws and deburring. Countersinking widens the drill hole and facilitates subsequent tapping. When countersinking screws, space is created for the screw head so that it closes with the surface of the workpiece.

What are the two main reasons to use a countersink?