Why are the heads of my A325 bolts marked with the letter “S”?
Under the new F3125 specification, which now governs A325 structural bolts, there is a supplementary requirement that allows A325 bolts to differ in head geometry and thread length (excluding fully threaded A325s) as required by the customer. When these alternate dimensions are required, the bolts shall be stamped “A325S”, with the “S” indicating special.
Under the existing A325 specification, these fasteners were required to only be heavy hex structural bolts dimensioned per ASME B18.2.6 with standardized thread lengths. This new supplement means that if your plan requires an A325 with a round head, for example, it is now acceptable, where previously you would need to move to the ASTM A449 specification.
If your project requires custom A325 bolts, give one of our helpful team members a call, and we will be happy to assist you with this.