Tap Drill Size
Tap Drill Sizes - Form Taps - Metric
Suggested Percentage of Full Thread in Tapped Holes Material *Deep Hole Tapping Average Commercial Work
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.
Thin Sheet Stock or Stamping
Aluminum, Brass, Bronze, Cast Iron, Copper, Mild Steel, Tool Steel Cast Steel, Drop Forging, Monel Metal, Nickel Steel, Stainless Steel
Free Cutting
60% - 70% 65% - 70%
75% - 85%
Hard or Tough Cutting
55% - 65% 60% - 70%
Minor Diameter (mm)
Pitch
Tap Drill Diameter - Form Taps
Tap Size
75% Thread
70% Thread
65% Thread
60% Thread
55% Thread
M MF Min. 6H 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 1.42 0.0559 1.43 0.0563 1.45 0.0571 1.46 0.0575 1.47 0.0579 – 1.321 1.421 1.56 0.0617 1.57 0.0620 1.58 0.0623 1.59 0.0627 1.60 0.0630 – 1.422 1.519 1.62 0.0638 1.63 0.0642 1.65 0.0650 1.66 0.0654 1.67 0.0657 – 1.567 1.679 1.80 0.0709 1.81 0.0713 1.82 0.0717 1.84 0.0724 1.85 0.0728 – 1.715 1.836 1.97 0.0776 1.99 0.0783 2.00 0.0787 2.02 0.0795 2.03 0.0799 – 2.013 2.138 2.27 0.0894 2.29 0.0902 2.30 0.0906 2.32 0.0913 2.33 0.0917 – 2.113 2.238 2.41 0.0949 2.42 0.0953 2.43 0.0957 2.44 0.0962 2.45 0.0966
M3 – 2.459 2.599 2.75 0.1083 2.76 0.1087 2.78 0.1094 2.80 0.1102 2.81 0.1106 – 0.35 2.621 2.721 2.86 0.1126 2.87 0.1130 2.88 0.1134 2.89 0.1138 2.90 0.1142 M3.5 0.6 – 2.850 3.010 3.19 0.1256 3.21 0.1264 3.23 0.1272 3.26 0.1283 3.28 0.1291 M4 0.7 – 3.242 3.422 3.64 0.1433 3.67 0.1445 3.69 0.1453 3.71 0.1461 3.74 0.1472 – 0.5 3.459 3.599 3.75 0.1476 3.76 0.1480 3.78 0.1488 3.80 0.1496 3.81 0.1500 M4.5 0.75 – 3.688 3.876 4.12 0.1622 4.14 0.1630 4.17 0.1642 4.19 0.1650 4.22 0.1661 M5 0.8 – 4.134 4.334 4.59 0.1807 4.62 0.1819 4.65 0.1831 4.67 0.1839 4.70 0.1850 – 0.5 4.458 4.600 4.75 0.1870 4.76 0.1874 4.78 0.1882 4.80 0.1890 4.81 0.1894 M6 1 – 4.917 5.153 5.49 0.2161 5.52 0.2173 5.56 0.2189 5.59 0.2201 5.63 0.2217 – 0.75 5.187 5.377 5.62 0.2213 5.64 0.2220 5.67 0.2232 5.69 0.2240 5.72 0.2252 M7 1 – 5.918 6.152 6.49 0.2555 6.52 0.2567 6.56 0.2583 6.59 0.2594 6.63 0.2610 0.5
1.25 – 6.647 6.912 7.36 0.2898 7.41 0.2917 7.45 0.2933 7.49 0.2949 7.53 0.2965 – 1 6.917 7.153 7.49 0.2949 7.52 0.2961 7.56 0.2976 7.59 0.2988 7.63 0.3004 – 0.75 7.187 7.377 7.62 0.3000 7.64 0.3008 7.67 0.3020 7.69 0.3028 7.72 0.3039 – 8.376 8.676 9.24 0.3638 9.29 0.3657 9.34 0.3677 9.39 0.3697 9.44 0.3717 – 1.25 8.647 8.912 9.36 0.3685 9.41 0.3705 9.45 0.3720 9.49 0.3736 9.53 0.3752 – 1 8.917 9.153 9.49 0.3736 9.52 0.3748 9.56 0.3764 9.59 0.3776 9.63 0.3791 – 0.75 9.188 9.378 9.62 0.3787 9.64 0.3795 9.67 0.3807 9.69 0.3815 9.72 0.3827 1.5
