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Discussion Starter · #1 ·
I am a beginning amateur repairman, and got an old wood clarinet to practice on. It has some chipping in the wood at the edge of a tenon. The joint rocks from side to side. Musical instrument Wind instrument Audio equipment Material property Automotive tire


What would be an appropriate material to use on this vulnerable spot to re-establish the full circumference of the tenon?

Thanks for any and all material science advice.
 

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If the joint rocks from side to side, then I would suspect both raised sections of the tenon need repairing not just the lower section
 

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If the joint rocks from side to side, then I would suspect both raised sections of the tenon need repairing not just the lower section
+1 on what Simso said.

Ideally you want to graft a new tenon on there - which requires, skill, patience, a good eye and a decent lathe and tools + the knowledge on how to use it.
 

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Option 1: A graft as mentioned above.
Option 2: Clean very thoroughly, then build it up with epoxy (tinted with black pigment powder), or granadilla dust and low viscosity superglue, then turn it to the correct diameter.
Option 3: As above for the end shoulder, then glue silver rings (of correct thickenss) on both shoulders for stability and strength. I often do this for wobbly tenons and I don't think one has ever failed. For the end one I form the ring over both edges of the shoulder, so glue is not really required. The devil, as for most repair work, is in the detail.
 

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Discussion Starter · #5 ·
Thanks for the suggestions, all.

First of all, I'm such a newb with clarinets that. I want to make sure I understand the terminology. When you refer the the "end shoulder" you're talking about the rim of wood most in the foreground in the photo?

Second, regarding the condition of the tenon overall, I see no other signs of damage on the other shoulder, or in the socket. That's not to say there isn't wear. A check with a vernier caliper suggests that the other shoulder is round (more round that the other tenon on that joint, for example), but it could certainly be worn evenly around. There may be wear, perhaps uneven wear, in the socket, too, but I don't think I have a good way to check that.

so I have a few questions about the repair suggestions.

Re: a tenon graft, out of the question for me right now.

Re: Option 2 below, do I understand correctly that you can mix cyanoacrylate glue into epoxy?

Re: Option 3 below: If i understand this, you're suggesting building up the missing area until it's round, and then binding it (on both shoulders) with band of flat silver.

A: does that require sanding down the good portions of the shoulder to accommodate the thickness of the silver? Or are you assuming both shoulders are too narrow, and it's pivoting on the cork when I rock it (it kinda feels like that might be the case) and the "right thickness" of silver is a shim that makes up the difference? Measuring the end shoulder across an apparently undamaged diameter, it is about 0.6mm smaller than the upper shoulder of the tenon. This makes the end shoulder about 1.0 mm smaller than the mouth of the socket, and the upper shoulder about 0.4 mm smaller than the socket.

B: what metal thickness of silver are you thinking about as a minimum?

C: I have a few samples of carbon fiber cloth laying around. Assuming I were able to cut the stuff to size, what about a ring of carbon fiber composite saturated in your epoxy/superglue binder, instead of the silver?

Also, seems like I will need to re-cork after this is done. Would it be better to leave the existing cork in place until the rest is finished? Or should I remove it and temporarily wrap something thicker around to act as "formwork" for the build-up?

Thanks for the help.

Option 2: Clean very thoroughly, then build it up with epoxy (tinted with black pigment powder), or granadilla dust and low viscosity superglue, then turn it to the correct diameter.

Option 3: As above for the end shoulder, then glue silver rings (of correct thickenss) on both shoulders for stability and strength. I often do this for wobbly tenons and I don't think one has ever failed. For the end one I form the ring over both edges of the shoulder, so glue is not really required. The devil, as for most repair work, is in the detail.
 

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IMO, like materials should be used to do the repair. IF you have a lathe, a full tenon replacement is not needed. The repair can be done by reducing the diameter of the tenon and putting a sleeve made of wood over the existing tenon. This will allow you to fit the full length of the tenon to the socket so it does not wobble, and it will not affect the bore of the instrument.

