Countersink(redirected from countersink bit)
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(Russian, zenkovka; from German senken, “to sink, lower”), a cutting tool used for countersinking. Countersinks usually form part of a set with centering drills. The sizes of countersinks in each set depend on the diameter of the hole; in all sets, the vertex angle is 60°. Coun tersinks are made for chamfering center holes with diameters of 0.5 to 1.5 mm (ordinary countersinks), for holes with diameters of 0.5 to 6 mm (with or without protective taper), and for holes with diameters of 8 to 12 mm (with tapered stem). Countersink cutting elements are made from high-speed steel; countersinks with tapered stems are welded and the stems are made from carbon structural steel.