Coordinate measuring machines shall be inspected regularly according to ISO quality standards 9000-9004. The procedure for acceptance and confirmation testing is described in detail in ISO 10360. The test specimens with their high-precision calibrated values, corresponding to the standard-compliant procedures for coordinate measuring machines according to VDI/VDE 2617 Sheet 5 and DIN EN ISO 10360, serve as a reference. In addition, VDA 5 and VDI/VDE 2617 Sheet 8 are decisive for determining the suitability of the test process. The test specimens are also suitable for testing contour measuring machines according to VDI/VDE Guideline 2629 for certain geometric elements the measurement uncertainty can be determined according to ISO 15530. Such a basic adjustment of the measuring instrument according to the standard is scheduled once a year. In addition, it is advisable if there are doubts about the accuracy, for example after temperature fluctuations or mechanical damage.