 The Clarinet BBoard
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Author: joevacc
Date: 2000-07-12 02:55
I have been slowly teaching myself how to repair and adjust my clarinet and have read many books on the subject. I have taken a couple of trashed clarinets and brought them back to nice playing condition. One thing that I have only been able to do by trial and error is adjust key and pad heights. I was wondering if there is a chart somewhere or is there a rule of thumb for these measurements?
Thank you in advance,
joevacc
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Author: paul
Date: 2000-07-12 13:43
There is a rule of thumb for you to use. The opening of the keypad from the tonehole is a fraction of the wavelength of the produced tone. Being technical in the clarinet isn't my forte, but there are exact calculations for the amount of surface area of the pad versus the amount of cubic area of clearance from the tone hole to not affect the note. As I recall, the rule of thumb fraction is 1/4 or so of the produced wavelength, but don't strictly follow this premise and think you have it fixed. You know the clarinet won't let you do that.
You're first assumption is right, in the end it's a matter of trial and error, especially when you get very close to the edge of shading versus not shading. If you have a good ear and you can make small adjustments in the keypad clearance, play the note and hold the pad pretty close, close, about where it should be compared to another horn, a little bit farther, and pretty far away. Listen for when you start to shade the note on the test clarinet and adjust the keypad clearance to just beyond the point of shading. Use a tuning meter as a guide, but use your own ear as the final judge. You might be surprised at how good your own ears are at finding the "just right" clearance height. When you are really close, don't adjust the set screws or springs for the keypad mechanism. Instead, very carefully and ever so slightly bend the keypad's arm or the key in the direction you want to go (up/down). If you have a good horn, the keypad arms and keys will be relatively stiff to bend with bare hands, but it can be done (and should be done instead of using pliers or other "hard" tools). On a good horn, the keypad arm or key will stay right where you bent it. Many horns perform better and sound better after they are regulated like this.
If there are multiple keypads that need to be open to play the note, work on notes that only need one keypad first, then work on the more challenging multiple keypad notes. If the multiple keypad note still sounds bad, make ever so slight adjustments in the single keypad notes. Remember, you can't get it perfect - the clarinet won't let you do that. But, get as close as you can, adjusting the least amount of keypads possible to get the note to sound good but still be balanced between other notes.
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Author: Lelia
Date: 2000-07-12 15:11
paul wrote:
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....Use a tuning meter as a guide, but use your own ear as the final judge. You might be surprised at how good your own ears are at finding the "just right" clearance height. When you are really close, don't adjust the set screws or springs for the keypad mechanism. Instead, very carefully and ever so slightly bend the keypad's arm or the key in the direction you want to go (up/down). If you have a good horn, the keypad arms and keys will be relatively stiff to bend with bare hands, but it can be done (and should be done instead of using pliers or other "hard" tools). On a good horn, the keypad arm or key will stay right where you bent it. Many horns perform better and sound better after they are regulated like this.
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That method works, but can break a key, too. If the key is cast alloy (white metal with a number cast into the bottom of it), I would do anything to avoid trying to bend it. That pot metal is very brittle. I've actually had a broken key on a 1958 Conn. I had bent it by accident. A repairman warned me it would probably break if he bent it back. Sure enough, it did. He had to hand-cast me a replacement. That's one reason why I don't like that type of key. IMHO, forged brass (with silver or nickel plating) is much better.
Brass is more ductile and can be worked. Bending a key is sometimes unavoidable. I agree with the advice to use the hands only, when this type of adjustment has to be done -- but IMHO, it's better to do the other types of adjustments *first* and bend a key only as a last resort. The problem is that the metal has been tempered, strengthened, by heating it and stretching it. Bending it removes some of the temper. Every time you bend it, it gets weaker, until metal fatigue sets in. Bending the key one way and then back the other is especially damaging. (Think of the way you destroy an old credit card, by bending it back and forth until it snaps. Same thing with metal.) When we buy a clarinet, we have no way of knowing how many times other people may have already adjusted a key by bending it. You could be the unlucky stiff who bends it once too often. Snap! If you do have to bend something, go very slowly and cautiously. Bend it *less* than you think you need to each time, so that you never have to bend it back the other way.
Key breakage is one of the greatest hazards of amateur repair work. I leave bending a key to a pro, on anything but an old beater that I'm using as a learning project. In restoring several old clarinets and saxes, I've found that other maladjustments are much more often the culprits than a bent key. The most common causes of a badly-fitting key are a worn-down key cork, a weakened spring or a pad that's crooked in the cup.
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Author: paul
Date: 2000-07-12 16:27
Gotta agree with Lelia's posting about overstressing the keys through bending, especially back and forth. Be very careful and do it as a last resort. She's also right, it shouldn't take very much at all, an almost imperceptible amount of bending is all that's usually needed. I also totally agree with her about the low quality of pot metal versus the high quality of brass/steel alloy with nickel or silver plating. If you have cheap pot metal keys, even the least amount of bending is simply out of the question. Don't even go there.
She's also right, check the pads in the pad cups (Make sure the pads are the right height here. Even if they are the right size, the glue thickness underneath affects the height.), the springs, the pins, the set screws, and especially the underlying cork for the keys. Look for shaved or nonexistent key corks and start there. A simple and cheap experiment is to use simple cellophane tape in several layers on a key cork to see if you can get the key to rest at the right height. Once you have it right, you can either fetch some new cork or you can leave the tape in place. Okay, it's awful ugly, but it's cheap and easily adjustable in the future. Plus, you aren't bending any keys in the process.
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Author: joevacc
Date: 2000-07-12 19:20
Thank you guys for all your insight. In my experience with these things, I found that most of the adjustments can be done by sanding foot corks or replacing them with thicker ones and sanding until I get what I am looking for. I did do a lot of work on a metal clarinet that does have pot metal keys and am painfully aware of the complications that you are talking about! (I won't bend that Ab/Eb key any more!) The reason for the post was to see if I was missing some piece of information. On the horn that play regularly it took me almost a week to get it perfect. I guess there is no substitute for experience.
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Author: J. Butler
Date: 2000-07-12 20:43
I avoid bending keys. The only time I bend a key is to get it back into the original position after some form of accident or abuse by the customer. Key height can be controlled by cork in most cases as well as the aforementioned correct installation of the pad in the cup. I would rather spend a few minutes extra on a key replacing or sanding the cork than to bend it. Another point is bending a key in which the pad already has a seat can cause a leak.
J. Butler
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Author: Don Berger
Date: 2000-07-12 22:12
J V - You have gotten a $1,000,000 worth of advice from the above, didn't realize Lelia was a metallurgist, Paul with experience and John [my chosen repair-person!!]. All I can add is, play the horn, if notes like C#/G# are "stuffy", consider a thinner pad [or cork adjustment] before any key-bending. Luck, Don
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