Unified Thread Recommended Tapping Drill and Clearance Hole Sizes
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Use these tables for calculating the relevant size drill bit and clearance hole for unified threads.
All dimensions are in millimeters (mm).
Screw Size | No. of Threads Per Inch | Minor Diameter | Tap Drills | Clearance Hole Drills - All Materials | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Aluminum, Brass & Plastics 75% Thread | Stainless Steel, Steels & Iron 50% Thread | Close Fit | Free Fit | ||||||||
No. or Diameter | Major Diameter | Drill Size | Decimal Equiv. | Drill Size | Decimal Equiv. | Drill Size | Decimal Equiv. | Drill Size | Decimal Equiv. | ||
0 | 0.06 | 80 | 0.0447 | 3/64 | 0.0469 | 55 | 0.052 | 52 | 0.0635 | 50 | 0.07 |
1 | 0.073 | 64 | 0.0538 | 53 | 0.0595 | 1/16 | 0.0625 | 48 | 0.076 | 46 | 0.081 |
72 | 0.056 | 53 | 0.0595 | 52 | 0.0635 | ||||||
2 | 0.086 | 56 | 0.0641 | 50 | 0.07 | 49 | 0.073 | 43 | 0.089 | 41 | 0.096 |
64 | 0.0668 | 50 | 0.07 | 48 | 0.076 | ||||||
3 | 0.099 | 48 | 0.0734 | 47 | 0.0785 | 44 | 0.086 | 37 | 0.104 | 35 | 0.11 |
56 | 0.0771 | 45 | 0.082 | 43 | 0.089 | ||||||
4 | 0.112 | 40 | 0.0813 | 43 | 0.089 | 41 | 0.096 | 32 | 0.116 | 30 | 0.1285 |
48 | 0.0864 | 42 | 0.0935 | 40 | 0.098 | ||||||
5 | 0.125 | 40 | 0.0943 | 38 | 0.1015 | 7/64 | 0.1094 | 30 | 0.1285 | 29 | 0.136 |
44 | 0.0971 | 37 | 0.104 | 35 | 0.11 | ||||||
6 | 0.138 | 32 | 0.0997 | 36 | 0.1065 | 32 | 0.116 | 27 | 0.144 | 25 | 0.1495 |
8 | 0.164 | 32 | 0.1257 | 29 | 0.136 | 27 | 0.144 | 18 | 0.1695 | 16 | 0.177 |
36 | 0.1299 | 29 | 0.136 | 26 | 0.147 | ||||||
10 | 0.19 | 24 | 0.1389 | 25 | 0.1495 | 20 | 0.161 | 9 | 0.196 | 7 | 0.201 |
32 | 0.1517 | 21 | 0.159 | 18 | 0.1695 | ||||||
12 | 0.216 | 24 | 0.1649 | 16 | 0.177 | 12 | 0.189 | 2 | 0.221 | 1 | 0.228 |
28 | 0.1722 | 14 | 0.182 | 10 | 0.1935 | ||||||
32 | 0.1777 | 13 | 0.185 | 9 | 0.196 | ||||||
1/4 | 0.25 | 20 | 0.1887 | 7 | 0.201 | 7/32 | 0.2188 | F | 0.257 | H | 0.266 |
28 | 0.2062 | 3 | 0.213 | 1 | 0.228 | ||||||
32 | 0.2117 | 7/32 | 0.2188 | 1 | 0.228 | ||||||
5/16 | 0.3125 | 18 | 0.2443 | F | 0.257 | J | 0.277 | P | 0.323 | Q | 0.332 |
24 | 0.2614 | I | 0.272 | 9/32 | 0.2812 | ||||||
32 | 0.2742 | 9/32 | 0.2812 | L | 0.29 | ||||||
3/8 | 0.375 | 16 | 0.2983 | 5/16 | 0.3125 | Q | 0.332 | W | 0.386 | X | 0.397 |
24 | 0.3239 | Q | 0.332 | S | 0.348 | ||||||
32 | 0.3367 | 11/32 | 0.3438 | T | 0.358 | ||||||
7/16 | 0.4375 | 14 | 0.3499 | U | 0.368 | 25/64 | 0.3906 | 29/64 | 0.4531 | 15/32 | 0.4687 |
20 | 0.3762 | 25/64 | 0.3906 | 13/32 | 0.4062 | ||||||
28 | 0.3937 | Y | 0.404 | Z | 0.413 | ||||||
1/2 | 0.5 | 13 | 0.4056 | 27/64 | 0.4219 | 29/64 | 0.4531 | 33/64 | 0.5156 | 17/32 | 0.5312 |
20 | 0.4387 | 29/64 | 0.4531 | 15/32 | 0.4688 | ||||||
28 | 0.4562 | 15/32 | 0.4688 | 15/32 | 0.4688 | ||||||
9/16 | 0.5625 | 12 | 0.4603 | 31/64 | 0.4844 | 33/64 | 0.5156 | 37/64 | 0.5781 | 19/32 | 0.5938 |
