© 2020 by GMC Luthier Tools


Guitar Nut Vice | GMC Luthier Tools

Our universal system makes it possible to profile a new top nut, choose the best string spacing and set the nut action with precision - all on one jig. The jig is designed for use in a bench vice whereby it is rigidly clamped and prevented from movement, and is positioned at a good height for working. Anybody struggling with close vision problems or neck ache as a result of poor posture will certainly benefit from using this tool!.

The system 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.

A unique feature of this system is the copying or replicating of an exact fingerboard nut slot depth and fingerboard radius onto the jig itself. (This is described in detail further below). This permits nut shaping, string spacing and nut filing, all to be performed off the instrument.



With standard spacing, the string positions are equal but the space in-between them decreases from treble to bass. This can be quite quite significant for heavy gauges.


With compensated spacing, the centre distance is gradually compensated from treble to bass by a very small amount so that the space in-between adjacent strings feels the same for all positions.


The advantage of this is easier fretting and less muting of adjacent strings. A disadvantage is that once you've tried this method, you might never revert to standard spacing!.


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.


This system is accurate and repeatable. A specially made string position marker and guiding template ensures the strings are precisely positioned along the nut. This avoids any discrepancies with individual hand marking out of each slot as all of the slots are cut in the same setting.


An original feature of this tool is its comparison of the instrument. The jig is set up directly from the guitar. Different string spacings can be easily experimented with and fretboard offcuts make ideal test pieces.


Should you need to do so, a precise re-make/copy of the nut is simple & fast using the same jig setup.



The central component of the jig is the Guitar Nut & Saddle Vice (shown above). This is a useful tool in its own right and is also available for purchase separately from the webstore.




The jig 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) are fitted at the lower stud to keep the profile plate parallel in the jig. 

For thicker nuts the loose clamp jaw can be fitted over the profile plate for extra rigidity.



The top of the nut is shaped to the template profile.

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 - Fitting the String Action Template).


This leaves a minimal amount for nut filing and improves string spacing accuracy as there is less tendency for the files to wander.

As can be seen, the shaped profile is accurate & uniform.



The semi-finished nut should be placed on the instrument and the outer string positions marked on the top.



The Nut Profile Template is removed from the vice and the the String Action Template fitted.

Guitar Nut Slot Filing | GMC Luthier Tools

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




The String Spacing Guide ensures precise string positioning and optimised spacing.

The slots are spaced with a small compensated increase in adjacent string positions from treble to bass.

The guide slots are numbered and diagrams are provided for easy reference.

The String Spacing Guide is fitted over the String Action Template. The guide is then adjusted left or right until the desired string spacing is found.

The string positions should be marked on the nut using the marking saw provided. The String Spacing Guide is designed with an arc/radius of movement. This is to aid contact of the marking saw with the top of the curved nut i.e. to avoid cutting at a slant and to keep the saw central in the slot.

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 below.

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. (Graduated rule not included!).

The string spacing guide is removed after marking the string positions.

Each slot can now be filed with the correct size nut file until flush with the top of the string action template. It is recommended to use gauged nut files for this task.

Relief, & action can all 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 be checked for any binding using an offcut of the same string gauge.


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


With the nut temporarily fitted on the instrument, tension the strings to pitch and check the string action at the 1st fret.

Re-fit the nut to the jig & insert a wire gauge underneath the nut as per photo below.


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 below, 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:


1) 0.012” / 0.3mm 

2) 0.016” / 0.4mm 

3) 0.020” / 0.5mm 

4) 0.024” / 0.6mm 

Use the smallest gauge for initial adjustment and increase the gauge size if further depth is required.



12 string slot configurations can be achieved by allowing approx 2.5mm extra for the outer string position at the bass side when marking out. 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) and positioned to mark the 2nd group of six with an initial spacing of 2mm at high 'E'. Each paired spacing will then increase proportionally up to low 'E'. (Approx 2.5mm).

Dependent on range selected and gauge of strings used, some minor adjustment of individual positions may be necessary.