Hardware Roulette

[jigray3]

I've got a thread going about replacing my keel bolt backing plates. I also intend to replace the hex nuts that pair with the stainless 316 threaded rod cast into the lead keel. Should be simple, right?

I'm looking for passivated 3/4' and 1-1/4" 316 Stainless Heavy Profile Grade 8 nuts, preferably stamped as such from a reliable high quality source. And I only need 2 of the small ones and 3 of the large ones, not 1000.

Best I have been able to find is 316 stainless heavy grade 8 from McMaster -Carr, but they arrived with only 8M stamped on it. No indication they are actually 316 other than the receipt, source on the website is listed as either China or UAE, and I'd have to passivate them myself with Winchinox or some such. Grainger punted and referred to their offering as "globally sourced".

Current 32 year old nuts are stamped 304, and are a precision made work of art. The ones I've purchased are pretty beat up and simply do not inspire confidence.

Am I stuck with mystery hardware, or is there a source?

[Shrew]

8M should denote the ASTM A193 grade "B8M" [B5; B6; B7; B8; B8M; etc]. They are denoted with "B", so they likely dropped it due to space restrictions.

This would indicate it is equivalent to AISI 316 stainless steel. Whether it's 316 or 316L or whether it's B8M Class 1, or B8M Class 2 is harder to tell.

[jigray3]

Thanks, Shrew. I understood 8 indicated it was graded for high-pressure high-temperature applications, good to know the addition of the M assures me it's 316(L).

[GordMay]

Grade B8M fasteners are used for high strength pipeline bolting applications.
A193 Grade B8M is chemically equivalent to AISI 316/316L stainless steel, with improved strength, categorized in two different tensile classes namely class 1 and class 2.
Grade B8M class 1 bolts are carbide solution treated, with maximum tensile strength requirement of 75 ksi or 515 MPa, yield 30 ksi or 205 MPa, and maximum hardness of 223 HBW.
Grade B8M class 2 bolts are carbide solution treated, and strain hardened to achieve higher tensile requirement of 110 ksi or 760 MPa, and 95 ksi or 655 MPa, and maximum hardness of 321 HBW or 35HRC.

“ASTM A193 Grade B8M Specification” ~ by Boltport [BPF]
➥ https://a193gradeb8m.com/specification/

[arsenelupiga]

i would definitely keep old ones as spares at least.

quality of marine parts since covid era is appaling.

[jigray3]

Originally Posted by arsenelupiga

i would definitely keep old ones as spares at least.

quality of marine parts since covid era is appaling.

I plan to keep them, but after 32 years without moving who knows what the threads look like, or even what getting them off looks like? I’ll probably need to rent a torque multiplier for the job, not sure where.

So no one has a better source for nuts like these? I sent an inquiry to Fair Winds Fasteners, but haven’t heard back. They don’t seem to have much large stuff, but do invite inquiries.

Anybody use Winchinox or something similar to passivate hardware?

[Jim Cate]

You mention that the original nuts, made of 304 s/s have held your keel on successfully for 30 years... and now you are demanding an improved fastener. You must be planning to keep that boat a very long time!

The term "overkill" comes to mind, but your boat, your choice.

Jim