It not uncommon for us to get requests or for bolt configurations that don’t match the specifications. Anchor bolts called out as headed Grade 8 bolts are only available with a hex head. From your description ASTM A354 BD would be the correct fastener. This specification has mechanical properties that are very similar to SAE Grade 8 bolts, 150 ksi minimum tensile and 130 ksi minimum yield. A354 BD indicates a hex head unless otherwise specified. So you can work with a manufacturer to meet the requirements of your prints to supply an A354 BD bolt with a heavy hex head. A490 bolts are meant for structural steel connections and have specific thread lengths. For example, a 1” diameter A490 will have 1-3/4” of thread, where as an A354 BD bolt has 2-1/2” of thread or you can specify longer threads as necessary.
Thread Length
The industry standard thread length for fasteners over 6” long is 2 times the diameter plus ½” and twice the diameter plus 1/4″ for anything shorter. Structural bolts, like A490, have special thread lengths that are shorter since they are used in structural connections.
Diameter Range
Here’s a chart that highlights some of the differences between these three specifications.
| Specification | Diameter Range | Min. Tensile Strength Range | Min. Yield Strength Range | Head Pattern | Thread Length |
|---|---|---|---|---|---|
| ASTM A354-BD | ¼ – 4” | 150 ksi, 140 ksi (2-5/8”+) | 130 ksi, 115 ksi (2-5/8”+) | Hex Head or as specified. | 2 X Diameter Plus ½” or as specified. |
| ASTM A490 | ½ – 1-1/2” | 150 ksi | 130 ksi | Heavy Hex Head | Specified Per Diameter |
| SAE Grade 8 | ¼ – 1-1/2” | 150 ksi | 130 ksi | Hex Head | 2 X Diameter Plus ½” |