| TAP DRILL SIZES FOR CUT AND FORMED THREADS | ||||
| TAP SIZE | TAP DRILL SIZE | |||
| Cut Thread | Formed Thread | |||
| 0-80 | 3/64 | .0469 | 54 | .0545 |
| 1-64 | 53 | .0595 | 1.65 mm | .065 |
| 1-72 | 53 | ,0595 | 1.7 mm | .0669 |
| 2-56 | 50 | .0700 | 5/64 | .0781 |
| 2-64 | 50 | .0700 | 2 mm | .0787 |
| 3-48 | 46 | .0810 | 43 | .089 |
| 3-56 | 45 | .0820 | 2.3 mm | .0906 |
| 4-40 | 43 | .0890 | 39 | .0995 |
| 4-48 | 3/32 | .0938 | 2.6 mm | .1024 |
| 5-40 | 38 | .1015 | 33 | .113 |
| 5-44 | 37 | .1040 | 2.9 mm | .1142 |
| 6-32 | 34 | .1110 | 1/8 | .125 |
| 6-40 | 32 | .1160 | 3.2 mm | .1260 |
| 8-32 | 29 | .1360 | 25 | .1495 |
| 8-36 | 29 | .1360 | 24 | .1520 |
| 10-24 | 23 | .1540 | 11/64 | .1719 |
| 10-32 | 20 | .1610 | 16 | .1770 |
| 12-24 | 15 | .1800 | 5 mm | .1968 |
| 12-28 | 13 | .1850 | 8 | .1990 |
| 1/4-20 | 13/64 | .2031 | 1 | .2280 |
| 1/4-28 | 7/32 | .2187 | A | .2340 |
| 5/16-18 | G | .2610 | 7.3 mm | .2874 |
| 5/16-24 | J | .2770 | M | .2950 |
| 3/8-16 | O | .3160 | S | .3480 |
| 3/8-24 | R | .3390 | T | .358 |
| 7/16-14 | U | .3680 | 13/32 | .406 |
| 7/16-20 | 25/64 | .3906 | 10.5 mm | .4134 |
| 1/2-13 | 27/64 | .4219 | * | .466 |
| 1/2-20 | 29/64 | .4531 | * | .478 |
| 9/16-12 | 31/64 | .4844 | * | .525 |
| 9/16-18 | 33/64 | .5156 | * | ,538 |
| 5/8-11 | 35/64 | .5469 | * | .584 |
| 5/8-18 | 37/64 | .5781 | * | .600 |
| 11/16-11 | 39/64 | .6094 | * | .646 |
| 11/16-16 | 5/8 | .6250 | * | .660 |
| 3/4-10 | 21/32 | .6562 | 45/64 | .7031 |
| 3/4-16 | 11/16 | .6875 | * | .722 |
| 7/8-9 | 49/64 | |||
| 7/8-14 | 13/16 | |||
| 1-8 | 7/8 | |||
| 1-4 | 15/16 | |||
| 1-1/8-7 | 63/64 | |||
| 1-1/8-12 | 1-3/64 | |||
CUT TAP NOTE: At times, you can drill a slightly larger hole to make the tapping process a bit easier. This can be done without sacrificing much of the thread’s strength. This is because most of a thread’s strength is found at its base. By making the hole larger, you are essentially cutting off the tip of a thread, not its base. You are also lowering the amount of resistance encountered while cutting the thread. This is a trick that some machinists use when they are concerned about breaking a tap tool in a hole, lowering the horsepower (HP) requirement for a self-reversing tap head or automatic tapping machine such as a Control Feed Tapper or Lead Screw tap machine.