How could this have happened? Well, you could possibly go so far as to call it a design flaw. On any guitar with an angled-back headstock, the area where it angles is naturally weak. This is because of a number of factors but primarily to do with the timber's grain direction and the fact that the area is pretty thin - the thinnest part of the neck. Add to this the fact that many instruments have a truss-rod access channel here, effectively removing even more wood from an already weak area, and you have a recipe for breaks.
The image on the left shows a Les Paul neck/headstock. I've added a dotted line to indicate, approximately, the depth that the truss-rod access cavity is cut. You can see there's not a lot left.
Many guitar makers try to alleviate the potential for trouble in this area with a variety of means; multi-ply 'sandwich' necks, truss rod-access moved elsewhere or reduced, scarfed headstocks, and the most common, a volute. A volute is simply a shaped/carved 'bulge' that's left in the weak area to strengthen it (although it might be more accurate to say 'not to weaken it').
Gibson are frequent stop-outs on this though. Although a volute was introduced on many Gibsons in the late '60s, it was phased out again and it's appearance on modern Gibsons is hit-or-miss. Most don't have one. Indeed, while all instruments with angled headstocks have breakage potential, Gibsons (SGs and Les Pauls in particular) top the charts in the headstock repairs I perform. If Gibson ever start strengthening this area, guitar repair guys all over the world are going to see their incomes drop.
My guitar neck is broken. What do I do?
If you do manage to break or crack your guitar's neck or peghead, don't panic. Almost anything is repairable. Here are the immediate steps to take.
- If the headstock is still attached to the neck (the headstock veneer often keeps it attached), gently - very, very gently - slacken off the strings. Pop it in it's case and get yourself to a good repair guy.
- If the headstock is just cracked, do the same - slacken off and get it repaired.
- If the headstock is completely detached, carefully wrap it up in something (a bag, newspaper, etc.) and try not to knock, damage or disturb those jagged splinters of wood poking out.
- Don't try to fit the headstock back to the neck as the joint should usually be examined and cleared of any misaligned splinters or loose timber before this is attempted.
- Check for any splinters that have come loose and if you find any, pop them in a bag - they'll help complete the jigsaw and assist in getting a good, clean repair.
Repairing a broken guitar neck
The first repair is the important one. If it's not done well, then you've got a reasonable chance of the guitar breaking along that fault again. Sometimes string tension alone can be enough to pull a badly repaired break apart. And, repairing along a previous repair is much more difficult, time-consuming and often more invasive. Not to mention more expensive.
The lesson? Don't break your guitar neck but, if you do, get it repaired properly first time around.
Talk to your repair guy and ask him/her to discuss the repair. A good repair guy will be happy to chat about their plans. What glue will be used is important for example. For most repairs either hot hide glue or aliphatic resin is the right choice. If your repair-guy decides immediately to slap in a load of epoxy, you might want to ask them why. While epoxy certainly has a place in headstock repair, it's generally a limited one. Epoxy is incredibly strong if used properly but its nature makes it difficult to penetrate cracks and it's not usually a first choice adhesive for most of these jobs.