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21. Taps for Pipe Threads 1. JIS Pipe Taps Description of products The pipe thread standard (JIS B 0202,0203) was revised in 1982 to meet ISO standard. In the same year, JIS B 4445 (straight pipe thread taps) and JIS B 4446 (taper pipe thread taps) were also revised. A part of the pipe thread standard was revised in 1966 to meet ISO, but in the 1982 revision, the ISO standard was defined in the main book of JIS and the old 1966 standard was defined in JIS Appendix. For Pipe Threads specified in the main book of JIS and JIS Appendix, thread symbols are different but the nominal size 1/8 to 6 inch are same. In the 1998 revision, the contents of the main book of JIS and JIS Appendix are not changed. ISO tap standard for pipe threads is different from the JIS tap standard in style, size and thread limit. Like the pipe thread standard, in JIS tap standards for pipe threads, style, size and thread limits of ISO standard are adopted in the main book of JIS and those of old JIS standard are in the JIS Appendix. For ISO standard (style and size), please refer to the next page. Thread limits of Rp and G taps are the same as the ISO standard. The thread limit of Rc taps is the same as the JIS class 2 of PT taps shown in JIS Appendix because Rc is not specified in the ISO standard. Therefore, both Rc taps and PT taps can be used interchangeably. For the relation between thread limit of internal threads and tap thread limit, please refer to the table below. Pipe Tap standard was revised in 1987. And tap designations shown in JIS Appendix were changed to PF taps for Parallel Pipe Thread, PT taps for Taper Pipe Thread, and PS taps for Parallel Pipe Thread. ■Symbol of Pipe threads Type Classification Standard JIS (ISO) JIS Appendix Type Internal Thread Taper Thread External Thread Taper Thread Parallel Thread Internal Thread External Thread Internal Thread PF, A class PF, B class Parallel Thread Parallel Thread External Thread G, A class PF, A class G, B class PF, B class ■Relation between classification/engagement of pipe threads and taps ■ Kind of Classification Main usage type Engagement Pipe taps thread Parallel PS Parallel internal thread PS D （Rp） ' D1D2 Basic diameter position Internal Taper internal thread In connection of pips, pipe threads D PT D2 Taper parts and fluid parts they Taper D1 pipe are used mainly for the PT threads purpose of pressure type （Rc） Taper internal thread joints. D D2 D1 t Pipe thread a f S-PT External Taper threads PT Taper external thread （R） d2 d1 d Internal PF Parallel internal thread Information Technical In connection of pipes, pipe threads （G） PF Parallel parts and fluid parts, they D2 D D1 pipe are used mainly for the threads purpose of mechanical type External PF d joints. d2 d1 Parallel external thread threads （G） Technical-56 827