A194 8M Heavy Hex Nuts
316 stainless heavy hex nut for B8M studs — molybdenum-bearing for chloride and marine service, 80 ksi proof load.
Robust fastener with a thicker, wider hexagonal shape for high-stress applications. Manufactured and stocked across ASTM A194 grades from 2H to 8MA, plain or coated.
ASTM A194 Grade 8M is the 316 stainless nut that completes an A193 or A320 B8M stud bolt set. Molybdenum gives it the pitting and crevice-corrosion resistance the 304-based Grade 8 lacks, so it is the nut for offshore, coastal, seawater and chemical flanges.
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What A194 8M must meet.
| Nut style and size (in.) | Proof load stress (ksi) | Hardness, min | Hardness, max |
|---|---|---|---|
| Heavy hex, all sizes | 80 | 126 HBW / 60 HRB | 300 HBW / 32 HRC |
| Hex (finished pattern), all sizes | 75 | 126 HBW / 60 HRB | 300 HBW / 32 HRC |
| Grade 8MA (solution treated in the finished condition), all sizes | 80 heavy hex · 75 hex | 126 HBW / 60 HRB | 192 HBW / 90 HRB |
Values per ASTM A194/A194M-24, Tables 1, 2 and 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Jam nuts: 46 % of the tabulated proof load. Strain-hardened Grade 8 nuts (S1) are proof tested to 125 / 115 / 105 / 100 ksi heavy hex by size and hardness limits do not apply.
Grade 8M nuts are hot or cold forged, or machined from hot-forged, hot-rolled or cold-drawn bar, with no heat-treatment requirement (A194 clause 6.6). The 8MA type is carbide solution treated after forging or machining (clause 6.7), which lowers hardness to the 126–192 HBW / 60–90 HRB window.
Full A194 8M data sheet: chemistry, physical properties and standards →
Made to standard or to your drawing.
- Offshore and marine flange bolting
- Seawater and desalination piping
- Chemical and pharmaceutical process equipment
- Coastal plant and pulp-mill bolting
- Sour service within NACE limits