ASTM A194 Grade 8 Heavy Hex Nuts
ASTM A194 Grade 8 heavy hex nuts — austenitic stainless steel, AISI Type 304 chemistry (Cr 18.0–20.0%, Ni 8.0–11.0%, UNS S30400), hardness 126–300 HB with the lowest proof-load ladder of the common grades (80,000 psi heavy hex: 2,540 lbf at 1/4" through 119,360 lbf at 1-1/2"), plus the strain-hardened option at substantially higher loads.
Last updated: 2026-11
Specifications
Grade 8 is the plain austenitic stainless grade of ASTM A194: AISI Type 304 chemistry (UNS S30400, 18.0–20.0% chromium, 8.0–11.0% nickel) with no deliberate molybdenum — that addition is what separates Grade 8M in chloride service. The austenitic structure is soft by the standard's standards: a 126–300 Brinell band with Rockwell C capped at 32 and Rockwell B at 60 minimum, which is why the standard proof-load ladder sits at 80,000 psi (heavy hex) and 75,000 psi (hex) — roughly half the carbon-steel grades. Where an assembly needs more strength from the 304 chemistry, the specification provides strain-hardened nuts tabulated separately (Table 8), which run on a stepped proof stress of 125,000 psi down to 100,000 psi by size — at 1-1/2", a strain-hardened Grade 8 heavy hex nut carries 149,200 lbf against 119,360 lbf in the standard condition. For corrosion-first selections pair Grade 8 with A193 B8 studs; for chloride or marine exposure, move to 8M.
| Standard | ASTM A194 — Grade 8 (austenitic stainless; scope 1/4" nominal and above) |
|---|---|
| Material | Austenitic stainless steel, AISI Type 304 chemistry (UNS S30400) |
| Chemistry (A194-11 Table 1) | C max 0.08%, Mn max 2.00%, P max 0.045%, S max 0.030%, Si max 1.00%, Cr 18.0–20.0%, Ni 8.0–11.0% |
| Hardness (A194-11 Table 2) | Completed nuts: Brinell 126–300, Rockwell C 32 max, Rockwell B 60 min |
| Proof-load basis | All Grade 8s: heavy hex 80,000 psi; hex pattern 75,000 psi (Table 3 stress-area basis) |
| Proof load, sampled sizes (heavy hex) | 1/4" → 2,540 lbf; 1/2" → 11,350 lbf; 3/4" → 26,720 lbf; 1" → 48,480 lbf; 1-1/2" → 119,360 lbf (full ladder table below) |
| Strain-hardened option (Table 8) | Stepped proof stress 125,000 psi (≤3/4") / 115,000 (7/8"–1") / 105,000 (1-1/8"–1-1/4") / 100,000 psi (1-3/8"–1-1/2"); sampled strain-hardened heavy hex at 1-1/2" → 149,200 lbf (vs 119,360 lbf standard condition) |
| Grade pairing | Pairs with A193 B8 studs — general corrosion service; upgrade to 8M (316 chemistry) for chloride/marine exposure |
| Jam nuts | Proof load 46% of the tabulated load, per the standard's note |
| Design note | Proof loads are not design loads (A194-11 note 1) |
| Nominal size | Threads per inch | Stress area (in²) | Proof load, heavy hex (lbf) | Proof load, hex (lbf) |
|---|---|---|---|---|
| 1/4 | 20 | 0.0316 | 2540 | 2380 |
| 5/16 | 18 | 0.0524 | 4190 | 3930 |
| 3/8 | 16 | 0.0774 | 6200 | 5810 |
| 7/16 | 14 | 0.1063 | 8500 | 7970 |
| 1/2 | 13 | 0.1419 | 11350 | 10640 |
| 9/16 | 12 | 0.182 | 14560 | 13650 |
| 5/8 | 11 | 0.226 | 18080 | 16950 |
| 3/4 | 10 | 0.334 | 26720 | 25050 |
| 7/8 | 9 | 0.462 | 36960 | 34650 |
| 1 | 8 | 0.606 | 48480 | 45450 |
| 1-1/8 | 8 | 0.79 | 63200 | 59250 |
| 1-1/4 | 8 | 1 | 80000 | 75000 |
| 1-3/8 | 8 | 1.233 | 98640 | 92450 |
| 1-1/2 | 8 | 1.492 | 119360 | 111900 |
Materials
- Austenitic stainless steel (AISI 304 / UNS S30400)
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 (ASTM A194 Grade 8 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
Why is the Grade 8 proof-load ladder so much lower than Grade 2H?
Metallurgy, not quality. Grade 8 is an austenitic stainless (Type 304 chemistry) whose crystal structure cannot be hardened by quench and temper; the standard rates it at 80,000 psi proof stress (heavy hex) with a 126–300 Brinell band, against 175,000 psi for quenched-and-tempered 2H. What austenitic 304 buys instead is corrosion resistance and low-temperature toughness. If the assembly needs the 304 chemistry with more strength, the specification's strain-hardened Grade 8 table runs a stepped proof stress from 125,000 down to 100,000 psi by size — still below 2H, but far above the soft condition.
When do I step up from Grade 8 to Grade 8M?
When the service medium contains chlorides. Grade 8 is the 304 chemistry; Grade 8M adds 2.00–3.00% molybdenum (316 chemistry), and molybdenum is what resists pitting and crevice corrosion in chloride-bearing environments — marine equipment, chemical processing, coastal exposure. In dry atmospheric or mildly corrosive service, plain Grade 8 paired with A193 B8 studs does the job at a lower cost.
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 (for example DIN 985 or DIN 6923), nominal thread size and pitch (metric coarse unless fine pitch is required), material and strength pairing with the mating bolt, finish (plain, zinc, or hot-dip galvanized where compatible), 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