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Originally Posted by unregistered
by "plain" you mean sleeve ?
they do work excellently,
HOW excellently depends on the materials, design, mfgn, etc.
the revised MCP600/ne 50Z have a large dia ceramic shaft with a grooved passageway down its length to promote fluid flow, but the impeller 'bearing' is the mere hole in the glass-filled acetal (Noryl ?)
- hardly the best bearing matl, but if the film is maintained then should last a long time
what is long ? who knows w/o testing
the sapphire on ceramic is interesting, know nothing about such
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I can see why sapphire is desirable as a bearing component, it is a form of the mineral corundrum, which also is what rubies are. The only difference is that the impurities present change the color of the resulting crystal. I believe the impurity that makes sapphire blue is boron (I believe it is chromium in ruby, I could be wrong). It is the second hardest material there is next to diamond (a distant second to be sure) and very tough. Good choice for a hard bearing. It can be produced synthetically with relative ease so long as the crystals are very small. Jewel grade ones are of course much harder to grow!