I am a beginning amateur repairman, and got an old wood clarinet to practice on. It has some chipping in the wood at the edge of a tenon. The joint rocks from side to side. View attachment 55646

What would be an appropriate material to use on this vulnerable spot to re-establish the full circumference of the tenon?

Thanks for any and all material science advice.
 

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Discussion Starter · #7 ·
IMO, like materials should be used to do the repair. IF you have a lathe, a full tenon replacement is not needed. The repair can be done by reducing the diameter of the tenon and putting a sleeve made of wood over the existing tenon. This will allow you to fit the full length of the tenon to the socket so it does not wobble, and it will not affect the bore of the instrument.
again, thanks for the suggestion, but since I don't have a lathe, I'm afraid it's a moot point.
 

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again, thanks for the suggestion, but since I don't have a lathe, I'm afraid it's a moot point.
Then you have a problem, pretty much any repair will really require you to have a lathe, be it to fabricate the part, or to turn the part or the repaired area you have made up circular to fit correctly

Filing a surface flat is very easy, you can use a T square as an aid, but filing a perfecly round circle is very hard to do.
 

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Then you have a problem, pretty much any repair will really require you to have a lathe, be it to fabricate the part, or to turn the part or the repaired area you have made up circular to fit correctly
I use my lathe every single day in the shop. It makes certain procedures possible and simplifies others.

I don't know how far you (the OP, not simso) is going to take your foray into instrument repair, but acquiring a lathe might be a good idea.

If you're not ready to buy a lathe yet, you could always outsource that part of the project and do the rest yourself...

BTW, I agree with simso's suggestion to turn down and sleeve the existing wood. If there's no crack, no need to replace the entire tenon...
 

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... When you refer the the "end shoulder" you're talking about the rim of wood most in the foreground in the photo?
Yes.

... Re: Option 2 below, do I understand correctly that you can mix cyanoacrylate glue into epoxy?
Definitely not! I used commas for a purpose - to separate tow quite different ideas.

... Re: Option 3 below: If i understand this, you're suggesting building up the missing area until it's round, and then binding it (on both shoulders) with band of flat silver.
Building it up exactly until it is round is pretty much impossible. You have to build it up too far , then turn it down to the correct diameter. Yes to the band of silver, but for the open-end band, I burnish it over the edgesw of the shoulder (to cover part of the end grain) for security if nothing else. That end gets quite a hiding if assembled slightly misaligned by the player.

A: does that require sanding down the good portions of the shoulder to accommodate the thickness of the silver?
In some cases yes; others no. There is often enough room for 0.12+ mm thickness of silver without removing material. But I certainly make it cylindrical - not oval as they often are. That really does need a needs a lathe, as has been said.

...Or are you assuming both shoulders are too narrow, and it's pivoting on the cork when I rock it (it kinda feels like that might be the case) and the "right thickness" of silver is a shim that makes up the difference? Measuring the end shoulder across an apparently undamaged diameter, it is about 0.6mm smaller than the upper shoulder of the tenon. This makes the end shoulder about 1.0 mm smaller than the mouth of the socket, and the upper shoulder about 0.4 mm smaller than the socket.
I treat the fit of a shoulder inside the tenon receiver as too sloppy if there is more than 0.2 mm difference in diameter. That results in a wobbly tenon, especially at the center of the clarinet. I use silver sheet rolling-milled to different thicknesses, with about 0.12 being the thinnest. (I file/buff down the resulting diameter of the band after installation if it is a tight fit in the socket, then buff it. BTW, I make the band from a narrow strip with chamferred ends, silver-soldered together. ( prefer to make it slightly on the small side, so that it it s a really tight fit on the timber. If it is too tight, I expand it using a flute tenon expander.

... C: I have a few samples of carbon fiber cloth laying around.
I don't know how well that would tidy up in a lathe.

