Function of the Nut
Sets string length at neck for proper intonation. Spaces strings on neck. Places strings at playing height off fingerboard.
Indictation of Problems with the Nut
Guitar won’t stay in tune. String buzz on first fret. Strings breaking at nut. Poor intonation.
What to look for
First make sure the nut is sitting in its proper position. In other words, make sure there are no gaps between the nut and the areas it sits against. (Tight against the fingerboard, etc.) (See Fig. #1) If there are gaps, you will need to take this to your local repairperson to fix.
Next, let’s look at the spacing between the strings. Looking straight down on the nut, do all the strings appear to have the same amount of space between them? They should.
Also, sometimes the two outside strings will be too close to the edge of the fingerboard and have a tendency to “fall off” when pressed down.
If any of these things happen, then you need to reposition one or more of the strings. To do this will require either a new nut or a repair technique beyond the scope of this manual. Consult your local repairperson.
If the nut is sitting properly on the neck, and the strings are spaced properly, then the next step is to look at the slots themselves. This is the most important (and often most overlooked) part of the nut, particularly as it relates to how well the instrument stays in tune.
The main thing to understand about the string slots on the nut, is that this is the point at which the string length begins. The nut slot must always be cut so the slot falls away from the leading edge (next to the fingerboard). (See Fig. 2) In other words, as the slot goes from front (front being next to the fingerboard) to back (headstock side), the slot should cut downwards as well. If this slot were cut straight through the nut (parallel with the strings), then the string would and could sit at different points within the slot, thus changing string length and causing tuning problems.
Since the strings themselves act like files as they drag through the slot (while tuning or string bending, etc.), over time you will wear the slots flat. You will then need to recut the slot to put the string length back properly to the front of the nut. Take the strings out of the slots and examine the bottom of the slots carefully. If the slot seems to go from front to back almost straight, without falling away from the string, it may need to be filed.
Note: If you are having trouble keeping the instrument in tune, then this is the FIRST area of potential problems and should be dealt with first.
The tools for cutting these slots are not common, everyday, around-the-house tools and can be expensive. For this reason, to do the job properly, you may want to take the instrument to your repairperson if you feel this needs attention.
But, if you have access to a suitable set of files (like small diameter needle files that can cut thin slots), and wish to do this yourself, remember to mask off all areas around the nut so your files won’t damage or mar the finish. (See Fig. #3)