This part of ISO 10791 specifies a method of checking the contouring performance of machining centres (or numerically controlled milling machines, etc., where applicable) by conducting circular tests in the three coordinate planes (XY, YZ and XZ) and by evaluating the radial deviation, F, and circular deviation, G, in accordance with ISO 230-4.

The purpose of the checks by circular tests described in this part of ISO 10791 is to verify the circular movement

• only in one position per coordinate plane of the machine,
• at only one feed rate, and
• to repeat the test once in the opposite contouring direction.

The purpose of this part of ISO 10791 is not to provide a means of analysing the causes for the measured circular deviations, but to offer the user a method for periodic checking of the machine tool. It is recommended to carry out the tests of this part of ISO 10791 once the machine tool has satisfactorily undergone the acceptance tests and to use these results as a basis for comparison when carrying out periodic checks. Therefore, acceptable deviations from the initial results shall be decided by the user.

If the tests are used for machine acceptance purposes, the supplier/manufacturer and the user shall agree on specific diameters, feed rates and tolerances for the tests.