Beaten to death elsewhere, the use of a magnet & other stuff…

By: frugalhorn

Dec 28 2012

Category: Uncategorized

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Aperture:f/2.8
Focal Length:6mm
ISO:200
Shutter:1/0 sec
Camera:DMC-FZ5

About ten years ago I first became aware of the MDRS (magnetic dent removal system) concept. I don’t know when it came oozing onto the repair scene, But it generally seemed to be used on larger instruments, like Tubas and baritones.  The idea is interesting, and I don’t have a pacemaker or any other items in my body that might be damaged using a powerful neodymium magnet. (Also if you fool around with this don’t leave this magnet near your computer or wallet with credit cards and other things that might have their magnetic properties altered…)

Below is the  magnet and one of the steel balls that I use. The magnet is about 2″ in diameter and the ball is about 1.5″. note that the plating on the magnet has failed. The steel balls were all acquired locally and not ordered via the internet. The magnet was purchased on the internet several years ago and I can’t remember the price, but it was fairly expensive.magnet-5

As you know, if you’ve rand much of my prior blather, most of the horns I work on are well used, abused and often need a bit of work… The model in this blog is an N series 8d that has a couple of patches and a trashed finish.  Because the finish is basically gone, I’ll use a seldom seen tool. The factory produced Dent systems go to great lengths to not damage the finish of an instrument.  If you search the internet you can find info on the commercial systems. The dent below is beyond where my arched rod can reach and we’ll use the magnet with a ball inside the horn to remove this dent.

magnet-2

This is one of the dents we’ll remove, and the other area if work is a bulge made from an overly worked dent raised above where the arch of the back bow was originally.magnet-3magnet-1

The seldom used tool mentioned above is a sword burnisher, which is basically chain mail attached to a leather pad. I don’t know if these are still made, mine came from France.  Possibly folks involves in the collecting of swords or medieval items might know where to find one.

magnet-4

Using the burnisher it is held in-between the ball, on the inside of the horn and the magnet as shown. As you move the magnet up and down, two things are accomplished, the bell arch is smoothed and burnished at the same time. The chain mail burnishes the Ni Si of the bell tail. magnet-6

magnet-7

As you get further inside the bell tail the ball is smaller and the magnetic pull is lessened and the burnisher absorbs too much of the magnetic force so I remove it and use a Mylar sheet which is floating on a thin layer of spray on non stick cooking oil. The mylar (when new) is very smooth and when used with the cooking oil is somewhat gentle if the finish (if it’s in good repair). If there is any tiny amount of dirt in-between the mylar and the finish it will scratch it.  I’ve tried using other “shields” but the mylar seems to work best. I use the mylar circles that are used to create a pouring spout in a wine bottle.  magnet-8

I’ve used this technique using balls as large as a 3″ cannon ball. ( Not on a horn)…

If you have ideas, additions,  complaints or stories about this technique contact the blog, and share.

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