ASME B1.20.2M-2006 pdf download.Pipe Threads,60 deg, General Purpose. 7 GAUGING OF TAPER PIPE THREAD, NPT 7.1 Gauging External Taper Threads In gauging external taper threads the L1 ring gauge, Fig. 6, is screwed hand-tight on the pipe or external thread. The thread is within the permissible tolerance when the gauging face of the working ring gauge is not more than...