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bridhb

Hollow sheave axle removal, before I screw it up

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Advice?  My boom has a typical aluminum casting at the mast connection.  It has 3 sheaves, top and bottom (6 total) for internal reef lines, etc.  The sheaves are crumbling.  They rotate on a 3/8" OD hollow stainless steel axle pressed into the casting and machine flared on both ends.  The sheaves are separated by cast aluminum spacers that the axle passes through.  I have no idea how tight it its in the casting, and it has been there for 30 years.

The only thing I can think of is to try and drill the flare off one end and tap it out with a punch.  The other was cut it out where the sheaves are and try to tap it out, or use it for a bushing for a bolt for the new sheaves to rotate on?  Worried about drilling into the aluminum casting, or cracking the casting by trying to tap it out.

Any advice?

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You'll have to grind or drill the flare off of at leas one end obviously. You might try heating the casting with a torch, as aluminum will expand faster than SS. You didn't say what the ID was, might be too small, but you could pass a bolt or threaded rod through, block on the other side, bar across with a hole through it for the bolt, then try to pull it out. 

If you can get it onto a milling machine, you could drill or mill it out. Doing that by hand is possible, but has much greater danger of damaging the casting.

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Pins or other smooth shafts seized in alloy can be removed, it's when threaded shafts are seized that you are pretty well screwed because the threads hold so much oxide powder.

Grind the flare off then heat and beat. It can help to heat it then spray with ATF and acetone 50/50. Do that a few times and it should come out. Obviously it requires judgement as to how hard you can beat on it to avoid breakage - that is different for every part. Patience and persistence are your friends.

I've just done it successfully that way on my tiller / rudder head assembly. Took about two hours to get one bolt out - after what I suspect was 35 years of undisturbed slumber.

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3 hours ago, bridhb said:

hollow stainless steel axle

If the ID is large enough to get a file or saw into you might be able to cut a slot in the tube. I wouldn't start there but if heating and tapping and penetrating fluid aren't doing it that might be plan C.

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Thanks for the suggestions.  

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I have had luck just drilling the axle right out. You do need a drill the same size as the OD of the axle. Cobalt drills really help.

Once you have the flare drilled off, frequently the axle will start spinning in the hole, in which case you're done.

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Hard to believe the shaft and the cast aluminum have not become one with each other over the years. I strongly suggest you find a replacement source for the casting before you proceed on your own. If you can't find a replacement or the cost seems outrageous, I'd take the entire boom to a machine shop and ask them to drill it out properly. You do not want to screw up that casting without understanding what you'll do next should that happen.

 

 

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Can you get a saw onto the axle alongside a sheave, to cut through the axle? Then insert a wedge (old screwdriver) between the axle bits to force them out (suitably lubricated). No need to try to grind off the flare.

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15 hours ago, Moonduster said:

Hard to believe the shaft and the cast aluminum have not become one with each other over the years. I strongly suggest you find a replacement source for the casting before you proceed on your own. If you can't find a replacement or the cost seems outrageous, I'd take the entire boom to a machine shop and ask them to drill it out properly. You do not want to screw up that casting without understanding what you'll do next should that happen.

 

 

This is the best advice. Give it to someone who does this kind of work all the time BEFORE you start to work on it. I would use an end mill to machine the old pin out, and replace with the next size up axle pin. Beating it to remove the old pin is probably the best way to need to find a replacement casting, which will not be easy, according to Murphy's law. 

Bam Miller 

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5 hours ago, bammiller said:

I would use an end mill to machine the old pin out, and replace with the next size up axle pin

There are some owners for whom I think that would be the best advice, others might be entertained by the DIY process. I haven't seen the part but since it's hollow there's a potential for step drilling it. You get heat, torque and ever thinning walls. If a bit breaks off it could be tapped out from the other side. That might be as safe as taking it to a shop. Wise or not, if it were me I would look at it before I took it to a shop. Out is only half the battle, of course. Hard to know what the best option for a replacement would be. I see lots of solid axles with SS spring clips in similar applications. A shop might help with that too if there isn't a ready made part available.

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19 hours ago, Fleetwood said:

Can you get a saw onto the axle alongside a sheave, to cut through the axle? Then insert a wedge (old screwdriver) between the axle bits to force them out (suitably lubricated). No need to try to grind off the flare.

That's what I would try too.  

Then put it back in a sensible way, this design sounds awful.  Who made it?

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If you break the casting trying to get the pin out glue it back together, take it to a local foundry and have a new casting made. Be sure to have the new casting anodized after drilling the pin hole otherwise you will have corrosion problems. Alternatively, if weight is not a concern, make the new casting out of bronze and avoid any corrosion problems. You can usually have something like this cast for a lot less than you can buy the part, even if you could find it. Look for an art foundry. They are used to dealing with strange shapes.

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Thanks for all the suggestions.  Sawed the axle with a cut off wheel on a side grinder and it slipped out each way with just a little persuasion and penetrating oil.  Ordered a new hollow SS tube from Mccmasters and new sheaves.  Only nicked the aluminum a little :-).  Plan to install this one with some washers and cotter pins.

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Coat it with Tef Gel where it is in contact with the alloy.

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On 12/8/2018 at 5:18 PM, SloopJonB said:

Coat it with Tef Gel where it is in contact with the alloy.

+1

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On 12/7/2018 at 10:53 PM, bridhb said:

Thanks for all the suggestions.  Sawed the axle with a cut off wheel on a side grinder and it slipped out each way with just a little persuasion and penetrating oil.  Ordered a new hollow SS tube from Mccmasters and new sheaves.  Only nicked the aluminum a little :-).  Plan to install this one with some washers and cotter pins.

Nice work! 

I would suggest that you polish the outside of that stainless steel tube to a mirror finish. We usually carefully chuck it up in a drill and hold it against a polishing wheel. The mirror surface is less likely to corrode and react with the stainless, and if it does, it will at least be easier to push out. +1 million for tef gel. 

You might consider drilling and tapping screws on either side to hold the pin in place. There wont be sharp cotter pins to hook lines or foul weather gear. 

Bam Miller  

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12 hours ago, Moonduster said:

I'm thinkin' the right solution here is a solid aluminum pin.

 

The casting and the pin probably wouldn't be the same alloy, and would likely have similar corrosion problems, and I don't think aluminum will make a good axle pin material for a spinning sheave. 

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Those sheaves really don't spin, either way. And while different alloys may grow some attachment to one another, it won't be anything like stainless and can be easily drilled out. Making an alloy pin takes about 20 minutes and doesn't involve a machine shop - you could probably replace it every year for the life of the boat for less than the cost of a single stainless pin. 

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Your point is taken but with all the other shit you have to do every year, why add to the list? Stainless should last forever or close enough to it and if liberally coated with Tef-Gel, won't be a problem.

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14 hours ago, IStream said:

Your point is taken but with all the other shit you have to do every year, why add to the list? Stainless should last forever or close enough to it and if liberally coated with Tef-Gel, won't be a problem.

+1, at least with me, the longer the annual to do list is, the less likely any of it gets done!

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I've had fairly good results with these when the budget is tight although YMMV.

image.png.81a9e7bbcaf531723aaabd94afcc1911.png

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Those give nearly guaranteed results but in my experience they are usually the most expensive option. :D

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