Improvised Bushing

[BigBoy1]

I have a spinning 3/8" brass shaft and it is in an alumimun housing. I don't like the idea of the dissimilar metals (brass and aluminum) riding on each other. I didn't have any brass tubing the correct size to make a bushing sleeve for inside of the aluminum housing but the item had to be fixed. In my searching I came across some .38 Special brass cartridge cases. Their outside diameter was 3/8" so they were pressed into the aluminum housing and trimmed flush. They made a perfect brass sleeve for the aluminum housing. They were bored to 0.350" internal diameter. I then turned the brass shaft down to 0.348" and now I have brass running on brass!

Bill

[SGW]

Neat trick, but IN GENERAL, I think dissimilar metals tend to make better bearing surfaces.

[Astronowanabe]

gauling situation

My limited understanding is you want materials with
*different* coefficients of friction and hardnesses because
when friction happens, both build sides refuse to give
until chunks start breaking off and snowballing.
Aluminum seems to be the poster child for this behavior.

might want to keep it well oiled till you replace one surface
with something harder.

[rantbot]

Hard material on hard (steel on steel, steel on cast iron) can be fine, hard on relatively soft (steel on bronze) can be fine, soft on soft is most often a recipe for disaster. Once one of the materials starts to gall, it will start the other part galling too (if there's relative motion), and in short order everything will weld together.

Steel on brass (or bronze) is known from long experience to be a particularly good pairing, which is why those two are so often seen in, say, worm gear sets. Stainless steels are not so good because many have galling tendencies. Hardened stainless (say, 400 series) isn't so bad.

Hard on very soft (say, steel on babbitt metal) is often best of all, because foreign particles which manage to find their way into the interface become embedded in the soft material, where they won't cause any more grief.