ASTM A563 Heavy Hex Nut | Grade DH for A325 A490 Bolt
ASTM A563 Heavy Hex Nut | Grade DH for A325 A490 Bolt
ASTM A563 / ASME B18.2.2 | Grade A / B / C / DH | 1/4"–4"| Carbon Steel / Weathering Steel / SS304 / SS316
ASTM A563 heavy hex nut designed for A325 and A490 structural bolt assemblies. Available in Grade A, B, C, and DH for marine hull structure, deck equipment, and crane rail baseplate connections. Full material traceability per EN 10204 3.1.
Product Overview
TheASTM A563 Heavy Hex Nut is manufactured to ASTM A563 specification for use with high-strength structural bolts including ASTM A325, ASTM A490, and ASTM F3125. Compared to finished hex nuts (ASTM A194 Grade 2H), the A563 heavy hex nut features larger width across flats and greater bearing surface area, providing higher proof load capacity required for structural steel connections in shipbuilding and heavy construction.
A563 nuts are available in four grades covering carbon steel, weathering steel, and quenched & tempered alloy steel. Grade DH provides the highest proof load (120 ksi for sizes ≤1", 105 ksi for sizes >1"to 1-1/2"), making it the standard pairing for A490 structural bolts in critical hull structure splice plates and primary framing connections.
Grade Specifications & Proof Load
| Grade | Material | Proof Load Stress | Paired Bolt | Typical Use |
|---|---|---|---|---|
| Grade A | Carbon Steel | 80 ksi (≤1"), 70 ksi (>1") | A307 | General purpose, non-structural |
| Grade B | Carbon Steel | 95 ksi (≤1"), 85 ksi (>1") | A325 Type 1 | General structural connections |
| Grade C | Carbon Steel, Improved Hardenability | 100 ksi (≤1"), 90 ksi (>1") | A325 Type 1 | Improved hardenability for thicker sections |
| Grade DH | Cr-Mo Alloy Steel, Q&T | 120 ksi (≤1"), 105 ksi (>1"–1-1/2") | A325 Type 3 / A490 | Critical structural & marine connections |
Note: Proof load values per ASTM A563 Table 3. For stainless steel variants (SS304/SS316), proof load follows ASTM F594 specification.
Technical Specifications
| Parameter | Value |
|---|---|
| Standard | ASTM A563 / ASME SA563 / ASME B18.2.2 |
| Type | Heavy Hex Nut (Coarse Thread UNC) |
| Size Range | 1/4"– 4"(M6 – M100 on request) |
| Material | Carbon Steel / Weathering Steel / Cr-Mo Alloy Steel / SS304 / SS316 |
| Surface Finish | Plain / Hot-Dip Galvanized (per ASTM A153) / Zinc Plated / Dacromet |
| Thread Standard | UNC (Unified National Coarse) |
| Hardness (Grade DH) | HRC 26–36 |
| Paired Bolts | ASTM A325 / A490 / F3125 |
| Marking | Grade symbol on nut face for identification |
Dimensional Data (Selected Sizes – Heavy Hex Nut per ASME B18.2.2)
| Bolt Size | Width Across Flats (in) | Width Across Corners (in) | Height (in) |
|---|---|---|---|
| 1/4" | 7/16 | 0.505 | 15/64 |
| 3/8" | 9/16 | 0.658 | 23/64 |
| 1/2" | 3/4 | 0.879 | 7/16 |
| 5/8" | 15/16 | 1.091 | 35/64 |
| 3/4" | 1-1/8 | 1.307 | 41/64 |
| 7/8" | 1-5/16 | 1.524 | 3/4 |
| 1" | 1-1/2 | 1.738 | 7/8 |
| 1-1/8" | 1-11/16 | 1.956 | 63/64 |
| 1-1/4" | 1-7/8 | 2.175 | 1-7/64 |
| 1-1/2" | 2-1/4 | 2.615 | 1-19/64 |
| 2" | 3 | 3.490 | 1-13/16 |
Note: Dimensions per ASME B18.2.2 for Heavy Hex Nuts. Contact us for metric equivalents and non-standard sizes.
