Countersink

Countersink - (him. Senker), metal-cutting tool designed for finishing the walls of the holes - reaming. Unlike the drill, the starter usually has from 3 to 6 cutting edges located obliquely or perpendicularly about the axis (at the end face of the starter). Z. are made solid from high-speed steel, welded (with shanks from carbon structural steel), national teams (with plug-in knives from hard alloy), mounted (with soldered plates from hard alloy), etc.