This part of ISO 10791 specifies certain standard test conditions for assessing the conventional length of the operating times spent by the machine to carry out different metal cutting functions. It considers two types of operating times, namely those taken by the functions of: — automatic tool change (see clause 5); — automatic pallet change (see clause 6). The purpose of the methods described in this part of ISO 10791 is to permit the comparison of the performance of different machining centres of similar size and features. The data obtained may also be used to establish conventional change times in technical literature in a uniform and comparable way. It is also possible to check them on a machine, both when it is new and during its working life.