ASTM A563
/ A563M
Structural Nuts
Why A563 Spans So Many Grades
ASTM A563 is genuinely organized differently from many nut standards on our site — rather than one composition, it defines a structured grade ladder (A, B, C, C3, D, DH, DH3, and others) purpose-built to match the range of structural bolt grades commonly used in building and bridge construction, from lighter-duty carbon steel bolts through the highest-strength A490 structural bolts.
Grade A and Grade B sit at the lighter end — general-purpose carbon steel nuts for lower-strength structural connections. Grade C steps up in strength, with Grade C3 adding weathering-steel compatible corrosion resistance for exposed structural steel applications. Grade D and DH represent the higher-strength tier, with DH specifically hardened to reliably match the strength demands of ASTM A325 and A490 high-strength structural bolts — DH3 further adds the same weathering-steel corrosion compatibility as C3, for high-strength exposed structural connections.
This grade structure exists because structural bolted connections genuinely need the nut’s strength to be reliably matched to the bolt’s strength — an under-strength nut on a high-strength structural bolt risks thread stripping or joint failure under design load, so A563’s DH designation specifically exists to give engineers a nut grade with guaranteed compatibility with A325/A490 bolting.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and our ASTM A563 / A563M nut range is manufactured and verified by chemical composition and mechanical testing under our ISO 9001:2015 quality system.
Where This Standard Genuinely Applies
Guaranteed Bolt-Nut Strength Matching
Grade DH specifically ensures compatibility with high-strength A325/A490 structural bolts.
Genuine Structural Steel Focus
Purpose-built for structural building and bridge connection requirements.
Inch & Metric Coverage
A563 for inch-based projects, A563M for metric-standard projects, same grade logic.
Verified Mechanical Properties
Batch testing confirms genuine hardness and proof load for every lot.
Choosing the Right A563 Grade
Grade A / Grade B
Standard carbon steel nuts for general-purpose, lower-strength structural connections.
Grade C / Grade C3
A genuine strength step up; C3 adds weathering-steel compatible corrosion resistance.
Grade D / Grade DH / DH3
Our most commonly requested tier — DH specifically hardened for A325/A490 bolt compatibility.
Grade DH vs Grade C — Quick Reference
Confirming which structural bolt grade you’re matching before specifying the nut, since bolt-nut strength matching is the whole reason this grade ladder exists. This table is the quick reference we use with buyers before quoting.
| Aspect | Grade DH | Grade C |
|---|---|---|
| Relative Strength | High, hardened | Mid-strength |
| Matches | ASTM A325 / A490 bolts | Lower-strength structural bolts |
| Weathering Steel Option | DH3 variant available | C3 variant available |
| Best Suited For | High-strength structural connections | General-to-moderate structural connections |
A563 / A563M Specification Details
Nominal Composition
- Base Type Carbon Steel (Grades A/B/C)
- Higher Grades Alloy Steel, Hardened (D/DH)
- Weathering Option Cu/Cr/Ni Bearing (C3/DH3)
- Sizing Systems A563 Inch, A563M Metric
Typical Mechanical Range
- Proof Load Varies by Grade, Per Standard
- Hardness Increases Through Grade Ladder
- Matching Bolt Grades A325, A490, F1554
- Standard ASTM A563 / A563M
Fastener Types We Manufacture
- Heavy Hex Structural Nuts All Grades
- Hex Nuts Standard Profile
- Metric Sizing A563M, On Request
- Custom Sizes On Request
Application Areas
Wherever structural steel bolted connections require guaranteed nut-to-bolt strength matching.
Structural Steel Building Connections
structural steel joints
Bridge & Heavy Infrastructure
bridge connection bolting
Foundation Anchor Bolt Assemblies
anchor bolt installations
Exposed Weathering Steel Structures
weathering steel compatibility
Standard Export Documentation
Prepared as standard practice for every A563 / A563M nut shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Hardness & Proof Load Test Report
Confirms compliance with the specified grade’s hardness and proof load requirements.
Certificate of Conformance
Confirms the shipment matches the purchase order grade/size specification in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
NABL Accredited Test Reports
Independent mechanical and dimensional testing available on request.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
ASTM F1554 Grade 55
Our standard weldable anchor bolt grade, commonly matched with A563 nuts.
View Grade 55 →ASTM F1554 Grade 105
Our highest-strength anchor bolt grade, matched with A563 Grade D/DH nuts for high-load anchoring.
View Grade 105 →ASTM A194 Grade 2 / 2M Nuts
Our standard pressure-vessel and piping nut grade, a different standard family for flange bolting.
View Grade 2 / 2M Nuts →Stainless Steel Fasteners Manufacturer India
Our broader fastener manufacturing capability across all major carbon, alloy, and stainless grades.
View SS Manufacturer Guide →Structural Bolting
or Anchor Nut Assemblies?
Tell us your matching bolt grade and sizing system (inch or metric) — we’ll confirm the correct A563 grade and quote with full documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in