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I got an old beater Yamaha 321 Eb tuba, which I want to use for street music. Unfortunately, one of the piston ports did not survive cleaning with vinegre acid and a brush, it has a thin spot and a hole now inside the port.

Its one of the old pistons with metal guard, so I think I am out of luck finding a new one which fits.

Is it possible to soft solder a thin brass patch over the hole inside the port?

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I'm willing to take the criticism for suggesting something that isn't very involved, but someone could swab some of the clear watery solder acid around the edge of the hole, and - with a very controlled low flame - just float some lead solder or plumbing solder over the hole.

If someone is good at painting a flame, it makes a pretty luxurious repair because there's no patch in there, and the solder looks just about like the brass that was there before, as far as the shape is concerned.

If it's so rotten that new holes form, it's probably time to buy a piston. Otherwise, if that lasts it lasts.

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Thanks, good to know that soft solder will stick to the plated surface, it looks like nickel plating to me. Also good to know that modern replacement valves will work.

I am nor sure though if a solder blob will cover the hole, its about 3 mm large and very fragile on the rim of the hole. The port material is there thin of corrosion.

I found a piece of a scrap brass trombone slide bow having the right curvature for a nice patch in my drawers, so I will try to patch it.

The hanks for the good thoughts.

1/8 of an inch hole is one that I would consider a good candidate for gapping, but the person doing it has to be able to paint the flame skillfully.

If the person isn't quite as good at controlling heat - but has maybe B grade skills, sawing off a thin little piece of 3/16 or 1/4 in brass rod and laying it over the hole (with the clear watery acid flux that I described previously) might increase the chances for success.

Having saved so many crapped out old pistons like this over the years, I would just cover the 1/8th inch hole with solder and control my flame and heat. Just like my friend who posted above suggested, plumbing solder might be the best choice, but lead-tin works.

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It can be done all at once if you stop just before it falls in the hole.

That's sort of brinkmanship, but so is tightrope walking.

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