ACOUSTIC GUITAR SET UP
By Steve Carmody
Let's begin by defining our terms. In the world of guitar repair,
the adjustment of the string height on a guitar for optimal
playability is called a "set-up". There are three steps in the
basic set-up of any guitar. They must be followed, in the order
I present them, to achieve optimum performance. In a basic set
up we are assuming that structural or fret wear issues either do
not exist (as, ideally, in most new guitars) or have already been
STEP 1 - CHECK AND ADJUST NECK
The first step in any guitar set-up is to check and adjust
the curve of the neck. We refer to this curvature as the "neck
Most modern guitars have an adjustable neck tension rod installed
under the fretboard. Martin guitars made prior to 1985 do not have
this feature, and affecting the curve of the neck in these
guitars can only be done by a skilled guitar repair technician.
For the purpose of this article we are only addressing those
guitars with adjustable tension rods.
Here is an easy way to check the curve of the fretboard in the
playing area: With the guitar tuned to pitch, hold the guitar
in the playing position and depress the low E string at the
14th fret with the index finger of one hand. While keeping
the string down on the 14th fret, depress the same string at
the first fret with the index finger of your other hand. The
bottom of the E string becomes a straight edge. Sight the area
under the string around the 5th to 7th frets. If the neck is
correctly tensioned there should be a hair breadth of space
in the middle of this area between the bottom of the string and
the top of the 6th or 7th frets.This gap gradually diminishes
to zero as the string reaches the 1st and 14th frets. (I gauge
this by eye, but if you were to measure this space it should be
no more than 1/64th inch, maximum).You can evaluate the
fretboard under each of the strings using this method. It is not
unusual to get slightly different readings from string to
string, though ideally they are all more or less the same.
On most guitars you can get away with a dead flat fretboard,
but a back-bowed neck will surely cause fret rattle. For this
reason, most repair techs will adjust for a slight forward bow.
Most guitar truss rods enable a lifting of the neck in the
center of the playing area by tightening, or turning clockwise,
the truss rod nut. Conversely, loosening the nut allows more
flex in this area. "Double action" truss rods actually push
in either direction depending on which way the nut is turned.
NOTE: Prerequisite to any neck adjustment, it must be confirmed
that the frets are in good condition, seated firmly, and level.
The most misunderstood aspect of guitar set up is the neck
adjustment. There is only one proper neck setting parameter
- dead flat to slightly forward bowed. Too much forward bow
causes excess height in the middle ( generally between frets 5 -9)
of the playing area on a guitar with 14 frets to the body,
and can also cause what's called "string rattle" or "fret buzz"
from the middle frets up the neck. A back bow can cause fret buzz
in the first five frets or so.
All too often, a guitar with high or low action has the neck
adjusted by a well meaning person - to "adjust" the action -
without paying any attention to the string height at the nut
or the saddle. While it is true that adjusting the neck truss
rod can affect the action, and sometimes this adjustment is all
that is necessary, there is only one correct parameter for the
neck setting.If the neck is flat to slightly forward bowed,
you have to look elsewhere to affect the string height - the
nut or the saddle.
NOTE: Adjusting the neck may need to be done periodically even
after a basic set-up has been performed. The exposed wood of
the fretboard absorbs and releases moisture as the relative
humidity in the environment it is living in changes.
45 - 50 % relative humidity is considered ideal for guitars
( and people). A guitar neck which is dry tends to bow
forward, raising the string height above the middle frets.
Conversely, a neck which has been over humidified
(for example, if the guitar is outside on a humid summer day),
may tend to back bow. Ideally, a guitar is not subjected to
these extremes of humidity, but in the real world it happens.
Nevertheless, the setting of the neck is only done to place
it within the aforementioned "correct parameter" - flat to
slightly forward bowed - not to adjust the action.
STEP 2 - CHECK AND ADJUST NUT SLOT HEIGHT
Once the neck curvature is set, the string height at the nut is
checked. With a correct neck curvature, there is one optimal
setting for each nut slot. In theory each nut-slot should sit
no higher than the preceding fret. Some builders use a "zero"
fret, and a nut sits behind the "zero" fret only to guide
each string on its path to the tuning peg. On most guitars
the string is both guided and height adjusted at the nut.
