Baking soda and super glue. You should find lots of instructions if you Google something like, "guitar nut baking soda glue." Probably not a long-term fix but enough to last you a while. Perhaps someone who knows more about it than I will chime in to elaborate.
For a more permanent fix, I prefer to glue in a new piece of bone. If you file a "V" groove just big enough to get rid of the old slot, then superglue in a small piece of bone, then file and sand it back to the profile of the nut, then file your new slot.
Postby Marcus Dominelli » Sun Jan 10, 2010 4:48 pm
I've never tried James' method. Sounds good though.
If you're in bind and cannot make a new nut you can use bone dust and crazy glue to fill the slots, but it will not last very long, especially for the wound strings, which have an abrasive affect on the nut slot as they're tuned up and down.
A better approach is to shim the nut by crazy gluing on some thin, white card stock to the bottom and trimming it flush. Then just re-adjust all the slots down by filing each, one at a time, with the guitar strung up under tension.
I tried raising a bone nut slightly by gluing on to the bottom a very thin shim of bone, with CA glue. The glue just would not hold the two pieces of bone together. I concluded that a bone-to-bone bond with CA glue didn't work, but it sounds like other people have had success. Is there a trick to get this to work?
I would strongly recommend one of the methods outlined by James and Marcus. The CA with soda or dust APPEARS to be OK, but becomes a major PITA on wound strings because the strings tend to stick in the slots just enough to make fine tuning difficult, even with graphite or other lubrication.
Robert: re the glue joint, I think CA should have worked (perhaps fingerprint oil or other contamination?), although I scratched the surfaces & used thin epoxy. It's easy to fool around too much with these sorts of things.