ASME B18.2.1 Hex Bolts
ASME B18.2.1 Standard Dimensions for Hex Bolts
| Nominal Size or Basic product Diameter | Full-Size Body Diameter, E | Width Across Flats, F | Width Across Corners, G | Head Height, H | Radius of Fillet, R | Thread Length for Bolt Lengths, LT | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 6 in. & Shorter | Over 6 in. | ||||||||||||
| Max. | Min. | Max. | Min. | Max. | Min. | Max. | Min. | Max. | Min. | Nom. | Nom. | ||
| 1/4 | 0.2500 | 0.260 | 0.237 | 0.438 | 0.425 | 0.505 | 0.484 | 0.188 | 0.150 | 0.03 | 0.01 | 0.750 | 1.000 |
| 5/16 | 0.3125 | 0.324 | 0.298 | 0.500 | 0.484 | 0.577 | 0.552 | 0.235 | 0.195 | 0.03 | 0.01 | 0.875 | 1.125 |
| 3/8 | 0.3750 | 0.388 | 0.360 | 0.562 | 0.544 | 0.650 | 0.620 | 0.268 | 0.226 | 0.03 | 0.01 | 1.000 | 1.250 |
| 7/16 | 0.4375 | 0.452 | 0.421 | 0.625 | 0.603 | 0.722 | 0.687 | 0.316 | 0.272 | 0.03 | 0.01 | 1.125 | 1.375 |
| 1/2 | 0.5000 | 0.515 | 0.482 | 0.750 | 0.725 | 0.866 | 0.826 | 0.364 | 0.302 | 0.03 | 0.01 | 1.250 | 1.500 |
| 5/8 | 0.6250 | 0.642 | 0.605 | 0.938 | 0.906 | 1.083 | 1.033 | 0.444 | 0.378 | 0.06 | 0.02 | 1.500 | 1.750 |
| 3/4 | 0.7500 | 0.768 | 0.729 | 1.125 | 1.088 | 1.299 | 1.240 | 0.524 | 0.455 | 0.06 | 0.02 | 1.750 | 2.000 |
| 7/8 | 0.8750 | 0.895 | 0.852 | 1.312 | 1.269 | 1.516 | 1.447 | 0.604 | 0.531 | 0.06 | 0.02 | 2.000 | 2.250 |
| 1 | 1.0000 | 1.022 | 0.976 | 1.500 | 1.450 | 1.732 | 1.653 | 0.700 | 0.591 | 0.09 | 0.03 | 2.250 | 2.500 |
| 1 1/8 | 1.1250 | 1.149 | 1.098 | 1.688 | 1.631 | 1.949 | 1.859 | 0.780 | 0.658 | 0.09 | 0.03 | 2.500 | 2.750 |
| 1 1/4 | 1.2500 | 1.277 | 1.223 | 1.875 | 1.812 | 2.165 | 2.066 | 0.876 | 0.749 | 0.09 | 0.03 | 2.750 | 3.000 |
| 1 3/8 | 1.3750 | 1.404 | 1.345 | 2.062 | 1.994 | 2.382 | 2.273 | 0.940 | 0.810 | 0.09 | 0.03 | 3.000 | 3.250 |
| 1 1/2 | 1.5000 | 1.531 | 1.470 | 2.250 | 2.175 | 2.598 | 2.480 | 1.036 | 0.902 | 0.09 | 0.03 | 3.250 | 3.500 |
| 1 5/8 | 1.6250 | 1.658 | 1.591 | 2.438 | 2.356 | 2.815 | 2.616 | 1.116 | 0.978 | 0.09 | 0.03 | 3.500 | 3.750 |
| 1 3/4 | 1.7500 | 1.785 | 1.716 | 2.625 | 2.538 | 3.031 | 2.893 | 1.196 | 1.054 | 0.12 | 0.04 | 3.750 | 4.000 |
| 1 7/8 | 1.8750 | 1.912 | 1.839 | 2.812 | 2.719 | 3.248 | 3.099 | 1.276 | 1.130 | 0.12 | 0.04 | 4.000 | 4.250 |
| 2 | 2.000 | 2.039 | 1.964 | 3.000 | 2.9000 | 3.464 | 3.306 | 1.388 | 1.175 | 0.12 | 0.04 | 4.250 | 4.500 |
| 2 1/4 | 2.2500 | 2.305 | 2.214 | 3.375 | 3.262 | 3.897 | 3.719 | 1.548 | 1.327 | 0.19 | 0.06 | 4.750 | 5.000 |
| 2 1/2 | 2.5000 | 2.559 | 2.461 | 3.750 | 3.625 | 4.330 | 4.133 | 1.708 | 1.479 | 0.19 | 0.06 | 5.250 | 5.500 |
| 2 3/4 | 2.7500 | 2.827 | 2.711 | 4.125 | 3.988 | 4.763 | 4.546 | 1.869 | 1.632 | 0.19 | 0.06 | 5.750 | 6.000 |
| 3 | 3.000 | 3.081 | 2.961 | 4.500 | 4.350 | 5.196 | 4.959 | 2.060 | 1.815 | 0.19 | 0.06 | 6.250 | 6.500 |
| 3 1/4 | 3.2500 | 3.335 | 3.210 | 4.875 | 4.712 | 5.629 | 5.372 | 2.251 | 1.936 | 0.19 | 0.06 | 6.750 | 7.000 |
| 3 1/2 | 3.5000 | 3.589 | 3.461 | 5.250 | 5.075 | 6.062 | 5.786 | 2.380 | 2.057 | 0.19 | 0.06 | 7.250 | 7.500 |
| 3 3/4 | 3.7500 | 3.858 | 3.726 | 5.625 | 5.437 | 6.495 | 6.198 | 2.572 | 2.241 | 0.19 | 0.06 | 7.750 | 8.000 |
| 4 | 4.000 | 4.111 | 3.975 | 6.000 | 5.800 | 6.928 | 6.612 | 2.764 | 2.424 | 0.19 | 0.06 | 8.250 | 8.500 |