ASME B18.2.6 Heavy Hex Structural Bolts (Inch, ASTM A325/A490)
ASME B18.2.6-2010 heavy hex structural bolts for ASTM A325 and A490 steels, 7/8 through 2-3/8 in: body diameter, width across flats and corners, head height and thread length — the inch structural-bolt head geometry ladder.
Last updated: 2026-11
Specifications
Heavy hex structural bolts are the head-below-shank workhorses of steel framing, and the B18.2.6-2010 table lays out their geometry from 7/8 to 2-3/8 inches. Width across flats s runs its familiar ladder (7/8 in at the 7/8 bolt through 2-3/8 in wrench at the 2-3/8 bolt, with the max/min tolerance band behind it), across-corners e from 1.01 to 2.742 in, head height k nominally 5/16 at the small end climbing to 15/16 (max 0.974) at 2-3/8, body diameter ds max/min per size (0.642/0.605 at 5/8... the ladder opens at 0.515/0.482), and the reference thread length b from 1.00 in at 7/8 up to 2.25 in at the two largest sizes. The collected page names the governing steels — ASTM A325 and A490 — in its title; the mechanical grades themselves are the ASTM standards' job, not this geometry table. The metric sibling of this identity (ASME B18.2.6M) is the registered metric structural page; this is the inch series.
| Standard / scope | ASME B18.2.6-2010 heavy hex structural bolts for ASTM A325 / A490 steels — sizes 7/8 through 2-3/8 in as tabulated |
|---|---|
| Width across flats s | 7/8 (0.875/0.85) to 2-3/8 in (2.375/2.3 max/min) |
| Width across corners e | Max/min: 1.01/0.969 (7/8) to 2.742/2.622 in (2-3/8) |
| Head height k | Nominal 5/16 (0.323/0.302) to 15/32... to 15/16 (0.974/0.902) at 2-3/8 |
| Body diameter ds / thread length b | ds max/min 0.515/0.482 (7/8) to 1.531/1.47 (2-3/8); b Ref. 1.00 to 2.25 in (2 and 2-3/8) |
| Not tabulated | Mechanical properties (per ASTM A325/A490), lengths beyond thread reference, finishes, witness-hole and chamfer details — per RFQ |
Materials
- The geometry fits two steel grades named by the collected page: A325 (medium-carbon, the common structural bolt) and A490 (alloy, higher strength, and the one that forbids galvanizing). Structural supply is normally hot-dip galvanized A325 or bare A490 — state the grade, coating and any slip-critical requirement explicitly on the RFQ, because the head dimensions are identical and only the marking and certificate tell them apart
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ASME B18.2.6 Heavy Hex Structural Bolts (Inch, ASTM A325/A490)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
How does the inch B18.2.6 ladder relate to the registered metric B18.2.6M page?
They are parallel standards, not conversions. ASME B18.2.6 is the inch structural bolt (ASTM A325/A490 steels); B18.2.6M is its metric counterpart for ASTM A325M/A490M. The head proportions are deliberately similar but the size ladders are disjoint — this page runs 7/8 to 2-3/8 in, the metric page M12 to M36 — and a drawing metricated from an inch structure needs the actual series named. Ordering "the same bolt" across the two series is how mis-fit holes and wrong-wrench sites happen; quote the standard designation exactly as the drawing prints it.
What does the "b — Ref." thread length row mean for take-off quantities?
It is the reference thread length under the head — 1.00 in at 7/8 up to 2.25 in at the largest sizes — the minimum usable thread the standard geometries the bolt to. For take-offs it tells you how much thread is available for grip plus nut plus washer at each diameter: a heavy hex structural joint with a long grip may need the next size up if the reference thread cannot cover grip, nut and stick-through. The exact body length ordered is a separate dimension per RFQ; the table geometries the head and the thread reference, not the full length ladder.
Related knowledge
- What Bolt Property Classes 8.8, 10.9 and 12.9 Encode — and When High Strength Stops Being the Right Choice
- Bolt Grade Selection: ISO 898-1 8.8/10.9/12.9 vs ASTM A307 and A325
- 8.8 vs 10.9 vs 12.9 Bolts: Strength, Hardness and Cost — What the Evidence Settles
- Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
- How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint
- Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
- Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support