Brazing together bronze nuts

brino said:
Okay, I see.
Is there any reason you could not connect the sacrificial zinc right to the stainless threaded shaft?
https://www.thechandleryonline.com/product_info.php?products_id=8201
That one woulnd't tighten onto a 3/4 inch shaft, but zinc is soft so taking a little off the mating faces to make the thru hole smaller is easy.
Just don't breathe it if you sand/grind it off!

I guess you still want a second nut to jamb the first one.....maybe the shaft isn't long enough?

-brino
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The shaft is tapered: it's 1" stock, which has a slight taper onto which the mating taper of the prop fits (with a key as well); then there are two nuts, the first of which snugs up the prop on the taper, and the second of which pushes on the first, and is typically either castellated or has a through-hole, and gets a cotter pin into a small hole on the very end of the shaft (which is turned down to about 1/2". So there's not really any shaft left behind that second nut. (Sigh), and it's certainly not 1" material.

If you ever want to hear a fun debate, ask 2 boaters whether the nut next to the prop should be the thin or the thick one. If you ask any two boaters, you'll get three different answers (often with diagrams and fancy discussions of shaft elongation and other entertaining --- but not quantitative --- things.)

As for your earlier suggestion of clamping the zinc directly to the shaft --- that's what's usually done, typically just ahead of the prop. There isn't clearance for it on my boat. (Sigh again). Another possibility is to chisel a hex cutout into a 1" donut, and clamp that down onto the big nut. But then there's the cotter pin to deal with (and having to remember to make TWO modified zincs, so that when I need to replace it mid-season, diving under the boat holding my breath, I don't end up swearing a whole lot!)
 
RJSakowski said:
If brass will work, https://www.mcmaster.com/#brass-coupling-nuts/=1bp5r39
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Silicone bronze works pretty well in salt water; the zinc is meant to reduce the already-fairly-low-corrosion-rate of the propeller (which is slightly raised by it sitting on a stainless rather than a bronze shaft). Brass, on the other hand, in most alloys tends to act like a battery, and first gets pink spots as the zinc in it disappears, and then begins to look like Meunster cheese. Not at all the right material to use in any critical application underwater. It's a pity, because that'd be a great starting place to work from.
 
markba633csi said:
Does even naval brass have this problem? I know silicon bronze is expensive
Mark
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I don't know exactly what "naval brass" is, but if it's the stuff that's used for naval clocks and other such things, then the answer is "yes." On deck, it rapidly develops verdigris. It's the sort of thing that used to keep sailors in the British Royal Navy very busy with their polishing rags. Fortunately, stuff on deck may sometimes get sprayed, but rarely suffered prolonged immersion of the kind that leads to serious corrosion. If it does, your ship's upside down, and you've got bigger problems to worry about. :)
 
Well, fortunately the part you are talking about would not be to hard to do, just costly to buy the material and the large tap required. Maybe have to buy a taper shank drill also unless you wanted to start with say a 1/2" twist drill and use boring bar to size. It could be done on most any small lathe.
Mark
 
spike7638 said:
Silicone bronze works pretty well in salt water; the zinc is meant to reduce the already-fairly-low-corrosion-rate of the propeller (which is slightly raised by it sitting on a stainless rather than a bronze shaft). Brass, on the other hand, in most alloys tends to act like a battery, and first gets pink spots as the zinc in it disappears, and then begins to look like Meunster cheese. Not at all the right material to use in any critical application underwater. It's a pity, because that'd be a great starting place to work from.
Click to expand...

Being a fresh water boater, not a problem here.

Here is an article that claims brass is superiuor to bronze for prop nuts. The catch is, he doesn't specify what alloy. There are more than two diozen brass alloys. https://www.passagemaker.com/channels/propeller-nut-myth-busting

I dd some searching and it doesn't appear that a bronze coupling nut is readily available. Making your own would require starting with a 1-3/16" round minimum. Technically, it shouldn't be too difficult to machine from scratch. If you follow Kieth Fenner on You Tube, he is as close as you can get to a boating machinist guru. He may be able to give you some advice.

If you decide to try the three nut approach, I would suggest TIG welding with the silicon bronze rod. Good luck!
 
If you only need the threads at the hex end, why not just use a single nut with a longer cylindrical bushing (1" OD, 3/4+" ID)?

Trying to braze three nuts together while keeping them aligned inside and out is more likely to be screwed up (no pun intended) than machining it from solid bar or hex stock. But you don't say what kind of machine tools you have available.

A drawing of the assembly would help us understand the application. Where is the hole for the cotter pin?

You're correct that you don't want a stainless nut on a stainless shaft.
 
While I don"t have the temperature information I have seen examples of bronze bushings and gears that got hot when people heated a bore for expansion and then pressed the bushing in or heated the gear to expand it. The bronze can harden and become very abrasive.
It will eat shafts!
 
FanMan said:
If you only need the threads at the hex end, why not just use a single nut with a longer cylindrical bushing (1" OD, 3/4+" ID)?
Click to expand...

And if you must guarantee electrical conductivity, any kind of soldering at the joint will do that.
 
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