Brazing new gear teeth on a sailboat propeller.

[rwm]

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.

 

[woodchucker]

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.

 

[C-Bag]

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.

 

[rwm]

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.

 

[mickri]

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.

 

[rwm]

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

 

[mickri]

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

 

[dirty tools]

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