out-of-spec
1.Referring to the hardness values specified in our recently issued tecnnical specification of twist drill and tap, the conversion values of Rockwell hardness HRC-Vickers hardness HV specified in relevant ISO standards. German DIN standards and our research work were studied and their mutual differences were discussed. The result pointed out that it was improper to unrealistically adopt identically vickers hardness values of HSS cutting tools spec-ified in ISO standards into our technical specification.

