MF FASTENER INDUSTRIES LLC Manufacturer of anchor bolts, studs & plate washers · Importer & stockist of fasteners

Technical datasheet ASTM A193 / A193M — Grade B8 & B8M stainless stud bolt

Reference only — for design, verification or contractual purposes refer to the current issue of the original standard. MF Fastener Industries LLC · sales@mfindllc.com · +971 6 767 2469 · mfindllc.com

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Dimensional datasheet

ASTM A193 B8 & B8M

Austenitic stainless steel stud bolts. B8 is Type 304, B8M is Type 316 with molybdenum for chloride resistance. Supplied Class 1 solution annealed, or Class 2 strain hardened for higher strength.

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d nominal thread diameterP thread pitchL stud length

Dimensions

inches

Class 2 is solution annealed then strain hardened, so its strength falls as diameter rises — the cold work reaches less far into a larger bar. Class 1 is uniform.

Size	B8 Cl.1 tensile	B8 Cl.1 yield	B8 Cl.2 tensile	B8 Cl.2 yield
1/2"	75 ksi	30 ksi	125 ksi	100 ksi
5/8"	75 ksi	30 ksi	125 ksi	100 ksi
3/4"	75 ksi	30 ksi	125 ksi	100 ksi
7/8"	75 ksi	30 ksi	115 ksi	80 ksi
1"	75 ksi	30 ksi	115 ksi	80 ksi
1-1/8"	75 ksi	30 ksi	105 ksi	65 ksi
1-1/4"	75 ksi	30 ksi	105 ksi	65 ksi
1-3/8"	75 ksi	30 ksi	100 ksi	50 ksi
1-1/2"	75 ksi	30 ksi	100 ksi	50 ksi

Class 2 is not simply a stronger Class 1

Class 2 gets its strength from cold work, not heat treatment. That strength relaxes at elevated temperature — Class 2 is generally not used above about 425 °C, where the cold work anneals out.

For sustained high temperature, Class 1 is the correct choice even though it is weaker at ambient.

Stainless galls

Austenitic stainless threads seize during assembly, particularly at larger diameters and with fast tightening. A galled stud usually has to be cut out.

Use an anti-seize compound, tighten slowly, and pair with a nut of a different alloy where the specification allows. Silver-plated or PTFE-coated studs are also common where galling has caused problems before.

B8M is not just a coating change

B8 is Type 304, B8M is Type 316 with 2 to 3% molybdenum. The molybdenum resists chloride pitting, which is why B8M is specified for marine, coastal and process streams containing chlorides.

In Gulf coastal conditions the difference between them is measured in years of service life.

B8M mechanical properties

Type 316

Size	B8M Cl.1 tensile	B8M Cl.1 yield	B8M Cl.2 tensile	B8M Cl.2 yield
1/2" – 3/4"	75 ksi	30 ksi	110 ksi	95 ksi
7/8" – 1"	75 ksi	30 ksi	100 ksi	80 ksi
1-1/8" – 1-1/4"	75 ksi	30 ksi	95 ksi	65 ksi
1-3/8" – 1-1/2"	75 ksi	30 ksi	90 ksi	50 ksi

B8M Class 2 is slightly weaker than B8 Class 2 at every size — Type 316 work hardens less readily than Type 304.

Grades and pairing

A193 / A194

Grade	Material	Matching nut	Typical service
B8 Class 1	Type 304, annealed	A194 Grade 8	High temperature, low load
B8 Class 2	Type 304, strain hardened	A194 Grade 8	Ambient, higher load
B8M Class 1	Type 316, annealed	A194 Grade 8M	Chloride, high temperature
B8M Class 2	Type 316, strain hardened	A194 Grade 8M	Chloride, higher load
B8T / B8C	321 / 347 stabilised	A194 Gr 8T / 8C	Sustained high temperature

Match the nut alloy to the stud. A Grade 8 nut on a B8M stud reintroduces the chloride weakness the B8M was specified to avoid.

At a glance

Standard	ASTM A193 · A193M
Grades	B8 · B8M · B8T · B8C
Material	B8 Type 304 · B8M Type 316
Classes	Class 1 annealed · Class 2 strain hardened
Thread	UNC to 1 in · 8 UN above
Matching nut	A194 Grade 8 · 8M
Carbon steel equivalent	A193 B7
Cryogenic version	A320 B8 / B8M — impact tested
Certification	Mill certificate against heat number

Supply

Stud bolts are manufactured at our own plant — cut to length, threaded, chamfered and coated to your specification, with nuts supplied to match.

Bar stock is sourced from certified mills with test results traceable to the heat number.

Finish

Plain	As machined, passivated
PTFE / Xylan	Reduces galling and eases removal
Silver plated	Anti-galling, high temperature
Certification	Mill certificate, EN 10204 3.1 as standard

Testing

Dimensional and thread inspection is carried out in our own plant on calibrated instruments. Tensile, hardness and chemical testing is carried out by independent UAE-accredited laboratories.

Reference only

This datasheet is published for reference. Dimensions and property values are reproduced in good faith from published standards, but for design, verification or contractual purposes always refer to the current issue of the original standard.

If a figure here conflicts with the standard, the standard governs.

Need a quotation?

Send the size, length, grade, class, nut grade, coating and quantity. Tell us the service temperature and whether chlorides are present.