Tap Drill Size
Tap Drill Sizes - Cut Taps - Metric
Suggested Percentage of Full Thread in Tapped Holes
To minimize tapping problems and lengthen tool life, use the largest drill possible to produce a minor diameter that will result in the lowest percentage of full thread consistent with adequate strength. A minor diameter that provides a 55% to 65% thread is sufficient for most requirements, but in some cases a higher percentage of thread may be necessary to conform with the minor diameter limits of the thread class specified. * Generally, deeper than 1 1/2 times the hole diameter.
*Deep Hole Tapping
Average Commercial Work
Thin Sheet Stock or Stamping
Material
Aluminum, Brass, Bronze, Cast Iron, Copper, Mild Steel, Tool Steel Cast Steel, Drop Forging, Monel Metal, Nickel Steel, Stainless Steel
Free Cutting Hard or Tough Cutting
60% - 70% 65% - 70%
75% - 85%
55% - 65% 60% - 70%
Tap Drill Diameter - Cut Taps
Pitch
Minor Dia. (mm)
80% Thread
75% Thread
70% Thread
65% Thread
60% Thread
Tap Size
Min. 6H
M MF
Max. 6H
(mm)
(in)
(mm)
(in)
(mm)
(in)
(mm)
(in)
(mm)
(in)
M1.6 0.35 M1.7 0.35 M1.8 0.35 M2.2 0.45 M2.5 0.45 M2.6 0.45 M2 0.4
– 1.221 1.321 1.24 0.0488 1.26 0.0496 1.28 0.0504 1.30 0.0512 1.33 0.0524 – 1.321 1.421 1.33 0.0524 1.36 0.0535 1.38 0.0543 1.40 0.0551 1.42 0.0559 – 1.422 1.519 1.44 0.0567 1.46 0.0575 1.48 0.0583 1.50 0.0591 1.53 0.0602 – 1.567 1.679 1.58 0.0622 1.61 0.0634 1.64 0.0646 1.66 0.0654 1.69 0.0665 – 1.715 1.836 1.73 0.0681 1.76 0.0693 1.79 0.0705 1.82 0.0717 1.85 0.0728 – 2.013 2.138 2.03 0.0799 2.06 0.0811 2.09 0.0823 2.12 0.0835 2.15 0.0846 – 2.113 2.238 2.13 0.0839 2.16 0.0850 2.19 0.0862 2.22 0.0874 2.25 0.0886
M3 – 2.459 2.599 2.48 0.0976 2.51 0.0988 2.55 0.1004 2.58 0.1016 2.61 0.1028 – 0.35 2.621 2.721 2.63 0.1035 2.66 0.1047 2.68 0.1055 2.70 0.1063 2.72 0.1071 M3.5 0.6 – 2.850 3.010 2.88 0.1134 2.92 0.1150 2.95 0.1161 2.99 0.1177 3.03 0.1193 M4 0.7 – 3.242 3.422 3.27 0.1287 3.32 0.1307 3.36 0.1323 3.41 0.1343 3.45 0.1358 – 0.5 3.459 3.599 3.48 0.1370 3.51 0.1382 3.54 0.1394 3.58 0.1409 3.61 0.1421 M4.5 0.75 – 3.688 3.876 3.72 0.1465 3.77 0.1484 3.82 0.1504 3.87 0.1524 3.92 0.1543 M5 0.8 – 4.134 4.334 4.17 0.1642 4.22 0.1661 4.27 0.1681 4.32 0.1701 4.38 0.1724 – 0.5 4.458 4.600 4.48 0.1764 4.51 0.1776 4.54 0.1787 4.58 0.1803 4.61 0.1815 M6 1 – 4.917 5.153 4.96 0.1953 5.03 0.1980 5.09 0.2004 5.16 0.2031 5.22 0.2055 – 0.75 5.187 5.377 5.22 0.2055 5.27 0.2075 5.32 0.2094 5.37 0.2114 5.41 0.2130 M7 1 – 5.918 6.152 5.96 0.2346 6.03 0.2374 6.09 0.2398 6.16 0.2425 6.22 0.2449 M8 1.25 – 6.647 6.912 6.70 0.2638 6.78 0.2669 6.86 0.2701 6.94 0.2732 7.03 0.2768 – 1 6.917 7.153 6.96 0.2740 7.03 0.2768 7.09 0.2791 7.16 0.2819 7.22 0.2843 – 0.75 7.187 7.377 7.22 0.2843 7.27 0.2862 7.32 0.2882 7.37 0.2902 7.41 0.2917 0.5
1.5 – 8.376 8.676 8.44 0.3323 8.54 0.3362 8.64 0.3402 8.73 0.3437 8.83 0.3476 – 1.25 8.647 8.912 8.70 0.3425 8.78 0.3457 8.86 0.3488 8.94 0.3520 9.03 0.3555 – 1 8.917 9.153 8.96 0.3528 9.03 0.3555 9.09 0.3579 9.16 0.3606 9.22 0.3630 – 0.75 9.188 9.378 9.22 0.3630 9.27 0.3650 9.32 0.3669 9.37 0.3689 9.41 0.3705
M10
