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Double Bass Pegbox cracked - how to repair

#21
Non-luthier here, just a guy who's been around basses and repairs for a long time and learned a few things by watching and asking questions. Now that that's out of the way, whether you like it or not, pegbox broken off combined with cracks in the cheeks is major damage. Therefore, it's in your best interest to use the best possible, most widely recommended, industry standard adhesive, hot hide glue made fresh from granules. Also, sorry to say, I'd be planning what to do when the DIY repair fails.
 
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#25
I used epoxy on a much more complicated scroll break. It has been previously "repaired" with gorilla glue. This made me concerned about the ability of hide glue to bond well. The epoxy worked but it would not be my first choice when the parts fit together well and it was a fresh break.
 
#26
Would not the nature of the damage to be repaired influence the choice of the glue? Things that would need to be separated on occasion, like a fingerboard or neck heel mortise/tenon, clearly should get hide glue. But if it is something that is not supposed to come apart, like the repair under discussion here or the signature Kay broken neck heel, would not epoxy perhaps be the better adhesive?

I had to repair a broken neck heel on an Engle EM-3. It was a clean break -- perhaps the cleanest I have ever seen -- and, not being on TB at the time and not knowing about hide glue, I used epoxy.

The repair has held up for twenty years.
 
#27
Hello all,
thanks for your responses.
From your posts it seems it is about 1:1 hide glue:epoxy.
I tend to using epoxy for... reasons. My gut feeling.

Another question is:
I disassembeld the pegbox. By softly twisting by hand I can see that the cracks goe throuth the side walls. Concerning wetting the cracks I would now glue these with Titebond Hide glue.
Or should I use Superglue Cyanoacrylate insted?


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#28
Bassix76 said:
Hello all,
thanks for your responses.
From your posts it seems it is about 1:1 hide glue:epoxy.
I tend to using epoxy for... reasons. My gut feeling.

Another question is:
I disassembeld the pegbox. By softly twisting by hand I can see that the cracks goe throuth the side walls. Concerning wetting the cracks I would now glue these with Titebond Hide glue.
Or should I use Superglue Cyanoacrylate insted?


View attachment 5158639
Click to expand...

Get hide glue granules. Make it your self. Check woodworking suppliers. I think Kremmer Pigmente is a German company. Make hot hide glue. Rub it into the crack, wipe off the excess and clamp it. Don't use super glue. Then toss out the tight bond hide glue. That stuff isn't any good. Yes its stuff you have to buy and learn but do it right or don't do it. Its epoxy for scroll breaks, hide glue for every thing else. Only thing you use superglue on is ebony.
 
#31
The hasenleim link you posted is perfect. Hide glue comes in different grades. In Germany and the Netherlands it is the traditional name for the highest grade. Fish glue might also be an option. I know of a luthier who uses it for a lot of repairs on DB, but I’m not sure if he uses it for high strength connections.

If you are more confident in working with epoxy that might be a valid reason to go that way. But hide glue isn’t that hard to use, maybe you can do a practice piece?
 
#32
SAlcott said:
Getting it back on will be easy; getting it to stay on is another matter.
Click to expand...
If you are committed to doing this yourself I recommend you dry clamp it. I have a caul that fits the scroll button and provides a decent angle for clamping so the clamp doesn’t slide much on the fingerboard at the nut. It also must be clamped laterally. It might fit and fool you that it won’t move but once the glue is on all bets are off. Glue tends to lubricate joints in weird ways. After doing several dozen repairs like this I’m beginning to do a good job.
 
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#34
Hello folks,

thank you for your help so far!
I started glueing the scrollbox with hide glue - looks good.

One question: I would like to remove the nut from the neck.
What would be the best method: wetten with water, heating with a hairdryer and lift off with a hot knife?

Any recommendations are welcome!

Regards, Alex
 
#36
Not sure if anyone mentioned, but there are different granule strengths of hide glue. The higher numbers dry harder. For this I'd go with 380 gram.

I think either hide glue or epoxy could be used when you definitely don't want it coming apart. The big difference is if you don't get it right at first you have a second, or third, chance with hide glue.

Re the reinforcement of the repair, carbon fibre rods work really well. I would glue that in with epoxy. After the peg box is glued back on, you want to pop off the nut. Then, into the surface that the nut was glued to, drill a hole for the rod from the front to the back of the neck. Measure the hole length carefully so that you go far enough to be joining the front and back, but stop before you come out of the back of the neck. If you stop in time, the the carbon fibre rod is only visible when the nut is off of the bass.

Let us know how it goes!
 
#38
eh_train said:
Not sure if anyone mentioned, but there are different granule strengths of hide glue. The higher numbers dry harder. For this I'd go with 380 gram.

I think either hide glue or epoxy could be used when you definitely don't want it coming apart. The big difference is if you don't get it right at first you have a second, or third, chance with hide glue.

Re the reinforcement of the repair, carbon fibre rods work really well. I would glue that in with epoxy. After the peg box is glued back on, you want to pop off the nut. Then, into the surface that the nut was glued to, drill a hole for the rod from the front to the back of the neck. Measure the hole length carefully so that you go far enough to be joining the front and back, but stop before you come out of the back of the neck. If you stop in time, the the carbon fibre rod is only visible when the nut is off of the bass.

Let us know how it goes!
Click to expand...

Dear Paul,

thanks for the information on how to reinforce with a carbon fibre rod.
Interestingly, this post here
Wirbelkastenbruch | Kontrabass-Blog
inserts two rods both on every side, laterally and not from front to back.
Can you explain why you would prefer the rod from front to back?
How thick would you choose the rod?
I could imagine that a thicker rod gives a better stabilization due to its lower curvature?

Thanks,

Alex
 
#39
Bassix76 said:
Dear Paul,

thanks for the information on how to reinforce with a carbon fibre rod.
Interestingly, this post here
Wirbelkastenbruch | Kontrabass-Blog
inserts two rods both on every side, laterally and not from front to back.
Can you explain why you would prefer the rod from front to back?
How thick would you choose the rod?
I could imagine that a thicker rod gives a better stabilization due to its lower curvature?

Thanks,

Alex
Click to expand...
Once again, every repair is different. I work with Bill and it's always case by case. Techniques changed over time. Last time I had a bass with a crack, not a broken scroll at the nut area, I put in a 1/4" metal rod. Counter sunk it and put a plug in it so you wont see it. You have to look at where the break is. Where does it line up. What direction would a straight line intersect. A metal or carbon fiber rod would be better than a wooden dowel
 
#40
I would have used epoxy but have successfully used hide glue on many repairs like this. Give it 24 hrs for the glue to set and knock the nut loose. I’d drill deep into the scroll under the nut as far as you can go without penetrating the back. I suppose CF might be best, but a 1/2” or 5/8” maple or oak dowel with the grain running vertically would be sufficient. Then use a pin through the cheek on the side where you actually have a cheek.
 

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