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Re: New tuba day!

Postby Donn » Wed Jan 02, 2019 4:21 pm

I like that. Must have big balls -- no, I mean, seriously, what sizes did you use?
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Re: New tuba day!

Postby bloke » Wed Jan 02, 2019 4:35 pm

Mark will report, but here are a couple of comments:

Magnet work is the opposite of regular from-the-inside burnishing.

When PUSHING dents out from the inside, the SMALLER/more-acutely-curved the curvature of the ball, the MORE pressure is concentrated on one spot.
Thus, SMALL balls (or bullet-shapes, or whatever) are used for the hefty pushes (undoing of severe damage), and larger-curvature (larger) balls/bullets are used for final smoothing...as larger-diameter balls/bullets distribute the force (more gently/less acutely) over a larger area.

When using magnets, LARGER MASS balls or oblongs (which tend to also be larger/flatter curvature) are pulled up more vigorously by the magnet, and thus they are used FIRST (to remove the epic/severe dents) and the SMALLER MASS (which tend to be more acutely curved) are pulled up by the magnet LESS vigorously, and - thus - are the ones used for final smoothing.

Other subtleties include using magnets of different thicknesses, as well as micro strength-adjustments of adding thicknesses of cloth to space the magnet (whether thin/weaker or thick/stronger) farther away from the surface.

bloke "A likely way of messing something up really well is to combine tools - which amplify most any effort, whether sublime or ill-advised - with inexperience." :lol:

=====================================

Ironing simultaneously from both the inside and outside (i.e. using a "dent machine") was not discussed in this post.
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Re: New tuba day!

Postby Mark Finley » Wed Jan 02, 2019 6:13 pm

Bloke pretty much summed up my experience.....
But... Here's something unorthodox I did. (repair guys close your eyes, you're probably not going to like this)

The big crater dent was so deep, my 2 inch dent ball did nothing. I dont have mandrels and threaded balls here, so I did what was my only option

The bottom bow is a hair over 3" across (ID) so I ordered a 3" dent ball. I stood the tuba up, and let the dent ball roll down the bell, (waterslide style) and it contacted the obstruction. It only took 12-20 times of doing that until it opened it up enough that I could start to work it with a magnet. Mostly I used the 3 inch and the 2 inch For the bow
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Re: New tuba day!

Postby bloke » Wed Jan 02, 2019 6:23 pm

Mark Finley wrote:Bloke pretty much summed up my experience.....
But... Here's something unorthodox I did. (repair guys close your eyes, you're probably not going to like this)

The big crater dent was so deep, my 2 inch dent ball did nothing. I dont have mandrels and threaded balls here, so I did what was my only option

The bottom bow is a hair over 3" across (ID) so I ordered a 3" dent ball. I stood the tuba up, and let the dent ball roll down the bell, (waterslide style) and it contacted the obstruction. It only took 12-20 times of doing that until it opened it up enough that I could start to work it with a magnet. Mostly I used the 3 inch and the 2 inch For the bow


Doing that can easily bulge out the INNER curve of a bottom bow, and then - my friend - you (well...I) am in $h!tzville.

Those bows on those tubas aren't hooked to anything other than adjacent bugle parts, so (particularly with no finish worth saving) I'd just pull the bow off, anneal that worse area and wham the bottom bow down against a curved rod, or against a curved rod with a ball screwed on to the end of it.

After that, I could sit down in my comfortable chair, listen to the radio, run the magnet tool over the bottom bow, and then solder it back in place.
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Re: New tuba day!

Postby Mark Finley » Wed Jan 02, 2019 6:29 pm

Of course I would have pulled the bow if I had those tools. I even looked up how much they cost. Then decided against it for a tuba that cost me $600

I checked the inner curve of the bow when I was done and didn't feel anything out of shape. And even if it was a little, the overall shape of the bow is much better now

I tried annealing it, couldn't get it hot enough with propane, realized I was out of MAP, and decided to try it without and see what the results were. 30 minutes later I was done. I'll get some MAP and work some stubborn areas that didn't come out quite so easy
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Re: New tuba day!

Postby bloke » Wed Jan 02, 2019 7:32 pm

The only "tools" to get the bow off would be torch, and the "tool" (though - sure - I have something a bit nicer and specifically engineered) to beat that bottom bow down against would be a steel pipe (or 3/4" rod) that was heated and bent. Again, once the most epic dents are roughed out (as you did via a different method) the magnets/balls can take over.
There's also a Bernzomatic nozzle - that gets hot enough for annealing - that you can use with propane.

tool.png
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Re: New tuba day!

Postby Three Valves » Wed Jan 02, 2019 7:35 pm

That’s pretty impressive!!
Who needs four valves??

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Re: New tuba day!

Postby bloke » Wed Jan 02, 2019 8:43 pm

Three Valves wrote:That’s pretty impressive!!


agreed
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