F3125 Frequently Asked Questions
Is ASTM A325 all thread rod available?
The Short answer is no.
According to the ASTM specification, A325 bolts must be headed. Historically the A325 bolt had to be a heavy hex head, however, in recent years the specification was modified to include any form of head. It is possible to get a round head or a square head bolt. Keep in mind that those are not readily available and will have to be custom-made. But the specification does allow for it.
A490 bolts on the other hand are allowed to be non-headed.
If you are looking for a non-headed bolt with similar mechanical properties to A325 check out ASTM A449.
Can I get A325 or A490 bolts above 1 ½” in diameter?
No, you cannot. The ASTM specification only allows for bolts in this grade to range from ½” to 1 ½”. If you need a larger diameter you will have to switch to another grade. It is common to see F3125 bolts specified above 1 ½” because of their strength, however the spec. does not allow for it. There are a few grades with very similar strength requirements and properties that can be used instead.
Why can’t I find ½” diameter A490 bolts?
While the specification allows for ½” A490 bolts, they are so uncommon that they are not mass-produced. This means they cannot be found on the shelf and would have to be custom-manufactured.
A workaround besides just moving to a larger diameter would be to switch to J429-8 because they are easily found in a ½” diameter and have almost the same chemical and mechanical properties. The only issue to consider would be that J429-8 bolts are manufactured with a standard hex head and A490 bolts are manufactured with a heavy hex head.
Of course, any substitutions should be approved by the engineer of record.
What changes have occurred to the ASTM A490 specification since it was incorporated into the F3125 specification?
The reason ASTM merged the structural bolt grades into the F3125 specification was to get rid of inconsistencies and make it easier to make adjustments to the grades in the future.
There were no large changes to the specifications, but there were a few minor changes. The main change is the nut tap allowances for zinc aluminum coatings on A490 bolts.
What changes have occurred to the ASTM A325 specification since it was incorporated into the F3125 specification?
The reason ASTM merged the structural bolt grades into the F3125 specification was to get rid of inconsistencies and make it easier to make adjustments to the grades in the future.
The bolts are basically the same as before the only changes being increasing mechanical properties of larger diameter A325 bolts.
MECHANICAL REQUIREMENTS
| A325 ½” – 1” | A325 above 1” | F3125 Gr.A325, all sizes | |
| Tensile, min ksi | 120 | 105 | 120 |
| Yield, min ksi | 92 | 81 | 92 |
| Elongation, min % | 14 | 14 | 14 |
| RA, min % | 35 | 35 | 35 |
| Hardness, HBN | 253-319 | 223-286 | 253-319 |
If the A325 type (1 or 3) is not specified on a request for quote or purchase order, which type would be supplied?
A325 type one will typically always be supplied unless otherwise specified. According to ASTM if you do not specify which type you’d like the supplier can choose which one they will supply.
However, A325 type 3 bolts are not nearly as common in the marketplace as type 1 so it is not common to be supplied with A325 type 3 bolts unless you request it.