A2 Stainless locknut with 303 stainless male thread.

[chopper75]

We are using a M10 locknut. The material is "A2" and the locking mechanism is a nylon ring at the end of the thread. Commonly called a "Nylock" in our area.

The make thread that it is going on is 303 Stainless.

Issue: severe gauling/seizing when we engage the locking mechanism.

Question: What would be the best grade of SS for the locknut to reduce gauling? I don't think I can change the 303 on the male thread.

 

[btrueblood]

- try slowing down the wrench speed. Don't use the nut to "take up" the joint, and minimize thread protrusion past the nut as much as possible.

- lubricate the threads with a good anti-seize

- yes, you can try a different grade of stainless nut material, if you can find it, but unless you can get nuts made from a gall-resistant alloy (gall tuff, nitronic ...) your results may vary. If you switch to a standard grade 5 alloy nut (i.e. steel, not stainless) it probably will never gall. You can get those in zinc plated versions...

 

[FACS]

Try A4 (316) Stainless. It is less prone to galling than A2 (304).
Hand tighten, don't over torque - and once installed it should not be taken on and off regularly without an anti seize. Unfortunately, 303 isn't as anti galling as 316 - too bad you are stuck with the thread.

good luck

 

[EdStainless]

Are the threads rolled? This is often a more serious issue with cut threads.

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P.E. Metallurgy, Plymouth Tube

 

[chopper75]

Ed, these are NOT rolled. The male thread is cut on a lathe....