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Written by Max Dickinson, Guest Contributor
Imagine just falling into the zone and playing guitar with no effort.
The feeling between the strings and the fretboard are critical to achieving this experience. The height of the strings over the frets dictates how easy it is to fret and how hard you can strum with no buzz. This is termed the “action,” and it goes a long way toward determining how a guitar feels and plays.
Bonding with this element is essential to finding that special place. There are other aspects that affect the feeling, such as the neck profile and width, scale length, number of frets, etc. However, this article will tackle only one aspect of this equation: the action.
Action is a Personal Preference
Everyone’s preference for what they want is different. A luthier can build a guitar to have the action as low as possible without buzzing on the frets–this is the way the builder sets up his or her guitars. Players of different styles may prefer different action as well. Someone who plays harder might want a higher action so that the strings don’t buzz, while a player with a delicate touch may want it lower for easy fretting.
There are three primary places we care about the action: the 1st, 5th and the 12th frets. For various reasons, you may want to raise or lower the action in one of these places.
The parts that control action are the truss rod, nut and bridge saddle.
Where and How to Adjust Action
There are five main ways that the action can be changed at these places. Three of them offer little to no drawbacks, while the last two are more difficult. If you have a desire to adjust your action, there are 5 main ways to do it.
1. Raising or Lowering Action by Adjusting the Truss Rod
The truss rod is a metal bar inside the guitar neck running the length of the fretboard. It’s fixed at two endpoints underneath the fretboard: one at the beginning of the nut, and the other at around the 14th fret. It uses tension to put a forward-bow or backward-bow into the fretboard.
The truss rod can generally be accessed from either inside the sound hole or from the top of the neck where the headstock meets the fretboard. It requires an allen wrench and turning it clockwise or counterclockwise will create a forward-bow or backward-bow in the fretboard–roughly in the middle of the neck, around the area of the 5th fret.
If you’d like higher action in the middle, turn the allen wrench counter-clockwise. If you’d like lower action, turn the allen wrench clockwise. Remember, this only changes the frets around the 5th fret more than at the 1st and 12th. Turning the truss rod too much can introduce fretboard buzz by creating an uneven plane for the strings to sit over.
Here, I’m adjusting the truss rod at the headstock:
Acoustic guitar truss rods are usually accessed through the sound hole, inside the body. This acoustic is one of the few with a headstock-adjustable truss rod.
An important thing to remember about fret buzz is that it might not be the guitar’s fault. Fret buzz can be caused by simply not fretting hard enough, or other issues related to your playing technique. Many of these are covered in the article: 8 Mistakes Guitar Players Make that Cause String Buzz.
Assuming you aren’t the cause, fretboard buzz can happen when the strings are set too low or the heights of the frets are uneven. Fret buzzing problems are common when adjustments are made. Raising the action will always decrease the amount of buzz, while lowering may introduce buzz at certain frets. The truss rod has the effect of both raising and lowering the action. The method we’ll talk about next only raises it.
2. Raising the Action by Shimming the Nut
The nut sits in a channel between the headstock and the fretboard. The strings pass over it which provides a fixed point for the scale length and fretboard to start at. Raising or lowering the nut affects the action primarily in the area of the first 5 frets, but has little effect on the action further up the neck. If you are wanting to change the action higher up the fretboard at… say… the 12th fret or above, then you’ll instead want to adjust the bridge saddle, which we’ll talk about later in this article.
Here, we’ll insert a piece of playing card stock to act as a shim underneath the nut. A handy trick is to use a pencil under the strings to hold them out of the way while you work.
You can also completely remove the strings if they need to be changed anyway
First, take a standard playing card and cut a thin strip about the size of the nut slot. De-tune the guitar and remove the nut*. Place the playing card into the channel then replace it and re-tune. Test out whether this feels right then repeat the step with another shim.
*Note: How to remove the nut
If your guitar’s nut doesn’t come out easily, or at all, it’s probably being held in place by lacquer, glue, or both. This is normal, but it means you need to do a little extra work to safely remove the nut. Don’t try to just brute-force it out. The video below shows you how to remove a stubborn nut, but if you’re not 100% comfortable doing this, take the guitar to your local repair shop instead.
