Wednesday, November 19, 2014

Removing a Saxophone Neck Dent

There are three requirements for removing a dent in a saxophone neck.  The first is proper tools.  The second is proper technique.  The third is common sense.  I'm going to concentrate on the first two.  By proper tools, I don't necessarily mean tools that are specifically made for horn dent removal (tool N81 is the "official" version of what I'm going to do).  Those would be nice, but we are going to use things that are readily available to the common man using common sense.   

Here's my project.  This is a vintage alto neck that has suffered a dent.  It is a fairly sharp crease.  Probably more a cosmetic issue than an intonation issue, but you never know.  Best to have it removed without creating any further damage.  That last part is always important.  
  The picture was taken with a low sun angle that highlights the dent.  It isn't quite as noticeable under most lighting situations.

Next to the neck is the first tool that I used.  It is actually a bar from an old motorcycle tool kit.  This was the bar that went through the spark plug socket to allow removal and replacement of the spark plug.  This type of bar is fairly common.  It is probably about 8mm thick and has a 90 degree bend in it.  I have added a little bend on the opposite end by placing in in my vice and adding a bend to the other end.  

The amount of bend that I've added is kind of important.  What I'm shooting for is to bend it enough so that it is out of plumb a little more than the inside diameter at the point of the dent.  It can't have too much bend or else it won't fit down the neck opening.  I then insert it down the neck in the direction shown in the picture and feel for the dent with the end.  The tip is against the dent, the straight section is against the opposite side of the neck, and I twist the 90 degree section to "wipe out" the dent.  Here's a crude picture of what I'm doing.

When removing the dent, make sure that the pressure against point A is spread out enough that you don't deform the opposite side of the neck.  The force on the dent should be a point load and the force on the opposite wall should be spread out.  This tool works great for quickly removing dimples.

This dent was kind of a sharp crease.  Those are the hardest to remove and the hardest to make completely disappear.  I could push it out a little with my tool, but complete removal was taking too much pressure.  Be very careful, start with a tiny amount of effort and slowly increase the pressure.  If you go too far and push a bulge out, you can push it back, but best not to go there.  When I got sufficiently spooked about trying for complete removal with my bar, I switched tactics.  

The above picture shows my initial results after using my "new" tool, a "dent chaser."
Here's another picture of the tool.  It's a home-made dent chaser using regular wrench sockets.  Here's the way it works.  First I find two little sockets that will pass all the way through the neck.  Then I find one socket that won't quite pass the dented area.  I thread the larger one and tie the other two to the ends of the twine.  I drop a small socket though from the tenon end and then use the twine to pull the larger socket up against the dent from the tenon end.  I carefully pull it under the dent, forcing the dent out from the inside, but, because of the snug fit, not deforming the neck on any other side (i.e., again a point load on the dent and a spread load on the opposite wall).

I need the smaller sockets on both ends to pull the chaser in to the damaged area and to make sure that I can get it back out.  Make sure that your string or twine is up to the task (maybe 50 lb test or more).  

If I'm lucky, I can find another socket that's slightly larger and repeat the process.  The largest I could use on this neck happened to be a 12mm socket.  Different brands of sockets have different diameters.  Different horns and different areas of the neck will require different sockets.  A large tool supply is needed although, as we have seen, they don't have to be "horn dent" specific tools.  I'm sure that there are other common items that can be substituted for sockets.

Not shown is what I did when the first socket was lodged in place behind the dent.  This type of dent creates kind of a "smile" with the edges of the dent actually higher than the undamaged surrounding metal.  So although it is dented down in the center, the creases on both sides are often proud of the neck tube and the hardest part to remove completely.  As I slowly work the socket in to remove the dent, I tap down on the dent end creases using a resin mallet.  Something like a piece of hardwood could also work.  Anything that doesn't damage the finish and allows the dent to be worked out.  I repeated that when I used a second, slightly larger, socket.
Here is the result with the harsh sun light showing the repaired dent at it's worst.   It is basically invisible for all practical purposes.  And this is still the biggest dent on this 1926 horn.