Cutless bearing - cutting?

Eeyore

Eeyore

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5 Oct 2007
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Location
Kudat, Malaysia
www.yachtrhumbdo.co.uk
I am in need of a new cutless bearing. The carrier is machined to accept one of 2.5 inches in length, yet all the GRP/rubber ones seem to be sold in 5 inch lengths, which of course is no good to me. So, can they safely be cut in any way, or is it going to ruin the bonding of rubber to GRP?
 
Eeyore said:
I am in need of a new cutless bearing. The carrier is machined to accept one of 2.5 inches in length, yet all the GRP/rubber ones seem to be sold in 5 inch lengths, which of course is no good to me. So, can they safely be cut in any way, or is it going to ruin the bonding of rubber to GRP?
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I ordered mine from T Norris but wasn't aware that they can cut them to length. They recommended cutting around the brass shell with a hacksaw very carefully without cutting into the rubber. Then use a scalpel to cut through the rubber. I cut mine with the shaft inserted to prevent collapsing the rubber and without scarring the shaft. Takes a bit of patience but doable.
 
No problem with cutting down. standard sizes are 4" for under 1 1/14" or 30mm and then 5" because that is the length required to provide support for the shaft when the cutless is the only bearing after the gearbox. However many older stern tubes and installations where there are 2 bearings use shorter length. For example the common Stuart Turner stern rubes had an inner bearing of 2" and an outer of 3 5/8" for a 1" shaft. Having said that 2.5" is extremely short and is likely to have a short life unless there is a significant bearing at the inboard end of the shaft. As an alternative to a cutless if you don't like the idea of cutting it down you might consider having a composite bearing made to size.
 
Thanks for the replies team. ASAP supplies said not to cut them as it may compromise the bonding, but they did recommend trying a bearing manufacturer such as Exalto, which I did. Exalto will cut and trim to size for the princely sum of £5. Result! My thoughts were the same as Saltram31 and I was going to try that exact method.
 
Last year had a new propshaft, cutless bearing and inboard coupling fitted on my Jeanneau. I was not present when the work was done, but on arriving just before relaunch saw that the cutless bearing was an original Jeanneau/Beneteau type, which are rubber only, and the inboard end protruded about 3 cm forward from the P-bracket. Did not seem to be a problem, so left it like that.

2 months later a charterer picked up a big chunk of rope round the prop. On getting son to dive and cut the mass of rope off found that the rope had clearly wound itself so tightly round the exposed rubber that it had twisted out much of the rubber cutless bearing inside the P-bracket, hence the horrible metal to metal banging as propshaft rattled around in P-bracket. New all-rubber one fitted during a quick lift out, but the exposed bit of rubber cut off.....

I doubt if a rope would grip a bit of exposed brass sleeve as much as it did the rubber, but just in case I would cut to fit properly.
 
I cut mine to length using a parting tool in a lathe to cut the brass very carefully until it almost reached the rubber, then finished cutting the brass with a fine-toothed saw.
I cut the rubber with a sharp knife, using water as a lubricant to prevent the rubber gripping the blade.
But you don't, of course, need a lathe. Perfectly OK to cut it by hand.
 
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