UNC
Unified National Coarse thread, Standardised in 1918. Derived from British Standard Whitworth and has the same thread angle of 60°.
| Size | Tapping Drill mm | Pitch mm | TPI | OD mm |
| 2-56 UNC | 1.85 | 0.45 | 56 | 2.18 |
| 3-48 UNC | 2.10 | 0.53 | 48 | 2.51 |
| 4-40 UNC | 2.35 | 0.64 | 40 | 2.84 |
| 6-32 UNC | 2.84 | 0.79 | 32 | 3.51 |
| 8-32 UNC | 3.50 | 0.79 | 32 | 4.17 |
| 10-24 UNC | 3.90 | 1.06 | 24 | 4.83 |
| 12-24 UNC | 4.55 | 1.06 | 24 | 5.49 |
| 1/4-20 UNC | 5.30 | 1.27 | 20 | 6.35 |
| 5/16-18 UNC | 6.60 | 1.41 | 18 | 7.94 |
| 3/8-16 UNC | 8.00 | 1.59 | 16 | 9.53 |
| 7/16-14 UNC | 9.40 | 1.81 | 14 | 11.11 |
| 1/2-13 UNC | 10.80 | 1.95 | 13 | 12.70 |
| 9/16-12 UNC | 12.25 | 2.12 | 12 | 14.29 |
| 5/8-11 UNC | 13.50 | 2.31 | 11 | 15.88 |
| 3/4-10 UNC | 16.50 | 2.54 | 10 | 19.05 |
| 7/8-9 UNC | 19.45 | 2.82 | 9 | 22.23 |
| 1-8 UNC | 22.25 | 3.18 | 8 | 25.40 |
See also: British Association Threads, British Standard Whitworth, Thread, UNF.
Subjects: Mechanical Engineering