You have a number of choices when it comes to gluing a guitar neck.
A good glue must be stronger than the wood it binds, and it must be left to set for the required period of time and cured appropriately. There are a number of choices of glues, both traditional and modern. Dan Erlewine, a luthier, considers this in the Stewart-Macdonald Trade Secrets newsletter.
The Right Glue for the Job
Dan Earlewine was once given a Martin D-35 acoustic guitar with a neck snapped nearly through, starting at the nut and extending almost to the second fret. After considering the alternatives, he chose a traditional solid hide glue dissolved in hot water, for these reasons: "Hide glue has a fairly low viscosity, so it can penetrate deeply into a crack. Hide glue cleans up easily with water, even after it's dry." He adds that the glue's strength is similar to epoxy, known for its rock-hard bonds.
Modern Glue Options
Earlewine also explained why he didn't use other, more modern glues, given the nature of the neck damage: "Epoxy would be hard to clean up in this situation, and most epoxies aren't thin enough to penetrate deeply into the recesses of this crack. Titebond is strong and cleans up easily, but it's rather thick and wouldn't penetrate as deeply as hot hide glue," he said. "Superglue works too fast for this job. Also, it will mar a lacquer finish, requiring a finish repair that isn't needed with hide glue."
Success
The hide glue was a success. After setting overnight, the crack was "nearly invisible," Earlewine said. He added this tip: "Work fast. Hot hide glue sets rapidly. If the squeeze-out is like sticky tapioca or gelatin, the glue has set. If you haven't finished clamping by that time, you should have. Practice with a dry run before using the glue."
