Fixing a Partially Cracked Headstock

[davegardner0]

A friend dropped off an Ibanez RGA121 for a refret, and during my initial inspection of the instrument I noticed a pretty nasty headstock crack. My friend has no idea how long it's been there, or how it happened:






(In the last photo I'm pulling the crack apart a little.) The crack is definitely longer and has a wider gap on the treble side, and it's much smaller/tighter on the bass side.

Even though the string tension isn't pulling the crack apart further I'd definitely like to try to fix this. I'm thinking the clamping won't be too hard as the headstock has a flat spot on its back. However what I'm not sure about is how to get the glue inside the crack. I was hoping I could get some opinions/thoughts.

On one hand, I'd like to use fish glue as it's my favorite for instruments and seems to stick to everything (in case there is a little dirt inside the crack). I was thinking of maybe thinning it with water a bit, and then using a syringe to get it inside the crack. The treble side seems doable, but I'm afraid I won't be able to get glue very deeply into the bass side.

The other option I thought of is to use super thin super glue, like you'd use to glue frets that are already installed. I was thinking this would wick into the crack. But, is CA glue really good for structural wood gluing?

And last thought, since the crack seems to be all the way through, do I need to worry about gluing the truss rod?

 

[AirCap]

Don't use superglue, I beg you. Yes - a little thinned down (not very thin) Titebond and a clamp or two will make it all better. Might not even need to be sanded or touched up if it behaves.

 

[Cagey]

I agree - Titebond works great. Joint will be stronger than the original wood.

Not so sure about the syringe trick. In order to get a small enough gauge needle to reach deep into the crack, you may have trouble getting glue through the needle. I bought a box of 25ga. needles and syringes to do fret gluing with and couldn't get CA 10 to flow through them, and that stuff is super-thin.

 

[davegardner0]

Hah! Ok no superglue then.

Any other ideas for getting the glue into the crack?

 

[Cagey]

It depends on the crack, but you might be able to smear glue around a both sides of a sheet of paper, spread the crack a bit, and slip the paper in. Release the tension on the crack so it closes, then pull the paper out. Haven't tried it, but it works in my head  :laughing7:

 

[aarontunes]

Possibly ignorant suggestion:

It's broke, bad. Is it better to preserve what little is still connected, and attempt to fix it with glue on only half the break, or might one be better off just finishing what's already nearly done, thereby allowing one's self to get glue on every part of the new connection?


Obviously, the ideal solution is to come up with a way to deliver glue throughout the break without breaking it any further, but if that's not possible...could much more harm be done by breaking it off?


Would the ends justify the means? I mean, the new bond will be stronger than the wood was anyway, right?

 

[davegardner0]

It depends on the crack, but you might be able to smear glue around a both sides of a sheet of paper, spread the crack a bit, and slip the paper in. Release the tension on the crack so it closes, then pull the paper out. Haven't tried it, but it works in my head  :laughing7:

This totally works in my head, too! Excellent idea, it might be worth a try...

 

[bagman67]

I'm leaning toward Aaron's idea on this one - if you can cleanly break it the rest of the way, you'll be assured of access to the entire surface that needs gluing.

 

[aarontunes]

It depends on the crack, but you might be able to smear glue around a both sides of a sheet of paper, spread the crack a bit, and slip the paper in. Release the tension on the crack so it closes, then pull the paper out. Haven't tried it, but it works in my head  :laughing7:

This totally works in my head, too! Excellent idea, it might be worth a try...

I foresee wet paper tearing off in the crack.


Umm...


Ugh... 

 

[davegardner0]

Possibly ignorant question:

It's broke, bad. Is it better to preserve what little is still connected, and attempt to fix it with glue on only half the break, or might one be better off just finishing what's already nearly done, thereby allowing one's self to get glue on ever part of the new connection?


Obviously, the ideal solution is to come up with a way to deliver glue throughout the break without breaking it any further, but if that's not possible...could much more harm be done by breaking it off?


