抄録
Nicks engraved on the cutting edges of twist drill divide chips into narrower ones and, as the result, bring about the reduced drilling forces and prolonged drill life. This report points out further contribution of nicks in improving the hole accuracy: Properly designed nicks suppress the tottering of drill at the intial stage of drilling, and improve the roundness and cylindricity of the hole produced. For the design of appropriate nicks, the effects of the geometry and position of nicks on drill performance are shown experimentally.
