 The Clarinet BBoard
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Author: stebinus
Date: 2008-11-28 07:27
I want to fit a thumbrest to a plastic horn but the holes in the clarinet are not the same distance apart as the holes in the thumbrest. Also the screws are too small for the holes in the clarinet. Is there some way I can fit this thing with just filling the holes in the clarinet with epoxy or something and drilling new holes for the screws? I'm trying to avoid taps and thread gauges.
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Author: tictactux ★2017
Date: 2008-11-28 08:33
Yes, fill the old holes with epoxy. Let thoroughly dry.
Might be an opportunity to check whether the new thumbrest really must be at the same position as the old one or if you want to move it up or down a bit.
--
Ben
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Author: huff n' puff
Date: 2008-11-28 11:45
Hi, stebinus......... agree with tictactux about maybe moving the rest....... if the new rest is a sort of curved plate that mimics the curve of the body, and you want to experiment, why not try attaching it temporarily with a piece of double sided tape....... some of these give a surprising grip, and if you handle it carefully you may get enough time to make a decision......... H&P.
PS clean both parts to get the best adhesion! also, there are spongy double side tapes that might help. good luck.
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Author: stebinus
Date: 2008-11-28 11:53
Thanks for the suggestions. When drilling new screw holes how do I judge what size bit to use?
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Author: tictactux ★2017
Date: 2008-11-28 12:07
> When drilling new screw holes how do I judge what size bit to use?
The drill should obviously be smaller than the outside diameter of the screw; a rule of thumb says by half the thread depth. Say if your screw is 3mm with threads and 2mm without (as if the threads had been stripped), then use a 2.5mm drill; the exact dimensions vary with material and type of screw. Elastic materials tend to be squeezed out between threads while wood won't. Better start on the small side and take a bigger one when it's too tight.
--
Ben
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Author: stebinus
Date: 2008-11-28 12:44
Thanks again. So considering epoxy (which I'm not sure you would call elastic or not; some epoxies dry quite hard) and hard plastic, or when you say material would be squeezed out would that mean using a smaller or larger bit in general than in wood?
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Author: Gordon (NZ)
Date: 2008-11-29 07:11
IMO:
1. I would regard epoxy filler as a cosmetic process only. This is because if you try to drill new holes in almost the same place, then if there is slight difference in the hardness of the plastic and the set epoxy, then the drill will wander towards the softer material. I think new holes should be drilled in new locations, even if these locations are only a couple of mm above where the old ones were.
2. I always drill then tap the correct thread for these screws. Talking about a plastic clarinet body only... If you just force a screw into a hole, and the hole is slightly too small in diameter, then it will not grip well enough. If the hole is slightly too small in diameter, then the head of the screw is likely to break off - they're mostly made form a soft, copper-based alloy - and the remains will be very difficult to remove.
3. If screws are forced in tightly into an unthreaded hole, then it is entirely possibly that a chunk of plastic involving the screw holes Can be forced to break out of the clarinet body, depending on the characteristics of the particular plastic. I have seen cases where this has happened, and I don't consider it worth the risk. If I were taking this risk, then I would cut the end of the screw with small flutes in such a manner that it behaved somewhat like a tap, and cut its own thread. In this case as for a tap, for the drill size for a metric thread, you subtract the pitch of the screw's thread from the thread's 'nominal' major diameter.
4. I disagree about using double-sided tape. This is not as strong as well-installed screws, especially for the 'peeling' forces that re involved, and with such a small surface area that likely does not perfectly match in curvature. If the thumb rest suddenly fails, then the clarinet is likely to drop to the floor. The result could be as bad as a clarinet broken in half at the centre tenon.
Of course, different technicians may well have different views on this, as with most other things. :-)
Post Edited (2008-11-29 07:16)
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Author: huff n' puff
Date: 2008-11-29 11:02
Hi.............. my suggestion about the double sided tape was solely to give stebinus a bit of time to choose a position for the new thumbrest........ I meant, but forgot, to say- hold the clarinet over a bed while doing this!