18 | 0.4943 | 33/64 | 0.5156 | 17/32 | 0.5312 | ||||||
24 | 0.5114 | 33/64 | 0.5156 | 17/32 | 0.5312 | ||||||
5/8 | 0.625 | 11 | 0.5135 | 17/32 | 0.5312 | 9/16 | 0.5625 | 41/64 | 0.6406 | 21/32 | 0.6562 |
18 | 0.5568 | 37/64 | 0.5781 | 19/32 | 0.5938 | ||||||
24 | 0.5739 | 37/64 | 0.5781 | 19/32 | 0.5938 | ||||||
11/16 | 0.6875 | 24 | 0.6364 | 41/64 | 0.6406 | 21/32 | 0.6562 | 45/64 | 0.7031 | 23/32 | 0.6562 |
3/4 | 0.75 | 10 | 0.6273 | 21/32 | 0.6562 | 11/16 | 0.6875 | 49/64 | 0.7656 | 25/32 | 0.7812 |
16 | 0.6733 | 11/16 | 0.6875 | 45/64 | 0.7031 | ||||||
20 | 0.6887 | 45/64 | 0.7031 | 23/32 | 0.7188 | ||||||
13/16 | 0.8125 | 20 | 0.7512 | 49/64 | 0.7656 | 25/32 | 0.7812 | 53/64 | 0.8281 | 27/32 | 0.8438 |
7/8 | 0.875 | 9 | 0.7387 | 49/64 | 0.7656 | 51/64 | 0.7969 | 57/64 | 0.8906 | 29/32 | 0.9062 |
14 | 0.7874 | 13/16 | 0.8125 | 53/64 | 0.8281 | ||||||
20 | 0.8137 | 53/64 | 0.8281 | 27/32 | 0.8438 | ||||||
15/16 | 0.9375 | 20 | 0.8762 | 57/64 | 0.8906 | 29/32 | 0.9062 | 61/64 | 0.9531 | 31/32 | 0.9688 |
1 | 1 | 8 | 0.8466 | 7/8 | 0.875 | 59/64 | 0.9219 | 1-1/64 | 1.0156 | 1-1/32 | 1.0313 |
12 | 0.8978 | 15/16 | 0.9375 | 61/64 | 0.9531 | ||||||
20 | 0.9387 | 61/64 | 0.9531 | 31/32 | 0.9688 | ||||||
1-1/16 | 1.0625 | 18 | 0.9943 | 1 | 1 | 1-1/64 | 1.0156 | 1-5/64 | 1.0781 | 1-3/32 | 1.0938 |
1-1/8 | 1.125 | 7 | 0.9497 | 63/64 | 0.9844 | 1-1/32 | 1.0313 | 1-9/64 | 1.1406 | 1-5/32 | 1.1562 |
12 | 1.0228 | 1-3/64 | 1.0469 | 1-5/64 | 1.0781 | ||||||
18 | 1.0568 | 1-1/16 | 1.0625 | 1-5/64 | 1.0781 | ||||||
1-3/16 | 1.1875 | 18 | 1.1193 | 1-1/8 | 1.125 | 1-9/64 | 1.1406 | 1-13/64 | 1.2031 | 1-7/32 | 1.2188 |
1-1/4 | 1.25 | 7 | 1.0747 | 1-7/64 | 1.1094 | 1-5/32 | 1.1562 | 1-17/64 | 1.2656 | 1-9/32 | 1.2812 |
12 | 1.1478 | 1-11/64 | 1.1719 | 1-13/64 | 1.2031 | ||||||
18 | 1.1818 | 1-3/16 | 1.1875 | 1-13/64 | 1.2031 | ||||||
1-5/16 | 1.3125 | 18 | 1.2443 | 1-1/4 | 1.25 | 1-17/64 | 1.2656 | 1-21/64 | 1.3281 | 1-11/32 | 1.3438 |
1-3/8 | 1.375 | 6 | 1.1705 | 1-7/32 | 1.2187 | 1-17/64 | 1.2656 | 1-25/64 | 1.3906 | 1-13/32 | 1.4062 |
12 | 1.2728 | 1-19/64 | 1.2969 | 1-21/64 | 1.3281 | ||||||
18 | 1.3068 | 1-5/16 | 1.3125 | 1-21/64 | 1.3281 | ||||||
1-7/16 | 1.4375 | 18 | 1.3693 | 1-3/8 | 1.375 | 1-25/64 | 1.3906 | 1-29/64 | 1.4531 | 1-15/32 | 1.4688 |
1-1/2 | 1.5 | 6 | 1.2955 | 1-11/32 | 1.3437 | 1-25/64 | 1.3906 | 1-33/64 | 1.5156 | 1-17/32 | 1.5312 |
12 | 1.3978 | 1-27/64 | 1.4219 | 1-7/16 | 1.4375 | ||||||
18 | 1.4318 | 1-7/16 | 1.4375 | 1-29/64 | 1.4531 | ||||||
1-9/16 | 1.5625 | 18 | 1.4943 | 1-12 | 1.5 | 1-33/64 | 1.5156 | 1-37/64 | 1.5781 | 1-19/32 | 1.5938 |
1-5/8 | 1.625 | 18 | 1.5568 | 1-9/16 | 1.5625 | 1-37/64 | 1.5781 | 1-41/64 | 1.6406 | 1-21/32 | 1.6562 |
1-11/16 | 1.6875 | 18 | 1.6193 | 1-5/8 | 1.625 | 1-41/64 | 1.6406 | 1-45/64 | 1.7031 | 1-23/32 | 1.7188 |
1-3/4 | 1.75 | 5 | 1.5046 | 1-9/16 | 1.5625 | 1-5/8 | 1.625 | 1-49/64 | 1.7659 | 1-25/32 | 1.7812 |
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