Dry film lubricant for Aluminum/Stainless Steel threaded joint

[chopper75]

I have a threaded joint that we are having problems with. The male thread is 304 Stainless and the hole is 6061-T6. thread is 8-32. We are starting to get some failures in the threads (gauling, aluminum shavings...). We continuously use the same steel thread and the aluminum part may see as much as 10 cycles.

Would a dry film lubricant be of benefit on the male thread (such as Loctite 39893). I've never used such a product.

 

[drawoh]

chopper75,

I have heard the horror stories about aluminium and stainless steel, but I have not experienced them. Loctite[ ]242 is a medium strength thread-locker, and it is a lubricant. Aluminium is a bad material for tapping. If you are disassembling and reassembling, you should use thread inserts. Helical thread inserts, self tapping inserts and self-clinching nuts all are good.

304[ ]stainless is very soft. Consider not re-using your screws.

--
JHG

 

[DAVIDSTECKER]

Yes, it should help a lot.
We use SSTL fasteners and since the guys finally started using anti-seize faithfully we haven't had any more issues with galling.

 

[MintJulep]

I will reduce the galling.

It will also increase the preload for the same tightening torque. Possibly leading to increased thread stripping in the aluminum.

Inserts good.

 

[desertfox]

Hi chopper75

Any chance you can fit a thread insert in the aluminium?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[racookpe1978]

I'd definitely recommend a permanent SStl thread insert in the Al. Then thread the new SStl fasteners into the insert each time. Fasteners are a few cents compared to replacing a tapped hole that has stripped out of your main part.

 

[tbuelna]

If you are seeing aluminum debris in the tapped holes after removing the screws, the problem is likely due to interference and/or excessive contact stress levels in the threads. So as others noted, the best approach would be installing a thread insert into the aluminum. Most thread inserts are available in durable cres materials (like A286) with DFL coatings. They are easy to install and replace if damaged.