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With rebound work, there is always the danger of the rod flexing back and putting an outward dent on the underside of a tuba bow - particularly if a bow's diameter is fairly small in the area being repaired. I wonder if anyone has ever experimented with asymmetrical threaded balls specifically for rebound work- whereby the side facing up is the side which pushes the dent out, and the underside is doesn't stick out very much at all. Obviously, it would have to end up being oriented a certain way once it is threaded on all the way.

...??

I cannot imagine this. Drawing?

the elephant wrote: ↑Mon Nov 28, 2022 4:09 pm I cannot imagine this. Drawing?

particularly when only PARTIALLY disassembling a tuba, and (prior to going back and really smoothing it out nicely with normal burnishing and ironing methods - ROUGHLY knocking out a typical horrible dent from an upper bow...

often through two layers of sheet metal...as (particularly with continental European-style upper bows) it's usually possible to make these very smooth and nice without removing upper bow caps.

(I find myself doing quite a bit of this b.s., lately...so I couldn't help but thing about a tool with which I might not have to be quite as careful...)

Oh, I see what you mean now.

I have never rebounded hard enough to have the bar slap the bottom of the tube like that. I guess I only rebound on the largest stuff where there is more than enough space for that (meaning I probably *have* done that but never had it contact the other face of the branch).

It seems like that would be a decent solution, but it also seems like you could take an old curved shoe from a dent machine and use the set screw to attach it to some straight rod of the correct diameter. I guess that would be too tall and *sharp-edged) for use, so never mind…

the elephant wrote: ↑Mon Nov 28, 2022 9:37 pm Oh, I see what you mean now.

I have never rebounded hard enough to have the bar slap the bottom of the tube like that. I guess I only rebound on the largest stuff where there is more than enough space for that (meaning I probably *have* done that but never had it contact the other face of the branch).

It seems like that would be a decent solution, but it also seems like you could take an old curved shoe from a dent machine and use the set screw to attach it to some straight rod of the correct diameter. I guess that would be too tall and *sharp-edged) for use, so never mind…

Yeah, Mrs. bloke knocks the hell out of curved/straight 3/4" rods (3 lb. sledge - perhaps a foot away from the bow or branch opening) to push ridiculous/malicious dents (ex: "angry" thread") out of bows and branches c. 90%, so I can work on them from that point forward. It works really well on compound creases, etc. me...?? I'm over at the business end of the thing - holding the worst part of the dent/crease right over the contact point of the threaded ball - while she's slamming the hell out of the rod.

It doesn't bother me to have to repair rebound marks (when I wasn't the one who - in the first place - affected the over-the-top damage), EXCEPT when I'm repairing something like that WITHOUT completely un-soldering an instrument and then have to go back with my polished-inside-curve busted pliers handle, and tap out those lumps by tapping on that with a rawhide mallet (which is tedious...I'm usually really eager to get a repair back in its case and turned into dough - whether $20 or $2000).

I was a bit worried about that same issue the first time I did some rebound work (less than a year ago and I think I’ve only had at it 2 or 3 times since, so obviously a total novice and not nearly as condescending as that sentence sounds).

I like your idea but would worry that the asymmetrical dent ball would rotate. That could be sorted out with a set screw but that would bung up the rod’s threads unless you had a larger diameter ‘shoulder’ machines into the dent ball and put the set screw there to bite into the rod’s full (smooth) diameter. Or you could use thread lock but that would take too long.

Other ideas (if the dent ball rotating would even be an issue)?

I guess either retightening or a lock screw..

I would have repaired a couple of bell creases and bell stem dents for nuthin'...but - these days - one might risk being accused of "running up the charges".