Stainless steel bolts in aluminium - a good idea?

Since I´m googlin' around the web searching for parts I´ve come across more and more ads with stainless steel bolts for practically the whole engine (Commando). My experience from using ss bolts isn´t the best, I think the thread cuts pretty easy, smaller bolts/screws snap off easy, and isn´t there a galvanic problem mixing ss and aluminium? I´m sceptical......... :?

They can be a disaster. But if you use top quality stainless and a thread lubricant like copper slip you will be fine.

It's stainless in stainless that's got sticky with me.

Save that SS jewelry for your boat.

i'm not particularly keen on SS bolts, however the kit that CNW puts together for the engine is nice, and it includes the proper ARP thread lubricant

there many pictures showing the nice bits, short of blasting and recoating the original fasteners, the ARP save time and headache for me.

I've had SS fasteners in the timing cover, rocker plates, and primary cover for nearly 30 years with no problems. They are all low stress areas and there's no sign of corrosion. I also have SS just about everywhere else on the bike such as Z plates, foot rests,switch gear, gear box, etc., but not axles. Wheel spokes are also SS. I've never stripped or broken a bolt. I have had to put a helicoil or two in things like the Z plates but those were well beat by the PO, not stripped by me.

For high stress engine bolts I would only use ARP type as supplied by CNW.

Edit: SS polishes on my wheel with ease and holds a shine.

Discussion about stainless steel fasteners come up more frequently than visits from Haley' comet; I read them all with keen interest; yeas seem have favor by about a 60/40 split. Rocky Point Cycle has been selling SS fasteners for over 30 years, with the exception of a small batch of long head bolts, where the threads weren't cut deep enough; my predecessor, Stan Smith and me haven't had a single complaint; that's thousands of pieces.

Stainless fasteners can be a real problem if fastened to other stainless fasteners if you do not coat the engagement point with a suitable anti-seize compound. 1/4" fasteners are made of 18-8, 5/16" and up are 316 or 304, all fasteners are rated above maximum torque settings for the application they are specified for. Stainless fasteners are highly rust/corrosion resistant; light years better than carbon steel equivalents. When you polish a stainless fastener it stays polished. My dad and me owned a blue water sail boat that made 5 round trips from Boston to Bermuda it was stainless fastened and after 28 years some of the stainless fasteners showed some degree of corrosion, oddly the boat was made in England, go figure.

I respect the purists that are building point bikes, but I haven't seen many (any) on this forum in the 9 years I have been a member??? Rocky Point Cycle has every nut and bolt, in stainless, for '71 and up with the exception of connecting rod bolts and a few specialized fasteners like the timing pinion and alternator fixing nut. We also have a decent offering of British Cycle threaded fasteners (22 & 26 TPI & BA). The specialized fasteners that we do offer are, for the most part, made in the USA.

In the late 80's I rebuilt a Commando using all Stainless fittings, brackets etc from D. Middleton. Still in business I believe. From memory I used copper slip on most, if not all.
The bike was a daily rider in the UK, all weathers.
The bike was also ridden hard.
I don't recall any issues whatsoever, it certainly made cleaning easier.

Will probably use them on mine, bit by bit over time!

peter12 said:

In the late 80's I rebuilt a Commando using all Stainless fittings, brackets etc from D. Middleton. Still in business I believe. From memory I used copper slip on most, if not all.
The bike was a daily rider in the UK, all weathers.
The bike was also ridden hard.
I don't recall any issues whatsoever, it certainly made cleaning easier.

Will probably use them on mine, bit by bit over time!

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+1 regarding D.Middleton quality, I've been using them for years too, not for Commando specific parts, but for general stocks of fasteners. Never had an issue with their quality. Very fast delivery too.

For this who don't know, or think it's exaggerated, the galling when using stainless on stainless is very real. I once temporarily fitted stainless nuts to a stainless shaft and they welded together solidly! Copper Slip, or similar, is a must.

300 series stainless in aluminum is not a problem if the joint is usually dry. Do not use stainless fasteners in aluminum in marine environment, and never use 400 series stainless with aluminum.

RustOleum makes a rattle can product called "cold galvanize" or some similar name (I am not where I can check it).
Spray it on the fasteners, let dry, and use with or without an anti-seize compound and don't worry about it.

Another option: use anti-seize on the threads of a ss bolt/screw, and use a copper or fiber washer under the head to insulate the stainless from the aluminum part.

Blue Loctite affords some cathodic protection as well.

Slick

texasSlick said:

Do not use stainless in marine environment,

Slick

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In the early 50s when I started sailing, fiberglass was making an entrance; wood with brass fasteners, deck hardware was triple chrome plated, blocks were made of wood plates and brass pins/pulleys and comprised the majority of the marine market. Today virtually all marine hardware is made from stainless and plastic. Stainless fasteners in a marine environment should not be used where the fastener surfaces will be deprived of oxygen,, typically below the water line and in applications where the fastener will be encapsulated; that leaves and amazing range in/on a boat for stainless. Blanket statements about not using stainless for marine applications need qualification.

