Reheating/hardening brass after dent work

[BBbmarcher]

After I've experimented with MDRS myself it got me thinking as to why no one (that I'm aware of anyways) reheats ares of a tuba where dents have been taken out to re-strengthen the brass there. Clearly the removal of dents (especially large ones) causes the brass to become weaker at those spots and are more prone to denting in the future. Is it an economic reason?

Thanks.

[BBbmarcher]

Thanks for the reply. Care to elaborate what buffing has to do with the annealing process? I don't get it.

[BBbmarcher]

Ok. That clarifies it, but if heating the brass after dent work makes it less brittle, wouldn't it be advantageous for the brass to do that? Clearly cracks and or even snaps/holes in an instrument should be avoided at all costs. I guess Joe's joke had a lot of good rationale behind it. All boils down to economics. But makes me wonder why people don't do it for extensive overhauls where they're going to strip the finish and put on a new one anyways.

[Lee Stofer]

BBbmarcher,
There are people out there, myself included, that do anneal sections of instrument parts as needed to make sure they are able to be safely worked, avoiding the awful spectre of cracking brass.

Even in the modern manufacture of brass instruments by hydraulically blowing parts to size, the parts are (should be) annealed after each step to prevent over-hardening and cracking. If you see a newer brass instrument with series of cracks but little or no associated dents, someone neglected to anneal the parts between blowing-out steps in the process.

Anyone who does any repairs on the old Holton 345's should be annealing any serious dent in the instrument, particularly in the top branch and the next three smaller branches, as long as they know how. I've seen too many of them cracked, as well as the bell flare areas of these horns, which can be avoided by annealing before they crack.

If there is a reason for more people not annealing parts that need it, it may be lack of experience of the tech, lack of tooling and facilities to do it, or a lack of desire to "go there", delving into a potentially very time- and labor-intensive job to clean up the cosmetic mess after the metal is repaired.

[Uncle Markie]

Lee has it right - of course.

Annealing is done throughout the manufacturing process especially with the larger parts of the horn - bows and bells. The art is in heating it up just enough to work it, but not too much that the brass becomes soft as grape. I suppose this skill is learned after ruining a few parts...

Better plumbers know this and anneal copper pipe to get certain bends just right.

Last week I had to fabricate a new transom drain tube from brass tubing stock (thank you McMasters) for my 1967 Boston Whaler. I needed to make a slightly swaged and flanged end to press an O-ring against the outside of the transom. Lacking the proper equipment I heated the tubing up on my gas kitchen stove, quenched it and used an old Yamaha tuba mouthpiece as a beating mandrel to swage it out enough to then flatten the end flange on my anvil.

Without annealing it would have cracked for sure and I would have been down to the Whaler dealer ordering an expensive part.

Mark Heter

[Dan Schultz]

.... again I have no experience but I'm guessing the instrument is disassembled for proper annealing and who would want to disassemble an instrument every time they got a dent taken out.

Even if this wasn't the case, annealing destroys silverplating and laquer which would make the horn ugly.

You don't need to anneal the entire horn to remove a single dent.... nor do you have to take a horn completely apart for dentwork. I'm working over some severely dented York 'Master' bows. The only places that need annealing are where the brass has been bent and folded nearly double. I anneal only the spot that needs attention plus maybe 1/2" or so beyond the area. Some of these 'spots' have to be annealed several times between working the fold/dent out. This is done with a torch.

It's very difficult to quantify but one can develop a 'feel' for when the brass is hard and needs to be annealed. You can actually 'feel' the brass getting harder as you work it.

In production situations... parts are annealed in batches in large ovens.