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post #12 of Old 09-24-2012
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Re: cutlass bearing

In answer to a few comments above, from the perspective of a bearing supplier.

Cutlass and cutless have become generic names for water lubricated rubber bearings (they are rubber bearngs as the bearing surface is rubber)

As the rubber needs support they often come in a carrier which can be bronze or composite, although some vessels use a rubber insert into the grp stern tube.

There are also other types of material for marine shaft bearings which have replaced and in some cases (Maritex) improved over rubber as a bearing surface. Many years of development have gone into new materials to improve on the performance of rubber.

These composite phenolic bearings are rarely a press fit as the manufacturers prefer a clearance fit bedded on epoxy which retains the ID, as there is no bore closure from the press fit option.

Clearances are different for different materials as they have widely differing thermal and moisture expansion rates. Each manufacturer has set clearances they work to.

So as an example...
a composite Maritex bearing for a 2" shaft in a 3" carrier
Running clearance new 0.24mm or just under 10 thou
Change bearing when radial displacement approaches 1.27mm
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