Countersinking

Countersinking has 2 functions in metalworking. the first is to produce a recessed hole which will accept a countersunk bolt. This will meant that the bolt is flush or just below the surface of the material and won't stick out at all.

The second function is, like chamfering, to break the sharp edges around a hole and make it easier to locate a pin or similar object into the hole.

Countersink bits come in a range of shapes and sizes for different applications. For metalworking tasks they will be made from High Speed Steel and may be coated in Titanium so they last longer before sharpening.