This part of ISO 230 specifies methods of testing and evaluating the bi-directional circular deviation, the mean bi-directional radial deviation, the circular deviation and the radial deviation of circular paths that are produced by the simultaneous movements of two linear axes. Relevant measuring instruments are described in ISO 230-1:1996, 6.63. The objective of this part of ISO 230 is to provide a method for the measurement of the contouring performance of a numerically controlled machine tool.