Thread Galling Issues

[Harry.]

We are using stainless steel components in our sub-assemblies. We don't want to use lubricant because we don't want them to work loose.

When using the same alloy grades, is there a method or lubricant which can avoid thread galling without having a negative impact on the effectiveness of threads?

 

[Tmoose]

Hi Harry,

There are many threads on stainless steel fasteners and galling. Searching in this forum, and the welding/fastening forum would very possibly fix your problems. There is a search button up there ^ .

Your post is mighty thin on information.
Are the fasteners SS also?
What grades of SS are you dealing with.
What galling experiences have you experienced so far. Thee fasteners, or the faying surfaces of the components?
Drawings and pictures of your bolted (?) assembly, and bolting procedures used are NECESSARY to understand what is going on.
I am unsure if it is a gasketed joint, a real life hard working structure, a name plate attached to a machine, or something else altogether.

"We don't want to use lubricant because we don't want them to work loose."
Read s little more about bolted joints that use bolt tension and preload to secure components and eliminate fastener fatigue and that concern will wither and fall to the ground as dust.

 

[Harry.]

We are attaching a mounting bracket to hollow section framework for a number plate for a boat.
Its well above the water level and we have been using stainless steel screws in 316 to attach the plates into the mounting bracket. If we change to a different type of stainless steel, I don't think it will offer as much corrosion protection? We have a customer wanting 316 steel because it is supposed to be the 'Marine Grade'and should last longer in terms of corrosion. It is difficult to install the screws into the plate without them galling. I don't want them to corrode because of being galled. I will look through the threads for a coating, plating or lubricant.

Thanks for pointing out that there are other threads on this matter.

 

[EdStainless]

One option is to use a low strength (non-permanent) thread lock compound.
This will provide some lubrication, it will seal the threads minimizing corrosion, and help hold it together.

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P.E. Metallurgy, Plymouth Tube

 

[dgallup]

Nitronic 60 is better at resisting galling and I think every bit as corrosion resistant as 316. I've never bought any, I expect they are very expensive.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[EdStainless]

I have used fasteners in Nit50 with rolled threads.
Better pitting resistance than 316 and very good galling resistance.

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P.E. Metallurgy, Plymouth Tube

 

[btrueblood]

You can buy Nitronic 60 helicoil inserts from Grainger; this gives you the gall resistance for stainless fasteners without having to buy expensive screws. But I'd try some anti-seize and mandate hand-tightening to start. Speed of installation (e.g. power tools) can have a dramatic impact on the tendency of ss fasteners to gall.

 

[drawoh]

Harry.,

Loctite[ ]242 is a lubricant. Lubricant gives you better control over thread torque. Using controlled torque tighten your fasteners down as hard as possible, keeps your fasteners from coming loose, even if the lubricant does not harden, like Loctite[ ]242.

--
JHG

 

[Tmoose]

"even if the lubricant does not harden, like Loctite 242."

I think Loctite 242 is the ubiquitous "blue" loctite thread locker.
It does cure. Not sure if something else was meant by "harden."

http://www.crlaurence.com/DataSheets/SpecData/242-EN.pdf

 

[glass99]

We use Never Seez. Its a lubricant but if you torque the bolt up it won't come loose.

 

[mighoser]

Nitronic 60 or 50 (better than 316 pitting resistance) locking helicoils. Or switch to nitronic bolts and use loctite

 

[drawoh]

Tmoose,

I was pointing out that lubricant is a way to tighten fasteners reliably, even if the lubricant does not set or harden. If it sets and hardens, so much the better.

--
JHG

 

[DAVIDSTECKER]

One of my venders uses silicone bronze nuts with the 316 bolts.
If he has to use stainless nuts he uses 18-8 (304) nuts to get some sort of dissimilar metals to ease galling.

 

[ZaneC]

We sometimes use Duplex with 316. You can get fixings with a pre-applied low strength thread locking compound.

 

[Harry.]

Thanks for your help. We used dissimilar metals in the end.

 

[JadeStarCat]

I would ask how the screws are being " set " as well. Stainless threads need to be run down very slowly and generally not with power tools when installed. Otherwise this material seems to generate extreme heat very quickly as the screw contacts the threads. Also no 2 screws will have the exact same characteristic in this respect. This is what I have noted.

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