The action of an acoustic guitar refers to the height of the strings as they sit above the fretboard. It is also a term that can be used to describe how acoustic guitars feel and how playable the guitar strings are. We typically measure a guitar string’s height at the 12th fret which is a center measurement as a reference to how high the strings are. You can also measure action from the first fret.
You may have heard people say that a guitar is high action. What they mean here is that the strings are sitting too high off the fretboard. If a guitar has low action it will be the opposite of this.
Now that you know what action is we need to discover why it’s so important. It’s actually probably the most important part of setting up your guitar properly. Having proper action on your acoustic guitar will control how comfortable and playable the guitar is. It also helps the instrument stay in tune and maintain its intonation.
An acoustic guitar has different action compared to an electric guitar because the strings need more room to vibrate. Acoustic strings tend to be thicker than electric ones too. An acoustic guitar needs to have a higher action to prevent fret buzz. The higher the action is, the more difficult the instrument will be to play. If you are finding that your guitar is uncomfortable to play then it could be that you need to adjust the action.
You’re probably wondering on how earth you can do this after reading all of this information. The action on your guitar will all depend on your playing style and it’s down to pure preference. Lower action will mean you can play faster without having to compromise on volume. In this guide, we are going to show you how to set your action to the industry standard setting. After that, you can fine-tune the action of your guitar so that it fits with your personal playing style.
Tools to Help Lower Guitar Action
To help you make the right adjustments to your guitar and lower the action you will need some tools. Below we’ve given you a few examples that are available online.
This basic guitar setup kit comes with everything you need to check how straight your guitar neck is which is important when straightening the truss rods of an acoustic guitar. There are also some gauges that will help you to measure the string action height along with the string and fretboard radius. If you want to completely set up acoustic guitars then this is the right kit to go for.
During your setup you want to make sure you are as accurate as possible with a low action to prevent any fret buzz. To do this you will need a string gauge height ruler. The ruler is also included in the full kit above but is sold separately if you don’t want the extras. It will also help you to measure all the key measurements such as your nut slot too.
You won’t be able to lower your strings evenly without first measuring your fretboard radius. The string radius should match up with the fretboard so that they are evenly spaced above the frets.
To lower the action of an acoustic guitar properly you have to adjust the truss rod and make sure that the guitar neck is straight at the same time. This set of wrenches will fit most truss rod nuts so you can adjust them easily no matter what type of guitar you have. They are also suitable for use with electric guitars.
When you want to straighten the neck of your guitar then this is a really useful tool to have. You will use these to measure the distance between the top of the fret and the string. They also have other uses for guitar setup and repairs.
To be able to lower the action of your guitar at the nut then you will need the appropriate nut notching files. These files have been designed accurately so that the measure is the right size notch for each of the strings. You will need three different sizes of file for a standard guitar nut.
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This tool may not be necessary but are handy to have just in case. These are a small nut file that files down and then levels out the nut slot. It has been designed so that it fits into the nut slot and evenly files down the seat so that your nut will sit flush in there.
Sanding down a guitar saddle takes a lot of precision and having an accurate set of sharp files will help you get the right edge.
In some cases, the saddle won’t be the problem. The saddle slot can be uneven or it can contain debris from a bad repair job. Having a saddle slot file makes it a lot easier to clean out the slot so that your saddle fits perfectly on your guitar.
What is the Cause of High Action on Acoustic Guitar?
Before we jump into adjusting your guitar’s action you should know what is causing the action of your instrument to change and the importance of doing a reset. Without understanding what could be affecting your guitar it will be harder to diagnose the core problem and then set the action properly. Here are some things that can contribute to your guitar having poor action.
Humidity and Temperature
Guitar’s are made from wood and this is a material that can be highly affected by humidity and temperature. An acoustic guitar is particularly susceptible to changes in humidity levels. If your instrument experiences drastic and quick changes to either of these elements it can change the overall shape of the wood. The same goes for electric guitars.
When humidity is in the air the wood of the guitar soaks up the water, causing it to expand and swell. If there is a lack of humidity then the opposite happens and the wood will shrink.
A big fluctuation in temperature can have the same effects as humidity. Both of these elements could cause the neck to bow or, in the worst-case scenario, even warp.
Changes to String Tension
Every guitar string puts a lot of tension onto the neck of the instrument. Changing your string tension to high or low can cause the back to bow or relief in the neck.
Regularly playing your guitar means there will be signs of use. A lot of playing will eventually wear away the saddle pieces and the nuts which causes problems with the action. Both of these things are very common with acoustic guitars and not taking care of them will lead to even more action problems.
Adjusting the Action on an Acoustic Guitar
Adjusting the action on your guitar will be a lot more of a process than just turning a wrench. It all depends on what is wrong with the instrument to what you will need to adjust. In the simplest case, you should be able to fix the cause of high and low action on the guitar by adjusting the truss rod. As long as their is no damage to the guitar then truss rod adjustments for action problems can be simple.
Generally the adjustment of the action will go through three steps which apply to electric guitar too. The truss rod, nut and bridge are where you have to adjust and make changes. Your instrument may play well enough if you only adjust the guitar’s truss rod but setting the action of all three will improve it much more. The following adjustments have to be done in order because one change will affect the next.
Adjusting the Truss Rod
When making adjustments to the truss rod you have to be incredibly careful. If you overtighten truss rods it can cause a lot of other problems for you such as snapping the rod, twisting the neck or warping the fretboard. These problems will mean you have to pay out for expensive repairs so be careful to not overtighten in the first place.
