Unified National Fine (UNF) Thread Chart
Industry Standard: ASME B1.1
Unified National Fine (UNF) threads feature a finer pitch (higher number of threads per inch) compared to the UNC series. UNF threads are the preferred standard in the automotive, aerospace, and precision manufacturing industries due to their high tensile strength and tight adjustment capabilities.
| Size | Ø Major (in) | TPI | Ø Pitch (in) | Ø Minor (in) | Tap Drill (in) | Stress Area (in²) |
|---|---|---|---|---|---|---|
| #0-80 UNF | 0.0600 | 80 | 0.0519 | 0.0465 | 0.0475 | 0.0018 |
| #1-72 UNF | 0.0730 | 72 | 0.0640 | 0.0580 | 0.0591 | 0.0028 |
| #2-64 UNF | 0.0860 | 64 | 0.0759 | 0.0691 | 0.0704 | 0.0039 |
| #3-56 UNF | 0.0990 | 56 | 0.0874 | 0.0797 | 0.0811 | 0.0052 |
| #4-48 UNF | 0.1120 | 48 | 0.0985 | 0.0894 | 0.0912 | 0.0066 |
| #5-44 UNF | 0.1250 | 44 | 0.1102 | 0.1004 | 0.1023 | 0.0083 |
| #6-40 UNF | 0.1380 | 40 | 0.1218 | 0.1109 | 0.1130 | 0.0101 |
| #8-36 UNF | 0.1640 | 36 | 0.1460 | 0.1339 | 0.1362 | 0.0147 |
| #10-32 UNF | 0.1900 | 32 | 0.1697 | 0.1562 | 0.1588 | 0.0200 |
| #12-28 UNF | 0.2160 | 28 | 0.1928 | 0.1773 | 0.1803 | 0.0258 |
| 1/4-28 UNF | 0.2500 | 28 | 0.2268 | 0.2113 | 0.2143 | 0.0364 |
| 5/16-24 UNF | 0.3125 | 24 | 0.2854 | 0.2674 | 0.2708 | 0.0581 |
| 3/8-24 UNF | 0.3750 | 24 | 0.3479 | 0.3299 | 0.3333 | 0.0878 |
| 7/16-20 UNF | 0.4375 | 20 | 0.4050 | 0.3834 | 0.3875 | 0.1187 |
| 1/2-20 UNF | 0.5000 | 20 | 0.4675 | 0.4459 | 0.4500 | 0.1600 |
| 9/16-18 UNF | 0.5625 | 18 | 0.5264 | 0.5024 | 0.5069 | 0.2030 |
| 5/8-18 UNF | 0.6250 | 18 | 0.5889 | 0.5649 | 0.5694 | 0.2560 |
| 3/4-16 UNF | 0.7500 | 16 | 0.7094 | 0.6823 | 0.6875 | 0.3730 |
| 7/8-14 UNF | 0.8750 | 14 | 0.8286 | 0.7977 | 0.8036 | 0.5095 |
| 1"-12 UNF | 1.0000 | 12 | 0.9459 | 0.9098 | 0.9167 | 0.6630 |
| 1-1/8-12 UNF | 1.1250 | 12 | 1.0709 | 1.0348 | 1.0417 | 0.8557 |
| 1-1/4-12 UNF | 1.2500 | 12 | 1.1959 | 1.1598 | 1.1667 | 1.0729 |
| 1-3/8-12 UNF | 1.3750 | 12 | 1.3209 | 1.2848 | 1.2917 | 1.3147 |
| 1-1/2-12 UNF | 1.5000 | 12 | 1.4459 | 1.4098 | 1.4167 | 1.5810 |
Standard FAQs
Does UNF have higher strength than UNC?
Yes. Because the threads are shallower, the core (minor diameter) of a UNF bolt is thicker than a UNC bolt of the same size, resulting in a larger stress area and higher tensile capacity.
Are UNF threads easily stripped?
No, but because they have a finer pitch, they require longer thread engagement and are more susceptible to cross-threading during assembly compared to UNC.