Nut–Bolt Pairing Guide
| Structural Bolt | Recommended A563 Grade | Notes |
|---|---|---|
| ASTM A325 Type 1 (Carbon Steel) | Grade A / B / C | Grade A for general use; Grade B/C for higher proof load requirements |
| ASTM A325 Type 3 (Weathering Steel) | Grade DH (Weathering Steel variant) | Matching weathering characteristics for atmospheric corrosion resistance |
| ASTM A490 | Grade DH | Mandatory pairing — Grade DH provides the proof load required for A490 |
| ASTM F3125 Grade A325 | Grade B / C | F3125 consolidates A325 requirements |
| ASTM F3125 Grade A490 | Grade DH | F3125 consolidates A490 requirements |
Marine Applications
- Hull Structure: Splice plates, frame connections, and bulkhead stiffener joints using A325/A490 bolts with A563 heavy hex nuts
- Deck Crane Rails: Crane pedestal baseplate bolting where high tensile strength and vibration resistance are required
- Equipment Mounting: Diesel generator, pump, and compressor base bolts in engine room installations
- Mooring Systems: Bollard foundation and cleat anchor bolt nuts subject to dynamic loading
- Offshore Structures: Jack-up rig leg chords, platform brace connections, and pipeline support clamps
Installation Notes
- Verify grade marking on nut face matches the bolt grade specification before installation.
- Use hardened flat washers (ASTM F436) under both the nut and bolt head to distribute bearing load and prevent surface damage.
- Follow the structural steel tightening procedure: snug-tight → calibrated wrench → turn-of-nut method per RCSC Specification for Structural Joints Using High-Strength Bolts.
- For hot-dip galvanized assemblies, allow for additional thread clearance. Over-tapping of nuts is performed per ASTM A563 Section 7.3.2 to ensure proper fit after galvanizing.
- Re-check torque after initial vibration exposure in marine service to confirm joint integrity.
Why Choose SINOFASTENER
- Full A563 grade range: A, B, C, and DH in both carbon steel and weathering steel
- Size range 1/4"–4"with metric equivalents M6–M100 available on request
- 100% dimensional inspection per ASME B18.2.2 and proof load tested per ASTM A563
- Heat number traceability and EN 10204 3.1 mill test certificates provided
- Hot-dip galvanized coating per ASTM A153 with minimum 50 μm thickness
- Annual production capacity 50,000 tons across all fastener categories
FAQ
What is the difference between ASTM A563 and ASTM A194 nuts?
ASTM A563 covers heavy hex nuts with larger width across flats, designed for structural bolting with A325/A490 bolts. ASTM A194 covers finished hex nuts (standard hex pattern) used with general-purpose bolts. A563 heavy hex nuts provide greater bearing surface and higher proof load for structural connections.
Which A563 grade should I use with A325 bolts?
For ASTM A325 Type 1 (carbon steel), Grade A, B, or C nuts are acceptable. Grade A is suitable for general structural connections; Grade B or C provides higher proof load for critical joints. For ASTM A325 Type 3 (weathering steel), use the weathering steel variant of Grade DH.
Is Grade DH required for A490 bolts?
Yes. ASTM A490 bolts have significantly higher tensile strength than A325, and the specification requires A563 Grade DH nuts to ensure the nut proof load matches or exceeds the bolt strength. Using a lower grade nut with A490 bolts would create a weak point in the joint.
What is the difference between Grade DH and Grade 2H?
Grade DH is per ASTM A563 (heavy hex nut pattern for structural bolts), while Grade 2H is per ASTM A194 (finished hex nut pattern). Both have similar proof load requirements (~120 ksi), but they differ in dimensional configuration. A563 Grade DH has larger across-flats dimensions than A194 Grade 2H for the same bolt size.
Can A563 heavy hex nuts be hot-dip galvanized?
Yes. Hot-dip galvanizing per ASTM A153 is a common surface treatment for A563 nuts in marine and outdoor applications. Nuts are over-tapped before galvanizing to ensure proper thread fit after the zinc coating is applied.
Contact Us
For ASTM A563 heavy hex nut inquiries, please contact:
E-mail:sales@sinofastener.com
SINOFASTENER — Marine Structural Fastener Supplier | Annual Capacity 50,000 Tons
