The guitar neck is the most unstable part of a guitar. It is notorious for bending uncontrollably in any direction that it wishes to go. This “non-controllable” characteristic of the neck led to the development of the truss rod. There are few truss rod designs that are used in guitar necks but there are just basically three categories:
- non-adjustable truss rods
- two-way adjustable truss rods
- one-way adjustable truss rods
In this article, I’m going to discuss the adjustable ones.
Before moving on, l will use terms which may not be familiar to you. Have a look at the terms and the simplified meaning below:
Definition of terms
Truss Rod – a non-adjustable or adjustable steel rod inserted inside the neck to function as reinforcement or stabilizer.
Warp – The word is commonly used to indicate a twisted neck, but anything that is not straight is warped. I will use the word “warp” for twisted neck in this article.
Forward bow or Up bow – the neck bends in the direction of the pull of the strings.
Back bow or Reverse bow – the neck bends away from the pull of the strings.
Relief – a slight forward bow intentionally done to prevent buzzing on the middle frets.
How the Truss Rod Work
There are two basic designs for the adjustable truss rod: the “compression” and “bending” designs. The compression truss rod works by compressing the bottom of the neck, forcing the top of the neck, including the fingerboard backward to correct a forward bow. I know it is quite difficult to understand, but here’s an analogy: try pressing the lower part of a cigarette end-to-end and see what happens. On the other hand, the bending truss rod literally bends inside the neck, taking along the neck with it.
Note: A one-way truss rod can only correct a forward bow while a two-way truss rod can correct both forward and back bows.
Limitations of the Truss Rod
Although the truss rod can correct forward and upward bows, it cannot fix a warped or twisted neck. If the neck develops as a “hump” or “rise” on the part of the neck where the body is joined, truss rod adjustment will not help.
Things you need to understand before Adjusting
You should only adjust the truss rod when:
- The neck needs additional relief or reduction of relief.
- The neck has developed a forward bow or back bow.
Do not adjust the truss rod when:
- The neck is warped.
- The neck develops a hump or rise.
- The neck setup (angle) is not correct.
Locating the Truss Rod Adjustment nut
The truss rod can only be adjusted in two areas of the neck – either on the headstock area or near the body. However, accessing the truss rod adjustment nut will vary from different guitar models and manufacturers.
- Many guitars have a plastic cover to hide the truss rod access cavity on the headstock. You must remove the plastic cover before you can adjust the truss rod.
- On other guitars, look for an access cavity beside the neck pick-up. for some guitars, you have to remove the pickguard to have access.
- Acoustic guitars may have their truss rod adjustments hidden inside the body. You have to look inside the soundhole to see it. In some instances, the truss rod adjustment is capped with wood to conceal it.
- Believe it or not, there are guitars that have their truss rods hidden completely. If you cannot find access from the previous locations, you need to detach the neck from the body by removing the screws that hold them together – you might see it there.
- Straightedge or long ruler
- Feeler Gauge
to remove truss rod cover or pick guard
- Truss Rod Wrench
For Truss Rod Adjustment nut or screw
*different guitars are built differently and when it comes to working tools such as Screwdrivers, Allen wrenches etc. checking what you need before buying will save you a lot of time and money.
Preliminary Step before Adjusting
Before making any adjustments to the truss rod, you should first check your guitar’s neck condition by sighting it at the headstock end or at the body. Another way of checking is to press the strings on the first and the last frets or use a straightedge. If the neck is not “reasonably straight”, you should determine where the neck is bending or if it is warped.
Steps in Adjusting the Truss Rod
- Once you have located the truss rod adjustment nut or screw, use the appropriate tool to adjust it.
- Loosen the strings before adjusting to relieve the neck from string tension.
- Gradually adjust the truss rod adjustment nut or screw about a quarter of a turn in each adjustment.
- To correct a forward bow, turn the truss rod nut clockwise. For a back bow, turn the truss rod nut counter clockwise.
- There is a neutral position when adjusting a 2-way truss rod. At some point, you will feel no resistance from the truss rod. Continue turning the nut until the truss rod engages and move in the reverse direction.
Caution: Do not force the nut when it doesn’t move. Forcing the nut may destroy the thread or the truss rod or even worse – the neck itself.
Tip: Try reversing the direction if the nut is very tight. If it still doesn’t move, give it a few drops of thin oil. When possible, remove the nut completely and lubricate it with wax.
- Sight the neck to see if it is already reasonably straight. You can also use the aid of a straightedge or a long ruler to check for straightness.
- Retune your guitar and play a note on all the frets to check if the adjustment you made is already good.
- When you think you need more adjustment, go back to step two and repeat the whole procedure.
- Setup for relief if desired. (Read the steps on how to setup relief below).
- Setup the action of your guitar following the steps in my previous article.
Steps in Adjusting for Relief
A very straight neck may buzz in the lower register especially when you pick the strings very hard. So to compensate for this, adding a little bit of relief may be necessary.
Here are simple steps to follow in adjusting for relief:
- Loosen the strings.
- Turn the truss rod nut counter clockwise to induce forward bow.
- Tune the strings and check your progress.
- Using the strings, put a capo on the first fret in order to eliminate the involvement of the nut (you can also use rubber band to wrap the strings on the first fret).
- Press the string on the fret where the neck meets the body.
- Measure the gap of the string and top of the fret by using a feeler gauge somewhere in the middle. Always measure in the playing position.
Tip: Remember to measure from the fret where you see the gap is the greatest. That could be anywhere in the middle of the first fret and where you pressed the string on the other end. This is the area where the truss rod nudges the neck.
- A good starting point is to set your relief at 0.012” and ease your way down until 0.006” or even 0.004” if it’s possible. Make sure that the relief is set to minimum without buzzing so that the action in that area will remain low.
Tip: It is not compulsory to measure. You can set your desired relief through trial and error to find out what suits you best. On the other hand, measuring will save you more time especially when you are setting many guitars.
- Repeat steps one through seven when necessary.
One last note – do not finalize your setup without the strings on and tuned. This is to ensure accuracy since the strings will pull the neck to a forward bow when the strings are tuned.