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 Crack repair
Author: Bill 
Date:   2019-09-03 22:55
Attachment:  20190903_144910.jpg (275k)
Attachment:  20190903_144839.jpg (437k)

Is there ever a situation in which repairs made with what looks like a black glue gun could be considered adequate? In the photo of the bell, the crack(s) go all the way through. The crack above the thumb rest in the other photo cannot be observed inside the tube.

I don't really care about the bell, but I'm concerned the repair to the bottom joint may not last. Thanks in advance.

Bill Fogle
Ellsworth, Maine
(formerly Washington, DC)

[subject title changed for clarity - GBK]

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 Re: Crack repair
Author: clarimad 
Date:   2019-09-03 23:16

Have the repairs been carried out by a professional technician? I sincerely doubt it as they are unacceptable and extremely poor.
Take the instrument back and demand a refund.

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 Re: Crack repair
Author: kdk 2017
Date:   2019-09-03 23:31

I don't know if the seal is technically sound, but it looks completely sloppy. I wouldn't find it acceptable.

Can the excess be trimmed with a sharp blade? If the repair still seals, the surface might at least be cleaned up. Is the stuff actually black, or is it clear (like epoxy) and you see the black wood through it? I can't tell from the pictures.


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 Re: Crack repair
Author: Mojo 
Date:   2019-09-04 18:13

It may be epoxy. I would bet it seals even though it does not look great.
Mojo Mouthpiece Work LLC

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 Re: Crack repair
Author: Chris P 
Date:   2019-09-04 23:50

That can all be cleaned off and the socket crack should be carbon fibre banded to add strength as socket cracks can spread down the joint if left unchecked.

The bell crack can be repaired by cleaning up and the socket ring and bell ring should keep it in check provided they're good and tight. If need be, it can also be banded.


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 Re: Crack repair
Author: rmk54 
Date:   2019-09-05 03:13

Have the repairs been carried out by a professional technician? I sincerely doubt it as they are unacceptable and extremely poor.
Take the instrument back and demand a refund.

I live in the same area as Bill and I can tell you that there is not a decent repair technician within 500 miles, so he may just have to live with the repair, or send the instruments to someone decent, as I do with mine.

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 Re: Crack repair
Author: Bob Bernardo 
Date:   2019-09-05 13:45

There are some really interesting videos on youtube. You may not want to fix the clarinet yourself after watching the youtube videos, but this will surely give you an idea of how repairs are done.

Here is one video -

Designer of - Vintage 1940 Cicero Mouthpieces and the La Vecchia mouthpieces

Yamaha Artist 2015

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 Re: Crack repair
Author: m1964 
Date:   2019-09-05 21:41

Chris P wrote:
"That can all be cleaned off and the socket crack should be carbon fibre banded to add strength as socket cracks can spread down the joint if left unchecked."

Hi Chris,
When you say "carbon fibre banded", do you mean pinned with carbon fibre rod or banded around the tenon with string or some other flexible material.


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 Re: Crack repair
Author: dorjepismo 2017
Date:   2019-09-05 23:12

After having a new instrument crack near the top of the upper joint, a couple respected folks here and a well-known player and vendor of accessories suggested that they've had good luck with glue-based solutions that one can do oneself, and that sometimes avoid problems one can run into with pinning or banding. In the end, it was repaired under warranty by carbon fiber banding, and that's been quite successful to the point where playing it has been completely unaffected by the repair (I don't know the exact process, but there are a couple bands around the joint made out of carbon fiber, so "carbon fibre banded" is an exact description). So, some serious professionals say that gluing cracks yourself can be successful if you're somewhat handy. A lot probably depends on one's tolerance for the cosmetics of a do-it-yourself job.

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 Re: Crack repair
Author: clarnibass 
Date:   2019-09-06 15:54

The thing about cracks is that nothing is 100% guaranteed...

Some cracks would be fine with no repairs, not growing or expanding. Some will "burst" any repair. Then there's anything in between.

I've seen a carbon fiber banded crack re-open. Not one I've done, but the repairer who had this happen had a 100% success rate for a long time until this happened.

Many now (including e.g. Yamaha) recommend just gluing cracks, without adding pins or bands. Over a long time I've found this is enough by far most of the time. I use other methods sometimes (pinning, carbon fiber banding). I'm sure some (if not most) repaired cracks would be ok with a less intrusive method... but you'd never know. The size of the crack is not necessarily a sign, since a large crack can just stop, while a tiny crack can gradually grow with extreme force.

There are several differences between threaded still pins and glued (non-threaded) carbon fiber pins (as shown in the video).
It's hard to have a direct comparison because it depends on the exact diameter of each... so this is a rough estimate.

Leaving material for now, the former relies on friction from the threads gripping the wood while the latter relies on the friction from the glue only. So it depends whether the glue can be as strong as the threading. I'd say it's not, even though most of the force is sheer which is good (the strongest for this type of glue).

Then there's the material. The weight difference is completely insignificant. You could use hardened tool steel which is stiffer than carbon fiber. Even regular mild steel is probably stiffer depending on the type of carbon fiber (e.g. how much resin is in it, etc.).

You could use smooth steel rod and then it could be a matter of how the glue is gluing to it (more friction).

When the wood is cracking, it is trying to stretch the pin, which is held by friction to both sides, resisting that force.
There's also the the tiniest amount of bending to the pin, but this is a minuscule amount that is almost nothing against the force of the crack. The video showed the person easily bending the pin by hand (not even on purpose) by more than that.
The pins put at an angle adds another direction to the bending, so a little more resisting by bending, but since the bending resistance is so little this makes next to no difference.
It is the "stretching" of the pins that is holding it.

In reality both methods are probably good enough for most cases. This is almost certainly why gluing carbon fiber pins is so successful. I guess a question is how many cracks are between them, so would re-open with glued pins but not with threaded pins. Who knows...

Post Edited (2019-09-11 08:45)

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 Re: Crack repair
Author: Tony F 
Date:   2019-09-06 19:26

I've repaired a few cracks with no failures so far. Mostly I use low-viscosity superglue (Hot Stuff or similar), or if the crack is larger I sometimes use epoxy. I generally use Araldite with a small amount of a colouring agent, wood dust or lamp black. I mix the epoxy in a plastic cup and then warm it by floating the cup in hot water. This reduces the viscosity so that it penetrates well into small cracks. I use the epoxy route where the crack is on or close to the tenon. Properly finished these repairs are pretty much invisible. I've carbon banded a couple, which worked very well. They were on my own instruments, as I didn't want to use a technique on someone else's instrument that I hadn't previously tested.

Tony F.

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 Re: Crack repair
Author: Bill 
Date:   2019-09-07 00:31

Thank you for the responses. Fascinating reading. I had always thought the gold standard was a threaded pin -- that anything else was unsuitable. Glad to see that's not true (or at least not true in the opinion of everyone).

Bill Fogle
Ellsworth, Maine
(formerly Washington, DC)

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 Re: Crack repair
Author: Chris P 
Date:   2019-09-07 14:01

Sockets are too thin to pin, so banding will be the best option and it will support the entire diameter of the socket as well.


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