Gordon......... you are quite right to urge caution when attempting to screw into plastic......... if stebinus is unfamiliar with drills and taps what is actually quite a simple job could turn nasty. There are so many types of screws on the market to deal with plastic.......... everything seems to be made of the stuff........ that I feel there must be a small good quality self tapping screw that could be used......... but don't ask me where to look for it........... does stebinus live in a city? What about the local TV repairman? A suitable sized self tapper could be used to prime the hole with a thread and a "proper" screw then put in it's place. Whatever you do- don't drill through into the bore!........ unless you want to play the clarinet with your left hand only.
This is not a difficult task, - why not find a piece of similar plastic........ what about a plastic knife handle or an old TV set or even the steering wheel of your car ( make sure you get your MOT first) and do a bit of practicing.
Bash on, but slowly............. H&P.
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Author: Gordon (NZ)
Date: 2008-11-29 11:37
<<Hi.............. my suggestion about the double sided tape was solely to give stebinus a bit of time to choose a position for the new thumbrest........ I meant, but forgot, to say- hold the clarinet over a bed while doing this!>>
Ah! Now I am happy.
<<Gordon......... you are quite right to urge caution when attempting to screw into plastic......... if stebinus is unfamiliar with drills and taps what is actually quite a simple job could turn nasty. >>
I agree. And that is why I think this apparently simple job is really one for a technician.
<<There are so many types of screws on the market to deal with plastic.......... everything seems to be made of the stuff........ that I feel there must be a small good quality self tapping screw that could be used>>
I have yet to find or see one suitable, even though I take a lot of gear apart to save the screws(mainly for non-instrument-repair stuff I do.
<< A suitable sized self tapper could be used to prime the hole with a thread and a "proper" screw then put in it's place.>>
The problem with a self-tapper versus a real tap, is that we are working in a blind hole, and there is nowhere for the swarf to go. So it collects under the screw at the bottom of the hole. In this situation there is precious little spare space at the bottom of the hole, so when you keep turning, trying to get the thread deep enough, with all that swarf down the hole, you either strip the thread in the soft plastic, or are in danger of pushing it through, the bottom of the hole, breaking through to the bore. A bottoming tap really is the only way to go.
One problem is that that although the threads used in these screws is reasonably standard across clarinets, it has quite a large pitch, and a suitable tap is not so easy to come by. It is specialist gear (and should be more readily available from repair technician supplies than it is. For one thread I finished up making my own tap from a steel screw.
<< Whatever you do- don't drill through into the bore!>>
It's actually very easy to do, unless one has means of restricting how far the drill goes down to a pre-determined distance.
For many repair operations, there is a can of worms awaiting around the corner, and it is especially true for installing thumb rests, even more so in a timber body.
The worst DIY jobs I have seen have used large headed, large diameter, tapered, now-rusty, steel wood screws that have split the body when that taper was forced into a this very unyielding material. You must treat the timber as if it were metal, rather than as the much softer wood that we know well.
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Author: stebinus
Date: 2008-12-01 08:00
Thanks for the advice everyone especially Gordon who kept me on my toes with this seemingly simple job. What I did was fill the old holes with epoxy, trimmed, sanded, colored with a Sharpie and polished, and then drilled new holes about 2 or 3 mm above. Started out with a drill a little bit small and then gradually needle filed the holes big enough, testing over and over to make sure I got the screws in just right. A very tricky operation without a tap I assure you and one I will not take lightly in the future. Everything seems to be holding well and I am keeping my fingers crossed or should I say thumbs. Much obliged.
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Author: huff n' puff
Date: 2008-12-01 09:59
Stebinus........Wow, that was a minor epic.
Glad that you seem to have reached a satisfactory conclusion, and I hope you didn't wreck your car in the process.
Gordon....... I have done similar jobs in the past- not on clarinets, and found that a self-tapping machine screw can be inserted and withdrawn repeatedly to allow the swarf to be blown out. But it is best just to use the self tapper as a tap, and finish the job with a proper machine screw and maybe even a drop of adhesive.
