Official Luthiers Forum!

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?

Epoxy does not "penetrate" the wood fibers.
Titebond and hide glue, etc. do - why because they have water in them, and the wood sucks it in.

_________________
"Act your age, not your shoe size" - Prince

I stay away from epoxy for almost any repairs, and never on real guitar repairs. I've had too many times that it didn't harden properly, as if it hadn't been mixed properly, or had exceeded it's shelf life. Some of those were freshly opened tubes, and were mixed according to instructions. I used to use epoxy frequently when building R/C airplanes, so I do have some experience with it, but that was a while back. I'd consider using it to resurect a beater, but not for repairing anything better.

_________________
A man hears what he wants to hear, and disreguards the rest. Paul Simon

I've done several of these cracks/breaks and always use Titebond I. Never had a problem. I can thin Titebond 10% and still get it to flow through a fairly small syringe needle. Then increase the clamp time to compensate for the thinning.

I think the biggest issue you face is getting the epoxy off of the wood you want to glue. I don't think any glue will stick to the epoxy. Of course it sounds like the epoxy didn't stick either, so I don't know what you'll have when you get in there. Harbor Freight has some small dental style tools and picks that may be helpful.

Best of luck, and please post some pics of what you find.

Some really good stuff in here! In my experience, once a joint has epoxy in it, it will never really be clean enough to re-epoxy without some kind of reinforcement. A re-glued break should always come with a signed waiver!

Epoxy has a shelf life. It is used in making airplanes but the builder has to prove to the FAA that it is fresh.
I like glueing reinforcement on the back better that trying to fit a tenon. I've had good results building the reinforcement by glueing on layers of veneer one at a time. It is flexible and bends around the curve. Trying to cut a piece of wood to fit there is too time-consuming for me.
I think we all hate fixing peghead breaks.

Also when you talk about using epoxy in guitar repair, it should be proper industrial grade epoxy resin, NOT the hardware 2 tube stuff which never really cures hard.
It also does need attention paid to application and clamping such as allowing time for absorbing into the surrounding wood (especially on end grain) before clamping, only clamping once, to ensure that the joint is not starved.

I specifically said in my first post that I had used the Stewart McDonald slow setting ("full bond strength in 8 hours"). What do you recommend?

What I use would not be available to you in the USA, just as the Stewmac epoxy is not available to me.
I notice it has a few bad reviews for staying soft, whether this is a problem with the product or the application?
West System seems to be popular.

Some times that is the best choice. It will make it easier to remove and clean the dried on glue residue but it will also give you much more gluing surface.
Use Titebond original or HHG and let it sit in clamps for at least 24 hrs. I would also route for and add 2 spline just for added insurance

Epoxy can and does penetrate wood fibers. How much depends on viscosity and species of wood.
Laminating epoxies have a very long shelf life. This from West Systems " With proper storage, resin and hardeners should remain usable for many years." The resin can get hard and crystaline just like honey does and just like honey you can bring it back by heating, (double boiler, in the sun on a hot day) with no appreciable loss of strength. "Old" epoxy doesn't worry me in the least, it is not hide glue or AR. What would worry me is improper use as in mixing or gluing or a general 2 part epoxy that will dry soft. (Like System 3, hate the stuff.)
For the OP I would suggest West systems. Heat the wood to be glued and wet out the joint (both surfaces) with un-thickened epoxy, leave a little extra in your mixing cup and thicken it with cab-o-sil and wood flour. Apply the thickened mixture and clamp only tight enough to bring things together. The trouble with epoxy is that unlike most all other glues it likes a thick glue line. So you have to deal with that. That is also the beauty of it. If there are a lot of fibers missing and lots of space for the glue epoxy will be very happy. (and in that case you can close the cometic part of the joint knowing there is space inside for the glue.) It is mechanical and does not require the glue line to be tight. It's best use is for contaminated joints and joints where there is lots of missing wood.
L.

_________________
Cut to size.....Beat to fit.....Paint to match.

Have you had a chance to get it back in hand for a good inspection? I would want to inspect that epoxy joint. Did the epoxy fail - or did it break again across the short grain. Or... Was the epoxy not really cured and was still a little sticky/pliable. I have had that happen several times.

2 things without having it in hand - which means it's just uninformed opinion.

1 is the epoxy, the second is curing.

I can attest that West systems structural standard epoxy (non-thixotropic) soaks deep into wood.... I lost a good top because I didn't think that epoxy would soak in... I used black dyed epoxy on a rosette channel... And it soaked 3" up into the wood.... I have used Devcon/Loctite hardware store epoxy and it won't.

Second.. The curing. I have had epoxy not fully cure on me many times. Cool weather is a notorious factor - but it can also react to contaminates from other poly finishes and not cure right. My standard procedure now is to wait the rated cure time or a day - whichever is greater. Then - I warm it with a hair dryer till it's noticeably warm to touch. Then - let it cool another whole day and check again for sticky/pliable. Usually - it never needs more than one go.... My problems with not-fully-cured epoxy are gone now.

Tell us what you find out when you get it in hand.

Thanks.