The Bench @ Keystone: Clarinet Tenon Rails

The rails are the thin strips at either end of a tenon. While the cork creates an airtight seal and prevents the joints from slipping apart once assembled, the rails provide structural support and prevent wobbling. This is perhaps best demonstrated on clarinet center tenons, which must bear a lot of stress from the weight of both the upper and lower joints. Ideally a long tenon would distribute that stress, but the center tenon has to be made relatively short because of the placement of the tone holes on either side. It's not surprising, then, that we see a lot of older clarinets with worn down rails on the center tenon, especially wooden instruments. A worn tenon will invariably wobble, causing the bridge key regulation to go in and out. It also just feels weird and wrong.

This clarinet had an especially bad center tenon. Beyond the natural wear, I suspect someone got overzealous and sloppy with their sandpaper when replacing the tenon cork at some point. The rails were almost gone, so the tenon was pretty much a uniform diameter. Sometimes silk-wrapping a tenon can address worn rails, but you need something to start from in order to do that. The only option here was to turn and install new rails, which is a more stable and accurate repair anyway.

After cutting away what was left of the old rails - and a little more on the lower end to create a nice square edge for the new rail to butt against. That groove on the upper end was for epoxy to get in and adhere, but I don't think I'd do it again as it makes the tenon a little weaker.