This International Standard gives details for the manufacture and use of gauges for checking IS0 general-purpose metric screw threads with a basic profile in accordance with IS0 68. It specifies the features of the types of gauges (listed in 4.1 and 4.2) which are recommended for checking external and internal screw threads of workpieces and for the setting and checking of certain of the screw gauges. It is recognized that other methods of checking may be used, for example measurements with indicating instruments. Checking with gauges in accordance with this International Standard is always decisive. The aim of this International Standard is to provide means of distinguishing between workpiece threads that comply with the limits of size and those that do not. In order to ensure the interchangeability of workpiece threads and to avoid disputes between the manufacturer and purchaser, the following principles should be applied: a) the manufacturer should not deliver any workpiece thread whose actual thread size (e.g. pitch diameter and virtual pitch diameter) lies outside the specified limits; b) the purchaser should not reject any workpiece thread whose actual thread size (e.g. pitch diameter