Guitar Nut Vice | GMC Luthier Tools

The Guitar Nut Replacement & String Spacing Jig is designed for use in a bench vice whereby it is firmly clamped and positioned at a comfortable height for working. The jig will assist the user in 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 5 main components.


  1. Guitar Nut & Saddle Vice.

  2. Nut Top Profile Template.

  3. String Action Template.

  4. String Spacing Guide.

  5. Wire Gauges for Fine Adjustment.



With equal spacing - as the string gauge diameter increases from treble to bass - the gap in between the strings decreases. This can be quite significant for adjacent roundwound bass strings and heavier gauges.


With compensated spacing, the centre distance is gradually increased from treble to bass by a very small amount so that the space in-between adjacent strings feels similar across the fretboard.


The advantage of this is easier fretting and less muting of adjacent strings.



The central component of the jig is the Guitar Nut & Saddle Vice. (This is also available for purchase separately from the webstore).


The vice incorporates two sliding reference plates. The plates are used to make a comparison of the instrument by gauging the bottom of the nut slot (similar to using a vernier depth gauge). This creates a step in the jig identical to the guitars nut slot depth.


The plates are then locked together when the comparison has been made.

Guitar Nut Slot Depth | GMC Luthier Tools



The Nut Top Profile Template is used as a guide to shaping the top face of the nut. Spacing washers (included) allow for different nut thicknesses. The shaped profile is accurate & uniform.

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 improves string spacing accuracy as there is less depth of material for the nut files to wander.

Guitar Nut Top Profile | GMC Luthier Tools
Guitar Nut Making | GMC Luthier tools



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

To get the best spacing for your guitar, we recommend increasing the overall string spacing to the maximum that the guitar will allow. A small increase without encroaching on the fret chamfers is usually achievable.

Guitar String Spacing At The Nut | GMC Luthier Tools
Guitar Nut Slot Filing | GMC Luthier Tools



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

Note - the top face of the nut (shaped when using the Nut Profile Template) increases in height from 0.5mm at the RH side (Treble) to 1.0mm at the LH side (Bass).



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

The string spacing guide & marking saw ensures precise positioning along the nut & avoids any discrepancies with individual hand marking out of each slot as all of the slots are cut in the same setting.

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

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).

Marking String Centres At The Nut | GMC Luthier Tools
Measuring String Centres At The Nut | GMC Luthier Tools

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.


Using A Guitar Nut File | GMC Luthier Tools
Setting The Guitar Nut String Action | GMC Luthier Tools
Checking For String Binding At The Nut | GMC Luthier Tools

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 dependent on several factors including the fret thickness, string gauge and also the bend radius of the strings over the nut).

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



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.

12 String Guitar Nut With Proportional String Spacing | GMC Luthier Tools


The system includes a feature that enables fine adjustment of string height to be performed on the jig itself.


This raises the height of the nut in the jig and enables the slots to be accurately filed to an increased depth. (Note in the photo, the bottom of the previously flush string slots are now proud of the jig plate).


Four colour coded wire gauges are included. These are spaced in 0.004” / 0.1mm increments:

Adjusting Sting Action Heigh At The Nut | GMC Luthier Tools