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DIN EN ISO 228-1:2003
Pipe threads where pressure-tight joints are not made on the threads - Part 1: Dimensions, tolerances and designation (ISO 228-1:2000); German version EN ISO 228-1:2003
This standard specifies the requirements for thread form, dimensions, tolerances and designation for fastening pipe threads, thread sizes 1/16 to 6 inclusive. Both internal and external threads are parallel threads and intended for the mechanical assembly of the component parts of fittings, cocks and valves, accessories, etc.
Deutsches Institut für Normung [din]