GUITAR NUT STRING SPACING JIG
GMC Luthier Tools Guitar Nut Replacement Jig is a unique system for shaping a guitar nut, marking out the string spacing and filing the string slots.
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COMPENSATED STRING SPACING
The system employs compensated string spacing. The string spacing is incrementally increased so that the space in-between adjacent strings is similar across the fretboard. This allows a little more room for easier playing on the heavier gauges. It is also possible to increase the overall 'E' to 'E' for greater comfort.
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To get the best spacing for your guitar, we recommend setting the overall string spacing to the maximum that the guitar will allow. A small increase without encroaching on the fret chamfers may be achievable.
The precision spacing guides ensure the string positions are correct & avoids errors of hand marking out as all of the string slots are cut in the same setting.
A unique feature of this tool is its comparison of the instrument. The jig is set up directly from the guitar. If necessary, a precise re-make or copy of the nut is straightforward with the jig already setup for the guitar.​
​Please see the Workshop Guitar Repair Blog for short videos of the tools application.
​1) GUITAR NUT & SADDLE VICE
​The central component of the jig is the Guitar Nut & Saddle Vice.
The vice simulates the instrument by gauging the bottom of the nut slot using a sliding plate arrangement (similar to using a vernier depth gauge).
After copying the nut slot depth, the jig plates are locked together. This creates a datum reference on the jig identical to the guitar.
2) NUT TOP PROFILE TEMPLATE
The nut is placed in the jig and located on the datum. The nut is clamped using the top profile template.
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The purpose of the template is to provide a guide for shaping the top profile whilst leaving a minimal amount of material for nut filing.
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The nut top profile template is designed with an increase in height from treble to bass. This will 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).
OVERALL STRING SPACING
After shaping the nut, it should be removed from the jig and the overall string spacing marked on the top with reference to the instrument.
3) STRING ACTION TEMPLATE
The nut is re-fitted to the vice and the the String Action Template fitted.
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Note - as the string action templates are smaller than the top profile templates, the top face of the nut profile can be seen with an increase in height from 0.5mm at the treble to 1.0mm at the bass.
4) STRING SPACING GUIDE
The spacing guide is supplied with a string position marking saw. Charts 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. The quantity of guides will depend on the jig option.
The guide is adjusted left or right until the required string spacing is found (2-slots on the spacing guide line up with previously marked overall positions on the nut - see photo). The charts can be used for reference to confirm the overall string spacing selected. To alter the string spacing: - moving the string spacing guide 1-pitch to the right in the photo would decrease the overall string spacing and moving 1-pitch to the left would increase this.​
The compensated increase in spacing can be seen in the example shown below by comparing the initial spacing (8.0mm) with the subsequent spacings ~ (the cumulative spacings being greater than multiples of 8mm).
The spacing guide is removed and each string slot filed using the string action template as a guide to final depth.
The nut can be fine tuned in the jig with occasional reference to the instrument. Using an offcut of the same gauge will also assist this.
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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.
12 STRING INSTRUMENTS
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.