This part of ISO 13041 specifies, with reference to ISO 230-1, the geometric tests on numerically controlled (NC) turning machines and turning centres, of normal accuracy, with horizontal work spindle(s) as defined in 3.1 and 3.2. This part of ISO 13041 specifies the applicable tolerances corresponding to the tests mentioned above. This part of ISO 13041 explains different concepts or configurations and common features of NC turning machines and turning centres. It also provides a terminology and designation of controlled axes (see Figure 1 and Table 1). This part of ISO 13041 deals only with the verification of the accuracy of the machine. It does not apply to the operational testing of the machine (e.g. vibration, abnormal noise, stick-slip motion of components), nor to machine characteristics (e.g. speeds, feeds) as such checks are generally carried out before testing the accuracy.