Stubborn prop nut and more!

[RichardS]

Oxy acetylene cutting torch.

Was there a glitch in the matrix around post #47?

Richard

 

[Davegriff]

One more thing, Tim, when you've decided which way to turn the nut, use a good fitting socket as others have said and a strong bar 2-3 feet long or even more. Scaffold bar is good. Support under the shaft if necessary. Apply good solid pressure - then wait. You shouldn't need to hammer anything, just maintain pressure for several long seconds. (Really should come off without the heat).

 

[PowerSlapper]

snip.

Tried a 36mm spanner which is obviously too big couldn't shift it but didn't try too hard. Will return to the fray in the week hopefully armed with correct size spanner!......and a blowtorch.....

Waste of time unless you can get your hands on an Oxyacetylene (aka a "gas axe") or oxy MAPP gas torch. These little plumbing torches, even the "turbo" versions are not much use for your job. You need to apply a lot of heat to the nut very quickly to expand the nut before the heat travels to the shaft and expands it as well.

 

[Happy Dayz]

A few dea'd afaik not mentioned before -:

oversized spanner, use wide screwdtiver blade to take up the slack, and hammer it in.

If using stiltsons or simular but some steel shim plate between tool jaws and nut.

Alan

 

[macd]

One more thing, Tim, when you've decided which way to turn the nut, use a good fitting socket...

If you should encounter a good-fitting socket for that nut, beware, because the OP might want to marry you. Did you actually look at the photo of it?

 

[Davegriff]

If you should encounter a good-fitting socket for that nut, beware, because the OP might want to marry you. Did you actually look at the photo of it?

Well, obviously I meant stilson/wrench/spanneror whatever. Posted in haste, apologies. After downloading, resizing and examining the pictures, what do you think? Did you actually read my other posts?

And sorry Tim, I'm spoken for.

 

[RichardS]

You need to apply a lot of heat to the nut very quickly to expand the nut before the heat travels to the shaft and expands it as well.

It doesn't matter how far the heat spreads, unless the metals are different the nut will always expand more than the shaft.

If the metals are different, the nut could expand considerably more ..... or considerably less.

Richard

 

[vyv_cox]

I've not noticed anyone mention how the shaft will be stopped from rotating while the forces of hell are being applied to turn this nut, is there some way to lock the shaft or will the o/p now need 2 sets of stilsons, 2 long tubes and another big bloke?

Alan

That's the easy bit. Place a length of timber between a prop blade and the ground.

 

[RichardS]

That's the easy bit. Place a length of timber between a prop blade and the ground.

Or between prop blade and hull like I do.

Or use the official Yanmar workshop manual method and put the engine into gear and then put a great big spanner on the crankshaft nut and wedge that tight against the hull (or ask a mate to hold it if you have one available!) before swinging on the prop nut. And yes, it does work although I'm not trying it again!

Richard

 

[double_ender]

How about ...... Get a robust portable vice, offer it up to the nut and do the vice up like hell, gripping the nut. Then use long bar, or tool on the vice to give it Jipp.
M

 

[RichardS]

How about ...... Get a robust portable vice ....
M

It's called a stillson.

Richard

 

[pete]

How about ...... Get a robust portable vice, offer it up to the nut and do the vice up like hell, gripping the nut. Then use long bar, or tool on the vice to give it Jipp.
M

This is what I would try but using a suitable sized standard bench vice, there is less chance of ruining the nut and you can then just concentrate on turning it but don't let it drop on your toes

I have used ordinary propane blowlamps loads of times for expanding nuts with success but if it is windy rig up a wind break.

 

[PowerSlapper]

It doesn't matter how far the heat spreads, unless the metals are different the nut will always expand more than the shaft.

If the metals are different, the nut could expand considerably more ..... or considerably less.

Richard

Codswallop, B.S., or what ever.industry standard method of releasing tight nuts is RAPID application of heat to the nut to expand it before the heat has time to travel to the shaft/bolt. Likewise freeing studs frozen in blocks, tubesheets etc - drill a hole ½Ø of the stud down the center of the stud almost to the bottom then fill it with liquid Nitrogen then before the cold has had time to go to work on the block unscrew the stud. Neither the heating nor cooling process has anything to do with needing dissimilar metals according to HWMO (retired, old school, metallurgist) but rather the rate of heat input (or extraction) allowing one component to expand (or shrink) before the mating part is subject to expansion (or contraction)
Heat flow and thermal gradients 101.

 

[RichardS]

Codswallop, B.S., or what ever.industry standard method of releasing tight nuts is RAPID application of heat to the nut to expand it before the heat has time to travel to the shaft/bolt. Likewise freeing studs frozen in blocks, tubesheets etc - drill a hole ½Ø of the stud down the center of the stud almost to the bottom then fill it with liquid Nitrogen then before the cold has had time to go to work on the block unscrew the stud. Neither the heating nor cooling process has anything to do with needing dissimilar metals according to HWMO (retired, old school, metallurgist) but rather the rate of heat input (or extraction) allowing one component to expand (or shrink) before the mating part is subject to expansion (or contraction)
Heat flow and thermal gradients 101.

Oh dear .... I think somebody needs a course in the relative thermal expansion of metals.

I'll give you a simplified summary to start you off ...... the thermal expansion of metals is expressed as expansion of unit size of metal per degree rise in temperature. The larger the size at the start relative to the unit, the greater in absolute terms is the amount of expansion ....... you know what, I can't be bothered. So yes, your insult was justified.

Richard

 

[Tim O]

Ok...thought you might want to know how it all ended..which was a success!

Armed with the following...your advice, a 36mm spanner, a cheap toy sheet steel spanner to tap into the gap between 36mm spanner and 35mm nut, Plusgas and a three foot lever made from my emergency tiller I successfully got the nut off with the application of my weight to the lever....no damaged nuts (ouch) or any other drama...for a boat job this was as smooth as they come!

Thanks for all your advice and here are some pics.....now dont anyone tell me I should have fitted a scissor-type ropecutter!

 

[Arcady]

Well done - but what everyone wants to know is was it a left-hand or right-hand thread??!

 

[Tim O]

It was a normal thread....anticlockwise to undo!!

Tell you what...it took some serious grunt to tighten it back up to the exact spot to get the split pin back in....all cleaned up and greased so hopefully easier next time

 

[agurney]

Ok...thought you might want to know how it all ended..which was a success!

Armed with the following...your advice, a 36mm spanner, a cheap toy sheet steel spanner to tap into the gap between 36mm spanner and 35mm nut, Plusgas and a three foot lever made from my emergency tiller I successfully got the nut off with the application of my weight to the lever....no damaged nuts (ouch) or any other drama...for a boat job this was as smooth as they come!

Thanks for all your advice and here are some pics.....now dont anyone tell me I should have fitted a scissor-type ropecutter!
View attachment 61026View attachment 61027View attachment 61028

Crikey, your knuckles are still intact, well done.