# Brazing new gear teeth on a sailboat propeller.



## Eddyde (Jun 19, 2022)

Hi All, 
A friend of mine is restoring a 42' sailboat the "Anna" he bought in Portsmouth RI over a year ago. I helped him sail her to Kingston, NY last August, which was quite an adventure....
The other day, he found some of the gear teeth on the propeller blades to be worn (sailboat propellers fold flat when not in use to reduce drag), stripped and asked if I could repair them. I feel confident I can do the machining, but have some questions and problems to work out before I get started. 
1. I am not 100% sure of the material. My research so far found, Nickel-Bronze-Aluminum is a common alloy used in such propellers and has a more yellow "Brassy" color, than the more common Bronzes, so that is my best guess. Is there any way to test it?
2. I have no experience brazing Bronze. Is it possible to simply build up the teeth by laying down beads of filler, or do I have to braze on individual teeth? 
3. What is the best way to determine the pitch & pressure angle of the existing teeth?
4. Another approach would be to machine out all the teeth and braze in a semicircular piece of material and then machine the new teeth, Or braze on semicircular pieces of gear rack with pre-machined teeth. Another option to that approach would be to cut the sections out of an existing gear, if one could be found with the correct diameter, and braze them in place. Both those approaches eliminate me having to exactly match the existing gear-tooth geometry so I am starting to think they may be the best option but I am open to suggestions?

Has anyone here done anything like this before? 

Thanks in advance for your input and advice,

Eddy


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## mickri (Jun 19, 2022)

Contact Minneys in Newport Beach, CA.  They have hundreds of used propellers for sale.  The rational for the geared folding propellers is so one blade of the propeller does not flop down when the propeller is horizontal.  This can only happen at very low speeds when there is insufficient water flow to keep the blades folded.  Sailors that are anal about this mark the propeller shaft so they can orient the blades to be vertical when under sail.


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## C-Bag (Jun 19, 2022)

That particular project I’d be silly enough to try if was in my lap. I’m comfortable with brazing and with my last big project of fixing the screw wheel on my antique press and using oven to prep and let the temp down slow I had success. The fact it’s a straight gear is also encouraging. But the final piece is I think I could cut the teeth with my Atlas shaper. This not to say it would be easy and there’s a lot that would show I’m in over my head, but it looks like an interesting challenge but a total time sink fer sure.


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## Nutfarmer (Jun 19, 2022)

I would be concerned with the liability of the repair.


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## woodchucker (Jun 19, 2022)

It doesn't look like a hard repair. I'll be watching this to see how it goes. I'm thinking just build up the area with silicone bronze.. face off the flat areas top and bottom...
Then go cut teeth..


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## dirty tools (Jun 20, 2022)

TIG welding would be a better method


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## rwm (Jun 20, 2022)

dirty tools said:


> TIG welding would be a better method


Good idea. I am assuming you mean build up the material and re-cut the teeth? What exact filler rod would you select?


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## Eddyde (Jun 20, 2022)

mickri said:


> Contact Minneys in Newport Beach, CA.  They have hundreds of used propellers for sale.


He is going to buy a new propeller. His plans are to eventually sail overseas, so wants to fix this one for a back up.


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## woodchucker (Jun 20, 2022)

dirty tools said:


> TIG welding would be a better method


why? what does it do that a braze won't in this case?


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## C-Bag (Jun 20, 2022)

dirty tools said:


> TIG welding would be a better method


I would like to hear how it would be better than OA. And what that process would look like. I have machined some OA brazing and found it to be exceptionally pocket free. But it takes good equipment like cerrowool, a good oven and lots of attention to detail. I'm just contemplating getting a tig machine and getting into that whole world and the idea of brazing with tig is very new to me.


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## rwm (Jun 20, 2022)

This is complicated. Here's my take. In this case, where the base metal is bronze, you could use a filler similar to the base metal and build up the area. You could do this with OA just as effectively. In my opinion TIG would be technically easier but I am more familiar with that process so I am biased. I'm sure it could be done well with OA. Since the rod and the base metal are essentially the same metal, you will melt the base metal and this is technically welding, not brazing. TIG is often used to weld bronze sculpture, sometimes without filler.
"TIG brazing" is a little different and I personally have had very poor results with it. If you are TIG brazing ferrous metals with bronze rod it is virtually impossible to avoid melting the base metal into the brazing filler. The TIG arc is simply too hot. When this happens, the joint looks fine but is incredibly weak compared to a gas brazed joint. Jody on "welding tips and tricks" shows TIG brazing but other videos that show destruction testing show how weak these joints are. I only gas braze at this point.


