© 2019 by GMC Luthier Tools

GUITAR STRING ACTION & NECK RELIEF

Guitar String Action Height at the 12th fret for a 6-string electric guitar is typically 1.5mm at High 'E' rising to 2.0mm at Low 'E'. This is generally considered as providing good tone with medium finger strength required for playing. 

This gauge allows the action to be quickly and precisely set to the above values without any requirement for additional measuring tools.

From the initial setting, the string height can be adjusted up or down to suit playing requirements as detailed further below. 

Final action on the instrument should be determined by the feel of the guitar and its tone. 

String Action Height Gauge | GMC Luthier Tools
String Action Setting Gauge | GMC Luthier Tools

GUITAR STRING ACTION / GAUGE THICKNESS:

 

The thickness of the gauge increases progressively across the width of the fretboard to allow for the increase in string diameters.

 

String Action @ 1st  String:   1.50mm 

 

String Action @ 6th  String:   2.00mm

Setting String Action Height | GMC Luthier Tools

Simple to use!: Insert the gauge underneath the strings at the 12th fret and lower the bridge/saddles until the strings rest on the gauge.

SETTING THE ACTION:

 

Place the gauge underneath the strings at the 12th Fret. Lightly pluck/strum each string close to the bridge to minimise free vibration and lower the the saddles until the open notes are muted.

 

Test the instrument for a good while to assess playability.  (Fret condition, instrument quality, style of playing and sound will determine any final adjustments.)

 

ADJUSTING THE ACTION:

 

To lower the action: Move the gauge to the 13th fret and re-adjust the saddles/bridge until the strings are muted again.

 

To raise the action: Move the gauge to the 11th fret and re-adjust the saddles/bridge until the notes are audible again.

 

It is possible to set a combination of these i.e: Plain/Treble strings set with lower action using the 13th/14th fret positions and Bass/Roundwound strings set with higher action using the 10th/11th fret positions. 

 

GAUGE OPTIONS:

 

Five guitar gauge options are available:

7.25"

9.5-10"     

12"

15"            *(Suitable for 14" to 17" radius)

20"            *(Suitable for 18" to 20" radius)

*See diagram below for clarification

SETTING THE PICKUP HEIGHTS:

 

After setting the string action, the gauge can be used to set the pick up heights.

 

Place the gauge on top of the pick up poles and adjust the pick up height until the strings contact the gauge with the last fret position fretted.

Setting Guitar Pickup Heights | GMC Luthier Tools

GAUGE COMPARISONS:

 

The following diagram compares the geometry of the most widely used fingerboard radii with the gauges available in the listing. 

The diagram is drawn to scale and represents the relative theoretical differences between radii at the edge of the fretboard.

The gauge intervals available in the listing are indicated by the solid lines and bullets. 

The dashed intermediate lines indicate fingerboard radii that can be suitably accommodated with the adjacent gauge. 

Please note the minuscule differences with reference to each gauge size and the intermediate radii. A dimension is shown next to 9.5 -10" gauge to highlight this.

GUITAR NECK RELIEF SETUP & STRING ACTION GAUGE KIT

Guitar Neck Relief Setup | GMC Luthier Tools

The Guitar String Action Gauge can also be used to set the neck relief.

 

Set comprises of:-

  • Guitar String Action Gauge

  • 0.25mm Feeler Strip

  • 0.15mm Feeler Strip

  • Capo

 

 

SETTING UP YOUR INSTRUMENT

 

For best results, the following order of adjustment is recommended:

  1. Set Neck Relief.

  2. Set String Action.

  3. Set Pick Up Heights

 

GENERAL

 

There is no requirement with this system to use a straight edge. 

 

The procedure is based on depressing the string simultaneously at the 1st and last fret and measuring the relief at the 8th fret. The gauge enables this to be done in a manner that also leaves both hands free to make adjustments.

 

HOW MUCH RELIEF IS REQUIRED?

 

The neck should be slightly concave with a typical relief of 0.25mm from the top of the 8th fret to the underside of the strings for a 6-string Guitar. 

 

For fast light playing such as Jazz, the relief can be set lower to 0.15mm.

 

The amount of relief will ultimately be a matter of preference and how the instrument feels and sounds.

PROCEDURE:

Fit the Capo at the 1st fret and ensure all strings are fretted.

Feed the String Action Gauge through the strings below the last fret as shown in the following photo.

Guitar Neck Relief Setup | GMC Luthier Tools

Note 1st, 2nd, 4th & 5th strings pass over the gauge & the 3rd string runs underneath the gauge. The effect of this will cause the 3rd string to be fretted.

 

The string pressure and gauge curvature will ensure that fret contact is maintained and both hands are entirely free for truss rod adjustments and measuring.

 

Ensure the 3rd string is in contact with the last fret.

 

At this point if the current action is set high, and the 3rd string is not in contact with the fret, then the bridge should be lowered slightly until the 3rd string is fretted.

SETTING THE NECK RELIEF:

 

Position the feeler strip underneath the 3rd string between the 7th & 9th frets.

The truss should now be adjusted until the string rests gently on the feeler strip.

 

With the feeler in position as shown the relief can be clearly seen to increase or decrease when the truss rod is adjusted. Both hands are also free to make the adjustments.

 

The advantages to this are:-

  • Instant confirmation that the truss rod is working correctly.

  • Indication that the truss rod is being adjusted in the right direction.

  • The truss rod needs only to be adjusted once until the string contacts the feeler.

  • There is less likelihood of damage and wear to the truss rod end and the headstock which can occur from excessive adjustments.

  • The instrument can be adjusted in a comfortable position.

  • User confidence that the relief has been set correctly.

The string action should now be set as per separate instructions above.

Our String Action Gauge & Neck Relief Setup Kits are available from the Webstore.