Galling on Stainless steel levers

[yadnom1973]

I’m building a project and it has many clamping parts using levers threaded into aluminium parts, levers into bolts and bolts into nuts. It’s outdoors a lot so I ordered Stainless steel levers, nuts and bolts.

One of the parts seized up almost immediately and this is how I came to understand galling. It was not one of the levers into the aluminium parts thank god otherwise I’d of had to scrap the whole component but now I have a very real problem.

I don’t know if stainless into aluminium thread is as bad but if it’s possible then it’s not going to work. I tried to read up on solutions. Anodising, the aluminium parts will be hard coat anodised, anti-galling coatings and lubrication, but all these solutions in all the information I’ve found on line are directed at single use bolts. These levers and nuts and bolts are all repetitive use to some extent or another, being tightened and loosened ever time the parts position needs to be adjusted. I’m concerned that lubrication and coatings, even hard coat anodising will gradually wear away and the parts will seize in the future.

As far as I understand all non corrosive metals gall but if I used stainless steel inserts in the aluminium and steel studs on the levers, steel nuts on the stainless bolts. What I mean is matching stainless with steel threads, dose this solve the problem? Or dose stainless still gall even when paired with steel?

I hate to have to throw out all the stainless fittings and replace them with steel. Are there really coatings last indefinitely? Are there any solutions I’ve not thought of? There must be situations in damp or magnetic environments where levers like these are used, how do they solve this problem? Any advice appreciated.

[Dave54]

Personally I'd get in touch with one of the specialist lubricant suppliers. Rocol or Loctite perhaps.
Ask their tech people whats best for your application.

[aeromech3]

SS & Al alloy threads are very prone to galling when their surface is under pressure and friction from tightening, lubricants can help.
Galvanised Hardened steel bolts seldom suffer. We used cadmium plated fasteners in Al alloy for aircraft though it is a no no for Titanium!

[dewaltdisney]

I am intrigued with this thread Yadnom. Any chance you could post some pics of your project it will make it easier to understand what yu are trying to do. See posting pics posting-pictures-t14693.html

Cheers

DWD

[yadnom1973]

I don’t have any parts here but the principal is very basic in the cases where galling may occur. This is a part form another build which dose exactly the same job. A stainless lever that clamps the aluminium component onto the tube.


can you see this image?

I was looking to see if I could find brass inserts like Helicoils but had no luck so am looking at replacing the lever studs with brass studs. This will solve most of the issues but there are still a few where it’s bolts not levers.

To reduce the scope of the question a little I could ask dose anyone know if there are any coatings or lubricants that would last. An anti-galling coating designed to get a bolt in during assembly may not be expected to continue working after years of regular tightening and loosening of the same stud in the same thread.

[moderator7]

Hi yadnom1973.
We can't see the image, and I can't post it for you because the link just goes to a sign in page.
It's better to upload the pics here as per the instructions linked to by dewaltdisney above.

[yadnom1973]

This is a picture of a similar part

[yadnom1973]

I have no idea what happened there, it kept giving an error saying I cant access the file and I think it had me start a new thread somewhere.

[moderator2]

I think it had me start a new thread somewhere.

For some reason you did start a new thread. I merged them to avoid confusion.

[yadnom1973]

Thanks for the help there mod2

[Hitch]

How about swapping one or the other for brass? Or even zinc plated.


Now you have the components, a little copper slip on the threads would pretty much eliminate the problem from stainless to stainless, but if its constantly in use tightening and loosening, thats not ideal.

Stainless into aluminium, i imagine the thread in the aluminium will eventually pull out, is it a cut thread or a rolled thread in the aluminium?

[yadnom1973]

Brass parts. I spent last night trying to find all the threaded parts in brass. The levers are simple, I can just buy female ones and pin the right length of threaded brass stud in there but the other bolts have proved impossible to find. I’ll try again this morning but I’m beginning to think that nobody makes them.

[yadnom1973]

I’ve been looking at thread inserts. There are copper coated ones and in helicoil there are phosphor bronze one. My concern in putting bronze insets into aluminium is stripping. I was under the impression that bronze is not significantly stronger than aluminium?

I also found Helicoils made form an alloy called Nitronic 60. This is stainless steel but develop among other things specifically to resist galling. The product page sings it praises as a magic bullet solution and I want to believe them but again the repeated stress of tightening and loosening may be outside of what's expected of the these inserts.

[yadnom1973]

Yes a cut thread Hitch but I was always looking to put some kind of inset in there.

[yadnom1973]

I did some tests today using a A2 stainless steel nyloc nut. These things are a nightmare, they gall really quickly with A2 on A2 dry. To test I used the clamp and tightened it and loosened it back and forth quickly and solidly. A2 stainless steel galled in about 5 strokes. A4/316 did better, about 9 strokes. Titanium G5 did not gall at all, I stopped at 30 and the nut and bolt were hot to the touch when I took them out. I examined the threads with a magnifying glass, the titanium bolt's threads are much smoother than the stainless to start with and they looked the same with no damage as far as I could see.

Thought I’d add this in case anyone wanders here later who might find it useful.