Yes, the availability of taps can be a problem- even in a city. I cleared out a damaged pillar on my old Beuscher alto a long time back and almost gave up- then I discovered that it was an american thread...... was it UNC or UNF?
Miraculously a local engineer just happened to have one.
By the way, I have always referred to "plug taps", but I am sure that we are talking about the same thing as "bottoming " taps.
Time to take a sedative........ cheers to all.... H&P
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Author: Gordon (NZ)
Date: 2008-12-01 10:33
Pillar threads are quite coarse... So it would have been UNC or UN Special(ly large pitch)
Well done, Strebinus.
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Author: Gordon (NZ)
Date: 2008-12-02 10:29
"... I cleared out a damaged pillar on my old Beuscher alto a long time back and almost gave up- then I discovered that it was an american thread...... 3 NC"
That is 3-48.
48 threads per inch That's extremely fine for a pillar presumably screwing into timber.
And 3-48 is only 2.5 mm diameter, which is extremely small for a pillar thread.
Something wacky here.
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Author: Gordon (NZ)
Date: 2008-12-02 14:57
huff n' puff wrote
<<By the way, I have always referred to "plug taps", but I am sure that we are talking about the same thing as "bottoming " taps.>>
Actually no. A bottoming tap taps right to the bottom of a hole. A plug tap is an intermediate one, between taper and bottoming.
See http://en.wikipedia.org/wiki/Tap_and_die#Tap
So for these short holes, no deeper than necessary, a taper tap is useless. Ideally start with a plug tap and finish with a bottoming tap. Because it is only timber, a bottoming tap used with care can probably do the whole job.
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Author: huff n' puff
Date: 2008-12-04 10:42
Hi, Gordon........ Looked up the website of a tap supplier, and they refer to taper, second and bottom. The tap that I have been using is clearly a "Bottom", and I have been incorrectly referring to it as a plug. When I built my collection of taps and dies, you could pick them up by the handful at car boot sales etc, and apart from that one NC tap, I have never actually bought a tap! I have probably picked up the incorrect terminology in conversation, and never had any reason to check.
Thanks for putting me right on this.
The NC tap is quite fine.......... I used it to clear out the slightly damaged thread in the pillar that took a pivot rod- so it is in no way associated with woodwork. A bit of confusion here? I was working on a silver plate Beuscher alto sax.
Thanks again........... H&P
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Author: Gordon (NZ)
Date: 2008-12-04 11:08
Yes, a bit of confusion.
My fault. I was thinking of clarinet posts screwed into timber. (But you wrote "...not clarinet.." I skimmed past the "not".) Sorry.
:-)
3-48 (NC) is a common pivot screw thread.
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Author: stebinus
Date: 2008-12-04 14:14
Well the screws didn't hold quite tight. The holes are too wide at the top and aren't forming a thread there. All this arcane talk of taps is making me seriously think of just putting a wee drop of superglue in each hole and screwing it all back down again. Would it be so wrong? It's only an older Bundy. Alternatively I've been scouring the internet and found a way of molding new threads with epoxy and the screws themselves, putting carnauba wax on them as a release agent. What say you all?
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Author: chris moffatt
Date: 2008-12-05 00:52
well as long as you still have that epoxy why not epoxy the thumbrest direct to the bottom joint. If it holds aircraft wings to fuselages it should be strong enough for a thumb rest. Alternatively you could do as you suggest, remove screws, inject super glue, replace screws, cleanup mess and be unable to remove the rest again ever - but what the hey it's just an old Bundy...the wax thing sounds like a little overkill to me
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Author: stebinus
Date: 2008-12-05 02:34
OK but if you epoxy the thumbrest on direct isn't that going to be pretty impossible to get off also? And I don't think one little drop of superglue into the hole is going to cause that much mess, is it?
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Author: huff n' puff
Date: 2008-12-05 14:23
Strewth...... I thought that this one had nosedived into oblivion!
If I have any bright ideas, I will make contact.
