 The Clarinet BBoard
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Author: paker
Date: 2012-07-28 03:29
Clarinet: Common plastic
Broken part: Bottom tenon of the upper joint, 1-2 mm above the cork line. A very clean fracture.
1) Will epoxy be strong enough?
2) If not, what if I first glue the pieces together and then drill holes (parallel to the bore) and insert pins?
I thought I would look cool holding a red clarinet on Christmas card. But it was a dream.
Thanks.
Post Edited (2012-09-03 05:10)
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Author: clarnibass
Date: 2012-07-28 05:57
From what side of the cork is it broken? It's not clear if it's just a piece missing at the end, after the cork, or the entire tenon including the cork. Can you post a photo?
If it's the entire tenon, epoxy might be strong enough, but might not be. It's risky. The type of epoxy is also important, you need a stronger slow setting one and even that might not be strong enough for this purpose.
If it's just the end of the tenon then very strong slow setting epoxy will probably be ok even without reinforcement pins but it's still a small risk.
My preferred method for gluing broken tenons (prefer to grafting) is to glue with strong epoxy and reinforcement of stainless steel pins that are parallel to the bore like you described. However, the critical thing about doing this is that the pins need to have air vents from the blind end of the hole. The pins need to have complete support of glue inside the holes, with no air. Without air vents you will get air bubbles inside the holes (so bad support) or you won't be able to insert the pins (because of air pressure forcing them out). I use a 0.5mm drill for the air vents and they are almost invisible because they are so small. They are just small holes drill from the blind end of the pin holes from the side of the body (just to the hole, not deeper). I then force the epoxy into the pin holes from a syringe, slightly rough and smear glue on the pins and put them in the holes. For the tenon end of the holes, you might not need air vents since you will have "automatic" ones by the area of the tenon ring.
Another option is a solvent glue like this which was recommended by a couple of repairers http://www.oatey.com/Channel/Shared/ProductGroupDetail/1/All+Purpose+Cement.html
This type of glue sort of welds the two sides. This company has a lot of specific glues, but the all purpose one is used because you don't really know what type of plastic the clarinet is. It's often a combination of several plastics, I think. It's not a weld that would make it as strong as it originally was, but reports suggest it is very strong so there's no problem.
I prefer the epoxy with pins, eventhough it takes longer (but usually not as long as a graft), because it is most likely stronger than the original, which broke. As long as you treat the clarinet normally, almsot as strong as the original is probably stronger than it needs to be, but I rather not risk it and make it as strong as I can.
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Author: jmsa
Date: 2012-07-28 06:30
You can also put masking tape around the end of the tenon with the sticky side on the inside and pour finely ground grenadilla powder ( Ferrees sells this) and then apply very thin and runny Cyanoacrylate. Then after it dries simply remove the tape and sand to proper length. Works great on chips and missing pieces at the end of tenons.
jmsa
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Author: Ralph Katz
Date: 2012-07-28 11:14
Have you tried contacting the manufacturer? They might sell you a new, unfractured upper joint.
jmsa: this is not a wood clarinet.
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Author: Tony F
Date: 2012-07-28 16:21
When drilling the holes for the pins on a broken tenon, I've found that if you use a syringe with a wide-bore needle, still small enough to go into the hole, you can inject the epoxy right to the base of the hole. When the roughened pins are pushed into the hole the surplus will be expelled. The hole is then completely filled, with no air gaps. This eliminates the need for air bleed holes and makes a slightly stronger repair. I usually insert 6 pins. Never had one break yet. I use Monel metal nails cut slightly shorter than the depth of the hole with the heads clipped off.
Tony F.
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Author: paker
Date: 2012-07-28 16:52
This is what it looks like. Thanks for the advice.
Post Edited (2012-09-03 05:11)
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Author: BartHx
Date: 2012-07-28 18:56
I have successfully repaired the center tenon on a resin clarinet using your option 2. However, it is critical that the wire you use and the holes you drill be carefully matched. Resin is brittle and drilled holes do not leave you very thick walls on your holes. I used wires mainly to resist twisting forces at the fracture line. If you were to use a standard replacement tenon, it would also work fine since it would be completely hidden when the instrument is assembled.
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Author: clarnibass
Date: 2012-07-29 05:41
For pinning, I have tried the method described above, no vent holes and using a smalerl neelde to start filling the glue from the end of the hole. There are two reasons I prefer not to do this.
First, my friend who taught me this method saw a failed repair when no vent holes were drilled.
Second, when I've tried this, I decided it is not good enough to guarantee that the hole is completely filled. It might have air bubbles and there is no real way to know if there are any. I've checked this by using a very small transparent tube, same diameter as the pin holes. Sometimes there were air bubbles, sometimes there weren't.
I disagree that this is slighty stronger, or rather, that this is significant. The air vent holes are filled with the epoxy and IMO are insignificant to the strength of the repair. However the guarantee that the entire hole is filled with glue with no bubbles is very important to me.
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Author: Tony F
Date: 2012-07-29 16:38
Hi. I quite appreciate your reasons for using your method. Something I didn't mention was that when I pin a tenon, I first warm the tenon gently with a hair drier and also warm the epoxy by floating it in a plastic cup in hot water. This considerably reduces the viscosity of the epoxy and also speeds the setting. By half-filling the warmed hole with warmed epoxy and then slowly inserting an epoxy-wiped pin I can be pretty sure there are no voids. I generally us Araldite full-strength for this. I stress that this is my method and seems to work for me. Your mileage may vary.☺
Tony F.
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Author: clarnibass
Date: 2012-07-29 17:01
Yes, I agree that most likely there wouldn't be air gaps... but I just prefer the other method to be sure. I also warm the epoxy to make it thinner viscosity and I've used a few types, the strongest Araldite being one of my favorites.
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