Heavy hex bolts have a larger head than a standard hex bolt, measuring 1/8 of an inch larger than a finished hex bolt of the same diameter. To determine hex size, the formula is one-and-a-half times the diameter plus 1/8″.
Heavy hex bolts are generally specified for high temperature or high pressure applications, particularly where bolt heads will bear against flanges. Commonly used in a variety of high strength industrial applications such as steel fabrication and construction including bridges, highway structures and buildings.
Standard diameters are 1/2″ and larger.
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| E | F | H | ||
| Nominal | Body Diameter | Across Flats | Height | |
| Size | Max | Min | Basic | Basic |
| 1/2 | 0.515 | 0.482 | 7/8 | 11/32 |
| 5/8 | 0.642 | 0.605 | 11/16 | 27/64 |
| 3/4 | 0.768 | 0.729 | 1-1/4 | 1/2 |
| 7/8 | 0.895 | 0.852 | 1-7/16 | 37/64 |
| 1-1/8 | 1.149 | 1.098 | 1-13/16 | 3/4 |
| 1-1/4 | 1.277 | 1.223 | 2 | 27/32 |
| 1-3/8 | 1.404 | 1.345 | 2-3/16 | 29/32 |
| 1-1/2 | 1.531 | 1.470 | 2-3/8 | 1 |
| 1-3/4 | 1.785 | 1.716 | 2-3/4 | 1-5/32 |
| 2 | 2.039 | 1.964 | 3-1/8 | 1-11/32 |
| 2-1/4 | 2.305 | 2.214 | 3-1/2 | 1-1/2 |
| 2-1/2 | 2.559 | 2.461 | 3-7/8 | 1-21/32 |
| 2-3/4 | 2.827 | 2.711 | 4-1/4 | 1-13/16 |
| 3 | 3.081 | 2.961 | 4-5/8 | 2 |
