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Tap Drill Sizes For Universal Screw Threads Tap Size Tap Drill Size Decimal Equiv. of Tap Drill (Inches) Theoretical Percent of Thread % Probable Mean Oversize (Inches) Probable Hole Size (Inches) Probable Percent of Thread % 0-80 56 3/64 1.20mm 1.25mm .0465 .0469 .0472 .0492 83 81 79 67 .0015 .0015 .0015 .0015 .0480 .0484 .0487 .0507 74 71 69 57 1-64 54 1.45mm 53 .0550 .0571 .0595 89 78 67 .0015 .0015 .0015 .0565 .0586 .0610 81 71 59 1-72 1.5mm 53 1.55mm .0591 .0595 .0610 77 75 67 .0015 .0015 .0015 .0606 .0610 .0606 68 67 68 2-56 51 1.75mm 50 1.80mm .0670 .0689 .0700 .0709 82 73 69 65 .0017 .0017 .0017 .0017 .0687 .0706 .0717 .0726 74 66 62 58 2-64 50 1.80mm 49 .0700 .0709 .0730 79 74 64 .0017 .0017 .0017 .0717 .0726 .0747 70 66 56 3-48 48 5/64 47 2.00mm 46 45 .0760 .0781 .0785 .0787 .0810 .0820 85 77 76 75 67 63 .0019 .0019 .0019 .0019 .0019 .0019 .0779 .0800 .0804 .0806 .0829 .0839 78 70 69 68 60 56 3-56 46 45 2.10mm 2.15mm .0810 .0820 .0827 .0846 78 73 70 62 .0019 .0019 .0019 .0019 .0829 .0839 .0846 .0865 69 65 62 54 4-40 44 2.20mm 43 2.30mm .0860 .0866 .0890 .0906 80 78 71 66 .0020 .0020 .0020 .0020 .0880 .0886 .0910 .0926 74 72 65 60 4-48 2.35mm 42 3/32 2.40mm .0925 .0935 .0938 .0945 72 68 68 65 .0020 .0020 .0020 .0020 .0926 .0955 .0958 .0965 72 61 60 57 5-40 40 39 38 2.60mm .0980 .0995 .1015 .1024 83 79 72 70 .0023 .0023 .0023 .0023 .1003 .1018 .1038 .1047 76 71 65 63 5-44 38 2.60mm 37 .1015 .1024 .1040 79 77 71 .0023 .0023 .0023 .1038 .1047 .1063 72 69 63 6-32 37 36 7/64 35 34 .1040 .1065 .1094 .1100 .1100 84 78 70 69 67 .0023 .0023 .0026 .0026 .0026 .1063 .1088 .1120 .1126 .1136 78 72 64 63 60 6-40 34 33 2.90mm 32 .1110 .1130 .1142 .1160 83 77 73 68 .0026 .0026 .0026 .0026 .1136 .1156 .1168 .1186 75 69 65 60 8-32 3.40mm 29 .1339 .1360 74 69 .0029 .0029 .1368 .1389 67 62 8-36 29 3.5mm .1360 .1378 78 72 .0029 .0029 .1389 .1407 70 65 10-24 27 3.70mm 26 25 24 .1440 .1457 .1470 .1495 .1520 85 82 79 75 70 .0032 .0032 .0032 .0032 .0032 .1472 .1489 .1502 .1527 .1552 79 76 74 69 64 10-32 5/32 22 21 .1563 .1570 .1590 83 81 76 .0032 .0032 .0032 .1595 .1602 .1622 75 73 68 12-24 11/64 17 16 .1719 .1730 .1770 82 79 72 .0035 .0035 .0035 .1754 .1765 .1805 75 73 66 12-28 16 15 4.60mm 14 .1770 .1800 .1811 .1820 84 78 75 73 .0035 .0035 .0035 .0035 .1805 .1835 .1846 .1855 77 70 67 66 1/4-20 9 8 7 13/64 .1960 .1990 .2010 .2031 83 79 75 72 .0038 .0038 .0038 .0038 .1998 .2028 .2048 .2069 77 73 70 66 1/4-28 5.40mm 3 .2126 .2130 81 80 .0038 .0038 .2164 .2168 72 72 5/16-18 F 6.60mm G .2570 .2598 .2610 77 73 71 .0038 .0038 .0041 .2608 .2636 .2651 72 68 66 5/16-24 H 6.80mm I .2660 .2677 .2720 86 83 75 .0041 .0041 .0041 .2701 .2718 .2761 78 75 67 3/8-16 7.80mm 7.90mm 5/16 O .3071 .3110 .3125 .3160 84 79 77 73 .0044 .0044 .0044 .0044 .3115 .3154 .3169 .3204 78 73 72 68 3/8-24 21/64 8.40mm Q 8.50mm .3281 .3307 .3320 .3346 87 82 79 75 .0044 .0044 .0044 .0044 .3325 .3351 .3364 .3390 79 74 71 67 7/16-14 T 23/64 9.20mm 9.30mm U 9.40mm .3580 .3594 .3622 .3661 .3680 .3701 86 84 81 77 75 73 .0046 .0046 .0046 .0046 .0046 .0046 .3626 .3640 .3668 .3707 .3726 .3747 81 79 76 72 70 68 7/16-20 W 25/64 .3860 .3906 79 72 .0046 .0046 .3906 .3952 72 65 1/2-13 10.50mm 27/64 .4134 .4219 87 78 .0047 .0047 .4181 .4266 82 73 1/2-20 29/64 .4531 72 .0047 .4578 65

Tap Drill Sizes For Metric M-Profile Screw Threads Tap Size Tap Drill Size Decimal Equiv. of Tap Drill (Inches) Theoretical Percent of Thread % Probable Mean Oversize (Inches) Probable Hole Size (Inches) Probable Percent of Thread % M1.6 x 0.35 1.20mm 1.25mm .0472 .0492 88 77 .0014 .0014 .0486 .0506 80 69 M2 x 0.4 1/16 1.60mm 52 .0625 .0630 .0635 79 77 74 .0015 .0017 .0017 .0640 .0647 .0652 72 69 66 M2.5 x 0.45 2.05mm 46 45 .0807 .0810 .0820 77 76 71 .0019 .0019 .0019 .0826 .0829 .0839 69 67 63 M3 x 0.5 40 2.5mm 39 .0980 .0984 .0995 79 77 73 .0023 .0023 .0023 .1003 .1007 .1018 70 68 64 M3.5 x 0.6 33 2.9mm 32 .1130 .1142 .1160 81 77 71 .0026 .0026 .0026 .1156 .1168 .1186 72 68 63 M4 x 0.7 3.2mm 30 3.3mm .1260 .1285 .1299 88 81 77 .0029 .0029 .0029 .1289 .1314 .1328 80 73 69 M4.5 x 0.75 3.7mm 26 25 .1457 .1470 .1495 82 79 72 .0032 .0032 .0032 .1489 .1502 .1527 74 70 64 M5 x 0.8 4.2mm 19 .1654 .1660 77 75 0032 0032 .1686 .1692 69 68 M6 x 1 10 9 5mm 8 .1935 .1960 .1969 .1990 84 79 77 73 .0038 .0038 .0038 .0038 .1973 .1998 .2006 .2028 76 71 70 65 M7 x 1 A 6mm B .2340 .2362 .2380 81 77 74 .0038 .0038 .0038 .2378 .2400 .2418 74 70 66 M8 x 1.25 6.7mm 17/64 H 6.8mm .2638 .2656 .2660 .2677 80 77 77 74 .0041 .0041 .0041 .0041 .2679 .2697 .2701 .2718 74 71 70 68 M10 x 1.5 8.4mm Q 8.5mm .3307 .3320 .3346 82 80 77 .0044 .0044 .0044 .3351 .3364 .3390 76 75 71 M12 x 1.5 10.4mm Z .4094 .4130 81 77 .0047 .0047 .4141 .4177 75 71 M12 x 1.75 10.20mm Y 13/32 .4016 .4040 .4062 79 76 74 .0047 .0047 .0047 .4063 .4087 .4109 74 71 69