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## woodchucker (Jun 20, 2022)

rwm said:


> This is complicated. Here's my take. In this case, where the base metal is bronze, you could use a filler similar to the base metal and build up the area. You could do this with OA just as effectively. In my opinion TIG would be technically easier but I am more familiar with that process so I am biased. I'm sure it could be done well with OA. Since the rod and the base metal are essentially the same metal, you will melt the base metal and this is technically welding, not brazing. TIG is often used to weld bronze sculpture, sometimes without filler.
> "TIG brazing" is a little different and I personally have had very poor results with it. If you are TIG brazing ferrous metals with bronze rod it is virtually impossible to avoid melting the base metal into the brazing filler. The TIG arc is simply too hot. When this happens, the joint looks fine but is incredibly weak compared to a gas brazed joint. Jody on "welding tips and tricks" shows TIG brazing but other videos that show destruction testing show how weak these joints are. I only gas braze at this point.


so Robert, you made a better case for brazing than you did for tig.
Brazing is a reliable way to join two metals of dissimilar types. It also works great on similar types. I have not tig welded, but I have brazed a number of times, and never had it fail.


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## C-Bag (Jun 20, 2022)

rwm said:


> This is complicated. Here's my take. In this case, where the base metal is bronze, you could use a filler similar to the base metal and build up the area. You could do this with OA just as effectively. In my opinion TIG would be technically easier but I am more familiar with that process so I am biased. I'm sure it could be done well with OA. Since the rod and the base metal are essentially the same metal, you will melt the base metal and this is technically welding, not brazing. TIG is often used to weld bronze sculpture, sometimes without filler.
> "TIG brazing" is a little different and I personally have had very poor results with it. If you are TIG brazing ferrous metals with bronze rod it is virtually impossible to avoid melting the base metal into the brazing filler. The TIG arc is simply too hot. When this happens, the joint looks fine but is incredibly weak compared to a gas brazed joint. Jody on "welding tips and tricks" shows TIG brazing but other videos that show destruction testing show how weak these joints are. I only gas braze at this point.


Thanks Robert for the complete explanation. One of the first processes I ever did in high school was OA braze and was one of the few in my metal shop class that had mine pass the test. So it’s been what I’ve done the longest. I’ve been contemplating tig for aluminum welding because I’ve not had great luck with OA welding AL.


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## rwm (Jun 20, 2022)

woodchucker said:


> so Robert, you made a better case for brazing than you did for tig.
> Brazing is a reliable way to join two metals of dissimilar types. It also works great on similar types. I have not tig welded, but I have brazed a number of times, and never had it fail.


Not exactly. What I was saying is that whether you use OA or TIG with a bronze rod, in this case you are not brazing. You are welding. Either method is acceptable. The process is not defined by the filler rod, it is dependent on whether you melt the base metal. If you use a bronze rod on bronze you are melting the base metal at least superficially. This is one reason welding dissimilar metals doesn't work. 
As an aside, here is an example of a "TIG brazed" joint:


You can see it failed shortly after it was put into use. I ground off the material and re-brazed this joint using OA and it is still in service today.


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## mickri (Jun 20, 2022)

Minneys may have the same propeller.  Their propellers are not expensive.  

Before spending any time trying to fix this propeller, you need to figure out why the teeth were broken off.  One of the big problems with older folding propellers is excessive wear on the pins and in the bores that the blades rotate on.  There could be so much slop in these parts that the repaired teeth will just break off.  Also have you looked at the other blade to see what it looks like.  Hard to imagine one blade having broken teeth and the other blade being in good condition. The teeth on both blades mesh together.  The teeth aren't needed for the propeller to function.  As I posted above their only purpose is to prevent a blade from hanging down at slow speeds under sail.  The extra drag from a drooping blade is minimal.  The only people who care about this are hard core racers.

The best backup propeller is a fixed blade propeller.  Some folding propellers have small parts that are not easy to assemble in the water.  And can be easily lost if dropped.  No need to ask how I know this.  A fixed blade propeller can be installed anywhere.  Even at sea hundreds of miles from land.

You are putting the cart before the horse if you forge ahead with a repair before determining the cause of the failure.


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## rwm (Jun 20, 2022)

Jodi has a good video here if you are interested. He is pretty good at not melting the base metal. Better than me!


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## mickri (Jun 20, 2022)

The picture shows how the teeth on the blades mesh together.


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## dirty tools (Jun 20, 2022)

Easier to build just the teeth 
less machine, less heat 
depending how you’re skills might be able to fill the tooth buildup


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