Unified National Coarse (UNC) Thread Chart
Industry Standard: ASME B1.1
Unified National Coarse (UNC) threads are the standard coarse thread series used primarily in the United States and Canada. Regulated under the ASME B1.1 standard, UNC threads are widely used for general engineering, construction, and assembly applications where quick assembly and resistance to thread stripping are desired.
| Size | Ø Major (in) | TPI | Ø Pitch (in) | Ø Minor (in) | Tap Drill (in) | Stress Area (in²) |
|---|---|---|---|---|---|---|
| #0-80 UNC | 0.0600 | 80 | 0.0519 | 0.0465 | 0.0475 | 0.0018 |
| #1-64 UNC | 0.0730 | 64 | 0.0629 | 0.0561 | 0.0574 | 0.0026 |
| #2-56 UNC | 0.0860 | 56 | 0.0744 | 0.0667 | 0.0681 | 0.0037 |
| #3-48 UNC | 0.0990 | 48 | 0.0855 | 0.0764 | 0.0782 | 0.0049 |
| #4-40 UNC | 0.1120 | 40 | 0.0958 | 0.0849 | 0.0870 | 0.0060 |
| #5-40 UNC | 0.1250 | 40 | 0.1088 | 0.0979 | 0.1000 | 0.0080 |
| #6-32 UNC | 0.1380 | 32 | 0.1177 | 0.1042 | 0.1068 | 0.0091 |
| #8-32 UNC | 0.1640 | 32 | 0.1437 | 0.1302 | 0.1328 | 0.0140 |
| #10-24 UNC | 0.1900 | 24 | 0.1629 | 0.1449 | 0.1483 | 0.0175 |
| #12-24 UNC | 0.2160 | 24 | 0.1889 | 0.1709 | 0.1743 | 0.0242 |
| 1/4-20 UNC | 0.2500 | 20 | 0.2175 | 0.1959 | 0.2000 | 0.0318 |
| 5/16-18 UNC | 0.3125 | 18 | 0.2764 | 0.2524 | 0.2569 | 0.0524 |
| 3/8-16 UNC | 0.3750 | 16 | 0.3344 | 0.3073 | 0.3125 | 0.0775 |
| 7/16-14 UNC | 0.4375 | 14 | 0.3911 | 0.3602 | 0.3661 | 0.1063 |
| 1/2-13 UNC | 0.5000 | 13 | 0.4500 | 0.4167 | 0.4231 | 0.1419 |
| 9/16-12 UNC | 0.5625 | 12 | 0.5084 | 0.4723 | 0.4792 | 0.1819 |
| 5/8-11 UNC | 0.6250 | 11 | 0.5660 | 0.5266 | 0.5341 | 0.2260 |
| 3/4-10 UNC | 0.7500 | 10 | 0.6850 | 0.6417 | 0.6500 | 0.3345 |
| 7/8-9 UNC | 0.8750 | 9 | 0.8028 | 0.7547 | 0.7639 | 0.4617 |
| 1"-8 UNC | 1.0000 | 8 | 0.9188 | 0.8647 | 0.8750 | 0.6057 |
| 1-1/8-7 UNC | 1.1250 | 7 | 1.0322 | 0.9704 | 0.9821 | 0.7633 |
| 1-1/4-7 UNC | 1.2500 | 7 | 1.1572 | 1.0954 | 1.1071 | 0.9691 |
| 1-3/8-6 UNC | 1.3750 | 6 | 1.2667 | 1.1946 | 1.2083 | 1.1549 |
| 1-1/2-6 UNC | 1.5000 | 6 | 1.3917 | 1.3196 | 1.3333 | 1.4052 |
| 1-3/4-5 UNC | 1.7500 | 5 | 1.6201 | 1.5335 | 1.5500 | 1.8995 |
| 2"-4.5 UNC | 2.0000 | 4.5 | 1.8557 | 1.7594 | 1.7778 | 2.4982 |
| 2-1/4-4.5 UNC | 2.2500 | 4.5 | 2.1057 | 2.0094 | 2.0278 | 3.2477 |
| 2-1/2-4 UNC | 2.5000 | 4 | 2.3376 | 2.2294 | 2.2500 | 3.9988 |
| 2-3/4-4 UNC | 2.7500 | 4 | 2.5876 | 2.4794 | 2.5000 | 4.9340 |
| 3"-4 UNC | 3.0000 | 4 | 2.8376 | 2.7294 | 2.7500 | 5.9674 |
| 3-1/4-4 UNC | 3.2500 | 4 | 3.0876 | 2.9794 | 3.0000 | 7.0989 |
| 3-1/2-4 UNC | 3.5000 | 4 | 3.3376 | 3.2294 | 3.2500 | 8.3286 |
| 3-3/4-4 UNC | 3.7500 | 4 | 3.5876 | 3.4794 | 3.5000 | 9.6565 |
| 4"-4 UNC | 4.0000 | 4 | 3.8376 | 3.7294 | 3.7500 | 11.0825 |
Standard FAQs
What is the difference between UNC and UNF threads?
UNC threads have fewer threads per inch (coarse pitch), whereas UNF threads have more threads per inch (fine pitch). UNC is preferred for general fastening, while UNF is used where higher tensile strength and vibration resistance are required.
What thread angle is used in Unified threads?
Unified threads (UNC, UNF, UNEF) use a 60-degree thread angle, identical to the ISO metric standard, but with imperial measurements (inches).