Threading Technology – Clamping Technology 520

156 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 NPT American tapered pipe thread, ANSI/ASME B1.20.1 For threads with dryseal material , taper 1:16 Nominal Size P [T.P.I.] D 1 D 2 D 3 (+0.002) t 1 1 / 16 27 0.2421 0.2343 0.2516 0.4646 1 / 8 27 0.3346 0.3268 0.3441 0.4685 1 / 4 18 0.4331 0.4232 0.4472 0.6850 3 / 8 18 0.5669 0.5571 0.5827 0.6969 1 / 2 14 0.7008 0.6870 0.7213 0.9094 3 / 4 14 0.9114 0.8976 0.9319 0.9291 1 11 1 / 2 1.1437 1.1280 1.1689 1.1181 1 1 / 4 11 1 / 2 1.4882 1.4705 1.5138 1.1378 1 1 / 2 11 1 / 2 1.7264 1.7106 1.7528 1.1378 2 11 1 / 2 2.1988 2.1831 2.2268 1.1535 Rc (BSPT) Tapered Whitworth pipe thread DIN EN 10226-2 and ISO 7-1 Where pressure-tight joints are made on the threads, taper 1:16 Nominal Size P [T.P.I.] D 1 [mm] D 2 [mm] D 3 (JS11) [mm] t 1 [mm] Rc 1 / 16 28 6.15 6.1 6.56 11.1 Rc 1 / 8 28 8.15 8.1 8.57 11.1 Rc 1 / 4 19 10.85 10.75 11.45 16.3 Rc 3 / 8 19 14.3 14.25 14.95 16.7 Rc 1 / 2 14 17.8 17.7 18.63 22.3 Rc 3 / 4 14 23.2 23.1 24.12 23.6 Rc 1 11 29.2 29.1 30.29 28.3 NPTF American tapered pipe thread, ANSI B1.20.3 For threads without dryseal material , taper 1:16 Nominal Size P [T.P.I.] D 1 D 2 D 3 (+0.002) t 1 1 / 16 27 0.2402 0.2343 0.2524 0.4646 1 / 8 27 0.3327 0.3268 0.3449 0.4685 1 / 4 18 0.4291 0.4232 0.4488 0.6850 3 / 8 18 0.5630 0.5571 0.5843 0.6969 1 / 2 14 0.6929 0.6870 0.7217 0.9094 3 / 4 14 0.9055 0.8976 0.9323 0.9291 1 11 1 / 2 1.1319 1.1280 1.1701 1.1181 1 1 / 4 11 1 / 2 1.4764 1.4705 1.5150 1.1378 1 1 / 2 11 1 / 2 1.7224 1.7106 1.7539 1.1378 2 11 1 / 2 2.1949 2.1831 2.2280 1.1535 Taper Pipe Threads Taper 1:16 60° P 55° P Taper 1:16 D 1 t 1 Drill cylindrically without using a reamer D 3 t 1 D 2 Taper 1:16 Drill cylindrically and prepare tapered hole with reamer The minimum drilling depth t 1 includes the reach of screw by hand L 1 and the effective depth L 3 to ANSI/ASME B1.20.1 as well as the chamfer of the tap. Additional drilling-down has to be determined by the user according to the construction of the workpiece. For series production it is recommended that the minor thread dia. be made as per B. Special taps are required for blind holes where the minimum depths t 1 as listed in the above table cannot be met. In this case please supply a sketch with blind hole dimensions along with the order.