ASME B18.2.2 Heavy Hex Nuts
Heavy hex nuts per ASME B18.2.2 — the wide-body hex nut of the inch series, 1/4" through 4" nominal size, larger and thicker than a standard hex nut at the same thread size for heavy-duty and structural bolting. The standard partner for A325/A490 structural bolts.
Last updated: 2026-11
Specifications
The heavy hex nut is the wide-body counterpart of the ordinary hex nut in the inch series. At the same thread size it runs a larger width across flats and a thicker section — a 1/2" heavy hex nut spans 7/8" across flats at 31/64" basic thickness, against roughly 3/4" and a lighter section for the standard hex pattern — so it carries higher clamp loads and bears on more surface. That proportioning is why structural and heavy-duty bolting defaults to it: it is the standard partner for A325 and A490 structural bolts, and construction and engineering inspection practice expects the specification printed on the nut's top face. The size line runs from 1/4" up to 4" nominal thread size, with width across flats, width across corners and thickness tabulated basic, max and min for every step. Common supply is durable steels and stainless steels, plain, zinc-finished or hot-dip galvanized. Material grade is a separate decision — see the ASTM A563 grades page.
| Standard | ASME B18.2.2 — heavy hex nuts, inch series |
|---|---|
| Size range | 1/4" – 4" nominal thread size |
| Dimensions at 1/2" | Width across flats 7/8" basic (0.850–0.875 in); width across corners 0.969–1.010 in; thickness 31/64" basic (0.464–0.504 in) |
| Vs standard hex | Larger and thicker than a standard hex nut at the same size — 1/2" hex runs 0.736–0.750 in across flats — for higher load and more bearing surface |
| Bolt pairing | Standard partner for A325 / A490 structural bolts; grade chosen per the compatibility chart (A563 C/C3/D/DH/DH3, A194 2H) |
| Face marking | Specification printed on the top face for construction and engineering inspection |
| Materials and finishes | Durable steels and stainless steels; plain, zinc-finished or hot-dip galvanized |
| Typical use | Structural connections, metal beams and girders, heavy-duty construction and engineering joints |
| Nominal Size | Basic Major Dia. of Thread | F — Across Flats (basic) | F (min) | F (max) | G — Across Corners (min) | G (max) | H — Thickness (basic) | H (min) | H (max) | H1 — Jam Thickness (basic) | H1 (min) | H1 (max) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/4 | 0.2500 | 1/2 | 0.488 | 0.500 | 0.556 | 0.577 | 15/64 | 0.218 | 0.250 | 11/64 | 0.156 | 0.188 |
| 5/16 | 0.3125 | 9/16 | 0.546 | 0.562 | 0.622 | 0.650 | 19/64 | 0.280 | 0.314 | 13/64 | 0.186 | 0.220 |
| 3/8 | 0.3750 | 11/16 | 0.669 | 0.688 | 0.763 | 0.794 | 23/64 | 0.341 | 0.377 | 15/64 | 0.216 | 0.252 |
| 7/16 | 0.4375 | 3/4 | 0.728 | 0.750 | 0.830 | 0.866 | 27/64 | 0.403 | 0.441 | 17/64 | 0.247 | 0.285 |
| 1/2 | 0.5000 | 7/8 | 0.850 | 0.875 | 0.969 | 1.010 | 31/64 | 0.464 | 0.504 | 19/64 | 0.277 | 0.317 |
| 9/16 | 0.5625 | 15/16 | 0.909 | 0.938 | 1.037 | 1.083 | 35/64 | 0.526 | 0.568 | 21/64 | 0.307 | 0.349 |
| 5/8 | 0.6250 | 1 1/16 | 1.031 | 1.062 | 1.175 | 1.227 | 39/64 | 0.587 | 0.631 | 23/64 | 0.337 | 0.381 |
| 3/4 | 0.7500 | 1 1/4 | 1.212 | 1.250 | 1.382 | 1.443 | 47/64 | 0.710 | 0.758 | 27/64 | 0.398 | 0.446 |
| 7/8 | 0.8750 | 1 7/16 | 1.394 | 1.438 | 1.589 | 1.660 | 55/64 | 0.833 | 0.885 | 31/64 | 0.458 | 0.510 |
| 1 | 1.0000 | 1 5/18 | 1.575 | 1.625 | 1.796 | 1.876 | 63/64 | 0.956 | 1.012 | 35/64 | 0.519 | 0.575 |
| 1 1/8 | 1.1250 | 1 13/16 | 1.756 | 1.812 | 2.002 | 2.093 | 1 7/64 | 1.079 | 1.139 | 39/64 | 0.579 | 0.639 |
| 1 1/4 | 1.2500 | 2 | 1.938 | 2.000 | 2.209 | 2.309 | 1 7/32 | 1.187 | 1.251 | 23/32 | 0.687 | 0.751 |
| 1 3/8 | 1.3750 | 2 3/16 | 2.119 | 2.188 | 2.416 | 2.526 | 1 11/32 | 1.310 | 1.378 | 25/32 | 0.747 | 0.815 |
| 1 1/2 | 1.5000 | 2 3/8 | 2.300 | 2.375 | 2.622 | 2.742 | 1 15/32 | 1.433 | 1.505 | 27/32 | 0.808 | 0.880 |
