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Discussion Starter · #1 ·
Any of you guys who have worked in a music store know it's always good for business when you get a band director out of hot water. Boy did I get a doosey last week.
One of his students got a swab caught in the upper joint of a Buffet E11 clarinet. To try and get it out he shoved a big drum stick into the middle tenon to try and push it out the top. CRACK!!!!! Three long cracks starting in the middle tenon and going almost 1/2 way up the joint. Miraculously the cracks did not go through any tone holes.
Normally I wouldn't do a job like this. I would strongly suggest replacing the joint. But when your biggest school account is asking for a really big favor, you do what ever you can.
The bottom 1/2 of the joint was very unstable. No way could I put it in a lathe for carbon fiber banding. I couln't find any place to do the carbon fiber banding with out a post or tone hole getting in the way. (I don't like that technique anyway). I had to figure out a way to stablize the tenon enough to machine it down to accept a sleeve.
I finally spread the cracks a little by pushing the joint up on a trumpet mandrel and forcing Elmers carpenters glue into the cracks. I put a band clamp on the tenon and let it set for 24 hours. When I removed the clamp I was surprised at how stable the tenon was.
So I put one pin in each crack as low on the joint as possible to further stabalize the joint. Then I very carefully machined the tenon down and installed a snug sleeve.
After the epoxy was set I sized the tenon, cut a cork track, put in 6 more pins, did all the fill and dress, and was done. I still can't believe how well it turned out. I've never put 9 pins in a joint before and never want to do it again.
Elmers carpenters glue is some really strong stuff. I'm surprised I never thought of using it before on woodwinds.
 

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Nice! You might want to check out some of the techniques that violinmakers use. I believe they use hyde glue which is reversible if you should ever want to remove the glue (I'm not sure if you would want to anyway). Elmer's is not reversible.
 

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AFAIK, hide glue can be freed on the likes of violin bodies, by the use of a hot knife. And that is a major reason it is used,.

But if it turns out unsuitable in a crack on a clarinet, you will never get it out with a hot knife!

AFAIK Elmers glue is not a good filler, because of shrinkage as it dries. And often filling qualities are appropriate or necessary for clarinet cracks. Epoxy is an excellent adhesive and filler.

For clarinet splits there is considerable merit in getting the adhesive right down to the bottom of the crack. One way to attempt this with higher viscosity glues such as epoxy, is to force the glue in using a thumb (perhaps covered by a surgical glove.)

However probably the ideal way is to use a very low viscosity glue that wicks to the bottom by capillary action. And that is the benefit in using a low-viscosity superglue, that is appropriately applied. This too, is a poor filler, so it needs to be repeatedly applied until the gap is filled. For wider splits, where more filling is required, IMO there are two appropriate solutions: Either use epoxy on its own (or with a black powder pigment mixed in for cosmetic reasons) , or superglue in conjunction with grenadilla dust used as a filler.

If using epoxy, the slower setting formulations tend to glue better than the fast setting, perhaps because they have time to seep better into the surface structure of the timber.
 

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Discussion Starter · #4 ·
Hi Gordon, The Elmers wasn't intended to "fix" the cracks. The Elmers was only to stablize the cracks enough to allow me to machine the tenon so I could fit a tenon sleeve. The "fix" was the sleeve and the pins. I do fill with superglue and grenadilla dust.
 

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Distinguished Technician & SOTW Columnist. RIP, Yo
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:) :)
 
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