This part of ISO 3442 specifies 90° and 60° serrations and jaw nuts applicable to 90° and 60° serrations for mounting the top jaws on the base jaws of power chucks, in order to ensure interchangeability. It also describes, with reference to ISO 230-1, the geometric tests for self-centring, power-operated chucks with two or more two-piece jaws (serrated type), and the corresponding tolerances which apply.