Boat propeller shaft material. Tolerance of standard bright bar. Recommended supplier?

[tigdlo]

Anyone know if boat propeller shafts are always made out of ground shafting? 316 round bar looks to have a decent surface in pictures but I guess that's like the mcdonalds menu. My plan was to straighten it then polish the surface, maybe lap the bearing and seal sufaces with an aluminium makeshift lap or lap the whole thing if it's not round enough. my main concern would be the diameter by the time it is round and smooth enough.

Can anyone suggest a type of 316 round bar that would have a good finish and is supplied to close tolerances? Or know how good "normal" bright bar is?

Are there any good suppliers in the midlands for 1300mm of 7/8" bar? I've had a good quote in sheffield but its a 120mile round trip.

I can spend a couple of days making a shaft but don't have £250 spare to buy a new one.

Thanks, for any help.

 

[Brad93]

Prop shafts are usually a specific stainless steel alloy. Forget the name now.

Standard bright stainless bar can be a good few thou out in a few places down the bar. It's not dead straight. I think it's just centreless ground and then semi polished.

 

[Brad93]

F51 was the grade I was thinking of. In the states it has a brand name, if you have a look at Turnwright Machine works he has many videos of making shafts from scratch.

Most shafts are ground then straightened.

 

[tigdlo]

Thanks, for the reply. I've watched most of Keiths videos on this kind of thing which is where I got the idea I could possibly make a shaft myself.

Shafts seams to mostly be offered in 316 with F51 duplex as an uprade.

 

[Screwdriver]

Huge fan of Keith Fenner here too so the sum total of my entire knowledge of the subject is based on his videos. I will be massively impressed if you can manufacture one from scratch for less than £250! TBH that sounds like a pretty good price if it's a long shaft. Would love to see how you get on with it.

I think it would be more a labour of love than a cost saving exercise though. Getting those tapers ground in looks tricky enough plus you'll be needing some rollers, oxy/fuel kit and a very long shed!

 

[tigdlo]

I think it would be more a labour of love than a cost saving exercise though.

As of last week I'm unemployed and need something to regain sanity lost dealing with recruitment agents, working towards getting my boat sailing should help

1300mm of 7/8" bar is about £65 with the fuel to pick it up, I'll call the supplier to see what finish the bar is before gambling on making it myself.

Spent yesterday sorting out the prop that had a 1:13 taper, the shaft is 1:12 which is a standard taper.

Caliper measurements for radial runout the dial indicator for axial. It's close but I need to check the other side of the blades for axial runout and radial runout 90degrees to the blades before the final lap using the aluminium mandrel.

 

[Screwdriver]

Looks like great fun. I imagine it will be immensely satisfying too once its all set up.

 

[Milkybars]

How long and what dimensions ..i have a few that are on the shelf that i saved from the scrap

 

[Newlands]

For both my last two boats that I re-engined I used standard 316 stainless. Both had a Yanmar 10 hp diesel on the end of them. Maybe if you were fitting an 80 hp fast revving diesel you might need to think about something fancy, but I wouldn’t bother for anything less than about 30 hp.
I certainly wouldn’t worry about lapping or polishing - the only bearing on most boats is the cutless bearing which is designed to have around 10 thou slop in it so the water can keep it cool. Plus of course the engine wobbles around on its mounts so you need the clearance. With a very long shaft you might need an intermediate pillow block bearing to prevent it whipping, but in that case you’re still relying on the length of the shaft to allow it to flex. If you try and constrain the shaft too much you just knock out the rear bearing in the gearbox.
All the above applies to a conventional setup - ie cutless bearing, stern gland, flexible coupling at the gearbox end and an engine on rubber mounts. If you’ve got a Halyard Aquadrive mounted on a thrust plate it’s a bit different.

 

[Rannsachair]

I modified a propshaft to suit a different prop a few years ago, am sure it was 316, The seal area was just turned and polished from memory and worked fine.

 

[Screwdriver]

I used to enjoy watching his videos, but every time now (well until I stopped watching his videos) his opening minute(s) put me off.

Yep same here. I stopped watching ages ago and sort of dip back in once in a while (and skip the first minute!).

All went a bit Pete Tong I think some time ago when he swapped workshops (probably some personal issue I feel no need to pry into).

 

[Keith 66]

Interesting stuff, i will be sorting a shaft for my vintage launch before long, not going to be cheap, its 1 1/4" dia & about 15ft long,
I have a bronze shaft that came with the boat but not sure if its up to the engine hp & revs.

 

[mcostello]

AquaMet I think is the name of the shafting. Best sit down when viewing prices.

 

[zzr1200]

Yep same here. I stopped watching ages ago and sort of dip back in once in a while (and skip the first minute!).

All went a bit Pete Tong I think some time ago when he swapped workshops (probably some personal issue I feel no need to pry into).

Divorce I suspect......I've been there got the T shirt....

 

[Newlands]

Interesting stuff, i will be sorting a shaft for my vintage launch before long, not going to be cheap, its 1 1/4" dia & about 15ft long,
I have a bronze shaft that came with the boat but not sure if its up to the engine hp & revs.

I had a bronze shaft in my Nelson launch, with a Perkins 35hp engine. Absolutely the best material for a prop shaft as it doesn’t suffer from crevice corrosion like 316.

 

[Keith 66]

We will see what the shaft is like, it dates back to the 1940's & was standing lashed to a drainpipe on the ex owners house for at least 40 years. See what it cleans up like!

 

[Hood]

Chances are standard 316 will not be straight. I have made a few from it but have had to reject most bars. I usually just get ground bar now from a place in Englandshire, not that much more expensive. I forget the name but will post later once I remember

 

[Hood]

Ok, I remembered, millstock stainless.

 

[Brad93]

AquaMet I think is the name of the shafting. Best sit down when viewing prices.

That's the brand name I was thinking of

 

[jerrytug]

If its any help, Clements Engineering in Beds. made a new propshaft for my barge; it is not 316, but something else meant to be better. They are quite helpful with advice, an old established engineering shop.