ISO 3294:1975

Parallel shank countersinks for angles 60, 90 and 120 degrees inclusive

Specifies only metric dimensions of these countersinks. Metric dimensions being regarded as the only recommended dimensions in the future, for these countersinks with cutting diameters in the range 8 to 25 mm. The dimensions given apply only to tools made from high speed steel or a suitable carbon steel. These countersinks will be usually right-hand cutting.