What is an A325T bolt?
An A325T bolt is a fully threaded version of an A325 heavy hex structural bolt. The A325 specification is very specific when it addresses thread lengths. Standard A325 bolts have very short thread lengths due to their application as a bolt intended for use in structural steel connections since often it is undesirable for threads to be included the shear plane. Verbiage within the ASTM specification makes it very clear that ASTM specification A449 should be used when altering the standard thread lengths on A325 bolts. However, there is an exception under Supplementary Requirement (S1) that allows for a fully threaded version of the A325 heavy hex structural bolt. Section 7.1.2 of the A325 specification reads as follows:
7.1.2 The thread length shall not be changed except as provided in Supplementary Requirement S1. Bolts with thread lengths other than those required by this specification shall be ordered under Specification A449.
Fully threaded A325 bolts are marked on the head of the bolt with “A325T” instead of “A325”. Another very important aspect of an A325T bolts is that they are limited to 4 times the diameter in length. For example, 3/4″ A325T bolts cannot exceed 3″ (four times 3/4″) in length and 1″ diameter A325T bolts cannot exceed 4″ (four times 1″) in length.