Hannemann’s Music Corner: Changing a Tenon Cork
By RICHARD HANNEMANN
Clarinets come in sections. Each section attaches to the other by means of a tenon and sleeve joint – one section has the sleeve, the other has the tenon which protrudes from the body of the section.
There is a cork on each tenon which allows a snug, and most importantly, air-tight fit.
Cork is wunnerful stuff. But it doesn’t last forever. Eventually it mashes down and wears out and then the joint gets wobbly, leaks air, and your instrument won’t play right. Time to change the tenon cork.
Now. I could do this for you. I charge $36/hr and it takes between and hour and an hour and a half. Or you could do it.
You will need:
A pocket knife which is really sharp. A piece of sheet cork 1mm to 2 mm in thickness – this will depend on your instrument. An emery board. Some reasonably strong rubber bands. Glue – I use the Pad and Cork Cement by Micro. Some techs are going with super glue but remember what goes on has to eventually come off next time you change the cork. By the way, I use this only for corks not for pads. A cutting board. A piece of string.
It is really convenient to have a really good caliper that will measure in very small increments.
You also need a lot of patience.
1) Carefully carve off the old cork. Make certain you get off every bit of cork and old glue. You can do this with your pocket knife. Don’t use sandpaper to get off the last of the old glue – odds are you will wind up removing material from the tenon. A really sharp knife used judiciously will clean the surface nicely – rub it lightly back and forth as a scraper. Don’t bother with solvents – they won’t make the job go any quicker and some could damage the tenon material.
2) Measure the depth of the tenon cork groove. The outside diameter of the tenon minus the groove diameter will give you the thickness of the tenon cork. Use a thickness that is a shade bit thicker than the depth of the groove, but don’t over-do this. You want a tight fit but you don’t want to put undue pressure on the sleeve (it could split).
3) Measure the circumference of the groove to get the length you need. Piece of string here is helpful.
4) Measure the width of the groove.
5) Cut a piece of sheet cork to your dimensions — make it just a tad bit longer than needed.
6) With your emery board, bevel one side of one end of your cork strip. About a 30 degree angle to a sharp edge. When you wrap your cork around the other end will over-lap on this bevel – gives a better fit and reduces the chance of an air-leak at the join.
7) Decide which edge will be your “leading edge” – the edge that will be entering the sleeve. You want to bevel this edge – again about a 30 degree angle.
This won’t be a sharp angle as you used before – it shouldn’t be any thinner than the depth of the groove. You are simply making a bit of an entrance ramp for better ease of inserting the tenon into the sleeve.
8) You can, if you want, slightly round the following edge.
While doing steps 5 – 8 you will want to be constantly checking your result by wrapping your cork strip around the tenon. It should be an exact fit as far as width.
Your leading edge bevel should be no thinner than the depth of the tenon cork groove. The end you didn’t bevel should lap your beveled end nicely leaving just a tiny bit of a tail which you will remove later.
9) Apply the glue to the inside of the cork (the side going against the tenon), to the top of the lap bevel, and to the tenon groove. This doesn’t require much, but you will have to spread it evenly and completely. Unfortunately, the best way to do this is with your finger (although a popsicle stick or a flat toothpick can be useful). Let the glue get tacky.
10) Starting with the bevel lap end, wrap the cork into place making certain to firmly press it on as you work your way around. Bring it over the lap and press it firmly into place.
If you are doing the center joint the process will be a bit tricky since the long Bb bridge is going to be in the way. You can work around this so you don’t really need to take the key off. Take your time about this. Let the surfaces really bond together as you work it around.
11) Wrap your rubber bands around the cork to act as a clamp. Make sure you cover the whole thing across its entire width. Let it sit for 24 hours.
12) 24 hours later take off the rubber bands. Your cork will probably be showing lines where the rubber bands were. Let it sit another couple of hours while your cork revives.
13) Trim the tail off nice and flat to the cork. You can do this with a very sharp knife or razor blade but be careful – cork doesn’t like being cut across the grain and can sometimes crumble or split. You can also simply sand it off with your emery board. This takes a bit longer but you wind up smoothing the upper lap into the lower lap rather nicely. I prefer sanding to cutting.
14) Dry test the cork. Put the tenon into the sleeve – the fit should be snug but not too tight. If it seems it will require a lot of work to get it in your cork is too thick. Carefully begin to sand the cork down to its final thickness. Make certain you do this evenly so that the cork remains the same thickness around.
Congratulations – you just changed your tenon cork and your instrument will be playing much better. Of course, if one cork needs to be replaced then likely the others will as well. You have 2 more to do (3 if your mouthpiece cork needs replacing). Have fun 🙂