Playing cards are about 0.1 inches thick–the perfect amount to raise the nut. Here, I’ve left excess hanging out for demonstration, but you’d actually trim the card to the proper width first.
3. Lowering the Action by Sanding the nut
This is the opposite of method two. Instead of raising the nut, we’re going to lower it. This isn’t recommended for the less adventurous because it’s possible to sand off too much material and create problems.
The process is to sand the bottom side of the nut on a piece of sandpaper, lowering the overall height of the nut. This is a tedious process as the strings must be removed and reattached multiple times to test out the nut height.
Beware, sanding the nut too far will make it too low and cause fretboard buzz.
Sand the flat underside of the nut to lower the action of all 6 strings equally and preserve the shape of the top and the string slots. I like to use ProSand 120-grit sandpaper for this.
The amount to sand away is a judgment call, based on how high the action is and how much lower you want it to be. If the nut is altered too much it might be necessary to head to a repair shop for a new nut. Or, you might have to turn right back around and use method #2 to shim it back up.
4. Raising the Action by Shimming the Bridge Saddle
Similar to what we did in method #2, we’ll now use the same method of shimming to raise the bridge saddle. The saddle is a solid piece of bone or plastic that sits securely within the guitar’s bridge, which is mounted to the belly of the guitar and holds the endpoint of the strings. By changing the saddle’s height, the action will be changed more at the 12the fret than the 1st. This is the best method to use to raise the action further up the fretboard–from about the 12th fret and above.
The parts needed are a strip of playing card and your guitar’s bridge saddle.
First, cut off a piece of playing card that is approximately the same width and length as the slot your bridge saddle fits into. You’ll need to make it slightly smaller than the slot so that it’ll lie flat against the bottom of the slot.
Cut a piece of playing card so that it lies flat beneath the bridge saddle.
Once you feel you’ve got a good fit, where the card shim lies flat in the channel, replace your bridge saddle on top of it and restring your guitar. DO NOT GLUE. An acoustic guitar’s bridge saddle should never be glued in place.
5. Lowering Action by Sanding the Bridge Saddle
Like method #3, this one involves sanding the saddle to the desired height. It has similar advantages and disadvantages to sanding the nut. However, there’s an additional factor here that we have to pay attention to: the saddle must be a certain height to prevent the strings from buzzing.
Sand the flat underside of the bridge saddle to lower the action of all 6 strings equally and preserve the shape of the top. I like to use ProSand 120-grit sandpaper for this.
The nice thing about these methods is they can be used together. For example, if you sand away too much of the nut or saddle and make it too low, then a shim can be added, and vice-versa. However, there’s a limit to the number of shims you can use before the saddle will start to rock back and forth. It isn’t a good idea to use more than one or two shims as the nut or saddle becomes less stable and might move around while playing.
These 5 methods of adjusting the truss rod, nut, and bridge saddle give you some ability to change your guitar’s action on your own. Changing the action even a small amount will make a big difference in how the guitar plays. A conservative approach is to make a change and then live with it for a few days.
Sanding the nut and saddle can be risky procedures that should be performed with caution. Go slowly while doing them and check your progress often. Action is one of the most important aspects of your guitar’s playability, so consider trying one of these methods if you feel that yours needs some improvement.
Want More Info on Acoustic Guitar Setups?
If you’d like a step-by-step guide on how to set up your acoustic guitar, check out the guide: Sketchy Setups #7: Acoustic Guitars.
Written by Max Dickinson
Max Dickinson is both the outreach coordinator and a luthier for the boutique lutherie: Portland Guitar. Portland Guitar specializes in high quality yet affordable acoustic and acoustic-electric guitars whose features include modern designs such as wave patterned marquetry, perfect intonation bridges and an action adjustable neck. If you’re interested in a luthier’s voice on guitar topics check out the website.
Bobby Davis is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.
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