UNRF and UNREF Thread Chart
| BASIC DIMENSIONS AND PITCH | |||
|---|---|---|---|
| Root form / size | Basic major diameter (in) | Pitch (in) | TPI |
| 1/4-28 UNRF | 0.2500 | 0.03571 | 28 |
| 5/16-24 UNRF | 0.3125 | 0.04167 | 24 |
| 3/8-24 UNRF | 0.3750 | 0.04167 | 24 |
| 7/16-20 UNRF | 0.4375 | 0.05000 | 20 |
| 1/2-20 UNRF | 0.5000 | 0.05000 | 20 |
| 5/8-18 UNRF | 0.6250 | 0.05556 | 18 |
| 3/4-16 UNRF | 0.7500 | 0.06250 | 16 |
| 1-12 UNRF | 1.0000 | 0.08333 | 12 |
| 1/4-32 UNREF | 0.2500 | 0.03125 | 32 |
| 5/16-32 UNREF | 0.3125 | 0.03125 | 32 |
| 3/8-32 UNREF | 0.3750 | 0.03125 | 32 |
| 7/16-28 UNREF | 0.4375 | 0.03571 | 28 |
| 1/2-28 UNREF | 0.5000 | 0.03571 | 28 |
| 5/8-24 UNREF | 0.6250 | 0.04167 | 24 |
These rows show representative fine and extra-fine rolled-root callouts. The root profile does not change the nominal diameter/pitch notation; consult ASME B1.1 for the standard combination and dimensional limits.