Study of the Distribution of the Life of HSS Tools

Numerous life tests carried out with high speed steel tools in machining low carbon steel indicate that tool life values are subject to a statistical distribution which can be approximated by the normal distribution with a coefficient of variation of about 0.3. Accelerated and normal tests show similar distribution patterns, which indicates a possibility for a wider use of accelerated tests. The conventionally accepted concepts of tool life “constant” and “exponent” should be considered only as representing statistical mean values which are not sufficient for the prediction of the life of any individual tool put to work. It is recommended that tool life predictions be made on a probabilistic basis, and the desired direction of further studies is indicated.