Carbon Steel Or Stainless Cylinder Base Nuts.

[John Bowen]

I'm probably overthinking this but is there any reason not to use stainless at such a fairly critical application? Does the heating and cooling cycle affect these fasteners? I'm looking for the hex configuration and Classic Bike Parts Cheshire are the only vendor for carbon steel I've found.

[scotty]

I have no metal science knowledge but I'm using stainless nuts on my swing arm A10 cylinder base with no issues to report......

[Brian]

Stainless nuts will be fine.

Some years ago just as a project I built a plunger A10 exclusively using stainless. With the exception of the conrod bolts every nut, bolt, washer, axle etc etc was stainless.

[Nourish]

I think the problem is with using stainless for studs and critical bolts where some report stretching - although I've not!

[jhg1958]

I know of two general problems with stainless steel fasteners although given my roots in the nuclear industry I use stainless whenever I can.

First is the binding between stainless nuts and bolts. This is mitigated by using copper slip grease and dissimilar stainless steels for nut and bolt.

Second is the preferential corrosion with two metals in close contact. The stainless nut could cause the studs to corrode. I have noticed that stainless washers on mild steel nut and bolt causing this problem.

Given the oil that is always about and the area is easily cleaned I cannot see this being a problem.

John

[John Bowen]

That does it then, no more sleepless nights worrying about stainless cylinder nut failure. Got a chuckle out of JHG 1958's statement about "oil that is always about" helping to prevent corrosion. Reminds me of Jeff Beck's tune O.I.L (Can't Get Enough Of That Sticky) from his last studio album. Thank you to all who answered!

John

[Swarfcut]

  Locking compound on the threads solves the problem of the two threads binding. Some folks call this "Spalling" and the film of compound will also mitigate the effects of electrolytic corrosion. So the best of both worlds. Now we consider the base flange washers, plain, spring, locking...   and so the debate continues.
 Me..  I just use whatever is in the salvaged fixings tray. At least the metallurgy was correct, if not the final aesthetics, that's patina for you and it's far cheaper.

 Swarfy.

[Rex]

Which is probably the safest way, if those salvaged bits came from Small Heath.
The biggest problem with stainless stuff is hoping the the maker understands metallurgy enough to use the right material. There was a spate of stainless cylinder and head studs on sale a few years back which were made from an unsuitably "soft" grade and had the head gaskets blowing on a regular basis.

[John Bowen]

I'd gladly use original fasteners, but it's not easy to find any quantity here in the states, especially for machines of this vintage. I'm planning on SRM head bolts and stainless from Dave Middleton. Any recommendations would be gratefully appreciated.

Thans, John

[chaterlea25]

Hi All,
My SR has stainless studs and nuts,
No issues over the last 24 years

John

[Nourish]

Which is probably the safest way, if those salvaged bits came from Small Heath.
The biggest problem with stainless stuff is hoping the the maker understands metallurgy enough to use the right material. There was a spate of stainless cylinder and head studs on sale a few years back which were made from an unsuitably "soft" grade and had the head gaskets blowing on a regular basis.

What would be the preferred Stainless steel grade for head bolts?

[chaterlea25]

Hi Nourish,
Head bolts are a different matter!
The grade of SS is critical
Offhand I think it was Molnar stainless i got them from 
They have not given any issues since i built the bike c2002

The SS head bolts for Gold Star alloy engines available from Dave Flintoft are closely matched to the expansion rate of the alloy, and priced to match!

John

[John Bowen]

The SRM head bolts are drop forged carbon steel which is why I like those, don't know that I'd trust stainless head bolts. I'd like stainless for the rocker box bolts and nuts though. Appreciate all the replies, thank you.

John