Countersinks

The classic countersinks and countersink drills are designed for countersunk screws (with a conical underside). However, there are a variety of screws whose underside is flat. Sometimes you also want to insert a washer under the screw head. If such a carriage bolt or cylinder head screw is to be countersunk, the countersink must be made as a blind hole with a flat bottom. For this purpose, a countersink is used. These tools are similar to Forstner drills. They either have a central centring bit with which the through hole for the screw is drilled, or they are fitted with a tang which is inserted into a pre-drilled hole in order to place the countersink correctly.