21. Taps for Pipe Threads ■Comparison of the thread limit of taper pipe tap Description of products Basic diameter position Basic diameter position Basic diameter position ha : upper deviation ha P = 25.4/n hd n = Number of threads hd : upper deviation Taper hd : lower deviation Axis of tap Unit : mm Appendix (PT) Thread Limit ISO (Rc) Basic major PT Thread S-PT Thread Size Number of Dia. of Threads※ Basic Diameter Basic Diameter Basic Diameter Gauge Plane Thread Length Position Thread Length Position Thread Length Position Basic Size Tolerance Basic Size Tolerance (μm) (μm) / 16 1 〜 /8 1 〜 /4 1 〜 /8 3 〜 /2 1 〜 /4 3 〜 〜 /4 1 〜 /2 1 〜 〜 /2 1 〜 〜 〜 Information Technical 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