| 1 5/8 | 1.6250 | 2 9/16 | 2.481 | 2.562 | 2.828 | 2.959 | 1 19/32 | 1.556 | 1.632 | 29/32 | 0.868 | 0.944 |
| 1 3/4 | 1.7500 | 2 3/4 | 2.662 | 2.750 | 3.035 | 3.175 | 1 23/32 | 1.679 | 1.759 | 31/32 | 0.929 | 1.009 |
| 1 7/8 | 1.8750 | 2 15/16 | 2.844 | 2.938 | 3.242 | 3.392 | 1 27/32 | 1.802 | 1.886 | 1 1/32 | 0.989 | 1.073 |
| 2 | 2.0000 | 3 1/8 | 3.025 | 3.125 | 3.449 | 3.608 | 1 31/32 | 1.925 | 2.013 | 1 3/32 | 1.050 | 1.138 |
| 2 1/4 | 2.2500 | 3 1/2 | 3.388 | 3.500 | 3.862 | 4.041 | 2 13/64 | 2.155 | 2.251 | 1 13/64 | 1.155 | 1.251 |
| 2 1/2 | 2.5000 | 3 7/8 | 3.750 | 3.875 | 4.275 | 4.474 | 2 29/64 | 2.401 | 2.505 | 1 29/64 | 1.401 | 1.505 |
| 2 3/4 | 2.7500 | 4 1/4 | 4.112 | 4.250 | 4.688 | 4.907 | 2 45/64 | 2.647 | 2.759 | 1 37/64 | 1.522 | 1.634 |
| 3 | 3.0000 | 4 5/8 | 4.475 | 4.625 | 5.102 | 5.340 | 2 61/64 | 2.893 | 3.013 | 1 45/64 | 1.643 | 1.763 |
| 3 1/4 | 3.2500 | 5 | 4.838 | 5.000 | 5.515 | 5.774 | 3 3/16 | 3.124 | 3.252 | 1 13/16 | 1.748 | 1.876 |
| 3 1/2 | 3.5000 | 5 3/8 | 5.200 | 5.375 | 5.928 | 6.207 | 3 7/16 | 3.370 | 3.506 | 1 15/16 | 1.870 | 2.006 |
| 3 3/4 | 3.7500 | 5 3/4 | 5.562 | 5.750 | 6.341 | 6.640 | 3 11/16 | 3.616 | 3.760 | 2 1/16 | 1.990 | 2.134 |
| 4 | 4.0000 | 6 1/8 | 5.925 | 6.125 | 6.755 | 7.073 | 3 15/16 | 3.862 | 4.014 | 2 3/16 | 2.112 | 2.264 |
- Row 10 (1): The source prints the 1 in row's across-flats basic as "1 5/18" — read as 1 5/8 against its min/max cells (1.575–1.625).
Where this grade fits
The heavy hex body exists to match high-strength structural bolts: it is the standard partner for A325 and A490, with the grade chosen per the compatibility chart (A563 C/C3/D/DH/DH3 or A194 2H). Pairing rule in one line: the nut must develop the bolt's full proof load, so an upgraded bolt always pulls an upgraded nut with it.
Deep read: Pairing a Nut to a Bolt: Property Class, Height, Engagement and Flange vs Hex
Materials
- Steel
- Stainless steel
- Hot-dip galvanized steel
- Zinc-finished steel
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 B18.2.2 Heavy Hex Nuts) 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 10,000 pieces. Stock items run 3–7 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
Heavy hex or standard hex nut — when does the heavy pattern matter?
Wherever the load or the inspection regime calls for it. The heavy hex pattern gives a wider wrench span and a thicker section at the same thread size, so it bears on more surface and carries the high clamp loads of structural and heavy-duty joints — which is why A325/A490 structural bolting pairs with heavy hex nuts rather than standard hex. The thicker body also suits hot-dip galvanized assemblies, where coating build-up eats into thread allowance. If the joint is a light-duty enclosure or bracket assembly, a standard hex nut is usually sufficient and cheaper.
Does "heavy hex" tell me the nut's strength grade?
No — ASME B18.2.2 fixes the geometry, not the material strength. Two 1/2" heavy hex nuts can be very different nuts depending on grade: an ASTM A563 Grade A general-purpose nut and a Grade DH structural nut share the same dimensions. That is why structural RFQs name both the pattern and the grade (for example "heavy hex nut, ASTM A563 Grade DH, 1"-8 UNC"). See the ASTM A563 grades page for what each grade delivers.
What is the MOQ and lead time for this nut type?
The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Common diameters in this nut type are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
What should an RFQ for this nut type state?
State the standard designation (ASME B18.2.2 heavy hex, with the ASTM A563 or A194 grade called out), nominal thread size and threads-per-inch series, material and finish (plain, zinc-plated, or hot-dip galvanized where compatible), any required certificates such as a mill test report per EN 10204 3.1, and quantity per size — plus destination country.
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