B8M Class 2 metric 1

[BowTied]

Hi all,

I am dealing with a spec for 'B8M Class 2' socket head cap screws in 10, 12, 14, and 16mm diameters in a couple of different lengths. My purchasing group says they can't find such a thing. High strength fasteners are a new area for me - is this spec nonsense and these don't exist? If they do, can anyone point me to a supplier in North America? I am in Canada but willing to look in the US as well.

The intended use is in the engine rooms of commercial vessels on equipment designed to process ballast water (non-wetted). Perhaps I should be recommending an alternate material? Any help is appreciated.
Cheers,
Ron

 

[unclesyd]

If anyone would have them it would be Maryland Metrics. Normally metric SS SHCS are made from A2 and A4. I don't have a copy of the standards, but if the threads are roll on you sizes you will Class 2.

Tomorrow I'll call and check and see if anyone is making them to your standard.

http://mdmetric.com/index.html

 

[btrueblood]

Looks like somebody doesn't know their spec's.

Hex head fasteners per ASTM A193 (ASME SA193 for code work)(add M to the ASTM spec for metric fasteners) can be purchased to grade "B8M Class 2", which is a 316ss equivalent alloy, strain-hardened to 96000 psi min. yield strength up to 3/4" sizes.

But that spec. doesn't cover socket head cap screws. For stainless socket head cap screws, you can spec. fasteners per ASTM F837, Group 1, Condition CW1 (102 ksi min. yld.); more commonly available however is condition CW at 80 ksi min yield. But, the material can be anything from 303 to 316 stainless.

 

[BowTied]

Thanks for the responses, it is appreciated.

So I should instead be looking for ASTM F837 Gr1, CW1 or 2 depending on my yeild requirements. I am remain uncertain about your comment on material - can I specify 316 material or is the spec open ended? I expect to need the corrosion resistance of 316 for this application.

Thanks again,
Ron

 

[btrueblood]

Yes, except you specify CW for 80 ksi yields and CW1 for 100+ ksi yield. To be equivalent to a B8M strength, you would spec. the CW1 condition.

Fastener companies would probably be perfectly happy to sell you a 316 or A4 equivalent steel, with strength meeting the requirements of ASTM F837, just ask them. The spec. is open ended on material, but it is always the case that you can specify stricter, or looser requirements, it's your money after all. Maryland Fasteners I believe will sell you fasteners meeting a BS standard. I know our sister company does their own certifying of those to meet an internal fastener strength requirement, testing a random sample of each lot they purchase and having a 3rd party do the tensile tests.

 

[BowTied]

Thanks so much for the response!! Have a great weekend.

 

[adamuk]

Also maybe have a look at (if you want stainless)

ISO 3506-1 Mechanical properties of corrosion-resistant stainless steel fasteners Part 1: Bolts, screws and studs

and

ISO 4762 Hexagon socket head cap screws

Which should help you with strengths and dimensions for metric socket head cap screws.

Hope this helps.



Adam Potter MEng CEng MIMechE

http://www.ax-ea.co.uk