|
[About Us] [Guestbook] [Contact] [Info] |
A R T I C L E S
The Function and Shaping of Fretted Instrument Nuts
by Bruce Morrison
The nut of a fretted instrument serves three purposes. It transmits string energy to the neck, helps determine the string action, and sets string spacing at the low end of the fretboard.
As with the saddle, the choice of materials and the fit are critical to producing good sound. Bone is the material of choice for fretted instrument nuts because its hardness and density make it an excellent transmitter of string energy. The nut must fit the nut shelf and the end of the fretboard precisely, with the front face of the nut square and perpendicular to the end of the fretboard. If it isn't accurately fit, two problems arise. Less string energy is transmitted to the neck resulting in a loss of tone and volume, and the distance from the nut to the frets is altered, producing incorrect intonation at every fret position. The nut should be glued in place with hot hide glue. Also known as violin maker's glue, among the available adhesives hot hide glue is the best transmitter of string energy.
The depth of the nut slots sets the action at the lower end of the fretboard. This frequently neglected factor makes a big difference in the way an instrument feels. With a capo between the 3rd and 4th frets, there should be a gap of .002" measured with a feeler gauge between the top of the 1st fret and the bottom of the 1st and 2nd strings. A .003" gap is required for the 3rd and 4th strings, while a .004" gap is used to set the 5th and 6th strings. When the clearance is too great the instrument may be uncomfortable to play. Insufficient clearance will allow the strings to rattle and buzz.
Nut slots should be cut parallel to the face of the headstock, with their highest point at the end where the strings extend over the fretboard. The slot ends should flare open where they face the tuners. Because the strings enter the slots at an angle, this flaring prevents the string windings from hanging up. The bottom of the slots should be level, with a round cross section to ensure maximum string contact and transmission of string energy. Once the slots have been cut to the correct depth and properly shaped, the top of the nut is arched to match the arch of the fretboard and saddle, with the upper halves of the wound strings exposed above the top of the nut.
There are two ways to determine string spacing. While it's generally agreed that there should be 1/8th" from the outer edges of the nut to the outer edges of the 1st and 6th strings, some people prefer to set the string spacing with dividers, marking an equal distance from the center of one slot to the center of the next. I prefer using repairman Don Teeter's mathematical formula which calculates an equal air space between each string.
Having the nut and saddle properly shaped and precisely fit are among the most important factors in having an instrument reach its potential sound and playability.
Back to Top of Page Return to Articles by Bruce Morrison index page]
[About Us] [Guestbook] [Contact] [Info]