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Adjusting the action of an acoustic guitar isn’t as easy as it may seem. There are a lot of things that can go wrong and cause permanent damage to your axe if you’re not careful. Plus, I’ve seen several guides miss out on intricate details of the process.
So I’ve come up with this step-by-step guide to adjusting your acoustic guitar’s action, with tips from my personal experience as well as from luthiers I’ve talked to. Soon, you’ll be able to play much more comfortably with the right setup on your guitar.
How to Adjust the Action on an Acoustic Guitar?
Measure the current action of your acoustic guitar, and check the neck relief. Start by slowly adjusting the truss rod using an Allen key to make the neck straight again. Then, adjust the bridge saddle to lower/decrease the action. Finally, make sure the nut is level.
But adjusting action by yourself can be frustrating and intimidating, and you don’t wanna risk damage to your guitar. So here’s the whole process step-by-step.
Step-by-Step Solution to Adjust the Action on an Acoustic Guitar
- Acoustic Guitar
- Set of Allen Keys/Hex Wrench
- String Action Gauge/Ruler
- Screwdriver (in case of any screwed-on covers)
1. Measure the action of your acoustic guitar
The first step is to know exactly what your current action is, and the best way to measure this is using a string action gauge (like this Dunlop one that I use personally). These gauges have precise markings that make it super easy to measure action.
Just put the gauge flat against the 12th fret (on top of the fret, not the wood), and check the distance from the top of the fret to the bottom of the string.
Do this for the 6th and 1st strings, and you’ll see that there’s usually a bit of a difference. The 6th string is usually a bit higher than the first string, with a gradual decline in action across each string.
If you don’t want to get a string gauge, you may use a reliable ruler, but it must start at ‘0’ at the bottom of the scale, with no gap (such as a Fritz ruler).
Once you know the action, note it down somewhere (two readings) so you can refer later on.
2. Check the neck relief and its curvature
Now, you also need to check the curvature of the neck. Place a capo or your first finger on the first fret on the 6th string. Next, use your other hand to fret the very last fret of your neck (could be 21, 22, or 24).
While holding these two, look at the 8th to 12th frets and observe the distance (neck relief) between the bottom of the 6th string and the fret. If there’s a lot of gap, your neck is bent down too much (too loose). And if it’s touching the frets, it’s bent upwards (too tight).
The ideal neck relief is just a hair’s width away from the frets. You can use a thin piece of paper or a thin card and slide it under to see if it goes through. You can also buy specific neck relief gauges to get precise readings if you feel the need.
Another thing to do is to hold your guitar upwards and look from the bridge to the nut at a parallel angle, such that you can see the neck as a straight line. If it doesn’t look straight, that’ll also help guide you during the next step.
3. Adjust the truss rod using an Allen key
Now that you know how your neck is curved, it’s time to fix it by adjusting the truss rod. If you find that it’s bent backward, it means it’s too loose, while if it’s bent upwards, it’s too tight.
And remember, turning a screw clockwise (CW) = tightening it, and anticlockwise (ACW) = loosening it. The same applies here. When you tighten the truss rod, the action decreases, and when you loosen it, it increases.
The truss rod may be accessible from both the headstock and the bottom of the fretboard, depending on the model. On acoustics, it’s often hidden underneath the soundhole, where the body meets the neck. You may need to open a truss rod cover if it’s there.
Use an Allen key or a hex wrench of 4mm in length (5/32”) and try to adjust the truss rod by turning CW or ACW as necessary. If that doesn’t fit, try a few other sizes. Turn it in very small steps, about a quarter of a turn, so you don’t overdo it or potentially damage your guitar.
So be careful, and only make small adjustments. Wait a while, then check the action and the neck relief again. This is a slow process as the neck wood takes time to adjust to the new tension and will respond accordingly.
Also, as you adjust, you’ll find your guitar goes out of tune. It’s essential to bring it back in tune at every step because your measurements will not be precise otherwise. Always take readings when the guitar is fully in tune.
Contrary to what many say, you should always refrain from adjusting action from the bridge saddle. Instead, ensure the truss rod is properly set up and the neck is straight (this is a pro tip I learned from an expert luthier).
While most acoustic guitars have truss rods, you may be out of luck if you have a cheap model. In this case, if your neck is severely bent out of shape, it’ll be very hard to get a nice even action across the fretboard. So consider upgrading to a better model instead of wasting time.
