Sleeving the Upper Joint of a Clarinet

Every now and then, an instrument comes along that makes you say "What?" and/or "Huh?" and/or "Seriously, what?" This clarinet quickly went from a request for a tune-up, to an overhaul, to a major bore repair. The story is that many years ago, the top of the instrument was smashed, cracked, and started to split apart. Two enormous cracks testified to that, as did two flush bands and a tenon ring installed by a previous technician. Actually, a flush band would have to be flush by definition, so really it had one flush band and one, uh, hose clamp? It was a very nice hose clamp, though.

Whoever did that repair clearly cared about their work, and was proud enough to have engraved their name on the tenon ring. I'd like to think that if he were doing this job today, with access to modern adhesives, materials, and know-how, he would have taken a different approach and done a really nice, attractive repair. But 40-50 years of being constricted by those bands really took a toll on the instrument. With nowhere to go as it swelled and contracted, the wood split and splintered into the bore. The original cracks, held together only with shellac, reopened and extended. By the time we got to this instrument, it was in sad shape.

The previous repair, with hose clamp, flush band (really nicely installed) and a tenon ring/cap.

After removing the hose clamp and washing the wood to remove old oils and shellac.

Inside the bore, looking down from the top of the joint.

Another vew, showing just how severe the damage was and how far the splinters protruded into the bor.

With the bore in that condition, the instrument was uplayable, even if it hadn't been leaking through the cracks. We weren't sure how to proceed,so we tried several methods to smooth it out. After removing both bands to relieve the constriction/tension, we tried humidifying the wood, then letting it rest, then pushed it over a fitted steel mandrel and left it there for days (the Votaw .585" mandrel happened to fit perfectly, which was a bad sign because the bore of this upper joint should have been .576"), then let it rest for even more time, but nothing moved. 

It seemed like a loss, but the owner has a strong attachment to this instrument. I had arrived at the limit of my experience, so we reached out to Mark Jacoby, a legendary clarinet specialist in Philadelphia. He was kind enough to give us some of time to evaluate the instrument and strategize. He tried a few things that helped somewhat, but we all agreed it wasn't enough. He let us hang around in the shop a while, though, and in passing mentioned the possibility of installing a sleeve in the joint. That would mean boring out the damaged section of wood and machining a plastic insert to replace it. After we departed (reluctantly, as Mark is a really great guy and a font of knowledge), that idea stuck in my head. I was drawn to it for a simple reason: I was about to send off my own english horn to David Teitelbaum in New York to have a sleeve installed in the upper joint, and was inspired by his incredible work to stretch my own skills. I knew I couldn't do such a job on an oboe or english horn (yet), but a clarinet seemed feasible. How serendipitous it was that I happened to have this instrument in the shop. When my english horn came back playing like new, there was no doubt I was going to attempt this job. Cue the A-Team theme (with NBC Television's OK)...

ABS stock for the insert is set up in the lathe and center-drilled.

The insert was drilled out to .500"with a regular drill bit. The finished bore dimension will be .576" at the top, and tapered down from there

After drilling the inside but before boring, the outside dimensions are turned. The outside of the sleeve had to be .875" in diameter to match the cutter that would bore out the damaged wood from the upper joint.

Sleeving the upper joint requires the original tenon to be removed, and the replacement tenon is integral with the sleeve. Here the groove is being cut to hold the tenon cork.

The (mostly) finished tenon.

Boring out the insert to be closer to the final dimensions. I chose to do this before installing it, as my lathe isn't large enough securely hold the entire upper joint for boring.

Boring left a surprisingly smooth finish, but it will be reamed later to create the necessary (slight) taper.

Measuring the internal dimension of the insert. With that done, it was time to move to the instrument.

The original tenon was chucked up and cut off.

A .875" aircraft counterbore was used to bore out the upper joint. The cutter is centered by a pilot that passes through a fitted plastic guide inserted into the bore. The hose clamp (an actual hose clamp this time) is to prevent the joint from flexing and splitting along the existing cracks. Removing so much wood significantly thins out and weakens the wall of the joint, thus the need for reinforcement.

One of the cutter teeth visible through the Bb trill tone hole. About 2.5 inches had to be removed, to just above the Throat A tone hole.

Two views of the upper joint after boring is complete. The counterbore left a very nice finish. The two spots visible in the second picture are the holes for the register key posts.

With the insert in place. The insert was left long to allow room for error. Not that I make those.

Cutting off the excess.

The upper joint and insert just before assembly.

The insert was epoxied in place and set on the lathe to cure. The lathe here is simply serving as a work fixture - its rigidity prevents anything from moving as the epoxy sets.

With the epoxy set and cleaned up, the seam between the body and tenon is nearly invisible.

Looking down the now straight and even bore

All that remains now is to redrill the three tone holes covered up by the sleeve, ream the insert (with Mark's help, as I don't have the necessary reamers), band the cracks with carbon fiber to prevent them from extending any further, then oil the joint and proceed with a normal overhaul. In just a few weeks this instrument will be up and running like nothing ever happened.

Incidentally, if I actually had played the A-Team Theme song while I worked on this, it would have played 184.6 times before I was done. I really took my time to avoid any potential catastrophes. Meanwhile, the actual A-Team could have retrofitted 500 vans for non-lethal battle and still had ample time left over for Mr. T to pity several fools.