How To Adjust The Action On An Acoustic Guitar

acoustic guitar action adjustment
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So you’ve been playing on your favorite acoustic guitar for a few years now and it’s starting to develop a fret buzz or rattle. Or maybe you’ve noticed you’re working harder to finger notes and chords.

If it seems your strings are too high off the fretboard, or if they’re touching one or more of the fret markers, you more than likely need to adjust your guitar’s action.

What Is Guitar Action?

The height of a guitar’s strings above the fretboard is referred to as a guitar’s “action.” When measuring guitar action, a guitar tech will usually measure the string height at the first and twelfth frets.

Adjusting a guitar’s action is among the most crucial components of a guitar setup. The action affects a guitar’s sound and playability and also protects the instrument from undue stress, helps maintain intonation, and helps keep the guitar in tune.

How High Should The Action Be On An Acoustic Guitar?

The action on an acoustic guitar, or any guitar for that matter, needs to be low enough to be comfortable without actually rubbing against the guitar’s fretboard. An acoustic guitar will need a higher action than an electric guitar; this is true for a few reasons.

Acoustic guitar strings need more space to vibrate than electric guitar strings. On an electric guitar, the pickups do a lot of the heavy lifting regarding sound production. Acoustic guitars, on the other hand, rely solely on body shape and string vibration to amplify sound.

Another reason acoustic guitars require higher actions than electrics is string size. Acoustic guitar strings are thicker than electric strings and require more space to do their jobs.

The average acoustic guitar action, measured at the twelfth fret, is roughly three millimeters (3.0mm) from the fretboard to the low E string and about two millimeters (2.0mm) from the fretboard to the high E string.

What Causes High Action?

In order to understand guitar action, it helps to know the factors that affect it. A guitar’s action can be affected, over time, by several things.

Temperature And Humidity

Acoustic guitars are extremely susceptible to heat and humidity. If you’ve ever visited the acoustic guitar room at Guitar Center, a sort of six-string humidor, you know how seriously professionals take these environmental factors.

When exposed to high humidity, acoustic guitars absorb moisture, causing their wood to swell and expand. The opposite is true in overly-dry conditions; the guitar will lose moisture, leaving the wood brittle and dry.

Sudden, drastic changes in temperature or humidity can wreak havoc on your guitar’s action, but even small changes, over time, will cause your guitar’s action to change.

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The right temperature and perfect humidity level are required to keep your instrument in a good shape for a very long time. So check out some best ways to humidify a guitar.

Changes In String Tension

Under normal circumstances, strings place a considerable amount of stress on your guitar’s neck. Over time, this tension alone can affect your guitar’s action.

At some point, though, many of us experiment with different gauge strings. It may be that we’re emulating a favorite guitarist who uses a different string thickness, or perhaps a drop tuning we’re experimenting with necessitates a thicker gauge.

Whatever the reason, it’s important to know that changing the gauge of your strings can cause too much relief or a back bow in your guitar’s neck.

Normal Use (And Abuse)

Though we take it for granted, our guitars are literally always under stress. Everyday wear and years of playing take their toll on guitars, eventually wearing at the saddle and nut. Once these crucial components are sufficiently compromised, you’ll find your guitar’s action is too.

How To Lower The Action On An Acoustic Guitar

Depending on why your guitar’s action has gone out of whack, it may need to be adjusted in more than one place. Often, adjusting your guitar’s truss rod is all it will take to fix a high or low action. Sometimes, though, it takes more; you may need to adjust the nut and bridge of your guitar too.

What You’ll Need

In order to properly adjust the action on your acoustic guitar, there are a few tools you’ll need before you begin.

String Action Gauge Height Ruler

String Action Ruler Gauge,Guitar Repairing Tool for Luthier,Fit for Guitar,Ukulele,Bass,Banjo,Mandolin

A string height ruler is indispensable when setting up a guitar. Part three-inch steel rule and part wide-scale depth-finder, string height rulers are right and left-handed. You can measure nut slot, action, and a host of other measurements with this versatile tool.

String And Fretboard Radius Gauge

Lowering your guitar’s action means more than lowering its strings; it means lowering its strings evenly. To do this, you’ll need a set of string and fretboard radius gauges. These will help you match your string radius to your fretboard radius so that all six strings are the same height above the fretboard.

Truss Rod Wrenches

If you want to make truss rod adjustments to your acoustic guitar, you’ll likely need a set of truss rod wrenches. These wrenches come in sets of three that should fit most any truss rod.

