DIY Brass instrument repair?

August 21, 2012 3:06 PM

How do I hammer my brass instrument back into shape?

I've got an old mellophone I play a few times a year during football season for alumni band. Unfortunately my 3yo son dropped the horn and introduced a nice warp to the bell. As you can tell from the pictures, it's just a beater, so I'm not upset about it. I thought it might be fun to try to hammer it back it shape myself. Any tips on how to go about this without destroying it? Thanks!

Pictures: http://imgur.com/a/HmuBj

posted by rdhatt to sports, hobbies, & recreation (4 answers total)

brass repair guys use a rubber (or maybe a wood?) hammer, a form that they place the bell on as they straighten it out, and lots and lots of training and technique. The lacquer will still have some scarring, but they can usually get it into the right shape.

Me, I'd take it to a local music store... they usually will do this pretty cheap if you're not asking them to relacquer it.
posted by randomkeystrike at 3:14 PM on August 21, 2012

It doesn't look too bad. At the narrow end of the bell it's very close to being creased but I still think you can bang out the bigger dents if you take your time.

I'd fill a pillowcase with enough sand or rice so that the outside of the bell is well supported. then I'd find a leather mallet and lightly pulverize one of the striking surfaces so that it looks like suede. (Stab it with a screwdriver or something for a little while.)

Then go to work. Keep the bell supported with your rice or sand and the bag should be loose enough for the bell to sink in half way without bottoming out.

The only real trick to it is to keep from causing creases in the metal. To do that keep moving the mallet. Start at one end of the dent, work along it and work back again. In this case, I would alternate between the two dents to keep the metal from stressing at any particular point.

After a few whacks, you'll get a feel for what you're doing.

Good luck and have fun!
posted by snsranch at 6:17 PM on August 21, 2012

There are tools designed to do this, but you will probably need to go to someone who already has them: they're fairly expensive. If it's bad enough (your picture won't load, so I'm kind of guessing blindly here) the repair would involve removing and brazing in place a new bell. Sections of crumpled tubing can be replaced in the same way, and the lacquer, if damaged, can be stripped and replaced.

Tubing that needs to be bent can be filled with something solid but malleable first so it won't collapse. I've heard of pitch being used because it melts at a manageable temperature.

To work out the creases in a bell, you would use a mallet first to get it in the neighborhood of straight and then an English wheel. If you know someone who makes stuff out of sheet metal, they may have one you could use.

For dents in smaller diameter sections, you drop or push a series of precisely sized steel beads called "dent balls" through the tubing to work it back out to the proper shape. These can be strung on a string or placed at the end of a flexible metal rod.
posted by pullayup at 6:21 PM on August 21, 2012

I haven't tried this personally, but it looks really cool, and perhaps more available to everyday people:

http://boingboing.net/2011/10/26/howto-make-a-magnetic-reverse-hammer-to-remove-dents-from-brass-instruments.html
posted by sarah_pdx at 7:32 PM on August 21, 2012 [1 favorite]