Stainless steel contains chromium and nickel and a low level of iron. Chromium does not like chloride ion. In conjuction with pure aluminium chromium often has a passivation effect. However most alloys used in motorcycles are not pure aluminium. If you are using 4000 series aluminium, it probably contains relatively high levels of copper and you might get inter-granular corrosion, especially if there is any salt around.

I think the actual experience of those who have successfully used SS on their bikes outweigh the theoretical corrosion possibilities presented here.

So far I've not heard of anyone saying their SS spokes corroded the heck out of their hubs, timing, covers, etc., just theories.

Most boats, especially high end, use SS fasteners because plain steel simply rusts in the salt environment. Galvanized eventually gives up and rusts.

That being said there are dissimilar corrosion issues that are mitigated by a less noble sacrificial anode metal than the aluminum.

Here's a quote from an aluminum boat manufacture:

Except for sacrificial anodes, don't mount any metal to the hull other than aluminum or high quality stainless steel. If you use fasteners they should be plastic or stainless, not zinc, brass, copper or iron based. Inside the boat, don't let any metal sit in the same spot in the bilge for long. Lead sinkers, fish hooks as mentioned earlier copper even a penny sitting in one spot can be a starting point for electrolysis.

So theories aside, dress up your Norton with polished stainless and don't worry about corrosion.

If you're a purest, install all stock plated screws for the judges.

Original post edited to clarify .... stainless fasteners in marine environment are preferred, but never in contact with aluminum. copper, or zinc.
Slick

Ok, thanks for all the input, you´ve calmed me down.... 8) Seems like there´s not much of a problem so maybe I´ll go for some stainless sets.
Tommy

texasSlick said:

Original post edited to clarify .... stainless fasteners in marine environment are preferred, but never in contact with aluminum. copper, or zinc.
Slick

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I presume you want this statement out:

"Another option: use anti-seize on the threads of a ss bolt/screw, and use a copper or fiber washer under the head to insulate the stainless from the aluminum part."

I wholeheartedly agree that 400 series SS should not be used on a boat.

My aluminum outdrives used 316 SS to assemble AND had a big block of zinc bolted to them as well. The aluminum props had another anode as they were installed on a SS shaft.

My shaft drive boats has zinc collars on the SS shafts to protect the bronze props.

No matter the sacrificial anode on the outdrives they still got a little corrosion in the bolt holes as the anode could not protect them there. I used a coating, the name of which I cannot recall, which did a good job.

I certainly would NOT use copper based never-seize.

All of this is about dissimilar metals submerged in a electrolyte bath of salt water, not holding motorcycle parts together!

@JimNH

In a dry environment, such as using ss fasteners in a Norton timing cover, ("dry" allows one to get caught in the rain occasionally) the cathodic potential difference between ss and aluminum, copper, or zinc is minimal, and there is little risk of corrosion, particularly if anti-seize (the non metal type) or anti electrolytic is applied to the threads and an insulating washer of fiber or nylon is used under the fasteners head. In lieu of an insulating washer, a copper washer under the head makes the washer the sacrificial metal rather than the aluminum threads, and if usually dry, even this is likely to be minimal.

In the marine environment, or if the bike frequently runs over wet roads with de-icing salts, this produces an electrolyte that makes the ss and Al, Cu, or Zn combination a battery with metal sacrifice as you point out. Thus, Stainless fasteners in an aluminum part should be avoided.

A fastener materials compatibility chart is available thru this link:

http://www.engineersedge.com/hardware/f ... _13354.htm

My Atlas (bought new in '63) came with aluminum washers under the cheese head timing cover screws. After I chewed up the heads on the original screws, I replaced them with ss socket head cap screws that have been in place for over 50 years. Back in the 60's I used non hardening Form-a-Gasket as an anti electrolytic and thread sealer. These days I use the RustOleum cold galvanize on the ss threads with either blue locktite or Teflon anti seize.

Slick

fiatfan said:

Since I´m googlin' around the web searching for parts I´ve come across more and more ads with stainless steel bolts for practically the whole engine (Commando). My experience from using ss bolts isn´t the best, I think the thread cuts pretty easy, smaller bolts/screws snap off easy, and isn´t there a galvanic problem mixing ss and aluminium? I´m sceptical......... :?

Click to expand...

Thats why on my numerous Commando BMW Guzzi rebuilds I allways use either blue loctite or Nickel anti sieze- problem solved.

Good ol' Rust-O-Leum.

Gotta love it.

Regardless of what all the experts say...use a good thread compound on your stainless bolts into aluminum. You will never be sorry for it. For things that are heavily loaded, select bolts that have the mechanical properties needed regardless of what they are made from. You will never be sorry for that either.