Is the thread length of A193 Grade B7 bolts the same as A325 bolts?

In short, no, the thread length of A193 B7 bolts is not the same as the thread length of A325 bolts.

The F3125 Grade A325 specification covers heavy hex structural bolts which have standard fixed thread lengths shown in the table below. The thread lengths can be altered, but A325 bolts with nonstandard thread lengths must be made to the F3125 Grade A325S specification meaning they are “special” A325s with nonstandard qualities. These “A325S” bolts have to be specially manufactured and will not be available off-the-shelf.

F3125 Grade A325 Fixed Thread Lengths

Click table to show drawing
Bolt Diameter D F C H T
Body Diameter Width Across Flats Width Across Corners Height Thread Length
Max Basic Max Min Max Min Basic Max Min Basic
12 0.515 78 0.875 0.850 1.010 0.969 516 0.323 0.302 1.00
58 0.642 1116 1.062 1.031 1.227 1.175 2564 0.403 0.378 1.25
34 0.768 114 1.250 1.212 1.443 1.383 1532 0.483 0.455 1.38
78 0.895 1716 1.438 1.394 1.660 1.589 3564 0.563 0.531 1.50
1 1.022 158 1.625 1.575 1.876 1.796 3964 0.627 0.591 1.75
118 1.149 11316 1.812 1.756 2.093 2.002 1116 0.718 0.658 2.00
114 1.277 2 2.00 1.938 2.309 2.209 2532 0.813 0.749 2.00
138 1.404 2316 2.188 2.119 2.526 2.416 2732 0.878 0.810 2.25
112 1.531 238 2.375 2.300 2.742 2.622 1516 0.974 0.902 2.25

Dimensions per ASME B18.2.6 2011

In comparison, A193 Grade B7 heavy hex bolts follow a standard threading formula of 2 times the bolt diameter plus 1/4″ if 6” in length or less or plus 1/2″ if above 6” in length. As with the A325 specification, the A193 Grade B7 bolts can have different thread lengths if needed, but the bolts would have to be specially manufactured.

A193 Grade B7 Thread Length Formula

Bolt lengths ≤ 6″: Thread length = (2 X diameter) + 1/4″
Bolt lengths > 6″: Thread length = (2 X diameter) + 1/2″

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