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hastur (Mechanical) (OP)
2 Jun 03 14:27
My project specifications call for the use of ASTM A325N bolts.   However, I have not found a bolt supplier or manufacturer who can tell me what the “N” in A 325N stands for.   Can someone tell me what the “N” designation means?  Thanks…
Helpful Member!(2)  Taro (Structural)
2 Jun 03 17:32
N means the threads are permitted to be included in the faying plane.  X means the threads are excluded.  X produces stronger shear values, but requires more attention (and washers) to make sure the threads are not included.  See for more information.
mikedcm (Civil/Environmental)
20 Jun 03 14:17

Structural applications A325 "N" means threads included in shear plane. X means threads excluded from shear plane.  Results in different allowable shear values for the bolt.

Helpful Member!  jrmack (Structural)
15 Jul 03 0:19
Yes X is better than N, but there is only one A325 bolt.  The A325 bolts are the same geometrically for a specific length and diameter, so there is not a special A325 bolt (one that is the N and one that is the X).  The bolts attract an N or an X if the threads are included or excluded from the shear plane.  A 3/8" plate on the nut side on a properly installed bolt will result in the X. Some use 1/2" (rather than 3/8").  

Hope that this makes it clear.  One bolt, two shear capacities depending on whether the threads are included (not good..N) or excluded (good..X)from the shear plane.  The thicker plate on the nut side pushes the shear plane closer to the head of the bolt (hopefully in the shank portion, not in the treaded portion).  

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