Screw galling - seizing

Hi,

A question about galling; when two metals (typically screws / threads) bind together due to various reasons, and seize solid. I'm after information, charts, metallurgy specs, etc.. this is a work request, and I figured I'd pick a few brains here..

We're looking at a feasibility study, to see what we might need to change to get better reliability out of our designs & assembly procedures.

Right now, we're typically stainless on stainless, and see issues..

dr wogz said:

Hi,

A question about galling; when two metals (typically screws / threads) bind together due to various reasons, and seize solid. I'm after information, charts, metallurgy specs, etc.. this is a work request, and I figured I'd pick a few brains here..

We're looking at a feasibility study, to see what we might need to change to get better reliability out of our designs & assembly procedures.

Right now, we're typically stainless on stainless, and see issues..

Click to expand...

Having built & piloted dragracing motorcycles for as many years as a rocketeer, I have had my issues with thread galling and to the point of snapping off bolts. These engines are not strengthen enough in areas but are stressed to the limit.

It depends on the metals that are used.
Stainless screws in any ferrous metal hole is at risk of galling and/or seizing due to corrosion. Threads on most stainless screws have very sharp edges, somewhat hard which causes them to gall and eventually seize.
We use "Anti-seize" compound, it is available from auto parts stores.
Stainless or Steel screws in aluminum threaded holes are everywhere in a hi-performance motorcycle engine. We use anti-seize there as well. We have to be careful of the amount of torque or you can seize and strip aluminum threads. Then you are doing heli-coil inserts.
You only need a small amount of compound, 1 drop on a screw and it will not gall for a long time.

I do not have any data but follow any larger racing business, NASCAR, NHRA, OFF-ROAD, there should be plenty of data.
Some of the major nut and bolt manufacturers have data as well.

Thanks Dave,

exactly what I'm after. I've reviewed a number of fastener pages and all seem to report the same findings. We manufacture for the food industry, so, we have a lot of stainless!! And heated too!! so, both of these compound to the galling issue. Anti-seize compound or 'lubricated' fasteners seem to be the prevailing recommendations, as well as using dissimilar grades of stainless.

the other issue we have is our fabricators using too much heat to weld in weld nuts & weld studs. So, the threads are disfigured!

We assemble chillers and motor controllers for Navy boats. Various grades of stainless and aluminum, and we use GOBS of this stuff:

Banzai88 said:

We assemble chillers and motor controllers for Navy boats. Various grades of stainless and aluminum, and we use GOBS of this stuff:

Click to expand...

Bingo!

yep, we got that stuff too, but we only use in in one application.. Why not others? Dunno, but that's gonna change. There is also recommendations of "Moly" lube and "waxed" fasteners.. We're gathering info for a 'soon to be' company shift on fasteners..

I've worked in a food grade fabricating environment where I had to deal with compliance inspectors. One major issue for us was that a lot of the anti-seize compounds I wanted to use are not food grade. Here's the food grade stuff: https://www.loctite.com.au/3320_AUE_HTML.htm?nodeid=8802635677697

As far as welding nuts and studs, just expect to be chasing lots of threads...

blue moly is used on our stainless-on-stainless applications...regular moly would still occasionally seize
https://www.chempoint.com/products/catalog/bostik-inc/bostik-mro-lubricants/never-seez-blue-moly

We have this problem, typically with lock nuts (nylock) as they "pre-load" the threads. We buy all of the sst nylon lock nuts "waxed" from our bolt supplier. Also, driving the nuts aggressively with air tools or power drivers makes it worse

Yeah I used a lot of stainless lock nuts and bolts on my dragbike. Without anti-seize, you can snap sum off.

Stainless bolts/screws into stainless nuts/threaded inserts have caused some grief where I work. Fix was to go back to standard inserts instead of SS.

We changed to SS because of perceived corrosion problems. It was never a serious problem anyway.