Seized sheaves

mprewett

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The three sheaves on the forward end of the boom of my new boat, which are used for single line reefing, are seized. There is no obvious way to remove the sheaves because their axle appears to be a stainless tube, the ends of which are flush with the casting in which the sheeves sit. What holds the tube in place is not immediately clear, but I suspect that it might be screwed in, although there is no apparent way of getting any purchase on it.

I guess the boom is original equipment, which makes it about 25 years old.

Any suggestions about how to get the sheaves moving?

Thanks.
 

Aja

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It could be an interference fit with the s/s shaft needing to be driven out.

Donald
 

Poignard

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Difficult to help without a picture but the best thing would be to remove the end fitting from the boom because it's much easier to work on a bench and if you need to apply force it's more effective than having it resting on someone's knees.

The axle on my boom is just a press fit into the casting. That is stainless steel in an alloy casting. If yours is the same, corrosion will make the axle difficult to remove so you will need Plus Gas, heat and some kind of press, if possible. If you have to hammer it use a well fitting brass drift and a heavy hammer with the casting properly supported.

Convince yourself you will not fail [and find out where you can get another fitting in case you destroy it]
 

aitchw

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Agree that the casting should be removed to work on if at all possible but would be very cautious about trying to drift the tube out. These type of castings can be quite brittle and if you cannot support the webs the tube is fitted in it would be easy to crack them. In drifting the pin out you will have to break the seal between the tube and casting on both sides and even when you have done that you have the 3 sheaves to break free as well before the tube can exit.

Assuming the sheaves are either stainless steel or alloy I would use heat (quite a lot of it) on the sheaves, trying to avoid heating anything else, to expand the sheaves. Heating and cooling a few times may break them free enough to turn a little. Plenty of PlusGas/WD40 may then get them turning easier.

It woud be easier if I could see the thing.
 
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