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Replacing a low C tone hole chimney for a 1919 Martin C melody

At the risk of everyone laughing- you CAN make your own tubing out of
sheet stock, if you work at it long enough. A 3- roller setup helps a lot, but
careful work on an appropriate strip by hand over a mandrel
with everything from a roller to a hammer and dolly
can work. Brass being the soft metal that it is....

t
 
At the risk of everyone laughing- you CAN make your own tubing out of
sheet stock, if you work at it long enough. A 3- roller setup helps a lot, but
careful work on an appropriate strip by hand over a mandrel
with everything from a roller to a hammer and dolly
can work. Brass being the soft metal that it is....

t
That’s doable but how do you bond the seam joint ? TIG weld with brass rod ?
 
@djarossens do you have a lathe ?

Attach a round flat stock disk on a required size mandrel. Roll form the metal over the mandrel. Remove part. Trim the part radius to fit the body. Gently place part back onto the mandrel. Spot solder to hold the part. Part off the cap end to the needed socket height.
 
That’s doable but how do you bond the seam joint ? TIG weld with brass rod ?
Silver solder will be fine. You can up the ante to bronze brazing if you like, but I've never found it necessary.
It's worth putting a chamfer on the two ends though - just to increase the bonding surface. The big drawback with the 'cut and shut' method is that you only get one go at it - and it has to be spot on. The joint will tolerate a bit of rounding (the brass will have been annealed) but if you need to expand the tube thereafter it gets a bit risky.
 
Stephen beat me to it- yeah, in this case, silver solder.
A friend who welds says TIGging isn't recommended because of the zinc
content of the brass, but that yootoobers seem to do it all the time.
I was thinking that the next time I had the TIG out, I might try it.

Also, no reason not to gas weld it, if you're better at that than I am...

t
 
Let me know how it goes.. :)
Stephen beat me to it- yeah, in this case, silver solder.
A friend who welds says TIGging isn't recommended because of the zinc
content of the brass, but that yootoobers seem to do it all the time.
I was thinking that the next time I had the TIG out, I might try it.

Also, no reason not to gas weld it, if you're better at that than I am...

t
I have MIG, Gas & AC/DC Arc welders. Zero experience TIG welding.
Thinking of how delicate the task is. I was wondering if TIG would apply ? I have a friend who’s quite talented in TIG work. I’ve seen the man put a pretty nice bead on a butt joint of two razor blades.
I need to take a trip to the local welding supply in the near future. I will inquire. The technician there is quite talented. The nickel-bronze rod he recommended for brazing a chromoly steel motorcycle frame was fabulous. Low heat and strong joints were extremely important.
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Now that's interesting. I knew Selmer had been using spot welding techniques for positioning some parts to the body, but I had no idea they were TIGging seams. So yeah - it's official, it can be done.
 
Now that's interesting. I knew Selmer had been using spot welding techniques for positioning some parts to the body, but I had no idea they were TIGging seams. So yeah - it's official, it can be done.
I’m sure they went through an R&D learning curve. I’m suspicious that they may have altered their brass mixture.
 
I’m sure they went through an R&D learning curve. I’m suspicious that they may have altered their brass mixture.

That could well be likely. Funnily enough I was checking out a Yamaha 875EX tenor last night and noticed that the internal seam on the bottom bow looked quite wide and smooth....more like a weld than a braze. Maybe it's slipped into common practice these days?
 
There should be no inherent issues in TIGing brass. The TIG process is so extremely adjustable that almost anything that can be welded can be welded using TIG. The shielding gas eliminates the common issue of atmospheric contamination of welds. A welding expert ought to be able to provide guidance on the correct TIG setup which then would be tweaked based on tests done with the actual material and equipment.
Because a tone hole chimney is an extremely low-stress joint operating in extremely benign conditions, weld quality isn't going to be super critical - main requirement will be "must not crack and fall apart".

Tiging the seam for a neck is a higher stress situation due to subsequent forming.
 
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