Technical Description of productsInformation hahd 21. Taps for Pipe Threads ■Comparison of the thread limit of taper pipe tap Basic diameter position Basic diameter position Basic diameter position ha : upper deviation P = 25.4/n n = Number of threads hd : upper deviation Taper hd : lower deviation Axis of tap Unit : mm Appendix (PT) Thread Limit ISO (Rc) Size Basic major Dia. of Gauge Plane Number of Threads※ Thread Length Basic Diameter Position PT Thread Basic Diameter Thread Length Position S-PT Thread Basic Diameter Thread Length Position Basic Size Tolerance(μm)Basic Size Tolerance(μm) 1/ 16 〜 1/ 8 〜 1/ 4 〜 3/ 8 〜 1/ 2 〜 3/ 4 〜 〜 1/ 4 〜 1/ 2 〜 〜 1/ 2 〜 〜 〜 Note : JIS standard has 2 types of Taper pipe thread, PT and S-PT taps. ISO standard has one type of Taper pipe thread Rc. ※ : No. of threads: Every 25.4 mm. Technical-65