Threading Technology – Clamping Technology 520

153 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 UNC Unified coarse thread ASME B1.1, Table 2 Nominal Size Minor thread dia. of the internal thread (Tol. 2B) Rec. tap drill size D P [T.P.I.] D 1 min. D 1 max. No. 1 (0.073) 64 0.0561 0.0622 0.0595 No. 2 (0.086) 56 0.0667 0.0737 0.0700 No. 3 (0.099) 48 0.0764 0.0845 0.0820 No. 4 (0.112) 40 0.0849 0.0939 0.0890 No. 5 (0.125) 40 0.0979 0.1062 0.1015 No. 6 (0.138) 32 0.1040 0.1140 0.1110 No. 8 (0.164) 32 0.1300 0.1390 0.1360 No. 10 (0.190) 24 0.1450 0.1550 0.1520 No. 12 (0.216) 24 0.1710 0.1810 0.1770 1 / 4 20 0.1960 0.2070 0.2040 5 / 16 18 0.2520 0.2650 0.2610 3 / 8 16 0.3070 0.3210 0.3160 7 / 16 14 0.3600 0.3760 0.3680 1 / 2 13 0.4170 0.4340 0.4219 9 / 16 12 0.4720 0.4900 0.4844 5 / 8 11 0.5270 0.5460 0.5313 3 / 4 10 0.6420 0.6630 0.6563 7 / 8 9 0.7550 0.7780 0.7656 1 8 0.8650 0.8900 0.8750 1 1 / 8 7 0.9700 0.9980 0.9843 1 1 / 4 7 1.0950 1.1230 1.1094 1 3 / 8 6 1.1950 1.2250 1.2205 1 1 / 2 6 1.3200 1.3500 1.3386 1 3 / 4 5 1.5330 1.5670 1.5551 2 4 1 / 2 1.7590 1.7950 1.7812 2 1 / 4 4 1 / 2 2.0090 2.0450 2.0312 2 1 / 2 4 2.2290 2.2670 2.2500 2 3 / 4 4 2.4790 2.5170 2.5000 3 4 2.7290 2.7670 2.7500 UNEF Unified extra fine thread ASME B1.1, Table 2 Nominal Size Minor thread dia. of the internal thread (Tol. 2B) Rec. tap drill size D P [T.P.I.] D 1 min. D 1 max. No. 12 (0.216) 32 0.1820 0.1900 0.1875 1 / 4 32 0.2160 0.2240 0.2205 5 / 16 32 0.2790 0.2860 0.2835 3 / 8 32 0.3410 0.3490 0.3465 7 / 16 28 0.3990 0.4070 0.4040 1 / 2 28 0.4610 0.4700 0.4646 9 / 16 24 0.5170 0.5270 0.5236 5 / 8 24 0.5800 0.5900 0.5807 3 / 4 20 0.6960 0.7070 0.6988 7 / 8 20 0.8210 0.8320 0.8268 1 20 0.9460 0.9570 0.9531 1 1 / 8 18 1.0650 1.0780 1.0728 1 1 / 4 18 1.1900 1.2030 1.2008 1 3 / 8 18 1.3150 1.3280 1.3189 1 1 / 2 18 1.4400 1.4530 1.4488 UNF Unified fine thread ASME B1.1, Table 2 Nominal Size Minor thread dia. of the internal thread (Tol. 2B) Rec. tap drill size D P [T.P.I.] D 1 min. D 1 max. No. 0 (0.060) 80 0.0465 0.0514 0.0480 No. 1 (0.073) 72 0.0580 0.0634 0.0595 No. 2 (0.086) 64 0.0691 0.0752 0.0730 No. 3 (0.099) 56 0.0797 0.0865 0.0827 No. 4 (0.112) 48 0.0894 0.0968 0.0945 No. 5 (0.125) 44 0.1004 0.1079 0.1063 No. 6 (0.138) 40 0.1110 0.1190 0.1181 No. 8 (0.164) 36 0.1340 0.1420 0.1378 No. 10 (0.190) 32 0.1560 0.1640 0.1614 No. 12 (0.216) 28 0.1770 0.1860 0.1820 1 / 4 28 0.2110 0.2200 0.2165 5 / 16 24 0.2670 0.2770 0.2717 3 / 8 24 0.3300 0.3400 0.3346 7 / 16 20 0.3830 0.3950 0.3898 1 / 2 20 0.4460 0.4570 0.4528 9 / 16 18 0.5020 0.5150 0.5118 5 / 8 18 0.5650 0.5780 0.5709 3 / 4 16 0.6820 0.6960 0.6890 7 / 8 14 0.7980 0.8130 0.8071 1 12 0.9100 0.9280 0.9219 1 1 / 8 12 1.0350 1.0530 1.0433 1 1 / 4 12 1.1600 1.1780 1.1719 1 3 / 8 12 1.2850 1.3030 1.2992 1 1 / 2 12 1.4100 1.4280 1.4173 UN-8 Unified thread ASME B1.1, Table 2 Nominal Size Minor thread dia. of the internal thread (Tol. 2B) Rec. tap drill size D P [T.P.I.] D 1 min. D 1 max. 1 1 / 8 8 0.9900 1.0150 1.0000 1 1 / 4 8 1.1150 1.1400 1.1250 1 3 / 8 8 1.2400 1.2650 1.2500 1 1 / 2 8 1.3650 1.3900 1.3750 1 5 / 8 8 1.4900 1.5150 1.5000 1 3 / 4 8 1.6150 1.6400 1.6250 1 7 / 8 8 1.7400 1.7650 1.7500 2 8 1.8650 1.8900 1.8750 2 1 / 4 8 2.1150 2.1400 2.1250 2 1 / 2 8 2.3650 2.3900 2.3750 2 3 / 4 8 2.6150 2.6400 2.6250 3 8 2.8650 2.8900 2.8750 3 1 / 2 8 3.3650 3.3900 3.3750 4 8 3.8650 3.8900 3.8750 4 1 / 2 8 4.3650 4.3900 4.3750 American Standard Threads 60° D D 1 P