Plain Bearing Material Problems

I have designed a small rotating assembly that runs at only 0 - 150 RPM with very very minimal load, it has a Stainless Steel (303) 3.0mm Dia shaft and a
brass (CZ121) bearing. When first assembled this it has a very smooth running action and very little stiction, but after a few days of use the bearings begin to squeek and seize. Can anyone tell me if there any problems with stainless and brass as a bearing assembly or point me in the right direction for information on suitable material pairs for bearings.
Regards Simon
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SGM Design Ltd wrote:

Can you replace the brass piece with a brass alloy containing lead? In a brass alloy with lead (called "clock brass"), the lead does not dissolve into the brass. It forms a dispersed phase of lead globules. As the brass wears down, it exposes new lead. As a very soft metal, the lead acts as a lubricant.
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with
a
Did you lubricate the thing? Is that brass bearing a plain piece cut off of CZ121 or is it a technical (sintered?) bearing. If it's a regular porous bearing try to boil it for a while in engine oil; if a piece of "regular" brass - make on it a few notches parallel to the shaft's axis of rotation and lube with some kind of grease.
--
melon



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I've followed a thread by this same fellow in comp.cad.solidworks. He needs to stay away from lubricants if possible, although he did not say so. It's in an environment where lint from fabrics can collect and gum up the works.
Mark 'Sporky' Stapleton Charlotte, NC
melon wrote:

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1. IF the only move that shaft makes is rotation he can go with cartridge bearing. 2. Use teflon "outer" race with teflon/polyethylene(HDPE / UHMW PE) pipe slided onto the shaft ("very very minimal load"). 3. Seal the bastard.
--
melon



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The problem may be that the materials are too close together in hardness. This situation can lead to galling and seizing as noted. Lubricants may help as suggested. Another option is to change one of the materials to achieve a greater hardness difference. For the shaft, hardened 440C would be a good choice assuming you want stainless. If you would prefer to change the bearing I would suggest a filled polymer system based on nylon or PTFE.
RT
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