Heavy Hex Structural Nut
Description
Technical Parameters
Heavy hex structural nuts are internally threaded fasteners used in high-strength bolted connections for structural steelwork, bridges, industrial buildings, and other steel assemblies. Their larger across-flats dimensions and greater height distinguish them from standard finished hex nuts. They are commonly specified for structural connections using compatible high-strength bolts.
ASTM A563 is a principal material and mechanical property specification for carbon and alloy steel nuts used in structural bolting. ASTM A194 Grade 2H nuts are also used in certain structural bolting assemblies where permitted by the applicable connection specification. These standards have different scopes and grade systems and should be specified separately.
Product Features
Heavy Hex Geometry: The larger hexagonal profile provides wrench clearance and dimensions specified for heavy hex structural applications. Across-flats dimension, nut height, and thread engagement must comply with the applicable dimensional standard.
Grade-Specific Mechanical Properties: ASTM A563 grades have defined hardness and proof load requirements. The required values depend on nut grade, size, thread series, nut style, and surface finish.
Metric and Inch Thread Options: Inch-threaded products can be specified with UNC or 8-UN threads where applicable. Metric products use the specified metric thread designation and tolerance.
Surface Finish Options: Plain and hot-dip galvanized finishes are available product configurations. Coated nuts require appropriate internal thread dimensions and compatibility with the mating bolts.
Inspection Documentation: Inspection records can cover dimensional measurements, thread gauges, hardness, and proof load testing according to the applicable product specification and purchase requirements.
Technical Specifications
|
Parameter |
Technical Specification |
|
Product Type |
Heavy Hex Structural Nut |
|
Product Standard |
ASTM A563/A563M |
|
Inch-Series Dimensional Standard |
ASME B18.2.6 |
|
Metric-Series Dimensional Standard |
ASME B18.2.6M |
|
Nut Grades |
ASTM A563 Grades C, C3, D, DH, DH3 |
|
Alternative Nut Grade |
ASTM A194 Grade 2H |
|
Inch Size Range |
1/2 in to 2 in |
|
Example UNC Thread Sizes |
1/2-13 UNC, 5/8-11 UNC, 3/4-10 UNC, 7/8-9 UNC, 1-8 UNC |
|
Example Large-Diameter Thread Sizes |
1-1/8-7 UNC, 1-1/4-7 UNC, 1-1/2-6 UNC, 1-3/4-5 UNC, 2-4.5 UNC |
|
Thread Tolerance |
ASME B1.1 Class 2B for inch internal threads |
|
Across-Flats Dimension |
1/2 in nut: 7/8 in; 3/4 in nut: 1-1/4 in; 1 in nut: 1-5/8 in |
|
Nut Height |
1/2 in nut: approximately 15/32 in; 3/4 in nut: approximately 3/4 in; 1 in nut: approximately 1 in |
|
ASTM A563 Grade DH Hardness |
Rockwell C24–C38 |
|
Grade DH Proof Load Stress |
175 ksi for applicable plain-finish heavy hex nuts; 150 ksi for applicable zinc-coated heavy hex nuts |
|
Surface Finish |
Plain; Hot-Dip Galvanized |
|
Hot-Dip Galvanizing Standard |
ASTM F2329/F2329M |
|
Inspection Items |
Dimensional inspection, thread gauging, hardness testing, proof load testing |
|
Quality Documentation |
Material test reports, mechanical test reports, dimensional inspection records |
Applications
Structural Steel Frames
Heavy hex nuts are used in compatible bolted beam, column, and steel splice connections where the structural design specifies high-strength bolting assemblies.
Bridge Structures
They are used in specified girder and truss connections. The nut grade and coating must match the approved bolting assembly requirements.
Industrial Buildings
Steel warehouses, factories, and equipment support structures may use heavy hex nuts for bolted structural joints.
Wind Energy Structures
Tower flange connections and related steel assemblies require nuts selected according to the engineering drawings, bolt grade, and environmental requirements.
Key Selection Factors
Nut and Bolt Compatibility: Confirm the bolt specification, grade, diameter, thread series, and coating before selecting the nut. For structural assemblies, use the nut grades permitted by the governing connection specification rather than assuming that similar strength designations are interchangeable.
Dimensions and Thread Fit: Verify across-flats dimension, nut height, thread pitch, and internal thread tolerance against the specified standard. For example, a 1 in-8 UNC nut must match the corresponding bolt thread.
Coating Requirements: Hot-dip galvanized nuts require internal thread dimensions compatible with the coated bolt. ASTM A563 contains specific requirements for overtapping zinc-coated nuts. Confirm coating standards and assembly compatibility in the purchase order.
Mechanical Requirements: Specify the exact grade and applicable proof load requirements. Do not use a single proof load or hardness value for every grade and size.
Inspection and Quality Assurance
Inspection requirements should be agreed upon before production or shipment.
Dimensional inspection verifies across-flats dimensions, nut height, and relevant tolerances. Thread gauges check internal thread conformity. Hardness testing and proof load testing are performed according to the applicable specification and required inspection plan. Coating inspection is included when required by the ordered finish and project documentation.
Material traceability, test reports, and third-party inspection should be confirmed against the supplier's actual quality procedures and purchase requirements.
Frequently Asked Questions
Q: Are ASTM A563 Grade DH and ASTM A194 Grade 2H interchangeable?
A: Not automatically. Grade 2H may be permitted as a substitute for Grade DH in specified structural bolting applications, but the governing connection requirements must be checked.
Q: Can heavy hex structural nuts be hot-dip galvanized?
A: Yes, when the specified product and coating requirements permit it. Internal thread dimensions and compatibility with the mating bolt must be verified.
Q: Can used structural nuts be reused?
A: Reuse depends on the applicable structural bolting specification, connection type, installation method, and condition of the fastener. Follow the project requirements rather than applying a universal reuse rule.
Q: What documents can buyers request?
A: Request the applicable material and mechanical test reports, dimensional inspection records, coating documentation, and any agreed third-party inspection reports.
Request a Quote
To obtain a quotation, provide the nut standard and grade, nominal diameter, thread series, surface finish, quantity, and delivery destination. Include the mating bolt specification and project requirements when available.
Sales Contact
Email: hyhuashenj@163.com
Phone / WhatsApp: +86 133 6235 5996
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