ASTM A193 B8 & B8M — Stainless Stud Bolts
The stainless versions of the B7 stud. B8 is 304 stainless, B8M is 316 — picked for corrosion resistance, not raw strength.
ASTM A193 covers bolting for high-temperature and pressure service. Grade B8 is 304 stainless and Grade B8M is 316 stainless (the molybdenum adds resistance to chlorides and salt). Each comes as Class 1 (annealed, lower strength) or Class 2 (strain hardened, stronger).
Covers
Stainless studs & bolts for flanges
Identify by
“B8” or “B8M” on the stud end
Typical use
Corrosive, chemical & food-plant piping
Strength — Class 1
| Grade | Yield | Tensile | Hardness |
|---|---|---|---|
| B8 & B8M, Class 1 | 30 | 75 | HRB 96 max |
Strength — Class 2 (by diameter)
| Diameter | B8 yield / tensile | B8M yield / tensile |
|---|---|---|
| Up to ¾″ | 100 / 125 | 95 / 110 |
| Over ¾ to 1″ | 80 / 115 | 80 / 100 |
| Over 1 to 1¼″ | 65 / 105 | 65 / 95 |
| Over 1¼ to 1½″ | 50 / 100 | 50 / 90 |
Not a stand-in for B7
B8 Class 1 is far weaker than B7 (75 vs 125 ksi tensile). Stainless is chosen for what it resists, not how much it holds — never swap B8 in where a B7 stud is specified without the engineer’s OK.
Matching nuts
B8 studs take A194 Grade 8 nuts; B8M studs take A194 Grade 8M. Stainless on stainless can gall (seize) when tightened — an anti-seize compound on the threads helps.
We stock B8 & B8M studs
Stainless B8 and B8M studs and all-thread, with the Grade 8 / 8M nuts to match. Give us the diameter, length and class.