Inconsistency in common cutting knowledge

摘要

Cutting has been used in manufacturing machine parts from old times. Fundamental phenomena are well known. That is said the common cutting knowledge. In case of the complex cutting phenomenon, its application is not simple. It is not always right that it is applied for the complex cutting phenomenon looking at one factor that seems important. According to the condition some factors must be noticed. Comparing with the turning, the drilling is complex. In studying the drilling mechanism of a new type twist drill, seemingly inconsistent results with the common cutting knowledge have been found. The results obtained are as follows: (1) The cutting ratio is very large such as 1.0 at the inner part of the conical helix type chip in free chip removal state in drilling the middle carbon steel with the conventional drill. (2) Depressed chip is hard to curl, and chip removal is prevented, however the cutting ratio increases under some cutting conditions.