Head Style Requirements
When selecting an ASTM grade of fastener for a particular application, the chemical and mechanical requirements are normally considered first, but there are some fastener specifications that require a certain head style as well. Below is a chart showing some common ASTM grades and whether or not they have requirements for the pattern of forged head. It is important to keep in mind that this chart only specifies requirements in regards to headed bolts.
| Specification | Grade | Specified Head Configuration |
|---|---|---|
| ASTM A307 | A | Standard Hex |
| B | Heavy Hex | |
| ASTM F3125 | A325 | Heavy Hex Structural |
| A490 | ||
| ASTM A449 | Standard Hex | |
| ASTM A193 | B7 | Heavy Hex |
| B8 | ||
| B8M | ||
| ASTM A320 | L7 | Heavy Hex |
| B8 | ||
| B8M | ||
| ASTM A354 | BC | Standard Hex |
| BD | ||
| ASTM F1554 | Grade 36 | Unspecified |
| Grade 55 | ||
| Grade 105 | ||
| ASTM F593 | Alloy Group 1 | Standard Hex |
| Alloy Group 2 | ||
| SAE J429 | Grade 2 | Standard Hex |
| Grade 5 | ||
| Grade 8 | ||
| Head styles are unless otherwise specified. | ||
As you can see, most of the grades shown in this chart have a head style for which they are normally specified, however in most cases this can be changed if needed. Many of these ASTM grades may also allow for other configurations such as bent anchor bolts and straight rods.
As you can see, most of the grades shown in this chart have a head style that they are normally specified as, however in most cases this can be changed if needed. Many of these ASTM grades may also allow for other configurations such as bent anchor bolts and straight rods.
The following are two charts detailing the dimensions for a standard hex head versus a heavy hex head:
Hex Bolt Dimensions
| Bolt Diameter | D | F | C | H | |||||
|---|---|---|---|---|---|---|---|---|---|
| Body Diameter | Width Across Flats | Width Across Corners | Height | ||||||
| Max | Basic | Max | Min | Max | Min | Basic | Max | Min | |
| 1⁄2 | 0.515 | 3⁄4 | 0.750 | 0.725 | 0.866 | 0.826 | 11⁄32 | 0.364 | 0.302 |
| 5⁄8 | 0.642 | 15⁄16 | 0.938 | 0.906 | 1.083 | 1.033 | 27⁄64 | 0.444 | 0.378 |
| 3⁄4 | 0.768 | 11⁄8 | 1.125 | 1.088 | 1.299 | 1.240 | 1⁄2 | 0.524 | 0.455 |
| 7⁄8 | 0.895 | 15⁄16 | 1.312 | 1.269 | 1.516 | 1.447 | 37⁄64 | 0.604 | 0.531 |
| 1 | 1.022 | 11⁄2 | 1.500 | 1.450 | 1.732 | 1.653 | 43⁄64 | 0.700 | 0.591 |
| 11⁄8 | 1.149 | 111⁄16 | 1.688 | 1.631 | 1.949 | 1.859 | 3⁄4 | 0.780 | 0.658 |
| 11⁄4 | 1.277 | 17⁄8 | 1.875 | 1.812 | 2.165 | 2.066 | 27⁄32 | 0.876 | 0.749 |
| 13⁄8 | 1.404 | 21⁄16 | 2.062 | 1.994 | 2.382 | 2.273 | 29⁄32 | 0.940 | 0.810 |
| 11⁄2 | 1.531 | 21⁄4 | 2.250 | 2.175 | 2.598 | 2.480 | 1 | 1.036 | 0.902 |
| 15⁄8 | 1.658 | 27⁄16 | 2.438 | 2.356 | 2.815 | 2.616 | 13⁄32 | 1.116 | 0.978 |
| 13⁄4 | 1.785 | 2-5/8 | 2.625 | 2.538 | 3.031 | 2.893 | 15⁄32 | 1.196 | 1.054 |
| 17⁄8 | 1.912 | 213⁄16 | 2.812 | 2.719 | 3.248 | 3.099 | 11⁄4 | 1.276 | 1.130 |
