In my hobby of repairing guitars I have had a dozen or so broken headstocks come across my bench. It is always a difficult choice of which glue to use and just how to go about the repair - I seem to spend more time making jigs and fixtures that than actually fixing. The additional delemma is how to repair finish and try to hide the break.
So far my philosophy (somewhat based on Dan Erlewine's repair book) has been to use Titebond for clean complete breaks with the grain and with little or no splintered wood. I do a scarfed headstock when I build and use Titebond on it - so far I have had very good results. There is a little skating around as I'm applying the clamps but I'm usually able to jig things up and get good alignment. I tried HHG once on a very clean break - it worked fine but I'm scared of any break that is going to require any open time at all.
For splintered breads or those that might not be completely open I have used StewMac slow setting epoxy (Erlewine talks about 24 hour epoxy being his choice for ugly breaks). So far that has seemed to work fine - I've even used their black epoxy to help hide the break on black headstocks.
I say "worked fine" until recently when I had a Guild 12 string with a partial break from the back of the neck to the headplate, but still held on by the headplate.
I mixed up a batch of the SM epoxy, wedged the break open from the back and worked epoxy up inside the crack with thin tools and even a piece of guitar string wire. I felt that I had pretty good penetration and coverage altho I couldn't see inside (squeeze out was good all around). Clamped it up tightly, let is set 24 hours and returned to the owner who strung it back up. The joint opened up again.
So, first question is how to approach this (I'm meeting with the owner next week and want my options in order). I think I should open the joint and clean it with tools and probably denatured alcohol. Should I go ahead and break the headstock or just try to really wedge it apart (which may break it). Once I get it as clean as possible should I redo it with epoxy (possibly another brand, the SM stuff gets pretty mixed reviews on their web page including people who have had failures). If its clean enough and I can get it open should I try Titebond?
Next question is reinforcement. I could build some sort of router sled and try to put CF splines in the joint or I could run the neck thru my Safety Planer and graft a back plate on it. I'm leaning to the back plate but I also know that will create a bunch of shaping and finish work - I'm sure the finish on the Guild is poly and it looks like the mahogany neck has some stain - I would be forced to try to finish the repair in lacquer (which I'm pretty comfortable with).
Last thought is that once this one is done I may move away from epoxy and just use AR. I probably will turn down some of those repairs that I feel uncomfortable with - I'm rarely happy with the finish and appearance - maybe someone else should do these.
Thoughts?
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