Threading Technology – Clamping Technology 520

157 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 STI-UNC Unified coarse thread ASME B18.29.1 For wire thread inserts Nominal Size Major thread dia. of the internal thread (Tol. 2B) Minor thread dia. of the internal thread (Tol. 2B) Rec. tap drill size P [T.P.I.] D STI min. D 1STI min. D 1STI max. STI-No. 2 56 0.1092 0.0899 0.0961 0.0906 STI-No. 3 48 0.1261 0.1036 0.1104 0.1063 STI-No. 4 40 0.1445 0.1175 0.1252 0.1220 STI-No. 5 40 0.1575 0.1305 0.1373 0.1339 STI-No. 6 32 0.1786 0.1448 0.1527 0.1496 STI-No. 8 32 0.2046 0.1708 0.1781 0.1732 STI-No. 10 24 0.2441 0.1990 0.2080 0.2047 STI-No. 12 24 0.2701 0.2250 0.2340 0.2283 STI- 1 / 4 20 0.3150 0.2608 0.2704 0.2638 STI- 5 / 16 18 0.3847 0.3245 0.3342 0.3307 STI- 3 / 8 16 0.4562 0.3885 0.3987 0.3937 STI- 7 / 16 14 0.5303 0.4530 0.4639 0.4567 STI- 1 / 2 13 0.5999 0.5166 0.5273 0.5236 STI- 9 / 16 12 0.6708 0.5806 0.5918 0.5866 STI- 5 / 8 11 0.7431 0.6447 0.6564 0.6496 STI- 3 / 4 10 0.8799 0.7716 0.7838 0.7776 STI- 7 / 8 9 1.0193 0.8990 0.9119 0.9055 STI- 1 8 1.1624 1.0271 1.0421 1.0335 STI- 1 1 / 8 7 1.3106 1.1559 1.1730 1.1614 STI- 1 1 / 4 7 1.4356 1.2809 1.2980 1.2894 STI- 1 3 / 8 6 1.5915 1.4110 1.4310 1.4173 STI- 1 1 / 2 6 1.7165 1.5360 1.5560 1.5453 STI-UNF Unified fine thread ASME B18.29.1 For wire thread inserts Nominal Size Major thread dia. of the internal thread (Tol. 2B) Minor thread dia. of the internal thread (Tol. 2B) Rec. tap drill size P [T.P.I.] D STI min. D 1STI min. D 1STI max. STI-No. 2 64 0.1063 0.0894 0.0947 0.0906 STI-No. 3 56 0.1222 0.1029 0.1086 0.1063 STI-No. 4 48 0.1391 0.1166 0.1229 0.1181 STI-No. 6 40 0.1705 0.1435 0.1503 0.1457 STI-No. 8 36 0.2001 0.1701 0.1771 0.1732 STI-No. 10 32 0.2306 0.1968 0.2041 0.2008 STI- 1 / 4 28 0.2964 0.2577 0.2646 0.2598 STI- 5 / 16 24 0.3666 0.3215 0.3288 0.3248 STI- 3 / 8 24 0.4291 0.3840 0.3910 0.3858 STI- 7 / 16 20 0.5025 0.4483 0.4561 0.4528 STI- 1 / 2 20 0.5650 0.5108 0.5186 0.5157 STI- 9 / 16 18 0.6347 0.5745 0.5826 0.5787 STI- 5 / 8 18 0.6972 0.6370 0.6451 0.6398 STI- 3 / 4 16 0.8312 0.7635 0.7720 0.7677 STI- 7 / 8 14 0.9678 0.8905 0.8994 0.8957 STI- 1 12 1.1083 1.0181 1.0281 1.0236 STI- 1 1 / 8 12 1.2333 1.1431 1.1531 1.1516 STI- 1 1 / 4 12 1.3583 1.2681 1.2781 1.2795 STI- 1 3 / 8 12 1.4833 1.3931 1.4031 1.3976 STI- 1 1 / 2 12 1.6083 1.5181 1.5281 1.5256 Screw Thread Insert Threads (STI) 60° D 1STI D STI P STI-M ISO Metric coarse thread DIN 8140-2 For wire thread inserts Nominal Size Major thread dia. of the internal thread (Tol. 6H mod.) Minor thread dia. of the internal thread (Tol. 6H mod.) Rec. tap drill size P [mm] D STI min. [mm] D 1STI min. [mm] D 1STI max. [mm] [mm] [inch] STI-M 2 0.4 2.520 2.087 2.177 2.1 0.0827 STI-M 2.5 0.45 3.084 2.597 2.697 2.65 0.1043 STI-M 3 0.5 3.650 3.108 3.220 3.15 0.1240 STI-M 4 0.7 4.910 4.152 4.292 4.2 0.1654 STI-M 5 0.8 6.040 5.174 5.334 5.25 0.2067 STI-M 6 1 7.300 6.217 6.407 6.3 0.2480 STI-M 8 1.25 9.624 8.271 8.483 8.4 0.3307 STI-M 10 1.5 11.948 10.324 10.560 10.5 0.4134 STI-M 12 1.75 14.274 12.379 12.644 12.5 0.4921 STI-M 14 2 16.598 14.433 14.733 14.5 0.5709 STI-M 16 2 18.598 16.433 16.733 16.5 0.6496 STI-M 18 2.5 21.248 18.541 18.896 18.75 0.7382 STI-M 20 2.5 23.248 20.541 20.896 20.75 0.8169 STI-M 22 2.5 25.248 22.541 22.896 22.75 0.8957 STI-M 24 3 27.897 24.649 25.049 24.75 0.9744 STI-M 27 3 30.897 27.649 28.049 27.75 1.0925 STI-M 30 3.5 34.546 30.757 31.207 31 1.2205