THEY’RE A CRITICAL COMPONENT FOR “IN-TUNE” PLAYING.
If a nut isn’t cut and fitted correctly, you’ll have trouble intonating the guitar, and maybe playing in tune at all. A nut’s front edge forms one terminus point for the “speaking length” of the strings, and if the strings don’t break across that point at precisely the right place, you’ll find yourself playing out of tune all up and down the neck—even when you seem to be “in tune” according to your chromatic tuner.
IN POOR CONDITION THEY CAN CAUSE TUNING HAVOC.
The condition and cleanliness of a guitar’s nut can have a major impact on the guitar’s ability to play in—and return to—pitch, even before it has become gunked up enough for you to notice there’s a problem. If a nut’s slots are overly worn, it will be difficult to accurately intonate the guitar, and you’re also likely to get a “ping” from strings in such slots as they hop from side to side when you bend them. Nuts with slots that are too tight are also a problem. Strings won’t slide through them smoothly when you try to tune up, and they’ll also pinch strings when you bend notes, preventing them from sliding back to pitch and likewise causing tuning problems. (This factor is part of what has led to the popularity of selflubricating Graph-Tech, Tusq, and Delrin nuts, even on guitars without vibrato units).
THE STUFF THEY ARE MADE FROM AFFECTS THE TONE OF YOUR ENTIRE GUITAR.
Since it forms one terminus for your strings’ speaking length (see #1), the nut is one of two main components responsible for transferring vibrational energy into the wood of the guitar, and therefore contributes to a guitar’s resonance and sustain, and, hence, its overall tone. Nuts made from bone, Corian, Micarta, brass, nylon, hollow plastic, Tusq, and Teflon-impregnated plastics all have different densities and will all sound a little different. Whether one sounds better than another is up to you.
THEY ARE REPLACEABLE.
Even on vintage guitars. Sometimes a good tech can fill and re-file a nut to give new life to over-worn slots, but when they are worn beyond confident repair, the nut needs to be replaced. Some people shy away from replacing nuts on high-valued vintage collectibles, and that’s understandable, but it’s a repair worth considering if you want the guitar to be anything more than an expensive wall hanger.
REPAIR AND REPLACEMENT ARE JOBS FOR A PRO.
Given points 1 and 2, repairing or replacing a nut is a job for a trained professional. A “nut job” might seem simple enough, but cut that slot in the wrong place, to the wrong width, or at the wrong break angle across the depth of the nut and your efforts are all for naught. A good guitar tech will have the experience to cut and install a nut precisely, and to suit it to your preferred string gauges besides. He or she should also take your personal tonal preferences to heart, as well as the vintage value of the instrument (if applicable), when selecting the material for the replacement .
Oh and by the way, if you have a guitar with a zero fret, you can cheerfully disregard much of the what’s been said here!