Guitar Nut Vice | GMC Luthier Tools

The Guitar Nut Replacement & String Spacing Jig is designed for shaping a new top nut, optimising the string spacing and setting the nut action with precision.

There are two jig options available:


 6 String Guitar Nut Replacement & String Spacing Jig.

 4-8 String Guitar Nut Replacement & String Spacing Jig.

The jig comprises of 4 main components.


  1. Guitar Nut & Saddle Vice.

  2. Nut Top Profile Templates.

  3. String Action Templates.

  4. String Spacing Guides.



With uniform/equal string centreline spacing, the gap between each string decreases from treble to bass. This can be quite significant for adjacent roundwound strings and heavy gauge sets.


With compensated spacing, the string spacing is incrementally increased so that the space in-between adjacent strings is similar across the fretboard. 



The central component of the jig is the Guitar Nut & Saddle Vise.


The vice makes a comparison of the instrument by gauging the bottom of the nut slot (similar to using a vernier depth gauge). This creates a datum reference on the jig identical to the guitars nut slot depth.

Guitar Nut Slot Depth | GMC Luthier Tools



The Nut Top Profile Template is used for shaping the top face of the nut.

The nut profile template is designed to leave approx 0.5mm (0.020”) stock material for nut filing at the treble side, and 1.0mm (0.040”) at the bass side. (See photo below - String Action Template). This ensures that there is minimal depth of material left for nut filing.

Luthier Tool - Making a Guitar Nut



The profiled nut should be removed from the jig and the overall string spacing marked with reference to the instrument.

Luthier Tool - Guitar Nut String Spacing Jig
Guitar Nut Top Profile Shape



The nut is re-fitted to the vice and the the String Action Template fitted.

(Note - the top face of the nut can be seen with an increase in height from 0.5mm at the Treble to 1.0mm at the Bass).



The Spacing Guide is supplied with a String Position Marking Saw. Diagrams are provided for easy reference to the spacings obtainable.

The system ensures precise positioning and avoids discrepancies with individual hand marking out of each slot.

Proportional Guitar String Spacing | GMC Luthier Tools
Guitar String Spacing Charts

The string spacing guide is adjusted left or right until the desired string spacing is found - see below. (i.e. slots align with previously marked overall spacing).

Note the slight progressive increase in adjacent string positions for a 6-String Bass Guitar with 42.1mm overall string centres - from highest to lowest indicated by the rule in the photo. Moving the string spacing guide 1-pitch to the right in the photo would reduce the overall centres to 41.4mm, and moving 1-pitch to the left would increase this to 42.9mm centres. (Steel rule not included).

Proportional String Spacing Guide
Proportional String Spacing Jig

Once the positions have been marked, the spacing guide is removed and each slot filed using a suitable nut file until flush with the top of the string action template.


Luthier Tool - Guitar Nut Filing Jig
Guitar Nut Filing Jig
Luthier Tool - Checking the string slot

Relief, & action can be fine tuned in the jig with occasional reference to the instrument.

The nominal action achieved using the jig before any final adjustment on the guitar will be approx 0.020” (0.5mm). This is a general guide and will be subject  to other factors including the fret heights and string gauges.

The nut string slots can also be conveniently checked for any binding using an offcut of the same string gauge.



The system can be used for 12 string guitars.


After marking the 1st group of six slots, the guide is then moved along to the next pitch (increased overall 'E' to 'E' on the guide) to mark the 2nd group of six.

Filing a 12 String Guitar Nut