Tapping Drill Tables
Tapping Drill Tables
The tapping drills given in the following pages include millimetre sizes for the convenience of those who are working in or intend to work predominantly in metric units.
Drills have been selected from standard sizes which, when used with reasonable care, will produce holes within the minor diameter limits shown.
From those drills the larger sizes are recommended to facilitate ease of tapping.
As a guide to relative clearances, index figures adjacent to the drill size show the difference between the nominal drill and minimum minor diameters.
ISO Metric Coarse Pitch Series
| Thread Size and Pitch | Minor Diameter of nut thread (A) | Tapping Drill Sizes for Commercial Tapping | |||
|---|---|---|---|---|---|
Maximum | Minimum | Recommended | Alternatives | ||
mm | mm | mm | mm | Inch | mm |
M1.6 x 0.35 | 1.321 | 1.221 | 1.303 | 3/640 | 1.251 |
M2 x 0.4 | 1.679 | 1.567 | 1.654 | 1/161 | 1.601 |
M2.5 x 0.45 | 2.138 | 2.013 | 2.103 | No. 469 | 2.051 |
M3 x 0.5 | 2.599 | 2.459 | 2.553 | No. 410 | 2.501 |
M4 x 0.7 | 3.422 | 3.242 | 3.406 | No. 301 | 3.302 |
M5 x 0.8 | 4.334 | 4.134 | 4.306 | No. 193 | 4.202 |
M6 x 1.00 | 5.133 | 4.917 | 5.107 | No. 92 | 5.003 |
M8 x 1.25 | 6.912 | 6.647 | 6.9010 | 17/644 | 6.806 |
M10 x 1.5 | 8.676 | 8.376 | 8.609 | Q2 | 8.505 |
M12 x 1.75 | 10.441 | 10.105 | 10.4011 | 13/328 | 10.204 |
M16 x 2.00 | 14.210 | 13.835 | 14.006 | 35/642 | - |
M20 x 2.5 | 17.744 | 17.294 | 17.508 | 11/167 | - |
M24 x 3.0 | 21.252 | 20.752 | 21.0010 | 53/6411 | - |
M30 x 3.5 | 26.771 | 26.211 | 26.5011 | 13/6415 | - |
M36x 4.0 | 32.270 | 31.670 | 32.0013 | 117/6419 | - |
The small index figures show the theoretical clearance in thousandths of an inch above the minimum minor diameter of the nut thread.
Letter and wire gauge drills are obsolescent and are being replaced by metric sizes.
British Standard Whitworth – BSW
| Thread Size and Pitch per inch | Minor Diameter of nut thread (A) | Tapping Drill Sizes for Commercial Tapping | |||
|---|---|---|---|---|---|
Maximum | Minimum | Recommended | Alternatives | ||
Inch | Inch | Inch | mm | Inch | |
1/8 - 40 | 0.1020 | 0.0930 | 397 | 2.557 | 405 |
3/16 - 24 | 0.1474 | 0.1341 | 2710 | 3.7012 | 286 |
1/4 - 20 | 0.2030 | 0.1860 | 910 | 5.0011 | 107 123 |
5/16 - 18 | 0.2594 | 0.2413 | 1/49 | 6.4011 | D5 C1 |
3/8 - 16 | 0.3145 | 0.2950 | N7 | 7.708 | 19/642 S2 |
7/16 - 14 | 0.3674 | 0.3461 | T12 | 9.1012 | Y11 X4 |
1/2 - 12 | 0.4169 | 0.3932 | 13/3213 | 10.4013 | - |
9/16 - 12 | 0.4794 | 0.4557 | 15/3213 | 12.007 | - |
5/8 - 11 | 0.5338 | 0.5086 | 17/3223 | 13.5023 | 33/647 |
3/4 - 10 | 0.6490 | 0.6220 | 41/6419 | 16.2517 | 5/83 |
7/8 - 9 | 0.7620 | 0.7328 | 3/417 | 19.0015 | 47/642 |
1 - 8 | 0.8720 | 0.8400 | 55/6419 | 22.0026 | 27/321 |
1 1/8 - 7 | 0.9776 | 0.9420 | 31/3217 | 24.5022 | 6 1/6411 |
1 1/4 - 7 | 1.1026 | 1.0670 | 13/3227 | 27.5016 | 1 5/6411 |
1 1/2 - 6 | 1.3269 | 1.2866 | 1 5/1626 | 33.0012 | 1 19/6411 |
1 3/4 - 5 | 1.5408 | 1.4938 | 1 17/3237 | 38.5022 | 1 33/6420 |
2 - 4.5 | 1.7668 | 1.7154 | 1 3/435 | 44.5037 | 1 47/6420 |
| (A) From AS B47 - normal and medium classes. | |||||
The small index figures show the theoretical clearance in thousandths of an inch above the minimum minor diameter of the nut thread.
Letter and wire gauge drills are obsolescent and are being replaced by metric sizes.