4. Adjust the bridge saddle or replace it
Once you’re done adjusting the truss rod, you’re confident that it’s relatively straight, and the neck relief is good, but if you’re still not finding the action comfortable, it’s time to look at the bridge saddle.
Remember, most guitars come with well-set bridge saddles from the factory, so making any adjustments here can often spoil a great setting already. So make sure you’ve done the truss rod step properly before proceeding because this isn’t easily reversible.
For this step, first, take the action readings again to see the current state. And also, measure the height of the saddle from the bridge to the saddle so you know how much to adjust.
You’ll have to remove the strings from the guitar to be able to take out the bridge saddle. Once you’ve removed them, just gently pull the saddle out (sometimes it’s glued in, but be gentle).
Now, take a ruler and measure the full height of the saddle. Compare this to the earlier height you measured, and you can find the difference you need to file off to get a good action. This process is simple but time-consuming and error-prone.
Mark the amount you need to file off using a thin black marker. Now, rub the bottom of the saddle on sandpaper in one direction repeatedly. You want to make sure the filing is perfectly even and stays straight, so go in one direction only.
Remember, do not file the top of the saddle. The top has a natural curve because that’s required for proper intonation of the strings. If you file that off, your intonation will get messed up, and your notes will sound off-tune.
In case the action is too low, and the saddle is too low, too, then you’ll need to buy a new saddle and replace it. If you’re unsure about this and have an expensive guitar you don’t wanna take chances with, I do recommend taking it to a luthier and getting professional work done.
5. Adjust the nut by filing ONLY if necessary
If the above two steps didn’t help, know that your guitar is in seriously bad condition and probably requires professional work to become great again. But if you’re a DIY kinda person, this step is for you.
Be warned, adjusting the nut is the hardest step so far, and messing it up means you’ll need to replace it again.
The nut is often glued to the guitar to stop it from moving around while restringing, but you can file it in place if you prefer.
You can use any filing tool you have, but if you don’t have any, you can also use old strings. For each string slot in the nut, use a piece of an appropriate old string and just rub it back and forth continuously to file it down. Don’t rush it; if you overdo it, your nut is ruined.
You have to do this for all six string slots, one by one. It’s difficult to check how much progress you’ve made until you restring it, so this can take a few tries and a lot of time. And remember, if your action gets too low, you’ll have to replace the nut.
6. Play your guitar and see how it feels now
Now that you’ve done all the steps as needed, you can play your guitar after tuning it back up and see how it feels now. Hopefully, it feels much better, and the proper action makes it easy for you to play your favorite songs and create new ideas.
In case you want a reference for optimal guitar action, try setting it around 1.75mm on the low E, and about 1.5mm on the low E. But this is just a factory setting, and personal preference differs.
Some players prefer a lower action, while others prefer a higher one. Just use your fingers to guide what feels comfortable to you and adjust accordingly.
But remember, if you’re getting any buzzing or blunt notes that don’t ring out properly, your action has been set too low and you’ll have to raise it again.
Check out the article on How to Play the Guitar Faster.
Tips for Getting the Right Action on Your Acoustic Guitar
- Adjust in small steps and double-check your work. Since even small adjustments to the truss rod, bridge, or nut can significantly change action, it’s best to work in small steps and keep measuring the action every time you make a change.
- Use new strings. Sometimes, using old strings can affect action, intonation, and overall feel because they get worn out and corroded, ruining the experience. So do this process with fresh strings and you’ll notice a difference.
- Be mindful when changing string tuning, tension, or gauge. Remember, the truss rod acts opposite to the tension applied by the strings. So, when you change the tuning, or the string gauge, the string tension changes, and the truss rod will react. This is going to affect action and intonation. So when you make any major changes, like shifting from 9s to 12s, you will see a significant action change and may have to make new adjustments.
- Temperature and humidity affect action too. As the seasons change and your local weather changes, the guitar body reacts a lot: the neck, truss rod, and everything changes slightly, which can change the action. This is especially true for certain woods such as wenge or rosewood.
Can the action be lowered on an acoustic guitar?
How high should the action be on an acoustic guitar?
How do I know if my acoustic guitar action is too high?
I hope this guide helped you set the perfect action on your acoustic guitar. Remember to take it slow: this whole process can take a few days of trial and error to get to the perfect setting for your playing style. Once you know that, you’ll be able to make quick adjustments in the future and set up all your guitars with the right action for you.
If this post helped you, feel free to share it with your friends who need to set up their guitars too and send in any suggestions or questions.