Adjusting The Truss Rod

Lowering the action on a guitar

Most modern acoustic guitars have threaded metal rods running the length of their necks. These “truss rods” provide added support to the guitar’s neck and help keep it straight. When strengthened or loosened, the truss rod will bow or flatten your guitar’s neck. Often, an adjustment to the truss rod is all it will take to bring your acoustic guitar’s action back in line.

Truss rods are a relatively recent innovation, and you won’t find them on older acoustic guitars. My Takamine dreadnaught, for example, doesn’t have a truss rod, and Martin guitars didn’t begin incorporating truss rods until the mid-1980s. If your acoustic is without a truss rod, move on to the next step, adjusting your guitar’s action at the nut.

There are two types of truss rods, single and dual action. Single action truss rods only bend the neck in one direction; relieving tension on a single action rod relieves pressure on the neck, allowing it to move in the other direction.

Dual action truss rods, on the other hand, bend the guitar neck forward or backward.

Depending on your acoustic guitar, you’ll be able to access the truss rod at the headstock, or from within the body. If the truss rod is accessible from within the body, you’ll need a truss rod wrench with a forty-five-degree bend so you won’t damage your guitar trying to get your hand inside the soundhole.

If your guitar’s truss rod access is via the headstock, you’ll have to remove the truss rod cover to expose the truss rod adjustment screw.

Also depending on the brand and model of your guitar, the truss rod adjustments may require a truss rod wrench with an Allen wrench, nut driver, or standard screwdriver tip.

Before we go any further, a word of caution: OVERTIGHTENING YOUR GUITAR’S TRUSS ROD CAN CAUSE COSTLY OR EVEN CATASTROPHIC DAMAGE.

Placing too much tension on your acoustic guitar’s neck can warp the fretboard, twist the neck, or even snap the truss rod. Remember to only turn your truss rod screw 1/8 turn at a time to avoid overstressing your guitar.

To adjust the truss rod on your acoustic guitar, use the following steps:

Tune Your Guitar

The first step in adjusting your acoustic guitar’s action is to bring your guitar to tune. If your instrument isn’t in tune, you won’t be able to accurately measure the flatness of your guitar’s neck, which is step two.

Check Neck Straightness/Measure Action

With a ruler or straight edge, check to see if your guitar’s neck is bowed or bent. If so, this can usually be fixed by adjusting the truss rod.

Next, use a guitar action gauge to measure your guitar’s action. To get an accurate measurement, remember to get readings at the first and twelfth frets. Record your findings and move to step three, turning the truss rod.

Turn The Truss Rod 1/8 Of A Turn

Now that you’ve tuned and measured, turn the truss rod adjustment screw 1/8 of a full turn. Again, don’t ever make more of an adjustment than that without first completing the last step.

Retune And Remeasure

A small turn on a truss rod screw can go a long way, and now’s the time to see if A) your initial turn has affected your guitar’s action, and B) if it has, is it moving in the desired direction?

Before you can accurately measure the effects of your first 1/8 turn, you’ll need to apply the proper string tension, and that means retuning your guitar. Now, it’s just a matter of measuring your action and repeating the entire process, slowly and carefully, until you get the setup you desire.

Adjusting Action At the Nut

How to adjust the action on an acoustic guitar

If adjusting the truss rod hasn’t fixed your action issues, or if your acoustic guitar doesn’t have a truss rod, the next thing to consider is your guitar’s nut.

Positioned just before the first fret, the nut is a thin bar of plastic or other material upon which the strings rest. The nut has six grooves to accommodate each string, holding them apart at the proper distance.

You’ll need to get a set of feeler gauges in order to measure your guitar’s action at the nut. Measure at the first fret, from the bottom of the string to the fretboard. If you don’t read close to the industry standard of .060 inches, it likely means your nut needs to be filed down.

To properly file the grooves in your guitar’s nut, you’ll need a set of nut groove files. Each file (or edge, in the case of double-edged files) corresponds to the diameter of each guitar string, so using the wrong sized file can yield disastrous results.

To adjust the action at the nut, use the following steps:

Tune Your Guitar

As is the case with any action adjustment, the first step is making sure your guitar is in tune; only then will you be able to make an accurate measurement.

Measure Action At The Nut

Using feeler gauges, measure your guitar’s action right at the nut. The standard measurement at this placement for an acoustic guitar should be about .030 inches. If your measurement is significantly higher than this, move on to the next step, filing the grooves in the nut.

Filing The Grooves

Now, loosen one string so you can pop it out of its slot on the nut. Place the appropriate file (or edge) in the slot at the same angle as your guitar’s headstock.

This is important because you want to file at an angle, thus creating a single point on which your string will sit. You don’t want the slots in the nut to be filed flat, or it will adversely affect the instrument’s sound.

