 The Clarinet BBoard
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Author: fuzzystradjazz
Date: 2015-10-04 01:46
As many of you know, I've recently started restoring an old hard rubber Conn (early 1920s). I removed one of the key springs (flat spring) today, and when I went to put the spring back in, I felt the screw "fall" into the receiving hole...like there was no thread. I checked to see if there was a "bottom" to the threads, and there is, but the thickness of the new spring is just enough to keep the screw from reaching the one or one-and-a-half threads which exist in the bottom of the screw's receiving hole. It appears the threading was stripped years ago, and the screw was barely being held in. (Using the original screw in the original hole.)
So, I'm guessing the answer is to use a slightly larger screw (which I don't have, because the 1920s screws are already quite large), or to tap out the hole, or both.
I don't have the tools to do this. To get by (the instrument is for my sole use), could I use some thin material to "shim" the receiving hole? (If so, what material is recommended?).
If there isn't a good fix short of tap/die...how does one measure such small screws in order to figure out which tap/die to purchase? I'm not sure I have much confidence in calipers for such small measurements. (Actually, I trust the calipers - I don't necessarily trust me.)
If best taken to a larger shop; could anyone recommend a good shop in the Wyoming/Colorado/Nebraska area?
Thanks in advance,
Fuzzy
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Author: Chris P
Date: 2015-10-04 02:03
The best remedy is to enlarge the screw hole and soft solder a piece of appropriately sized brass or nickel silver rod in there, file the end of the rod (that's protruding from the hole) flush with the underside of the key, then drill a new hole into the rod and tap the hole to receive the flat screw spring or a new one (with the same thread as the tap you used).
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: fuzzystradjazz
Date: 2015-10-04 03:16
Chris,
Thanks for the quick response! Just to make sure I understand...
You're suggesting that I drill the hole out to a known diameter of which I have an equal diameter of brass or silver rod. Solder that rod into the (now) larger hole, so as to plug it entirely. Then, drill a new hole to the size of the screw that I'll use, and tap it accordingly?
This sounds like a great fix to me if I understand you correctly.
However, I'm not sure which equipment I'll need. I have a drill press for working with wood, etc., but I don't have a setup for doing this kind of work (specifically) on instruments. Are there any special supplies I could buy (besides the tap/die) which would help me become equipped for this type of repair?
Thanks,
Fuzzy
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Author: GLHopkins
Date: 2015-10-04 06:40
The keys on that clarinet probably aren't nickle silver, but rather pot metal. I'd find a slightly larger screw and screw it in. It will most likely re-thread the hole as you're putting it in. Some of the saxophone flat spring screws are larger than those for clarinet. If need be you could probably mail the key to a respected shop and have it done for you. I'd send the spring you want to use along with the key so that they can enlarge the hole to fit the screw if needed.
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Author: clarnibass
Date: 2015-10-04 11:19
Since you don't need to give a warranty and only plan to play it yourself, there are a few DIY options.
You can use thread locker. Strong is probably best but also hardest to remove and would require significant heat. Usually not a problem but if it's close to a pad you might melt the glue or even burn the pad if you ever want to remove it. If upi thread it on now and it doesn't pull out easily or at all then this could be a good and the simplest option (if it doesn't pull at all I would consider medium thread locker).
As already suggested, you can use a sligthly larger screw and sort of let it half self thread half jam in there. I woul also grind two or three very thin channels lengthwise to shape the screw more like a tap, this makes it cut much better.
Does the screw hold with the spring off i.e. on those bottom threads it can't reach with the spring on? If it does, you can grind/file a bit off the key right where the hole is, to allow the screw to reach lower with the spring on (if you don't mind doing that).
If the length of the spring isn't critical, you can make a new threaded hole next to the original to avoid the soldering and possibly other work you can't do. Make sure it's not too close so there's enough thickness to support the threads.
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Author: Chris P
Date: 2015-10-05 01:42
Filling/redrilling stripped threaded screw holes can be done by hand using a bench motor, a drill bit from 1.7mm-2mm drilled into the key by around 2.5mm-3mm. Nickel silver or brass rod can then be made to fit into the hole with some very slight wobble or filed down to fit but left a bit rough so the solder will flow through the entire depth. Then once soldered in, the end of the rod is cut and filed flush with the underside of the key, then the rod is centre punched and redrilled with the appropriate size drill bit for the screw thread size you're planning to use (eg. a 1.1mm drill for a 12BA tap to take a 12BA flat spring screw).
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: fuzzystradjazz
Date: 2015-10-05 04:56
Thanks to everyone who responded! As "quick fixes" I really liked the ideas of strong thread locker, and even soft-soldering the spring to the key, but for a longer fix, I like the idea of plugging and re-drilling the hole, tapping it, etc.
I'll look into obtaining the necessary tools that I'll need, and I'll practice on some old broken parts I have.
Chris - thanks for the detailed explanation! I greatly appreciate your expertise, and want to especially thank you for taking the time to answer these questions.
Silversorcerer - thanks for the name of repair tech, if things take me too long, or don't turn out satisfactory, I'll be contacting Mr. Naylor.
Thanks again to everyone who offered ideas,
Fuzzy
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Author: clarnibass
Date: 2015-10-05 09:20
>> and even soft-soldering the spring to the key <<
The problem with that is the spring is so thin, even the heat for soft soldering can easily anneal it and remove its springiness. Even if not from its entire length, at least near where it's soldered, which is exactly where most of the springy force is applied. You can try but consider that.
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Author: Steven Ocone
Date: 2015-10-06 02:47
I usually just drill and tap another hole nearby. But then I've got all the tools and extra screws. Also, tapping for such a small screw can be tricky, but any seasoned tech should be able to do it.
Steve Ocone
Post Edited (2015-10-06 17:01)
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Author: Chris P
Date: 2015-10-06 18:40
If the screw has broken off in the hole and can't be extracted easily, then I'd drill a new hole near to the original. But if it's an empty screw hole, then I'd fill and redrill it.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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