Before you follow the steps below we recommend that you loosen your truss rod one full turn and then measure the neck with your ruler. If the truss rod is already tightened and the neck has relief then you can break something by taking it over its limits.
You can adjust your truss rod through two separate access points – either through the sound hole or the headstock. We have detailed both methods below.
Through the Sound Hole
Most acoustic guitars have truss rods that are accessible in the heel of the neck so there is no need for a truss rod cover which can clutter up the headstock. If you have the right tools you should be able to access your adjustable truss rod in this way. You will need a nut driver or an allen wrench to do so. An extra long one will work better that has a 45 degree angle bend so that you can turn it without having to stick your hand inside the guitar.
Check the neck of the guitar for relief or back bow and then loosen the strings. Use your tool to adjust the tod, only turning it 1/8 of a turn at a time. Once you have made that turn, return the guitar. Check the string tension on the neck and measure the relief. Repeat these steps as much as you need to until the neck is completely straight.
In the Headstock
You may have an instrument that allows you access to the truss rod through the headstock. This will be much easier than going through the sound hole.
Tune your guitar to pitch to create tension on the neck. Remove the cover and lubricate the truss rod nut. Turn the screw 1/8 of a turn each time then retune after each turn. Repeat these steps until the neck is straight and then replace the cover.
Adjusting the Nut
The first thing to do here is to bring your guitar up to pitch if you haven’t done so already. The next thing you will want to do is measure the action of the string above the fret so you can get an idea of how much you will need to file down the nut. Place your feeler gauges at the top of the first fret and check the highest of the lower E string.
Keep doing this with larger feeler gauges until the string starts to move which means the gauge is too big to fit into the gap. Choose the gauge that is the largest without moving the string. That is the correct distance between your string and the fret.
Loosen the tension on your sixth string until you are able to pull the string out of the nut notch. Be careful not to damage the nut when doing this because pulling on them can cause the outer edge of the nut to snap. You should loosen the string enough so that it can be easily pulled out of the notch.
Now you will need to get your nut file, typically a 0.60″ file for this sort of job. Take the correct file and place it in the notch. File at the same angle as the headstock, going towards the headstock. Never file the notches flat otherwise the instrument will sound like a sitar.
You want to file the notches at an angle so that there is a single point where your string can rest. File away the notches a very small amount each time so that you don’t get rid of too much at once. Replace the string, tune it up and then measure it to see if the nut needs filing down any more. Your standard measurement at the first fret is .030 inches so carry on filing until your string reaches that height. Once you have done this on the first fret then repeat it for the rest of the strings, making sure to use the correct size file and measurement for each nut.
Adjusting the Bridge
The last part in adjusting the action of your guitar is to change the bridge. There should be an acoustic guitar saddle which you will have to remove, sand down and then replace.
Before you carry out this repair you will need to measure the guitar action. Making saddle adjustments take a long time so make sure this step is absolutely necessary before jumping in. To measure the action of the guitar bridge, take your ruler and measure what the distance is between the 12th fret and bottom of the first and sixth strings. Typically the action will be at 2/32″ for the first string and 3/32″ for the sixth. Lower the action to this point and see how the middle strings feel at this string height. If you string height is coming in higher than this, move on to the next step.
When you look at the bridge saddle you will notice that it is wedged in so that it keeps the strings in place. To get the acoustic guitar saddle off you’re going to have to remove the strings. Detune your guitar until every string is floppy but do not remove them from the tuners. You want to provide enough clearance to pull the saddle out of the bridge with your fingers. If you find that the saddle is tight then you may want to use a pair of pliers, but be careful not to scratch the saddle in the process. You may notice that you only have to remove the bottom three strings before you can easily slide the bridge out. This is completely fine and means there is less work for you to do later on.
Once the saddle has been removed you can sand it down, keeping it as even as possible. A lot of the tone comes from the bridge saddle and having an uneven one will affect your tone. Don’t take too much off either, only sanding down a small amount at a time and then checking to see if the required results have happened. The best method is to stick some sand paper down to an even surface such as a bench or a piece of wood. Get a pencil and make a line around the edge of the saddle. Run the saddle across the paper until the pencil line has disappeared. It will all depend on how much the saddle needs lowering as to how many times you do this.
When the saddle has been sanded down you can put it back into the bridge slot. Replace your strings and retune your guitar. Check the overall action like you have been doing all along. If you feel that the bridge saddle needs further adjustments you can follow the same steps again.
Guitar action is completely up to your personal preference. Every guitar player likes their instrument to be set up in a different way. The guide we have given you above is using the industry standard measurements and settings which your instrument should have come with. Doing those steps will get you into the general area where the instrument is comfortable to play. You can then go on to fine tune your guitar and get it set up exactly as you like it. Now that you have got your guitar action god and low it’s time to play it. Have fun!
Can you adjust the action on an acoustic guitar?
Yes, you can. You will need to make changes to your guitar in order to adjust the action. You will need to make a guitar truss rod adjustment and then make further adjustments at the nut and saddle. You may only have to adjust one of these things or all three.
How do you fix high action on an acoustic guitar?
You will normally be able to do this by adjusting the saddle but you can use the guide above to lower the action on your acoustic guitar.
Which way do you turn the truss rod to lower action?
Lowering the action of your acoustic guitar means you will be reducing the amount of relief which will also make the guitar easier to play. To do this you have to tighten the truss rod which would involve turning the truss rod nut in a clockwise direction.
How high should my action be on acoustic guitar?
The typical amount of action on an acoustic guitar should be around 5/64″ on your high E string and 7/64″ on the low E string.