What changes have occurred to the ASTM A325 specification since it was incorporated into the F3125 specification?
In December 2015, ASTM committee F16 approved the new F3125 standard, which combined six structural bolt standards, A325, A325M, A490, A490M, F1852, and F2280. The goal was to clean up inconsistencies within those various standards and combine them, so that future updates would be easier and less costly.
The goal was not to drastically change any of the requirements of the bolts, as they had been used and functioning in the marketplace for decades without major issues. However, in order to better align with each other and with current design standards, minor changes were made. The most notable change was the increase in mechanical properties of large diameter A325 bolts. Originally, bolts ½” through 1” diameter had a minimum tensile requirement of 120ksi, whereas for bolts above 1” diameter, the requirement dropped to 105ksi. AISC design guides had used the 120ksi value for design loads all along regardless of bolt size, so this increase by ASTM aligns the design strength with the actual strength.
The table below outlines the mechanical changes. This is not meant to be a comprehensive comparison, there is much more information both on our website and within the F3125 standard at ASTM.org
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 |
Additional Revisions
After much clamoring by the industry, a supplemental requirement was added to address alternate bolt configurations. Supplement S2 allows the purchaser to specify nonstandard dimensions for thread length, head style, etc. Bolts ordered to S2 are marked with an “S” to signify that these bolts vary from the ASME B18.2.6 dimensional standard, for example A325S.
We have a projet that specifies countersunk head on A325 7/8 in.
What kind of head exist for these type of bolts? I’ve seen some bolts with allen key slot and others with a simple slot for flat screwdriver.
We need to tight these bolts by the turn-of-the-nut method, and we’ve experience some fractured head with those with the Allen key slot. What is your thoughts on this issue?
Thanks.
@Christian- We are occasionally asked for A325 countersunks bolts. We are able to manufacture with a slot in the head, but the installation is still a bit tricky since even with a slot it is hard to restrain the head from rotating. Additionally, the countersunk head is much smaller and less structurally competent compared to the heavy hex head. There was actually discussion in the ASTM meeting last month regarding this and there is talk of adding language prohibiting countersunks or at least warning the user that these aren’t as sound as standard A325 bolts.
Good Day,
As per my client requirement All bolts shall have a maximum Rockwell C hardness of 32, we have ASTM A193 B7, 316, & ISO 898-1 Gr. 10.9; however supplier says B7 Bolts Hardness can go up to a Max of 35 HRC and Gr. 10.9 has Min 32 HRC
@Rajani- We are not sure what your question is here. If you are having trouble locating bolts that meet your customer’s requirement, you might need to go back and discuss options with your customer. Most of the grades you list span that hardness range, but you are correct that none have a hard cap at 32HRC.
Dear Sir,
I hope you are fine and doing well
I am glad to be the part of this platform.
My client’s requirement is mentioned below.Please suggest me what grade shall I quote.
MACHINE BOLTS GRADE ASTM F3125, 1 No. HEAVY HEX NUT GRADE ASTM A563 WITH Washer 1No. ASTM F436/436M,HOT DIP SPUN GALVANIZED
@Raj- ASTM F3125 has more than one grade, so you should clarify what they are needing. Normally the A490 grade is not galvanized, so I would assume that the A325 grade is what they want. The corresponding nut would be A563 grade DH.
Dear Sir,
Good day!
I have question, That if purchaser do not mention the requirement as “Supplementary requirement” in purchase request for “Full Threaded” Bolt produced >4D. what will be head marking A325M or A325S ? where “S” is for special requirement as supplementary clauses S2.2.
please confirm
@Sajjad- If the bolt is manufactured with full thread, and it is 4x or less long, it should be marked A325T. If the bolt is longer than 4x, it should be marked A325S.
Good day Dane,
Thank you for posting this important message, I do have a query. The ASTM A325M-09 has the table 5, it shows the from M12 to M36 (Metric standard) the yield and tensile strength is same, so the revision in F3125 is only the standards that combines 4 different standards together to single platform. No difference in mechanical properties.
Reference : ASTM A325M-2009 , Table 5. Pg 5.
Your comment on this pls.
@Sathish- There were six structural standards combined, A325, A325M, A490, A490M, F1852, and F2280. The idea behind combining them was for ease of maintenance and to clear up some conflicting language in the individual standards. With one small exception, none of the mechanical or chemical requirements were changed, they were simply combined into one standard. An A325M manufactured under A325M-09 shouldn’t be any different from one made per F3125-17 gr.A325M.