 The Clarinet BBoard
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Author: kehammel
Date: 2022-03-20 21:06
The base plate for this thumb rest has three screws, which tend to loosen after repeated use of the clarinet, which is a circa 1925 Penzel-Mueller. No matter how carefully I attempt to re-tighten them, the screw head slots gradually become worn, which makes later repetition of the procedure even harder.
The tech who installed the base plate was concerned about its design. Its curvature has a smaller radius than the outside body of the instrument, so it does not make uniform contact. Instead, contact occurs only at the edges of the plate (i.e., the contact consists of two parallel lines). Perhaps the contact would be more uniform on a modern Buffet clarinet? The screws that were supplied also seemed too small, so she went up a little in size. Nevertheless, the problem keeps recurring.
She wonders if the screws might be secured better using a relatively weak 5- or 10-minute epoxy resin. Is that maybe a good idea? And could the screws subsequently be removed if necessary?
Another possibility might be to sandwich a sheet of some flexible, compressible material between the base plate and the clarinet. But I don't know what this material would be.
Any suggestions would be most welcome!
Ken
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Author: m1964
Date: 2022-03-21 00:07
kehammel wrote:
> The base plate for this thumb rest has three screws, which tend
> to loosen after repeated use of the clarinet, which is a circa
> 1925 Penzel-Mueller. No matter how carefully I attempt to
> re-tighten them, the screw head slots gradually become worn,
> which makes later repetition of the procedure even harder.
>
> The tech who installed the base plate was concerned about its
> design. Its curvature has a smaller radius than the outside
> body of the instrument, so it does not make uniform contact.
> Instead, contact occurs only at the edges of the plate (i.e.,
> the contact consists of two parallel lines).
I would place a piece of sand paper over the body of the clarinet and shave the base plate to the shape of the clarinet. I do not think it was a good idea to attach the base plate if it was not flash to the body of the clarinet.
Regarding the screws- you can get oversized screws from one of the sites like Ferree's or JLSmith.
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Author: Steven Ocone
Date: 2022-03-21 02:33
Flexible, compressible material will make the situation worse. You need a firm stable contact. This seems to be your issue. I've dealt with many thumb rest issues but I can't offer a solution without it in front of me.
Some possible fixes. Longer, not just wider screws might help some. Modifying the thumb rest may be possible. I have sometimes installed bushings in the clarinet that have internal threads and used machine screws to install a thumb rest. Thumb rest repair is tricky.
Steve Ocone
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Author: kehammel
Date: 2022-03-21 03:33
Attachment: base_plate.jpg (239k)
Good point about the need for a firm base, Steven. What do you think of using somewhat longer screws and also affixing them with some kind of adhesive?
Here's a picture of the clarinet side of the base plate, m1964. The two parallel ridges at the edges are apparently where contact with the instrument occurs. I would imagine this design is intended to address the situation that not all clarinets have the same circumference. A more uniform contact as you suggested could be better, but I think it would be tricky to achieve. For example, I would not want to use sandpaper that was wrapped around the clarinet, because (A) the extra thickness of the sandpaper would lead to an incorrect curvature, and (B) the clarinet might be damaged. In principle, one could machine a cylindrical template of aluminum that would provide the correct curvature once the sandpaper was applied to it. I know a machinist who said he could try this for me, but I haven't decided yet whether it's a good way to go.
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Author: m1964
Date: 2022-03-21 06:31
Ah,
I thought the base plate was made of plastic...
In this case, I'd check the length of the original screws minus original thumb rest thickness, and try to match that length with new screws to achieve similar length inserted into the body.
Maybe get a 2nd opinion. If there is no another clarinet tech near you, you could search for a good oboe tech or send the clarinet out (insured!).
What instrument is that?
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Author: clarnibass
Date: 2022-03-21 09:18
It's a part that is meant to use on any random clarinet, and it's good that it's touching on the two sides and not the middle, so it's actually a good thing that it's high on the sides. A part that would look like it fits better will still not completely touch, it doesn't matter it it's 1mm off or 0.01mm off. Unless the part itself flexes enough to compensate...
A flexible material might be bad... or good. It might compress and be pretty stable, pretty much from the direction it is compressed to from playing. It really depends on what the material is exactly, how it behaves when it compresses, the thickness in comparison with how much it compresses on thta specific part, etc. From what is possible to tell from that photo, that gap isn't tiny...? What is it? Maybe consider something like rubber cork that is just a friction fit in the gap? This would essentially be three points of contact which would be good (but probably unnecessary), assuming the lines are touching for most of their length.
Having said all that, although it's possible, it's not very likely that any of this is the reason the screws keep opening. They are probably not held very securely. Maybe the threads are a little stripped. If it got to a point that the slots are damaged then something is wrong (maybe even using a bad screwdriver less than carefully). If the threads are more or less ok, there is a solid feel of the screws tightening completely, then consider weak thread locker (like Loctite 222). Unlike epoxy it's not great at filling wide gaps, but it's weak, pretty easy to open with mild more force or at worst a little bit of heat. If there is a larger gap (the screws feel a little loose in the threads) then epoxy might be better, it can also be removed with some heat, but in this case I'd much rather fit screws that wouldn't be loose in the actual material, then use weak Loctite if necessary.
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Author: Tony F
Date: 2022-03-21 13:17
I had this problem years ago when I bought a Kooiman thumb rest. I contacted Ton directly and he was good enough to send some slightly larger screws with a slightly different thread pattern. I've had no problems since I installed them. With regard to the matter of altering the profile of the base, measure the diameter of the clarinet body and buy a length of dowel of that diameter from your local hardware store. Use that with some sandpaper wrapped round it to reprofile the base and then install it on the instrument. Use a piece of thin double-sided tape between the base and the instrument.
Tony F.
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Author: kehammel
Date: 2022-03-21 18:08
Those are good suggestions, thanks. I will get slightly larger screws (after double-checking the thickness of the clarinet wall). And I'll consider some Loctite 222. Also, the gap under the base plate in the middle is less than 1 mm, so maybe a strip of rubber cork as well...
K
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Author: Steven Ocone
Date: 2022-03-22 02:15
After seeing it, I agree with the previous comments. It's not the shape of the plate, but a problem with the screws.
Steve Ocone
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Author: kehammel
Date: 2022-03-22 18:05
That turns out to be correct about the screws. I removed them and had a look at the screw holes. The wood had chipped out around one of them.
I had this problem with another thumb rest installed by a tech on a different clarinet a few years ago. I filled those holes with a mixture of thin (Hot Stuff) cyanoacrylate glue and grenadilla dust. I sanded that down and re-drilled the holes with a pin vise. I had to control the hole angle by hand, but that worked OK. I then installed new, somewhat larger screws. The problem did not recur.
I don't know if the grenadilla dust was really necessary, vs. merely filling the chipped out area with the glue. But it worked fine, so I'll try the same with this new thumb rest problem.
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Author: kehammel
Date: 2022-03-22 19:41
PS- The Kooiman thumb rest solved my thumb pain problem, but there's one issue with how it works: There's always some torque on the base plate because your crooked thumb makes contact in two places (thumb tip and middle of the proximal thumb joint). As I got used to it, I used less leverage, but there's always some. I suspect this torque contributed to the screw hole damage that occurred. Using bushings to receive the screws might be a better design, but that kind of repair is way outside my expertise.
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Author: Chris P
Date: 2022-03-22 20:22
I never use the screws supplied with Kooiman thumbrests as they're dreadful.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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