Stainless Steel Nuts
Nuts are internally threaded fasteners (hex and heavy hex) that mate with bolts and studs. Pressure-bolting nuts are specified to ASTM A194 in grades matched to the bolt: 2H with B7, 8M with B8M, and so on.
Choose a grade below for specifications, composition, sizes and weight charts.
Stainless Steel nuts by grade
| Grade | Specification | Key characteristic | Typical use |
|---|---|---|---|
| SS 304 Nuts | ASTM A194 Grade 8 | Balanced corrosion resistance, formability and cost | Food, dairy and beverage processing equipment |
| SS 316 Nuts | ASTM A194 Grade 8M | 2–3% molybdenum for chloride pitting resistance | Chemical and petrochemical process equipment |
| SS 316L Nuts | ASTM A194 Grade 8ML / 8M | Carbon 0.030% max for weld-zone corrosion resistance | Chemical and fertiliser process piping |
| SS 321 Nuts | ASTM A194 Grade 8T | Titanium-stabilised: Ti ≥ 5×(C+N) | Exhaust systems and manifolds |
| SS 347 Nuts | ASTM A194 Grade 8C | Niobium-stabilised: Nb ≥ 10×C | Refinery piping and heater tubes |
| SS 410 Nuts | ASTM A194 Grade 6 | Hardenable by quench and temper | Pump and valve shafts |
| SS 904L Nuts | SS 904L nuts | High Ni-Mo-Cu for sulphuric and phosphoric acids | Sulphuric acid plants and coolers |
| Duplex 2205 Nuts | ASTM A194 duplex nuts | Yield strength about 450 MPa: roughly twice that of SS 316L | Oil and gas flowlines, manifolds and process piping |
| Super Duplex 2507 Nuts | S32750 nuts | PREN ≥ 40: suitable for seawater | Seawater cooling and firewater piping |
How stainless steel nuts are made, sized and tested
How it's madeHot-forged or cold-formed from bar, heat treated (for hardenable grades), tapped and coated if required.
- Size range
- M6 – M100 and ¼" – 4"; heavy hex to ASME B18.2.2; metric to ISO 4032 / 4033
- Finish
- Plain, zinc, galvanised (tapped oversize), fluoropolymer
Testing & documents
- Proof-load tests
- Hardness tests
- Chemical analysis
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Frequently asked questions
Why use heavy hex nuts on flanges?
Heavy hex nuts are thicker and wider across flats than regular hex nuts, which suits the high preloads and larger wrench bearing surfaces needed in pressure bolting.
Which stainless steel grades are available as nuts?
SS 304, SS 316, SS 316L, SS 321, SS 347, SS 410, SS 904L, Duplex 2205, Super Duplex 2507.
Which specifications cover stainless steel nuts?
ASTM A194, SS 904L nuts, S32750 nuts, depending on grade.
Need stainless steel nuts?
Send grade, size, quantity and destination.