Structural Hardware Guide - Grades, Strength and Identification

Structural hardware components like Grade DH nuts, flat washers, and beveled washers are critical for high-strength bolted connections in steel construction. These elements are used in conjunction with heavy hex structural bolts to ensure proper load distribution and joint integrity. Grade DH nuts meet ASTM A563 specifications and are designed to develop the full strength of ASTM A325 or A490 bolts. Flat washers provide even bearing surfaces, while beveled washers are used on sloped surfaces to maintain proper alignment in bolted assemblies. Proper selection and installation of these components are essential for meeting AISC and ASTM standards and ensuring reliable performance in structural applications.

^A A325 and A325M bolts lengths up to 4D which are fully threaded but which are not required to be fully threaded by the relevant ASME standard shall be marked with
a “T”, see Supplementary Requirement S1. Bolts with any other non-standard dimensions, including thread length, shall be marked with an “S”, see Supplementary
Requirement S2.
^B Manufactured to the latest revision at the time of manufacture, UNC for inch series and Metric Coarse (MC) for Metric Series.
^D Other distinguishing markings for type 3 are permitted at the manufacturers option.
^E ASTM A194/A194M 2H heavy hex inch nuts may be used in place of A563 DH nuts on type 1 A325, A490, F1852 and F2280 bolts. 2H heavy hex metric nuts may be
used in place of A563M 10S nuts on type 1 A325M and A490M bolts. When coated 2H nuts are used in place of DH or 10S nuts, the same requirements of A563, A563M,
and this specification, including Annex A1, shall apply. These include, but are not limited to, overtap amount, coating grade, lubrication requirements, and proof load testing.