This document specifies a process using limit gauges, for the validation of taper internal and external threads and parallel internal threads on piping systems components and other products, the dimensions and tolerances of which are detailed in EN 10226-1 and prEN 10226-2. The gauging system described may not be suitable, without special precautions, for gauging of threads on injection moulded plastic workpieces. This document does not cover completely all the requirements necessary for full control of thread quality and dimensions. Additional control of tools and equipment and visual inspection during production are required to ensure complete compliance with EN 10226-1 and prEN 10226-2, for example the length of useful thread on internally threaded workpieces should be checked by direct measurement. Annex A gives a summary of the gauges included in this document, together with details of the thread elements controlled by each gauge and gauge identification numbers. In the event of a dispute over compliance with the requirements of EN 10226-1 and prEN 10226-2, the gauges in this document are to be considered as decisive for the thread elements which they control on the workpiece.