File only a very little at a time, so you don’t wind up going too deep and ruining the nut. Also, be careful to protect your guitar as you file the nut.

After each filing, replace and retune the string. Measure the action of the string at the nut, and, if necessary, repeat the process. Once you’ve got the desired .030 inches, or thereabouts, move on to the next string and repeat.

Adjusting Action At The Bridge

Attending to your guitar’s truss rod and filing its nut is usually more than enough to bring the action on your beloved instrument back to fighting trim. If, after adjusting these two components, you still have issues, then you’ll need to check your guitar’s action at the bridge.

Lower action on acoustic guitar

Some acoustic guitars have bridges that can be adjusted with Allen wrenches, and some employ shims beneath the saddle to manipulate the guitar’s action. To adjust the action on most acoustic guitars, you’ll need to remove and shave down its saddle.

When sanding your guitar’s saddle, you want to be sure and measure how much you want to remove. Also, you need to be sure and sand the saddle evenly; an uneven saddle will cause you a world of technical issues.

The saddle should be held firmly, ideally in a vise, as you sand. An orbital sander works great for this job when using a vise, but sanding by hand is just as effective if a bit more time-consuming.

If you can use a vise, place the acoustic guitar saddle so that only the portion you want to remove is accessible; this way, the jaws of the vice itself will act as a guard to keep you from accidentally removing too much.

Once you’re done sanding, replace your guitar’s saddle, restring and retune. Measure your guitar’s action at the twelfth fret and repeat the process until your action is where you want it.

Oh, and don’t panic if you do sand unevenly or too far down on your saddle; they are relatively inexpensive and easy to acquire.

If you are still in doubt, check out Gibson Master Luthier, Jim DeCola’s DIY bridge adjuster video:

How To Raise The Action On an Acoustic Guitar

To raise the action on your acoustic guitar, follow the same steps as when lowering the action but turn the truss adjustment the other way. If your guitar’s action is too low because the nut or saddle has been worn down, they will need to be replaced.

Frequently Asked Questions

What Happens If Your Guitar Action Is Too Low?

Lowering the action on your guitar will improve its playability until it’s lowered too much. If the action on your acoustic guitar is too low, you’ll run into problems, the most obvious of which is buzzing. Rather than producing natural-sounding notes, strings that lay too close to the fretboard will buzz and rattle.

An action that’s too low also diminishes the sustain of notes played. In other words, the note will sound out far more quickly than usual. Another potential problem caused by a guitar’s action being too low is “fretting out.”

Fretting out is when a note produces no sound when played and is usually caused by interference from another fret on the affected string.

How Do I Know If My Guitar Action Is Too High Or Too Low?

How high or low the action should be on an acoustic guitar is generally a matter of personal preference. That said, sometimes the action on a guitar is so high or low that it impedes playability. As mentioned earlier, when the action on an acoustic guitar is too low, you’re likely to experience buzzing when you sound the strings.

When the action on an acoustic guitar is too high, the instrument becomes increasingly difficult to play, as more force is required to hold down each note. If suddenly you’re struggling to hold down notes and chords, your guitar’s action is likely too high.

Does A Lower Action Make A Guitar Easier To Play?

The short answer to this question is yes. Guitars with lower actions are generally easier to play, as it takes less force to finger each note or chord. For certain styles of guitar playing, such as slide guitar, a bit of a higher action can be beneficial.

Does Higher Action Give A Better Tone?

As a general rule, acoustic guitars with higher actions produce more resonant, full-sounding tones. This is because the guitar strings have more room to vibrate. If a guitar’s action is too high, the amount of pressure needed to finger a note can produce excess string tension, which can cause the note to go out of tune.

How Much Does It Cost To Lower The Action On An Acoustic Guitar?

Adjusting the action on a guitar isn’t overly difficult, but it can be daunting the first time you try. And why not? You’re performing a relatively delicate operation on a beloved friend, after all. So don’t panic or get discouraged if you run into difficulty; you can always turn to the professionals.

Having your guitar’s action adjusted by a professional guitar tech is a fast and relatively inexpensive process. On average, a setup on an acoustic guitar should cost between fifty to sixty dollars; if your guitar needs some extra attention, it could cost as much as one hundred dollars.

Why Do Cheap Guitars Have High Action?

Many inexpensive acoustic guitars have actions higher than the average, which can make them difficult to play. This is the case for two reasons. First, it takes extra time to fine-tune the action on a new guitar. To cut production costs, some manufacturers of inexpensive guitars choose to pass the cost of this value-adding process on to the consumer.

Often, smaller guitar companies have lower quality control standards than the big players; this is another reason cheap acoustic guitars sometimes have high actions.

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