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Re: Heavy Hex Nuts

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David,
 
The proof load of Gr. DH nuts far exceeds that of Gr. A nuts (175 zinc coated Gr. DH vs. 75 zinc coated Gr. A - UNC threads). Grade DH nuts are recommended for use with ASTM F1554 Grade 105 anchor rods. ASTM F1554 allows the substitution of style and grade if the proof load is greater than that required.
 
Rockwell hardness of Gr. DH nuts is C24-C38 vs. B68-C32 for Gr. A nuts.
 
Regards,
Bruce Vaughan
----- Original Message -----
Sent: Tuesday, July 01, 2003 8:15 AM
Subject: 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
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