Heavy Hex Bolts
Larger heads for higher bearing area in heavy construction and flange service.
Heavy pattern heads to ASME B18.2.1, commonly in A193 B7 and A325/A490 structural grades.
Specifications & technical data.
Heavy hex bolts to ASME B18.2.1 — the heavy pattern carries a wider, thicker head than a standard hex bolt of the same diameter, for flanged and high-load structural connections.
Download our heavy hex bolt dimensioning table (PDF)
| Nominal Size or Product Diameter | E | F | G | H | R | LT | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Full-size Body Diameter | Width Across Flats | Width Across Corners | Height | Radius of Fillet | Nominal Thread Length for Bolt Lengths | ||||||||||
| Max. | Min. | Basic | Max. | Min. | Max. | Min. | Basic | Max. | Min. | Max. | Min. | 6 in. & Shorter | Over 6 in. | ||
| 3/8" | 0.3750 | 0.388 | 0.360 | 11/16 | 0.688 | 0.669 | 0.794 | 0.763 | 1/4 | 0.268 | 0.226 | 0.03 | 0.01 | 1.000 | 1.250 |
| 1/2" | 0.5000 | 0.515 | 0.482 | 7/8 | 0.875 | 0.850 | 1.010 | 0.969 | 11/32 | 0.364 | 0.302 | 0.03 | 0.01 | 1.250 | 1.500 |
| 5/8" | 0.6250 | 0.642 | 0.605 | 1-1/16 | 1.062 | 1.031 | 1.227 | 1.175 | 27/64 | 0.444 | 0.378 | 0.06 | 0.02 | 1.500 | 1.750 |
| 3/4" | 0.7500 | 0.768 | 0.729 | 1-1/4 | 1.250 | 1.212 | 1.443 | 1.383 | 1/2 | 0.524 | 0.455 | 0.06 | 0.02 | 1.750 | 2.000 |
| 7/8" | 0.8750 | 0.895 | 0.852 | 1-7/16 | 1.438 | 1.394 | 1.660 | 1.589 | 37/64 | 0.604 | 0.531 | 0.06 | 0.02 | 2.000 | 2.250 |
| 1" | 1.0000 | 1.022 | 0.976 | 1-5/8 | 1.625 | 1.575 | 1.876 | 1.796 | 43/64 | 0.700 | 0.591 | 0.09 | 0.03 | 2.250 | 2.500 |
| 1-1/8" | 1.1250 | 1.149 | 1.098 | 1-13/16 | 1.812 | 1.756 | 2.093 | 2.002 | 3/4 | 0.780 | 0.658 | 0.09 | 0.03 | 2.500 | 2.750 |
| 1-1/4" | 1.2500 | 1.277 | 1.223 | 2 | 2.000 | 1.938 | 2.309 | 2.209 | 27/32 | 0.876 | 0.749 | 0.09 | 0.03 | 2.750 | 3.000 |
| 1-3/8" | 1.3750 | 1.404 | 1.345 | 2-3/16 | 2.188 | 2.119 | 2.526 | 2.416 | 29/32 | 0.940 | 0.810 | 0.09 | 0.03 | 3.000 | 3.250 |
| 1-1/2" | 1.5000 | 1.531 | 1.470 | 2-3/8 | 2.375 | 2.300 | 2.742 | 2.622 | 1 | 1.036 | 0.902 | 0.09 | 0.03 | 3.250 | 3.500 |
| 1-5/8" | 1.6250 | 1.658 | 1.591 | 2-9/16 | 2.562 | 2.481 | 2.959 | 2.829 | 1-3/32 | 1.116 | 0.978 | 0.09 | 0.03 | 3.500 | 3.750 |
| 1-3/4" | 1.7500 | 1.785 | 1.716 | 2-3/4 | 2.750 | 2.662 | 3.175 | 3.035 | 1-5/32 | 1.196 | 1.054 | 0.12 | 0.04 | 3.750 | 4.000 |
| 1-7/8" | 1.8750 | 1.912 | 1.839 | 2-15/16 | 2.938 | 2.844 | 3.392 | 3.242 | 1-1/4 | 1.276 | 1.130 | 0.12 | 0.04 | 4.000 | 4.250 |
| 2" | 2.0000 | 2.039 | 1.964 | 3-1/8 | 3.125 | 3.025 | 3.608 | 3.449 | 1-11/32 | 1.388 | 1.175 | 0.12 | 0.04 | 4.250 | 4.500 |
| 2-1/4" | 2.2500 | 2.305 | 2.214 | 3-1/2 | 3.500 | 3.388 | 4.041 | 3.862 | 1-1/2 | 1.548 | 1.327 | 0.19 | 0.06 | 4.750 | 5.000 |
| 2-1/2" | 2.5000 | 2.559 | 2.461 | 3-7/8 | 3.875 | 3.750 | 4.474 | 4.275 | 1-21/32 | 1.708 | 1.479 | 0.19 | 0.06 | 5.250 | 5.500 |
| 2-3/4" | 2.7500 | 2.827 | 2.711 | 4-1/4 | 4.250 | 4.112 | 4.907 | 4.688 | 1-13/16 | 1.869 | 1.632 | 0.19 | 0.06 | 5.750 | 6.000 |
| 3" | 3.0000 | 3.081 | 2.961 | 4-5/8 | 4.625 | 4.475 | 5.340 | 5.102 | 2 | 2.060 | 1.815 | 0.19 | 0.06 | 6.250 | 6.500 |
All dimensions in inches, per ASME B18.2.1-2012. L = nominal bolt length. Confirm requirements with our estimating team.
Standards.
What are heavy hex bolts?
A heavy hex bolt carries the heavy head pattern — wider across the flats and taller than the standard hex head on the same thread. The extra section spreads load over more bearing area and develops the full strength of high-strength materials, which is why pressure and structural specifications call for the heavy series.
- Heavy pattern head — more across-flats and height
- Pairs with heavy hex nuts
- The head style behind A325/A490-type structural bolting
- B7, B16, L7 and stainless as standard
Heavy hex bolts vs. heavy hex screws
The bolt runs a plain bearing face and wider tolerances for use with a nut; the heavy hex screw adds a washer face and closer tolerances. Flange and structural work almost always means the bolt.
Other names
- Heavy hexagon bolts
- Heavy pattern bolts
- Heavy hex machine bolts
Tips for purchasing
- Specify heavy pattern explicitly — a standard hex head in the same grade is not a substitute.
- Order nuts and washers as a certified set — 2H nuts with B7 bolts and through-hardened washers.
- Hot-dip galvanized assemblies need oversize-tapped nuts — we handle the fit.
- Full material test reports come standard.
Materials.
Representative capabilities — every item is manufactured or certified to your specification. Confirm requirements with our estimating team.
