Threading Technology – Clamping Technology 520

155 Machine Taps UNC UNF UNEF UN-8 M MF NPSF Rp (BSPP) G NPT NPTF Rc (BSPT) STI SELF-LOCK Accessories NPSM/NPSC Tech. Info v c Product Finder 1.16 Recommended tap drill sizes for tapping internal threads NPSM American Standard straight pipe thread ANSI/ASME B1.20.1 For mechanical joints (previously NPS) Nominal Size Minor thread dia. of the internal thread Rec. tap drill size D P [T.P.I.] D 1 min. D 1 max. [mm] [inch] 1 / 8 27 0.358 0.364 9.1 0.3583 1 / 4 18 0.468 0.481 12 0.4724 3 / 8 18 0.603 0.612 15.5 0.6102 1 / 2 14 0.747 0.759 19 0.7480 3 / 4 14 0.958 0.970 24.5 0.9646 1 11 1 / 2 1.201 1.211 30.5 1.2008 Rp (BSPP) Cylindrical Whitworth pipe thread DIN EN 10226-1 and ISO 7-1 Where pressure-tight joints are made on the threads Nominal Size Minor thread dia. of the internal thread Rec. tap drill size D P [T.P.I.] D 1 min. [mm] D 1 max. [mm] [mm] [inch] Rp 1 / 16 28 6.490 6.632 6.55 0.2579 Rp 1 / 8 28 8.495 8.637 8.6 0.3386 Rp 1 / 4 19 11.341 11.549 11.5 0.4528 Rp 3 / 8 19 14.846 15.054 15 0.5906 Rp 1 / 2 14 18.489 18.773 18.5 0.7283 Rp 3 / 4 14 23.975 24.259 24 0.9449 Rp 1 11 30.111 30.471 30.25 1.1909 G Whitworth pipe thread DIN EN ISO 228 Nominal Size Minor thread dia. of the internal thread Rec. tap drill size D P [T.P.I.] D 1 min. [mm] D 1 max. [mm] [mm] [inch] G 1 / 16 28 6.561 6.843 6.8 0.2677 G 1 / 8 28 8.566 8.848 8.8 0.3465 G 1 / 4 19 11.445 11.890 11.8 0.4646 G 3 / 8 19 14.950 15.395 15.25 0.6004 G 1 / 2 14 18.631 19.172 19 0.7480 G 5 / 8 14 20.587 21.128 21 0.8268 G 3 / 4 14 24.117 24.658 24.5 0.9646 G 7 / 8 14 27.877 28.418 28.25 1.1122 G 1 11 30.291 30.931 30.75 1.2106 G 1 1 / 8 11 34.939 35.579 35.5 1.3976 G 1 1 / 4 11 38.952 39.592 39.5 1.5551 G 1 3 / 8 11 41.365 42.005 41.75 1.6437 G 1 1 / 2 11 44.845 45.485 45.25 1.7815 G 1 5 / 8 11 49.030 49.670 49.5 1.9488 G 1 3 / 4 11 50.788 51.428 51 2.0079 G 2 11 56.656 57.296 57 2.2441 G 2 1 / 4 11 62.752 63.392 63.3 2.4921 G 2 1 / 2 11 72.226 72.866 72.8 2.8661 G 2 3 / 4 11 78.576 79.216 79.1 3.1142 G 3 11 84.926 85.566 85.5 3.3661 NPSC American Standard internal straight thread ANSI/ASME B1.20.1, Table A1 In pipe coupling Nominal Size Minor thread dia. of the internal thread Rec. tap drill size D P [T.P.I.] D 1 min. [mm] [inch] 1 / 8 27 0.340 8.75 0.344 1 / 4 18 0.442 11.1 0.438 3 / 8 18 0.577 14.7 0.578 1 / 2 14 0.715 18.25 0.719 3 / 4 14 0.925 23.4 0.922 1 11 1 / 2 1.161 29.35 1.156 NPSF American Standard straight pipe thread ANSI B1.20.3, Table B1 Dryseal internal straight pipe thread for fuel, combined with external tapered pipe thread NPTF or PTF-SAE-SHORT; Gage with tapered gages Nominal Size Minor thread dia. of the internal thread Rec. tap drill size D P [T.P.I.] D 1 min. [mm] [inch] 1 / 16 27 0.2482 6.25 0.246 1 / 8 27 0.3406 8.6 0.339 1 / 4 18 0.4422 11.15 0.438 3 / 8 18 0.5776 14.7 0.578 1 / 2 14 0.7133 17.85 0.703 3 / 4 14 0.9238 23.4 0.922 1 11 1 / 2 1.1600 29.35 1.156 Straight Pipe Threads 60° D D 1 P 55° D D 1 P