Best material for anti-galling on aluminium thread?
Best material for anti-galling on aluminium thread?
(OP)
Hi. I've got an M40x1 threaded hole in a 12mm plate of aluminium alloy (6082-T6). An threaded adjuster bar sits in the hole. What's the best material to make the bar out of to prevent galling? I'm thinking brass, bronze or aluminium bronze. I am also able to use lubricant e.g. grease.
Hobbs101
Mechanical Design Engineer





RE: Best material for anti-galling on aluminium thread?
Anodize the aluminium. We have no problem screwing anodized aluminium parts here.
My next choice would be brass or bronze.
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JHG
RE: Best material for anti-galling on aluminium thread?
I've always preferred ACME class 2G or 3G thread forms (not sure about a metric equivalent); seems like they are less prone to galling. Also the ability to use lube or anti-seize compound I see as a huge plus. Material-wise, I think your choices are OK, even steel (bare or phosphated depending on your particulars).
RE: Best material for anti-galling on aluminium thread?
Is the thread heavily loaded, may impact what mating material you can use. I don't think I've ever had an issue with zinc plated steel into aluminum but haven't played with threads that big. Once in a blue moon do have issues with small stainless fasteners seizing (I assume galling but haven't verified) in 6061-T6. Generally impractical to reliably anodize smaller threads. If it's an adjuster that is routinely actuated and heavily loaded I may have some concerns using anodize - wonder if the aluminum oxide layer would tend to wear the mating screw.
A trapezoidal thread does exist for 40 mm https://mdmetric.com/tech/thddat16.htm
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Best material for anti-galling on aluminium thread?
Is there a jam nut on the M40 adjuster bar.
RE: Best material for anti-galling on aluminium thread?
If anodizing the aluminum, recall that there is a significant change in diametral clearance due to build up. Clearance decreases by at least twice the anodize thickness (i'd have to check again, but it's because the threads are at a 30 degree slope and the radius change is thickness*1/tan(30)
RE: Best material for anti-galling on aluminium thread?
We've used NicoPTFE before on threaded parts and it is tough and very slippery.
Only issue is going to be build up on your M40x1 thread.
RE: Best material for anti-galling on aluminium thread?
The anodize process itself adds material, however, the anodizer usually etches the part to clean it and create a consistent finish. The total anodize process usually (not always) reduces the size a bit.
In any case, your drawings should have a note stating that the dimensions and tolerances apply after finishing.
I have designed lots of lens mounts with M50X0.5 threads, and even larger. The 1mm pitch seems rather large to me. If the same shop does both pieces, they will make them fit.
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JHG
RE: Best material for anti-galling on aluminium thread?
I'm using brass. The ally threads won't be anodised.
I understand with hard anodise the anodise build up is generally half of the anodise thickness.
Hobbs101
Mechanical Design Engineer
RE: Best material for anti-galling on aluminium thread?