American Na tional and Unified Coarse and Fine Thread Dimensions and Tap Drill Sizes p d f f 60º pitch diameter = D - .6495 N f = flat = p 8 p = pitch = 1 thread per inch d = depth = p x .649519 Size Threads per inch Outside Diameter (in) Pitch Diameter (in) Root Diameter (in) Tap Drill Approx. 75% Full Thread Decimal Equiv. of Tap Drill UNC UNF NC NF 0 – 80 .0600 .0519 .0438 3/64" .0469 1 64 – .0730 .0629 .0527 53 .0595 1 – 72 .0730 .0640 .0550 53 .0595 2 56 – .0860 .0744 .0628 50 .0700 2 – 64 .0860 .0759 .0657 50 .0700 3 48 – .0990 .0855 .0719 47 .0785 3 – 56 .0990 .0874 .0758 46 .0810 4 40 – .1120 .0958 .0795 43 .0890 4 – 48 .1120 .0985 .0849 42 .0935 5 40 – .1250 .1088 .0925 38 .1015 5 – 44 .1250 .1102 .0955 37 .1040 6 32 – .1380 .1177 .0974 36 .1065 6 – 40 .1380 .1218 .1055 33 .1130 8 32 – .1640 .1437 .1234 29 .1360 8 – 36 .1640 .1460 .1279 29 .1360 10 24 – .1900 .1629 .1359 26 .1470 10 – 32 .1900 .1697 .1494 21 .1590 12 24 – .2160 .1889 .1619 16 .1770 12 – 28 .2160 .1928 .1696 15 .1800 1/4" 20 – .2500 .2175 .1850 7 .2010 1/4" – 28 .2500 .2268 .2036 3 .2130 5/16" 18 – .3125 .2764 .2403 F .2570 5/16" – 24 .3125 .2854 .2584 I .2720 3/8" 16 – .3750 .3344 .2938 5/16" .3125 3/8" – 24 .3750 .3479 .3209 Q .3320 7/16" 14 – .4375 .3911 .3447 U .3680 7/16" – 20 .4375 .4050 .3726 25/64" .3906 1/2" 13 – .5000 .4500 .4001 27/64" .4219 1/2" – 20 .5000 .4675 .4351 29/64" .4531 9/16" 12 – .5625 .5084 .4542 31/64" .4844 9/16" – 18 .5625 .5264 .4903 33/64" .5156 5/8" 11 – .6250 .5660 .5069 17/32" .5312 5/8" – 18 .6250 .5889 .5528 37/64" .5781 3/4" 10 – .7500 .6850 .6201 21/32" .6562 3/4" – 16 .7500 .7094 .6688 11/16" .6875 7/8" 9 – .8750 .8028 .7307 49/64" .7656 7/8" – 14 .8750 .8286 .7822 13/16" .8125 1" 8 – 1.0000 .9188 .8376 7/8" .8750 1" – 12 1.0000 .9459 .8917 59/64" .9219 1-1/8" 7 – 1.1250 1.0322 .9394 63/64" .9844 1-1/8" – 12 1.1250 1.0709 1.0168 1-3/64" 1.0469 1-1/4" 7 – 1.2500 1.1572 1.0644 1-7/64" 1.1094 1-1/4" – 12 1.2500 1.1959 1.1418 1-11/64" 1.1719 1-3/8" 6 – 1.3750 1.2667 1.1585 1-7/32" 1.2187 1-3/8" – 12 1.3750 1.3209 1.2668 1-19/64" 1.2969 1-1/2" 6 – 1.5000 1.3917 1.2835 1-11/32" 1.3437 1-1/2" – 12 1.5000 1.4459 1.3918 1-27/64" 1.4219 1-3/4" 5 – 1.7500 1.6201 1.4902 1-9/16" 1.5625 2" 4-1/2 – 2.0000 1.8557 1.7113 1-25/32" 1.7812 2-1/4" 4-1/2 – 2.2500 2.1057 1.9613 2-1/32" 2.0313 2-1/2" 4-1/2 – 2.5000 2.3376 2.1752 2-1/4" 2.2500 2-3/4" 4 – 2.7500 2.5876 2.4252 2-1/2" 2.5000 3" 4 – 3.0000 2.8376 2.6752 2-3/4" 2.7500 3-1/4" 4 – 3.2500 3.0876 2.9252 3" 3.0000 3-1/2" 4 – 3.5000 3.3376 3.1752 3-1/4" 3.2500 3-3/4" 4 – 3.7500 3.5876 3.4252 3-1/2" 3.5000 4" 4 – 4.0000 3.3786 3.6752 3-3/4" 3.7500 582 R eference T ables