M12 1.75 – 10.106 10.441 10.18 0.4008 10.30 0.4055 10.41 0.4098 10.52 0.4142 10.64 0.4189 – 1.5 10.376 10.676 10.44 0.4110 10.54 0.4150 10.64 0.4189 10.73 0.4224 10.83 0.4264 – 1.25 10.647 10.912 10.70 0.4213 10.78 0.4244 10.86 0.4276 10.94 0.4307 11.03 0.4343 – 1 10.917 11.153 10.96 0.4315 11.03 0.4343 11.09 0.4366 11.16 0.4394 11.22 0.4417 M14 2 – 11.835 12.210 11.92 0.4693 12.05 0.4744 12.18 0.4795 12.31 0.4846 12.44 0.4898 – 1.5 12.376 12.676 12.44 0.4898 12.54 0.4937 12.64 0.4976 12.73 0.5012 12.83 0.5051 M16 2 – 13.835 14.210 13.92 0.5480 14.05 0.5531 14.18 0.5583 14.31 0.5634 14.44 0.5685 – 1.5 14.376 14.676 14.44 0.5685 14.54 0.5724 14.64 0.5764 14.73 0.5799 14.83 0.5839 M18 2.5 – 15.296 15.743 15.40 0.6063 15.56 0.6126 15.73 0.6193 15.89 0.6256 16.05 0.6319 – 1.5 16.376 16.676 16.44 0.6472 16.54 0.6512 16.64 0.6551 16.73 0.6587 16.83 0.6626 M20 2.5 – 17.294 17.744 17.40 0.6850 17.56 0.6913 17.73 0.6980 17.89 0.7043 18.05 0.7106 – 1.5 18.376 18.676 18.44 0.7260 18.54 0.7299 18.64 0.7339 18.73 0.7374 18.83 0.7413 – 1 18.917 19.153 18.96 0.7465 19.03 0.7492 19.09 0.7516 19.16 0.7543 19.22 0.7567 M22 2.5 – 19.294 19.744 19.40 0.7638 19.56 0.7701 19.73 0.7768 19.89 0.7831 20.05 0.7894 – 2 19.835 20.210 19.92 0.7843 20.05 0.7894 20.18 0.7945 20.31 0.7996 20.44 0.8047 – 1.5 20.376 20.676 20.44 0.8047 20.54 0.8087 20.64 0.8126 20.73 0.8161 20.83 0.8201 M24 3 – 20.752 21.252 20.88 0.8220 21.08 0.8299 21.27 0.8374 21.47 0.8453 21.66 0.8528 – 2 21.835 22.210 21.92 0.8630 22.05 0.8681 22.18 0.8732 22.31 0.8783 22.44 0.8835 – 1.5 22.376 22.676 22.44 0.8835 22.54 0.8874 22.64 0.8913 22.73 0.8949 22.83 0.8988 M27 3 – 23.752 24.252 23.88 0.9402 24.08 0.9480 24.27 0.9555 24.47 0.9634 24.66 0.9709 – 2 24.835 25.210 24.92 0.9811 25.05 0.9862 25.18 0.9913 25.31 0.9965 25.44 1.0016 – 1.5 25.376 25.676 25.44 1.0016 25.54 1.0055 25.64 1.0094 25.73 1.0130 25.83 1.0169 M30 3.5 – 26.211 26.771 26.36 1.0378 26.59 1.0469 26.82 1.0559 27.04 1.0646 27.27 1.0736 – 2 27.835 28.210 27.92 1.0992 28.05 1.1043 28.18 1.1094 28.31 1.1146 28.44 1.1197 – 1.5 28.376 28.676 28.44 1.1197 28.54 1.1236 28.64 1.1276 28.73 1.1311 28.83 1.1350 M33 3.5 – 29.211 29.771 29.36 1.1559 29.59 1.1650 29.82 1.1740 30.04 1.1827 30.27 1.1917 – 2 30.835 31.210 30.92 1.2173 31.05 1.2224 31.18 1.2276 31.31 1.2327 31.44 1.2378 M36 4 – 31.670 32.270 31.84 1.2535 32.10 1.2638 32.36 1.2740 32.62 1.2843 32.88 1.2945 – 3 32.752 33.252 32.88 1.2945 33.08 1.3024 33.27 1.3098 33.47 1.3177 33.66 1.3252 – 2 33.835 34.210 33.92 1.3354 34.05 1.3406 34.18 1.3457 34.31 1.3508 34.44 1.3559 M39 4 – 34.670 35.270 34.84 1.3717 35.10 1.3819 35.36 1.3921 35.62 1.4024 35.88 1.4126 – 2 36.835 37.210 36.92 1.4535 37.05 1.4587 37.18 1.4638 37.31 1.4689 37.44 1.4740 M42 4.5 – 37.129 37.799 37.32 1.4693 37.62 1.4811 37.91 1.4925 38.20 1.5039 38.49 1.5154 – 3 38.752 39.252 38.88 1.5307 39.08 1.5386 39.27 1.5461 39.47 1.5539 39.66 1.5614 – 2 39.835 40.210 39.92 1.5717 40.05 1.5768 40.18 1.5819 40.31 1.5870 40.44 1.5921
FORMULA: TAP DRILL SIZE
FORMULA: PERCENTAGE OF FULL THREAD
76.980 Pitch
Pitch x % of Full Thread 76.980
% of Full Thread = Threads Per Inch x
Drill Size = Tap Major Dia -
Example: to determine the % of thread for M12 x 1.75 Tap using 10.41mm drill
Example: to determine drill size for M12 x 1.75 tap, 70% thread Tap Major Ø = 12mm % of Full Thread = 70% Pitch = 1.75mm Drill Size = 12mm -
(1.75 x 70%) 76.980
# Threads per Inch = 20 Tap Major Ø = 0.2500” Drill Ø = 0.2045”
% of Thread = (12mm - 10.409mm) x (0.2500 - 0.2262) 0.0068
Drill Size = 12mm - 1.591mm = 10.409mm
% of Thread = 1.591mm x 43.989 = 70%
Threading Technical
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