colored solder?

Bruce L. Bergman wrote:


Nope. TIG is used in a few application in the instrument industry, but the fabrication process is really designed around it - often the workpiece is water cooled. Instrument brass is just too thin (.014"), and the zinc likes to vaporise out of it with some sputtering - had really bad results on stock twice that thick. Once place that uses tig starts with a double thick workpiece, no filler, and a water cooled mandrel, then grinds the result down.
I'd be hesitant to use soft solder for patching - it's for large area joints not for structure. But one of the lower temperature hard silver solders with a wide plastic range, and a really really tiny flame might be an option. Unfortunatley the low temp hard solders - 56% silver, etc have a silver rather than brass color. The brass colored ones are mostly high temp, unless you get one with cadmium in it.
If it's in cylindrical tubing I'd try to remanufacture the part. In a critical taper like a leadpipe, I'd want to replace the entire section. Only in a bell section or possibly bell branch would I be likely to try a patch.
You could always add a gratuitous water key...
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into
but
Bruce, I tried brazing some brass smarf from my lathe bed onto the tube but because they are both the same alloy they both had the same melting points. I fixed a 1/16 hole by turning it into a 1/2 hole : ) Yes, it was a bit of scrap tube or there would not be a smiley face on the end of the last sentence!
LB
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wrote:

I don't TIG myself, which is why I added the healthy disclaimer to experiment on scrap first, and find a master TIG welder that can deal with the details. But if you used a regular O-A torch on your experiment, that's like hitting a finishing nail with a pile driver.
You can make it a tiny little puddle with TIG, and you have the pedal for fine amperage control. If it had to be a gas heat source, one of the tiny jewelers torches might work.
I understand with brass and copper there's a tiny plastic zone between solid and melted, it's a very fine line between not enough heat and way too much - which is why you usually stick with brazing or soldering, because you choose the filler metal to stay below the melting temperature range of the base metal.
If you have a way to put a chill plate behind the repair area to act as a mold and keep the blob from falling through, it shouldn't matter if the whole area melts into a blob because it's supported from the back. Just keep the blob small, stir in filler to make it an amorphous solid blob, get the heat off it as soon as you can, then you can grind off the excess later.
I'm way out of my league and I know it, and I'm not afraid to admit it - but /in theory/ it should work. The devil is in the details.
And think of all the extra repair business you can get fixing pinholes if you figure out how to make it work... ;-)
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Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
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