Guitar Truss Rod Adjustment

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Guitar truss rod adjustment should be carried out with extreme care.

It IS something that most guitarists can (and should) deal with but unless the task is done correctly, and with caution, it is possible to ruin the neck of the guitar, or even make the instrument unusable.

If a guitar has a problem with the action, most times it can be attributed to the neck being out of shape in some way, twisted, warped or bowed.

The guitar neck should have a slight bow towards the body (concave), not be completely straight as the tension of the strings pulls on the headstock. Guitar truss rod adjustment allows compensation for this tension, helping the tone and action, giving a cleaner ringing note, and helps reduce fret buzz.

Truss rod adjustment should be used for minor (i.e small) alterations to the shape of the neck dip using a tool, which is usually provided with the guitar, called an allen or hex key. In some cases a screwdriver or spanner may be required. Ensure you have the correct tool before carrying out any adjustments, you do NOT want to destroy the truss rod by using a tool that is the wrong size. Guitars vary in where the adjustable end of the rod are located but most are at the headstock end of the guitar, behind the top nut, either uncovered or under a truss rod cover.

It is difficult to say what the exact measurements of the dip should be as each player will have their own preference depending on their type of guitar and playing style. For example a guitar set up to play slide guitar will generally have a higher action than a guitar set up for fast lead playing. However, as a general rule the dip in the neck should measure approximately 1/64'' (0.4mm). Follow the instruction below to adjust the dip if it is much higher than this (say 1/32" (0.8mm). The same instructions apply to both electric and acoustic guitar truss rod adjustments.

  • Check joints between neck and body to ensure there are no cracks if the neck is glued in, or gaps if the neck is a bolted on.
  • Fit a new set of strings and bring them up to pitch
  • Put a capo on the first fret
  • Hold the bass E string down one fret above the where the neck joins the guitar body
  • Measure the height of the string at the mid point, this will be between the 5th and 8th fret
  • If the measurement exceeds 0.5 mm give the truss rod nut a one-quarter turn clockwise. Retune the strings to pitch and measure the dip again, repeating the quarter turn if necessary.
  • If the measurement is less than 0.5 mm give the truss rod nut a one-quarter turn anti-clockwise. Retune the strings to pitch and measure the dip again, repeating the quarter turn if necessary.

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    Your guitar may need the attention of a professional repairman if you encounter any of the following problems with the truss rod;

  • It does not adjust the action
  • It provides no resistance when turned
  • It provides too much resistance
  • it requires large amounts of adjustment
  • It makes excessive creaking or grating sounds

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