Tone Hole Bushings

About once a year, a co-worker brings me her Eb clarinet and asks to have it looked at before she uses it in a performance. I've worked on it several times, but it's always a last-minute thing so I can only devote enough time to get it to limp along for a few weeks. Then it goes back into storage until the next emergency. This time was no different, except that things had deteriorated to the point that I couldn't let it go any more without doing some major work. The top of the body has a few cracks in it that had been previously repaired by someone else with little success. In addition, because the cracks ran through the top two trill tone holes, they'd attempted to seal and rebuild the tone hole rims with superglue. The result was pretty gnarly looking, and was still leaking. I thought this would be a perfect opportunity to give my new drilling jig a workout by replacing those two tone holes. I did a lot of other work, too, filling the cracks and banding the top of the joint with carbon fiber to repair it in a more permanent fashion than the previous technician. Those tone hole bushings, though...

Because she needed the instrument back in a hurry, I didn't have time to order a tool for cutting out the old tone holes. So I made this one by turning, drilling, and tapping a piece of steel. Then I filed and sharpened the twin cutting edges by hand. The two brass pilots thread into the cutter to keep it centered in the tone hole while cutting. The tone holes are different diameters, thus the need for two pilots.

You can see the previous work on the tone hole in the center of the photo and the one to its right. The rim is just superglue that's been layered on and then filed to something resembling flat. The rims are very wide, making it difficult to get a pad to seal. Not that it would have mattered, because the tone holes still leaked through the cracks. The tone hole in the center is about to be cut out on the drill press in this picture.

I turned these inserts on the lathe out of ABS. They'll be the new tone holes.

After drilling out the old damage, here's what's left. The inserts will drop right into those holes, with some fitting and adjusting.

The inserts are installed with epoxy, then dressed to make sure they sit flush. It's not a terrible result for my first time at this.

In order for the pitch and timbre to be correct, the inserts will need to be reamed with a tapered reamer. The straight holes I made in these are a little undersized to allow for that. I wasn't able to ream these before returning instrument so things are a little wonky, but it's a vast improvement over the leaky mess it was before, and I can complete the job by reaming them after my coworker is done with her gig.