Meanwhile, why not drill a 1/2" hole right through to the bore and fit a couple of nuts and bolts or Giant pop-rivets. At least this would be reversible........ Best wishes, H&P
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Author: huff n' puff
Date: 2008-12-06 11:43
Hi, stebinus,
Sorry, I was being silly......... Glueing the screws in might be as good a solution as any............. how often do you intend to remove the thumbrest in future?
A long time back, I repaired the handle on a radio with superglue, and I was amazed to find that the superglue actually dissolved the plastic and "welded" the handle to itself and the metal core in the handle. An absolutely perfect repair.
That was one particular superglue on one particular plastic, but you will only find out by experiment........... why not put a minute drop of glue on a bit of the clari that doesn't matter and see the plastic becomes tacky?
Bash on regardless......... as chris says, it's only a bit old plastic instrument.
All the best......... H&P.
PS.............. I would not expect epoxy to have any effect on plastic, which makes me a bit dubious about it's gripping power on the clari, but I haven't done it
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Author: Gordon (NZ)
Date: 2008-12-06 12:38
Re stebinus's release agent concept:
Good in theory, but a lot is demanded of those few turns of thread on a thumb rest screw. In my experience it is best if they are quite a firm fit, otherwise they quite easily strip out the timber (or whatever you have replaced it with.) The release agent stops glue being an adhesive, and makes it just a filler, with a reasonably loose fit between the metal screw and what it is screwed into. On the plus side, carnauba would made a rather rigid filler, and slightly adhesive.
Re using superglue (or epoxy) on the screws:
If this is successful, there is a reasonable chance that if anybody tries to remove the screws in future, the heads will break off. (Most of these screws are a relatively weak copper alloy.) But no worries... If that happens, just grind them off flush, and drill and tap near holes nearby. It's 'only an old Bundy'! :-)
Isn't it amazing how much discussion we can generate over every tiny aspect of an instrument. :-)
Post Edited (2008-12-11 21:24)
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Author: huff n' puff
Date: 2008-12-06 15:11
Hi,
meant to say to stebinus not to be too hard on himself about failure with tapping........ keeping the tap (or whatever) absolutely parallel to the axis of the drilled hole is very very difficult when done by hand and eye........ some might say near impossible........... H&P.
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Author: Gordon (NZ)
Date: 2008-12-07 11:20
With these small taps, into timber, I find it a lot easier to get the alignment right, and the thread started right when I hold the clarinet in one hand, and hold the tap in a PIN VISE - http://www.rnhorological.co.uk/images/Pin%20Vices/IMGA0700T-S107-4%20RN.jpg - rather than a tap holder, in the other hand.
Then the hands quickly sense any misalignment, and also a couple of the initial turns can be made without altering one's alignment and grip on the pin vice, turned between finger and thumb.
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Author: stebinus
Date: 2008-12-08 12:43
Thanks guys. Now I've got a clarinet (plastic Bundy wouldn'tcha know)with a stripped out post. More fun!!! Break out the superglue?
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Author: Gordon (NZ)
Date: 2008-12-09 10:41
Superglue is not a very good filler.
And where you ooze surplus over a plastic body (which it readily dissolves) you get one heck of a mess.
Slow setting (hence strong), reputable epoxy is possibly better.
A tip is to get a strip of self-adhesive tape - I use Sellotape. Punch a hole in it that matches the diameter of the base of the post, stick it on the body around the post hole, carry out the gluing. This reduces the clean-up needed.
(But superglue will more than likely wick under the tape!)
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Author: huff n' puff
Date: 2008-12-11 18:42
Hi, stebinus and Gordon... I know that everyone has different shaped thumbs, but I note that when I am playing or just holding the instrument, my thumb is only contacting the upper half of the thumbrest- which leads me to wonder if the metal rest could be thrown out, and a new shallower but much longer one moulded out of something along the lines of Cataloy- except that this might not grip the plastic body. It could be a couple of inches long, and as wide as reasonable. So if it fell off (or was removed- maybe build it up using some release agent) it could be restuck using a variety of substances.
Just a thought............ H&P
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