Countersinks and their applications

A countersink or countersink cutter is used to chamfer a drill hole or to make a countersink. When countersinking, the screw or bolt sits deeper in the material so it does not protrude above the surface of the material.

Before countersinks can be used, a hole must be drilled or cut. The countersink itself cannot be used for drilling holes in the material.

Countersinks are therefore used for: 

• Chamfering a hole to countersink a screw head into the material 
• Applying a chamfer to a hole before threading 
• Deburring a sharp edge of a hole