Structural Hardware

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.

	Inch		Metric		Inch		Metric
	120 ksi Min Tensile		830 MPa Min Tensile		150 ksi Min Tensile		1040 MPa Min Tensile
	Type 1	Type 3	Type 1	Type 3	Type 1	Type 3	Type 1	Type 3
Style - Heavy Hex Bolts
Dimensions, ASME^B	B18.2.6	B18.2.6	B18.2.6M	B18.2.6M	B18.2.6	B18.2.6	B18.2.6M	B18.2.6M
Thread Fit, ASME^B	B1.1 UNC 2A	B1.1 UNC 2A	B1.13M MC 6g	B1.13M MC 6g	B1.1 UNC 2A	B1.1 UNC 2A	B1.13M MC 6g	B1.13M MC 6g
Grade Marking^A,D	A325	A325	A325M	A325M	A490	A490	A490M	A490M
Recommended Nut and Washer
Recommended Nut and Washer
Plain Nut	A563 DH	A563 DH3	A563M 10S	A563M 10S3	A563 DH	A563 DH3	A563M 10S	A563M 10S3
Suitable Alternative^E	DH3, D, C, C3	C3	8S, 8S3, 10S3	8S3			10S3
Coated Nut	A563 DH	A563 DH3	A563M 10S	A563M 10S3	A563 DH	A563 DH3	A563M 10S	A563M 10S3
Flat, Bevel or Thick Washer if used	F436 - 1	F436 - 3	F436M - 1	F436M - 3	F436 - 1	F436 - 3	F436M - 1	F436M - 3

^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.

ASTM A563 Grade DH Nuts

ASTM A563 Grade DH Nuts are heavy hex nuts specified for use in high-strength structural applications, particularly in combination with high-strength bolts such as ASTM A325 and A490 bolts. These nuts are manufactured to meet the ASTM A563 specification, which covers the chemical and mechanical requirements for carbon and alloy steel nuts used on externally threaded fasteners.

ASTM F436 Flat Washers

ASTM F436 Flat Washers are hardened steel washers specifically designed for use in structural bolting applications, particularly with high-strength bolts such as those conforming to ASTM A325 and A490. They serve to distribute load, prevent embedment of the nut or bolt head into the connected material, and reduce surface friction during tightening.

ASTM F436 Beveled Washers

ASTM F436 Beveled Washers are specially manufactured, hardened steel washers designed for structural applications where the surfaces being connected are not parallel—typically when bolting through I-beams or channel flanges. The bevel compensates for the angle created by sloped flanges, allowing the bolt head or nut to sit squarely and distribute load evenly.