Would the ends justify the means? I mean, the new bond will be stronger than the wood was anyway, right?

I hadn't considered this but I definitely see where you're going with it, it's not a bad idea. I certainly could get the right amount of glue in there! And it would be functionally just like a scarf joint in a headstock so I wouldn't be too worried about it strength-wise. Plus jagged but interlocking wood pieces are absolutely the best to glue together from a strength point.

Also the requirement isn't "break the headstock completely off", it's just "open up the break more so I can get glue inside", right? So that makes me feel better about it.

Then again...not sure if I'm missing something obvious here? It does seem drastic. Maybe someone else will chime in with a yay or nay and some reasons...

 

[aarontunes]

It's not so much "drastic" as it is "counter intuitive", which makes it tough to wrap your heart/brain around it.  :icon_biggrin:

 

[Cagey]

I foresee wet paper tearing off in the crack.


Umm...


Ugh... 

Good point. And you'd never get the trapped bits out again. Back to the drawing board!

 

[bagman67]

Rather than use a piece of paper that may tear and leave fragments in the crack, you could use a .001 - .005 feeler gauge to wipe the glue in the crack.

 

[Cagey]

That might actually work better, as the crack is unlikely to be straight across, so a sheet of paper may not have wanted to go very deeply anyway. Something narrower (that can't tear) like a feeler gauge is likely to go deeper. Even if all it does is push the glue ahead of itself, that would be an improvement over hoping the glue migrates on its own.

 

[bagman67]

Yeah, I went on a tour of the various videos, forums, and blogs to see how folks are solving this problem.  A common approach seems to be to use a slot-head screwdriver to flex the crack a little wider, and then to just slather the joint with glue and hope for the best.  One guy on TGP, I think it was, shared the feeler-gauge trick.  I think combining the two approaches would get you where you want to be.

 

[AirCap]

Use wet-or-dry sandpaper (like 600 grit).... OR gravity. Also helps if you work the joint a bit, it will help push it down into the crack.

 

[davegardner0]

Ok I ended up using a combination of all of the really great suggestions here.

I pulled apart the crack just a little bit more (heard a little wood cracking) until I was able to get a syringe tip inside pretty much all of the crack. I will say that not breaking the headstock all the way off helped because I didn't need to worry about alignment when clamping, but I only stopped here because I could access the whole joint with my syringe.

I thinned down some fish glue using hot water (about 1:1) so it would easily flow throughout the crack. Then I mounted the neck in my bench vise so that gravity would help the glue flow down into the deep recesses of the crack. I held the crack open with a screwdriver and piped in a ton of glue. Then I "worked" the joint a few times to get the glue to flow and distribute more.

I had squeeze-out along the entire length of the crack on both sides! This seems like a really good thing. So now it's clamped up and drying, since i used extra water in my glue I think I'll leave it clamped for a few days... Then I'll seal the crack with a little finish since fish glue is water soluble after it has cured.




Oh and the syringes I have are about 0.89mm OD, 0.61mm ID. Not sure what gauge that makes them, but full-strength fish glue *barely* flows through, and thinned fish glue goes through easily.

 

[AirCap]

100% squeeze out is a good sign! I have no idea what gauge needle I use - I've had it so long. By the way - purchased at a veterinarian supply decades ago. It worked so well I gave away the rest of the syringes I purchased at the same time.

 

[mayfly]

try to make sure that the truss rod still functions after the glue cures.  I'm a little worried after you said "I pumped in a tonne of glue" that it went down the truss rod channel. Still - fish glue might not have much shear strength so it might be ok...

 

[davegardner0]

I'm a bit concerned about the truss rod too - didn't think of it until after the fact. I'm sure glue went into the slot, and who knows if they used a plastic sheath around the rod itself.
I'll try tightening it when I get home. Like you said, hopefully bonding to metal the fish glue doesn't have great adhesion/sheer strength. I'm thinking if it is glued solid I pretty much won't be able to tighten it at all, right?