Thread series cover designations of diameter/pitch combinations that are measured by the number of
threads per inch (TPI) applied to a single diameter.
Coarse Thread Series (UNC/UNRC) is the most common designation for general application bolts and
nuts. Coarse thread is beneficial, because they are less likely to cross thread, more tolerant in adverse
conditions and facilitate quick assembly.
| Nominal Size & Threads Per Inch |
Basic Pitch Diameter (Inches) |
Section at Minor Diameter (ln2) |
Tensile Stress Area (ln2) |
| 3 /8 – 16 | 0.3344 | 0.0678 | 0.0775 |
| 7/16- 14 | 0.3911 | 0.0933 | 0.1063 |
| 1 /2 – 13 | 0.4500 | 0.1257 | 0.1419 |
| 9/16-12 | 0.5084 | 0.162 | 0.182 |
| 5/8-11 | 0.5660 | 0.202 | 0.226 |
| 3/4- 10 | 0.6850 | 0.302 | 0.334 |
| 7/8-9 | 0.8028 | 0.419 | 0.462 |
| 1 – 8 | 0.9188 | 0.551 | 0.606 |
| 1-1/8 -7 | 1.0322 | 0.693 | 0.763 |
| 1-1/4-7 | 1.1572 | 0.890 | 0.969 |
| 1-3/8-6 | 1.2667 | 1.054 | 1.155 |
| 1-1/2- 6 | 1.3917 | 1.294 | 1.405 |
| 1-3/4 – 5 | 1.6201 | 1.74 | 1.90 |
| 2-4-1/2 | 1.8557 | 2.30 | 2.50 |
| 2-1/4- 4-1/2 | 2.1057 | 3.02 | 3.25 |
| 2 – 1 / 2 – 4 | 2.3376 | 3.72 | 4.00 |
| 2 – 3 / 4 – 4 | 2.5876 | 4.62 | 4.93 |
| 3 – 4 | 2.8376 | 5.62 | 5.97 |
| 3 – 1 / 4 – 4 | 3.0876 | 6.72 | 7.10 |
| 3 – 1 / 2 – 4 | 3.3376 | 7.92 | 8.33 |
| 3 – 3 / 4 – 4 | 3.5876 | 9.21 | 9.66 |
| 4 – 4 | 3.8376 | 10.61 | 11.08 |