| 2 | 2.039 | 3 | 3.000 | 2.900 | 3.464 | 3.306 | 111⁄32 | 1.388 | 1.175 |
| 21⁄4 | 2.305 | 33⁄8 | 3.375 | 3.262 | 3.897 | 3.719 | 11⁄2 | 1.548 | 1.327 |
| 21⁄2 | 2.559 | 33⁄4 | 3.750 | 3.625 | 4.330 | 4.133 | 121⁄32 | 1.708 | 1.479 |
| Dimensions per ASME B18.2.1 | |||||||||
Heavy Hex Dimensions
| Bolt Diameter | D | F | C | H | |||||
|---|---|---|---|---|---|---|---|---|---|
| Body Diameter | Width Across Flats | Width Across Corners | Height | ||||||
| Max | Basic | Max | Min | Max | Min | Basic | Max | Min | |
| 1⁄2 | 0.515 | 7⁄8 | 0.875 | 0.850 | 1.010 | 0.969 | 11⁄32 | 0.364 | 0.302 |
| 5⁄8 | 0.642 | 11⁄16 | 1.062 | 1.031 | 1.227 | 1.175 | 27⁄64 | 0.444 | 0.378 |
| 3⁄4 | 0.768 | 11⁄4 | 1.250 | 1.212 | 1.443 | 1.383 | 1⁄2 | 0.524 | 0.455 |
| 7⁄8 | 0.895 | 17⁄16 | 1.438 | 1.394 | 1.660 | 1.589 | 37⁄64 | 0.604 | 0.531 |
| 1 | 1.022 | 15⁄8 | 1.625 | 1.575 | 1.876 | 1.796 | 43⁄64 | 0.700 | 0.591 |
| 11⁄8 | 1.149 | 113⁄16 | 1.812 | 1.756 | 2.093 | 2.002 | 3⁄4 | 0.780 | 0.658 |
| 11⁄4 | 1.277 | 2 | 2.00 | 1.938 | 2.309 | 2.209 | 27⁄32 | 0.876 | 0.749 |
| 13⁄8 | 1.404 | 23⁄16 | 2.188 | 2.119 | 2.526 | 2.416 | 29⁄32 | 0.940 | 0.810 |
| 11⁄2 | 1.531 | 23⁄8 | 2.375 | 2.300 | 2.742 | 2.622 | 1 | 1.036 | 0.902 |
| 15⁄8 | 1.658 | 29⁄16 | 2.562 | 2.481 | 2.959 | 2.829 | 13⁄32 | 1.116 | 0.978 |
| 13⁄4 | 1.785 | 23⁄4 | 2.750 | 2.662 | 3.175 | 3.035 | 15⁄32 | 1.196 | 1.054 |
| 17⁄8 | 1.912 | 215⁄16 | 2.938 | 2.844 | 3.392 | 3.242 | 11⁄4 | 1.276 | 1.130 |
| 2 | 2.039 | 31⁄8 | 3.125 | 3.025 | 3.608 | 3.449 | 111⁄32 | 1.388 | 1.175 |
| 21⁄4 | 2.305 | 31⁄2 | 3.500 | 3.388 | 4.041 | 3.862 | 11⁄2 | 1.548 | 1.327 |
| 21⁄2 | 2.559 | 37⁄8 | 3.875 | 3.750 | 4.474 | 4.275 | 121⁄32 | 1.708 | 1.479 |
|
Dimensions per ASME B18.2.1 |
|||||||||
David Miller
Mr. Porreco,
Thank you for having this resource on your web site. I’m looking for two sets of ten bolts each for the end cover plates of two elevator motors that are no longer in use but remain as part of the décor at my condominium building in Houston, Texas. Motors are dated 1921. Appreciate some help.
There are four cover plates, two large and two small; each has six bolt holes. There were two bolts still in place on each type of cover plate. I removed two of the four bolts for measuring.
On both sizes of bolts, D = slightly more than 15/32″. F = 3/4″. On the longer bolts, L = 1-1/4″, T = 1″, and H = 3/16″. On the shorter bolts, L = 1″, T = 5/8″, and H = 5/32″. It looks like there are 13 threads per inch on both bolts. I can’t see any markings on the heads.
[I had to use a 13/16″ socket to remove them because my 3/4″ and 19mm sockets wouldn’t fit. I wonder why that is.]
Ordinarily, I would take these bolts to my local hardware store to buy duplicates, but now I’m doing practically all my shopping online, so I hope you can tell me exactly what to order, and perhaps suggest where to order them from.
Again, thank you very much.
Regards,