Unified National Extra Fine Thread Chart
22 thread sizes with dimensions calculated per ASME B1.1. Click any thread for full specifications.
| Thread | TPI | Major Ø (in) | Pitch Ø (in) | Minor Ø (in) | Tap Drill | Stress Area (in²) |
|---|---|---|---|---|---|---|
| #12-32 UNEF | 32 | 0.216 | 0.1957 | 0.1777 | #14 | 0.0270 |
| 1/4-32 UNEF | 32 | 0.25 | 0.2297 | 0.2117 | 7/32" | 0.0379 |
| 5/16-32 UNEF | 32 | 0.3125 | 0.2922 | 0.2742 | J | 0.0625 |
| 3/8-32 UNEF | 32 | 0.375 | 0.3547 | 0.3367 | R | 0.0932 |
| 7/16-28 UNEF | 28 | 0.4375 | 0.4143 | 0.3937 | X | 0.1274 |
| 1/2-28 UNEF | 28 | 0.5 | 0.4768 | 0.4562 | 15/32" | 0.1700 |
| 9/16-24 UNEF | 24 | 0.5625 | 0.5354 | 0.5114 | 33/64" | 0.2139 |
| 5/8-24 UNEF | 24 | 0.625 | 0.5979 | 0.5739 | 37/64" | 0.2682 |
| 3/4-20 UNEF | 20 | 0.75 | 0.7175 | 0.6887 | 45/64" | 0.3863 |
| 7/8-20 UNEF | 20 | 0.875 | 0.8425 | 0.8137 | 53/64" | 0.5362 |
| 1-20 UNEF | 20 | 1 | 0.9675 | 0.9387 | 61/64" | 0.7107 |
| 1-1/16-18 UNEF | 18 | 1.0625 | 1.0264 | 0.9943 | 1" | 0.7986 |
| 1-1/8-18 UNEF | 18 | 1.125 | 1.0889 | 1.0568 | 1-1/16" | 0.9007 |
| 1-3/16-18 UNEF | 18 | 1.1875 | 1.1514 | 1.1193 | 1-1/8" | 1.0089 |
| 1-1/4-18 UNEF | 18 | 1.25 | 1.2139 | 1.1818 | 1-3/16" | 1.1232 |
| 1-5/16-18 UNEF | 18 | 1.3125 | 1.2764 | 1.2443 | 1-1/4" | 1.2437 |
| 1-3/8-18 UNEF | 18 | 1.375 | 1.3389 | 1.3068 | 1-5/16" | 1.3703 |
| 1-7/16-18 UNEF | 18 | 1.4375 | 1.4014 | 1.3693 | 1-3/8" | 1.5030 |
| 1-1/2-18 UNEF | 18 | 1.5 | 1.4639 | 1.4318 | 1-7/16" | 1.6419 |
| 1-9/16-18 UNEF | 18 | 1.5625 | 1.5264 | 1.4943 | 1-1/2" | 1.7869 |
| 1-5/8-18 UNEF | 18 | 1.625 | 1.5889 | 1.5568 | 1-9/16" | 1.9381 |
| 1-11/16-18 UNEF | 18 | 1.6875 | 1.6514 | 1.6193 | 1-5/8" | 2.0954 |