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Re: Heavy Hex Nuts

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ASTM F1554 Section 6.6.1 allows galvanized Grade A nuts for grade 36 and 55 bolts but requires Grade DH for grade 105 bolts.

Hot dip galvanized Grade A nuts are acceptable for use with A307/A36 bolt material however it is very common to use Grade DH.  For use with galvanized ASTM A325 bolt material Grade DH nuts are required.  See ASTM A563 Appendix X1 and "Specification for Structural Joints Using ASTM A325 or A490 Bolts" Table 2.1.

Unless the fabricator is going to charge an absorbent price for the DH Grade nuts I would let it pass.  I typically call out Grade DH nuts for all galvanized applications.  It makes life simple.

Thomas Hunt, S.E.
ABS Consulting

"M. David Finley, P.E." <pec(--nospam--at)>

07/01/2003 06:15 AM

Please respond to

Heavy Hex Nuts

We specified ASTM A563 Grade A Heavy Hex Nuts for the anchor bolts of an overhead sign structure and the fabricator is showing Grade DH (still A563 Heavy Hex) on their shop drawings.  I've looked through the ASTM spec. to verify that the proof load for the Grade DH nuts exceeds the Grade A requirements.  Am I possibly missing something regarding chemical composition or hardness that would affect performance?  The nuts will be galvanized and the anchor bolts are ASTM F1554, Grade 55.
M. David Finley, P.E.
2086 SW Main Boulevard - Suite 111
Lake City, FL  32025