A string which sits too high at the nut can either feel
too hard to push down, or even play sharp. At a minimum the string
height should be lowered until it intones correctly, and
ideally it should be lowered till it also feels comfortable
If the height of the 1st fret above the fret board is known,
a metal gauge ( such as an auto mechanics "feeler" gauge - a
strip of metal of a known thickness) of the same height as
the existing frets , laid in front of the nut can be used as
a guide. With a file of appropriate width, the nut slot is
lowered until the file touches the gauge.
Without a gauge, the setting is done by eye. To calculate
the appropriate height, depress the string in question between
the second and third frets with your middle finger and
sight back to the first fret. If the string rises above
the first fret more than the thickness of a piece of paper
(just a hair) the slot should be lowered until just this
amount of gap is apparent. While holding the string down
between the second and third frets with the middle finger,
the index finger can be used to depress the string at the
first fret to discern this gap.
If the string sits on the first fret, while the position between
the second and third frets is being held down, the slot is
probably too low and the string will probably buzz if plucked
STEP 3 - CHECK AND ADJUST SADDLE HEIGHT
Once the neck curvature is correct, and the height at the nut
is set, ( and never before these steps are taken) the height of
the bridge saddle can be set. This adjustment is made by filing
or sanding the saddle piece to give the desired height for each
string. There is no "correct" height of the strings over the
fretboard. Playing style determines the appropriate setting.
A light finger-stylist can get away with very low action,
whereas a blue grass flat-picker will prefer it quite a bit
higher. My "shop setup" for acoustic guitar is generally
acceptable for both moderate flat-picking and finger-picking,
but favoring neither. As measured at the 12th fret I look
for 3/32" between the top of the 12th fret and the bottom
of the low E, A, D, &G strings, 2.5/32" at the B and 2/32"
at the high E string. Bluegrass players would find this too
low, pure finger-pickers would want this dropped a hair.
Variables besides style also include the size of the players
hands, the right hand picking attack of the player,
and their level of experience. New players often want a
lower string height to make it easier on their
undeveloped fingers, whereas more experienced players may
prefer a slightly higher string height.
IMPORTANT NOTE : Even assuming that the mechanical elements of
the guitar are correct - the frets are firmly seated and level,
the neck is correctly adjusted to near flat and under tension
from the truss rod reinforcement, the string slots at the nut
are at an acceptable height, the box of the guitar is stable
( no loose bracing), bridge and saddle are stable and correctly
fitted - there is still no guarantee that a guitar can be made
not to buzz at a given string height over the frets,
( I suppose you could set the strings extremely high over
the fretboard by raising the saddle way up). Playing style
is the key. Ultimately, how you pluck/drive/attack the strings
is the biggest determining factor in whether a given guitar
will buzz ( once again assuming correct settings of the neck
and nut slots, and level frets). The fact that a particular
guitar can be made to buzz reflects nothing about the quality
of the guitar or of the set up. If I drive my car such that the
tachometer is "redlining" ( reflecting overly high engine
rpm's) for a long enough period of time, the engine will likely
fail. But this is not a reflection of the quality of the
engine or it's adjustment, it is a reflection of my driving
style. And remember - a quality guitar can be adjusted to fit
many playing styles. Also, sometimes, for a given string height,
setting a guitar up for slightly heavier strings can make the
difference. And when all else fails, if you are getting string
rattle and can't abide by it, just keep raising the string height
at the saddle. Eventually, it will go away. Whether the guitar
will still be comfortable to play is another story. Ultimately,
as with many things in life, compromises must sometimes be
Which reminds me of the time renowned Telecaster playing
guitar-genius Bill Kirchen came to have his instrument
refretted at my shop. This guy can really get around on
a guitar, and he uses every note. I looked at his guitar,
aghast. Every fret was worn and pitted to what had finally
reached ( beyond) a critical stage. When I asked why he hadn't
had the refret done five years ago ( when it surely would
have been justified) he just said - "Well I just kept working
around all the wear" Just goes to show you that ones attitude
has a lot to do with what is or is not acceptable in a
That's it. Three basic steps in the set-up of an acoustic
guitar. They must be done in this order: neck then nut then
saddle. If the neck curvature is off, it won't help to adjust
the saddle or the nut slot heights. If the strings are high
at the nut, lowering the saddle will never get you where you
want to be. Neck, nut, saddle. Neck, nut, saddle. Neck, nut,
Steve Carmody is an independant guitar repairman and luthier with a shop in Silver Spring, Md.
He has been doing guitar repair and restoration full-time since 1990.
Questions about this article or anything else related to guitar repair?
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