When selecting a cutting tool for a machining process it is first necessary to determine which particular work-group the workpiece to be machined belongs to.


In 1958, ISO* set up a standard relating to the selection of cemented carbide for machining. After ISO set up this standard, the Japanese Industrial Standards (JIS) also set up a standard (JIS-B5043) based on the ISO standards.


In the initial standard, workpiece materials were classified into three P, M and K groups according to type of chip generated when machined. Each of these groups P, M and K groups were again subdivided into groups with two-digit number based on the method of machining and cutting conditions.


However, due to recent material development and diversification in workpiece materials, it has become hard to class all of the materials. Therefore in order to be able to class the increasing workpiece materials ISO put forward a new standard based on 6 main groups of workpiece material. The new groups consist of P, M, K, N, S, H groups based on material machinability. This new standard was bought into effect as of 2003.

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