This part of ISO 10791 specifies, with reference to ISO 230-1, the geometric tests for machining centres (or numerically controlled milling machines, boring machines, etc., where applicable) with integral indexable or continuous universal heads (vertical Z-axis). This part of ISO 10791 applies to machining centres having basically six numerically controlled axes, of which three are linear (X, Y and Z) up to 2 000 mm in length, and three are rotary (A or D and B on the head, and C' on the table). Movements other than those mentioned are considered as special features and the relevant tests are not included in this part of ISO 10791. This part of ISO 10791 describes geometric tests for three possible types of accessory universal heads, in the annexes: — annex A: Integral universal 45°split indexable heads (B and D axes), with mechanical indexing of the different angular positions of the two bodies (e.g. Hirth couplings): the relevant tests (AG1 to AG9) check only the resulting position of the spindle; — annex B: Integral universal swivel heads (B and A axes), with two numerically controlled rotary axes perpendicular to each other (tests BG1 to BG7); — annex C: Integral universal 45°split continuous heads (B and D axes), similar to the first type but provided with continuous positioning of the two numerically controlled rotary axes: the relevant tests (CG1 to CG7) check all the geometric features (planes and axes) which contribute to the resulting position of the spindle, excluding the positioning accuracy of the two rotary axes; these tests can also be used for a deeper investigation on the 45°indexable heads, if their movements and locks allow this. This part of ISO 10791 deals only with the verification of accuracy of the machine and does not apply to the testing of the machine operation, which should generally be checked separately. Certain tests concerning the performance of the machine operating under no-load or finishing conditions are included in other parts of ISO 10791.