Also, seems like I will need to re-cork after this is done. Would it be better to leave the existing cork in place until the rest is finished? Or should I remove it and temporarily wrap something thicker around to act as "formwork" for the build-up?
I remove the cork. Often the upper shoulder is slightly smaller diameter than the open end one, making it impossible to get the sized band on the upper shoulder without removing the cork. Besides, I need the cork off to burnish the band over the edge of the shoulder, against the wall at the end of the cork groove. For formwork, I use a short length of flexible plastic tube of suitable diameter, slit lengthwise. But it's not that important if one is going to build up too far, then turn it on a lathe to size.

BTW this band approach is not very orthodox. I don't know of any other technician doing it quite like this. You can buy end-caps to instal, but they are almost always of an unsuitable size for a precise result. But I know that what I do works very well, and for me is quite quick.
 

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IMO, like materials should be used to do the repair. IF you have a lathe, a full tenon replacement is not needed. The repair can be done by reducing the diameter of the tenon and putting a sleeve made of wood over the existing tenon. This will allow you to fit the full length of the tenon to the socket so it does not wobble, and it will not affect the bore of the instrument.
I agree that this is also a good approach. However to me, the down side is that the weakest part of the clarinet, where the tenon meets the rest of the body, is compromised somewhat further, unless you consider that an end-grain glue job (at the end of the glued-on sleeve) is as strong as the original timber, which I very much doubt.
 

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Then you have a problem, pretty much any repair will really require you to have a lathe, be it to fabricate the part, or to turn the part or the repaired area you have made up circular to fit correctly

Filing a surface flat is very easy, you can use a T square as an aid, but filing a perfecly round circle is very hard to do.
I agree. Technicians without lathes usually subcontract out this type of work.
There are even technicians who specialise in tenon (and tone hole) grafts.
 

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Discussion Starter · #13 ·
Thank you all for the ideas.

I agree that filing something to exact round could be a challenge (one which, as mentioned previously, the OEM of this instrument did not manage on the other tenon, the 'good' one). But since a lathe is not an option for me at the moment (and besides, it might compromise my amateur status), I was thinking about cutting a concave sanding block and trying to use that to approach rounditude. If I remove the cork, I might be able to lay something a little tougher in the groove temporarily to act as a sanding guide.

Gordon, thank you for pointing out the commas, as well as all the great detailed info.

I like the idea of the silver end ring, although I'm not sure my skills are up to it. Another learning curve I have to decide if I want to climb.

My notion with the carbon fiber was to select the polymer resin for the job, and use some of it to make a paste with grenadilla powder and fill the tenon until it is round at its current (too small) diameter. The good side of the tenon could even be used to make a mold for this purpose. Then, once more or less round, wrap it with a strip of carbon fiber, saturate with more resin, cure, and sand smooth (and hopefully round). The hope is to sand only resin, not the carbon.

The purists who advocate for like materials and wood sleeving are cringing, of course. Sorry, guys. The instrument does not merit outsourcing. It's only worth putting this much work into it for the education. Given that, I'd rather try an experimental method that I think I can perform successfully, than a traditional one that I am neither equipped nor skilled enough to pull off.

When I figure this out, I will post results. Thanks again.
 

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Metaforce, how about temporarily glue sand-paper inside the barrel's tenon socket, maybe several turns, until of similar diameter to what you desire for your centre tenon, and use that for sanding.
 

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I would either overbuild the worn area with grenadilla dust and a very thin super glue(hot stuff sold by ferrees works great), then machine it down after it sets up to the proper size, or replace the tenon. If you wish to pursue the trade, then a lathe and or bench motor are pretty much necessities.
 

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A cheap second hand lathe is a very good investment, if that's not possible then maybe consider a bench motor
My first lathe was a cheap wood lathe. The bed and swing were large enough to do all the clarinet and oboe work I needed to do. Eventually I grafted a compound onto it so I could use a tool holder and machine metal with it. Then I got a proper metal lathe.

I'd be concerned about using a bench motor for this project. With a lathe you can support both ends of the work piece.

I just checked Ferree's price list for their bench motors and a 7 x 12 mini-lathe (long enough and deep enough to work the bottom section of a clarinet) is not a whole lot more than what their bench motors cost.
 
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