Repairing a cast brass part

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EOsteam
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Repairing a cast brass part

Post by EOsteam »

Say someone screws up the machining of a cast brass part and wants save it. Is there a way to braze, weld or solder some material back into place and then correctly machine the part? If so what materials and tooling are appropriate?
armscor 1
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Re: Repairing a cast brass part

Post by armscor 1 »

Silver Solder.
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Harold_V
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Re: Repairing a cast brass part

Post by Harold_V »

Yep, I agree, but you can't build with silver solder, so you must make a piece that will get soldered to the casting. Surfaces should be good fits, and you can expect the joint to be in the neighborhood of .002" thick. Silver solder is not good at filling, as it flows too easily.

The repair, if done well, may be nearly as strong as the casting. Keep in mind that the heat required will eliminate any hardness that the casting may have, as well as hardness in the filler piece you select.

Silver solder follows heat, so once you have the pieces up to temperature, you can drag the solder around simply by moving the torch. Be careful to not melt the objects in question.

If you don't have any experience with silver solder, be aware that some of it contains cadmium, and can be deadly (fumes).

You will experience the best results by not applying heat to the solder, but to the pieces being soldered.

I highly recommend the black flux over the white flux, as it is more aggressive and tolerates overheating better.

H
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GlennW
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Re: Repairing a cast brass part

Post by GlennW »

I've TIG welded brass using silicone bronze filler rod so that may be an option depending on the repair needed.
Glenn

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EOsteam
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Re: Repairing a cast brass part

Post by EOsteam »

The repair is on a 5 inch radius with 3 degrees of taper. A custom form cutter was being used to place a 3/32” concave radius and the initial attempt at grinding the tool was faulty to say the least. The silicon bronze filler may be the best option. My TIG skills are OKish with steel but I have never brazed. Is there a technique one must follow for success? What are the key points?

Again, thank you for your replies. You are all bailing me out of another potential sinking ship!
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GlennW
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Re: Repairing a cast brass part

Post by GlennW »

I did it back in the 80's when I had discovered Silicone Bronze filler rod for TIG brazing steel. It was only an experiment, as I had a short piece of 2" brass tubing and a small piece of brass sheet and wondered what would happen if I tried welding them together. It worked pretty well as I was able to get a nice bead. Kind of weird with the green from the zinc though, and it welded a lot like magnesium in that you had to keep the filler rod in the argon and lots quick dabs once you got it to start welding.

I just googled it and found this, but I didn't watch it yet, so it may not help much.

https://www.youtube.com/watch?v=7udYchu ... l=Weld.com

Good luck!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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Harold_V
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Re: Repairing a cast brass part

Post by Harold_V »

Thanks for the link, Glenn.

H
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GlennW
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Re: Repairing a cast brass part

Post by GlennW »

You're welcome, Harold.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
EOsteam
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Re: Repairing a cast brass part

Post by EOsteam »

Thank you Glenn! The video has been viewed and the next step is a little practice on some scrap.
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