M8
M10
M12 1.75 – 10.106 10.441 11.11 0.4374 11.17 0.4398 11.23 0.4421 11.29 0.4445 11.35 0.4469 – 1.5 10.376 10.676 11.24 0.4425 11.29 0.4484 11.34 0.4465 11.39 0.4484 11.44 0.4504 – 1.25 10.647 10.912 11.36 0.4472 11.41 0.4492 11.45 0.4508 11.49 0.4524 11.53 0.4539 – 1 10.917 11.153 11.49 0.4524 11.52 0.4535 11.56 0.4551 11.59 0.4563 11.63 0.4579 M14 2 – 11.835 12.210 12.98 0.5110 13.05 0.5138 13.12 0.5165 13.18 0.5189 13.25 0.5217 – 1.5 12.376 12.676 13.24 0.5213 13.29 0.5232 13.34 0.5252 13.39 0.5272 13.44 0.5291 M16 2 – 13.835 14.210 14.98 0.5898 15.05 0.5925 15.12 0.5953 15.18 0.5976 15.25 0.6004 – 1.5 14.376 14.676 15.24 0.6000 15.29 0.6020 15.34 0.6039 15.39 0.6059 15.44 0.6079 M18 2.5 – 15.296 15.743 16.73 0.6587 16.81 0.6618 16.90 0.6654 16.98 0.6685 17.07 0.6720 – 1.5 16.376 16.676 17.24 0.6787 17.29 0.6807 17.34 0.6827 17.39 0.6846 17.44 0.6866
2.5 – 17.294 17.744 18.73 0.7374 18.81 0.7406 18.90 0.7441 18.98 0.7472 19.07 0.7508 – 1.5 18.376 18.676 19.24 0.7575 19.29 0.7594 19.34 0.7614 19.39 0.7634 19.44 0.7654 – 1 18.917 19.153 19.49 0.7673 19.52 0.7685 19.56 0.7701 19.59 0.7713 19.63 0.7728 2.5 – 19.294 19.744 20.73 0.8161 20.81 0.8193 20.90 0.8228 20.98 0.8260 21.07 0.8295 – 2 19.835 20.210 20.98 0.8260 21.05 0.8287 21.12 0.8315 21.18 0.8339 21.25 0.8366 – 1.5 20.376 20.676 21.24 0.8362 21.29 0.8382 21.34 0.8402 21.39 0.8421 21.44 0.8441 3 – 20.752 21.252 22.47 0.8846 22.57 0.8886 22.67 0.8925 22.78 0.8969 22.88 0.9008 – 2 21.835 22.210 22.98 0.9047 23.05 0.9075 23.12 0.9102 23.18 0.9126 23.25 0.9154 – 1.5 22.376 22.676 23.24 0.9150 23.29 0.9169 23.34 0.9189 23.39 0.9209 23.44 0.9228
M20
M22
M24
FORMULA: TAP DRILL SIZE
FORMULA: PERCENTAGE OF FULL THREAD
147.059 Pitch
Pitch x % of Full Thread 147.059
% of Full Thread = (Tap Major Dia - Drill Dia) x
Drill Size = Tap Major Dia -
% of Thread = (12mm - 11.167mm) x 147.059 1.75 Example: to determine the % of thread for M12 x 1.75 Tap using 11.17mm 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%) 147.059
# Threads per Inch = 20 Tap Major Ø = 0.2500” Drill Ø = 0.2045”
Drill Size = 12mm - 0.833mm = 11.167mm
% of Thread = (0.833mm) x 84.03 = 70%
Threading Technical
784
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