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Tap Size Tap Drill Size Decimal Equiv. of Tap Drill (Inches) Theoretical % of Thread Probable Mean Oversize (Inches) Probable Hole Size (Inches) Probable % of Thread 0-80 56 .0465 83 .0015 .0480 74   3/64 .0469 81 .0015 .0484 71 1-64 54 .0550 89 .0015 .0565 81   1.45 mm .0571 78 .0015 .0586 71 1-72 1.5 mm .0591 77 .0015 .0606 68   53 .0595 75 .0015 .0610 67 2-56 51 .0670 82 .0017 .0687 74   50 .0700 69 .0017 .0717 62 2-64 50 .0700 79 .0017 .0717 70   1.80 mm .0709 74 .0017 .0726 66 3-48 48 .0760 85 .0019 .0779 78   5/64 .0781 77 .0019 .0800 70 3-56 46 .0810 78 .0019 .0829 69   45 .0820 73 .0019 .0839 65 4-40 44 .0860 80 .0020 .0880 74   43 .0890 71 .0020 .0910 65 4-48 2.35 mm .0925 72 .0020 .0910 72   42 .0935 68 .0020 .0955 61 5-40 40 .0980 83 .0023 .1003 76   39 .0995 79 .0023 .1018 71   1.80 mm .0709 74 .0017 .0726 66   37 .1040 71 .0023 .1063 63 6-32 36 .1065 78 .0023 .1088 72   7/64 .1095 70 .0026 .1120 64 6-40 34 .1110 83 .0026 .1136 75   33 .1130 77 .0026 .1156 69 8-32 3.40 mm .1339 74 .0029 .1368 67   29 .1360 69 .0029 .1389 62 8-36 29 .1360 78 .0029 .1389 70   3.5 mm .1378 72 .0029 .1407 65 10-24 26 .1470 79 .0032 .1502 74   25 .1495 75 .0032 .1527 69 10-32 22 .1570 81 .0032 .1602 73   21 .1590 76 .0032 .1622 68 12-24 17 .1730 79 .0035 .1765 73   16 .1770 72 .0035 .1805 66 12-28 16 .1770 84 .0035 .1805 77   15 .1800 78 .0035 .1835 70 1/4-20 8 .1990 79 .0038 .2028 73   7 .2010 75 .0038 .2048 70 1/4-28 5.40 mm .2126 81 .0038 .2164 72   3 .2130 80 .0038 .2168 72 5/16-18 F .2570 77 .0038 .2608 72   6.60 mm .2598 73 .0038 .2636 68 5/16-24 H .2660 86 .0041 .2701 78   I .2720 75 .0041 .2761 67 3/8-16 5/16 .3125 77 .0044 .3169 72   O .3160 73 .0044 .3204 68 3/8-24 21/64 .3281 87 .0044 .3325 79   Q .3320 79 .0044 .3364 71 7/16-14 23/64 .3594 84 .0046 .3640 79   U .3680 75 .0046 .3726 70 7/16-20 W .3860 79 .0046 .3906 72   25/64 .3906 72 .0046 .3592 65 1/2-13 10.5 mm .4134 87 .0047 .4181 82   27/64 .4219 78 .0047 .4266 73 1/2-20 29/64 .4531 72 .0047 .4578 65 9/16-12 15/32 .4688 87 .0048 .4736 82   31/64 .4844 72 .0048 .4892 68 9/16-18 1/2 .5000 87 .0048 .5048 80   33/64 .5156 65 .0048 .5204 58 5/8-11 17/32 .5313 79 .0049 .5362 75 5/8-18 9/16 .5625 87 .0049 .5674 80   37/64 .5781 65 .0050 .5831 58 3/4-10 41/64 .6406 84 .0050 .6456 80   21/32 .6563 72 .0050 .6613 68 3/4-16 11/16 .6875 77 .0050 .6925 71   17.5 mm .6890 75 .0050 .6940 69 7/8-9 49/64 .7656 76 .0052 .7708 72 7/8-14 51/64 .7969 84 .0052 .8021 79   13/16 .8125 67 .0052 .8177 62 1-8 55/64 .8594 87 .0059 .8653 83   7/8 .8750 77 .0059 .8809 73 1-12 29/32 .9063 87 .0059 .9122 81   59/64 .9219 72 .0060 .9279 67 1-14 59/64 .9219 84 .0060 .9279 78 1-1/8-7 63/64 .9844 76 .0067 .9911 72 1-1/8-12 1-1/32 1.0313 87 .0059 1.0384 80   1-3/64 1.0469 72 .0072 1.0541 66 1-1/4-7 1-1/8 1.1250 67 Reaming Recommended 1-1/4-12 1-11/64 1.1719 72 Reaming Recommended 1-3/8-6 1-7/32 1.2188 72 Reaming Recommended 1-3/8-12 1-19/64 1.2969 72 Reaming Recommended 1-1/2-6 1-11/32 1.3438 72 Reaming Recommended 1-1/2-12 1-27/64 1.4219 72 Reaming Recommended