Minimum clearance for oscillating bushing lubed with grease and recommendation for bushing material

Hi everyone,
I would like to ask if anyone could please offer some advice on the
I have a cantilever mounted round steel housing about 1.5" long that I
want to oscillate on a 3/8" OD hardened steel dowel pin. I plan on
just pressing a bushing material into the full length of the housing,
and then drill & ream the bushing ID to fit over the dowel pin. I need
the clearance between the ID of the bushing and the OD of the dowel
pin to be as small as possible. I can only lube the bushing once at
assembly and then never again.
I would prefer that the maximum clearance between the dowel pin OD and
the bushing ID is not over .001" but I may be able to get away with .
002". I would like to use a high pressure grease to lube the bushing
and shaft, but how small can my clearance be before it won't allow the
grease to go and/or stay between the shaft OD and the bushing ID, or
before the low clearance defeats the lube somehow ?
The housing is just oscillated by hand intermittently. Any
recommendations for a bushing material, bushing ID surface finish, and
lube, would be appreciated.
Presently, I have no choice but to press some bushing material into an
existing housing, but in the future, would I be better off making the
housing itself out of some pre-hardened 4140 and then using the
housing itself as the bushing material ? Would this wear much better
than a bronze bushing ? Would non-hardened 4140 or non-hardened tool
steel wear better than bronze ?
I would like this thing to last as long as possible before the
clearance opens up too far. I also think I need to stay with a bushing
and not a rolling element bearing.
Any advice or personal experience with bushing materials, loads, and
estimated wear rates would be appreciated.
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The rule of thumb is hard against soft. Pre-lubed sintered bronze is probably the best plan - bushes can hold a tight ID - less than a thou should be possible without reaming. Plain bronze would wear longer than sintered if lubricated - but that's not an option apparently. Some people have used felt washers as oil/grease reservoirs. For intermittant turning by hand, either method of lubrication should hold up pretty well.
Brian Whatcott Altus OK
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Brian Whatcott

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