TM 9-254 5-9. Screw Thread - Continued Table 5-11.  Basic Coarse Thread Dimensions and Tap Drill Sizes Commercial Decimal Nominal size Outside Pitch Root tap drill to equivalent diameter diameter diameter produce approx of tap Inch Threads (in.) (in.) (in.) 75 percent drill per inch full thread 1/16-64 0.0625 0.0524 0.0422 3/64 0.0469 72 .0625 .0535 .0445 3/64 .0469 3/64-60 .0781 .0673 .0563 1/16 .0625 72 .0781 .0691 .0601 52 .0635 3/32-48 0.0938 0.0803 0.0667 49 0.0730 50 .0938 .0808 .0678 49 .0730 7/64-48 .1094 .0959 .0823 43 .0890 1/8-32 .1250 .1047 .0844 3/32 .0937 40 .1250 .1088 .0925 38 .1015 9/64-40 .1406 .1244 .1081 32 .1160 5/32-32 .1563 .1360 .1157 1/8 .1250 36 .1563 .1382 .1202 30 .1285 11/64-32 .1719 .1505 .1313 9/64 .1406 3/16-24 .1875 .1604 .1334 26 .1470 32 .1875 .1672 .1469 22 .1570 13/64-24 .2031 .1760 .1490 20 .1610 7/32-24 .2188 .1919 .1646 16 .1770 32 .2188 .1985 .1782 12 .1890 15/64-24 .2344 .2073 .1806 10 .1935 1/4-20 .2500 .2175 .1850 7 .2010 24 .2500 .2229 .1959 4 .2090 27 .2500 .2260 .2019 3 .2130 28 .2500 .2268 .2036 3 .2130 32 .2500 .2297 .2094 7/32 .2187 5/16-18 .3125 .2764 .2403 F .2570 20 .3125 .2800 .2476 17/64 .2656 24 .3125 .2854 .2584 I .2720 27 .3125 .2884 .2644 J .2770 32 .3125 .2922 .2719 9/32 .2812 3/8-16 .3750 .3344 .2938 5/16 .3125 20 .3750 .3425 .3100 21/64 .3281 24 .3750 .3479 .3209 Q .3320 27 .3750 .3509 .3269 R .3390 7/16-14 .4375 .3911 .3447 U .3680 20 .4375 .4050 .3726 25/64 .3906 24 .4375 .4104 .3834 X .3970 27 .4375 .4134 .3894 Y .4040 1/2-12 .5000 .4459 .3918 27/64 .4219 13 .5000 .4501 .4001 27/64 .4219 20 .5000 .4675 .4351 29/64 .4531 24 .5000 .4729 .4459 29/64 .4531 27 .5000 .4759 .4519 15/32 .4687 5-24