The nut is essential to the performance and playability of any fretted instrument. The nut establishes the spacing of the strings in relation to the edge of the fingerboard (see photos) as well as the spacing of the strings themselves. It also determines the height of strings in the first position of the instrument. Slots that are left too high will be harder to press down and if the slots are too low they will buzz on the frets when the string is played open.
Here are some other issues every player should be aware of:
- Slots that aren't cut properly or are worn out can cause tuning issues.
The string should "ring" from the very front of the nut next to the fingerboard. If not the guitar will play "out of tune" on open chords.
Strings can bind up in the slots in such a way that as soon as you play the guitar, the string slips and is once again out of tune. Do not assume you need new tuning machines if your guitar doesn't stay in tune. It could be the nut slots are worn or too small for the strings you're using.
- The fit of the nut to the "shelf" is very important.
When a nut is replaced a qualified luthier will be sure the shelf is prepped properly. You want the material of the nut to fit snug and tight to the neck material to ensure good coupling from the string to the nut to the wood. It is very common to find a nut shelf that needs to be flattened carefully before ever making a new nut.
A handmade nut will fit flush to the neck wood, fingerboard wood and be shaped to the proper height. If a nut is too tall the slots will often be too deep which adds unnecessary friction between the string and the nut so careful measurements and an attention to detail are needed to get this "right".
Most players never need to think about the detailed work that goes into making a nut, fitting frets or setting a neck and what it means to fit, make and shape something by hand nor should they. It's about playing the instrument, enjoying the instrument and creating something of their own and luthiers are here to make sure that's as effortless as possible.
- Pre-made nut blanks rarely work!
Guitar necks vary from one company to another and from one design to another. Buying a pre-made nut blank and hoping it fits the width and height needed is probably a waste of time. Unless you're trying to just "get by" or the instrument is very inexpensive I would simply avoid these. It is a critical component worth having made by a skilled luthier to repair, upgrade or optimize your favorite instrument.