Acoustic Guitar Adjustments
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By Harry Fleishman
Any useful discussion of acoustic guitar setup should include a close
look at the truss rod, the nut, and the saddle. Each of these parts
contributes significantly to the way your guitar plays, and each can
develop its own set of problems. You can make many of the adjustments
I'll describe yourself if you're careful and use a little common sense.
If you have a serious problem with your guitar, however, you should not
hesitate to take it to a reputable luthier.
The action, or string height above the fretboard, is one of the first
things to check when your guitar isn't playing quite right. Many
musicians mistakenly use the truss rod to adjust the action; they
tighten it, thinking that by arching the neck back they will lower the
strings toward the fingerboard. A tightened truss rod will lower
the action, but it often leads to a neck that buzzes severely. The
misguided home repair guy then starts filing away at his frets until the
neck is a basket case.
The truss rod's job is to straighten the neck and compensate for the
upward pull of the strings. It should not be used to adjust the action
of the neck. If the action is too high at the nut, it is the nut that
needs adjustment. If the action is too high in the middle and upper
positions, it is usually the saddle that needs to be lowered. Let's take
a look at the truss rod first. Once it is properly adjusted, we can move
on to the nut and the saddle.
THE TRUSS ROD
Adjusting the neck using the truss rod is a delicate operation. If it
is necessary to tighten your truss rod, I recommend setting aside plenty
of time to do it. When I build a guitar for a musician, I custom-design
the neck to meet his or her playing style and to accommodate a variety
of string gauges. Changing to a heavier string may require a slight
tightening of the rod. A lighter string may need a little backing off of
the rod. Occasionally a small adjustment can be made, and the guitar
will be ready to play immediately. Often, however, the neck will need
time to get used to its new position.
Most factory guitars, including Taylors, newer Martins, and Guilds,
use truss rods that are tightened with a clockwise turn. That is,
rotating the rod clockwise brings the strings closer to the fretboard.
Occasionally with double-action rods (rods that adjust in both
directions), a clockwise turn may actually raise the strings. If the
neck has not been damaged by heat or a long-neglected warp, a little
rotation should cause the desired effect. If your neck is badly warped,
get professional help.
On many guitars, the truss rod can be accessed via the headstock. For
others (including the guitars I build), you need to reach into the
soundhole. When the rod access is inside the soundhole, special care,
and probably special tools, may be needed. Take a deep breath, count to
ten, and if you're sure you want to do your own adjustment, go for it. I
like to make neck adjustments with the strings under normal tension; it
lets me see the real effect on the neck. I assume that most of you do
not have a fully equipped shop with guitar-holding fixtures. Therefore,
I suggest asking a friend to help by holding the guitar steady. First,
mark the rod's nut with a felt pen so you can return it to its starting
point. Then, slightly loosen the rod and see that it turns freely. If it
is bound or frozen, do not try to adjust it further unless you have a
great deal of experience or a deep-seated wish to break the rod and
replace the neck. If it moves smoothly, put a bit of lubricant on the
threads and work it in around the nut. I use a toothpick or a bit of old
guitar string for this job. Then put the truss rod nut back to where it
was when you started, using the mark you made as a reference.
All drawings by Harry Fleishman
The truss rod is either accessed via
the soundhole (left) or the headstock (right).
All drawings by Harry Fleishman.
Now is a good time to ask your friend to hold the guitar and press
down gently on the nut, making the truss rod's work easier. Gently give
the truss rod about a one-quarter turn. Now fret the guitar at the first
and last frets and use the string as a straight-edge to see if the neck
is getting flatter. The rod's effect is usually most apparent between
the fifth and seventh frets. I like to see a little light between the
string and the fret in the middle of the neck. If it looks right, wait a
few minutes and recheck. If it seems to need more tightening, be very
careful. If your rod is working correctly, you shouldn't have to crank
it hard to get good results.
Tightening the truss rod compensates
for the upward pull of the strings, and loosening it allows the neck to
If you are getting areas of buzz in an otherwise well-adjusted neck,
you may need a fret job. Fretwork is a very fussy job, demanding
accuracy to less than a thousandth of an inch. It also requires
specialized tools. Contact a reputable luthier to do your fretwork.
Often, guitarists adjust their truss rods when what really needs work
is either the nut or the bridge. If the first few frets feel stiff and
hard to play, the nut probably needs work. A nut that is not cut deeply
enough will make chords in the first few positions difficult to play. A
nut that is too deep will buzz like a sitar. If the strings are hard to
tune, again the nut may be to blame. Although it can be tricky to make a
nut play well, if you are careful and take your time, you can probably
improve the playability of your nut. You will need a few unusual tools
for this job, so unless you want to make a small investment, go to a
Very fine, small files allow you to make the grooves for the strings
with great precision. It is the careful fitting of these grooves that
makes the nut play well and sound clean. Nut files come in many sizes to
match the diameters of guitar strings. You don't need all of them. You
can make each file do the duty of many by rocking the file slightly as
you work. Pay special attention to the shape of the groove. The object
is to end up with a groove that neither binds the string nor causes it
to buzz. If you file too deeply, you can fill in the groove with a
little superglue and start over. Be careful, wear eye protection, and
don't overdo it. Place one tiny drop in the groove and sprinkle a bit of
baking soda over it as the glue sets. This will harden into a very good
simulation of bone, letting you regroove the nut as if you had not
messed up. Only you and I will know. Gently file until a scrap of paper from the Yellow Pages will slip in between
the first fret and the string when fretted at the second fret.
If your nut is the right height, you
should be able to fret the second fret and just fit a scrap of paper
from the Yellow Pages between the first fret and the string.
Even a well-fitted nut can bind and mess up your ability to tune. One
evening I received a phone call from Scott Bennett, who had been touring
the world and recording for 20 years on a guitar I made him. He was
backstage at the Boulder Theater waiting to go on, and the D string on
his guitar was binding and making a little squeaking noise whenever he
tuned it. You've probably had the same problem. I immediately drove
across town to fix his nut. After a moment's diagnosis I took out a no.
2 pencil and put a little graphite under each string in the groove of
his nut. The problem was solved. If you don't overdo it, you'll find
that a bit of graphite (pencil lead isn't really lead, you know) can
work wonders to stop strings from binding.
If your action still feels wrong and the neck has been properly
adjusted, it is time to look at the saddle. Lowering the action may
require removing a bit of material from the saddle. Raising it may mean
a new saddle or a shim under your existing saddle. If some strings are
fine and others are too high or low, you should consider re-contouring
the top of your saddle. Otherwise, it is simpler and safer to make
adjustments to the bottom. To raise the action, I recommend using a new,
properly fitted saddle, preferably made of bone—although many new
synthetics are available. It is not always practical to have a new
saddle made or to make one yourself. If you can't get one, I suggest
shimming what you have. Hardwood veneers are a good choice and readily
available. Veneers are commonly .032-inch thick. They can be sanded if
you need a thinner shim or stacked to achieve a taller one. At least
half of the saddle should be within the bridge slot or it may tip
forward or even break the leading edge of the bridge. Be extra careful
if you have an under-saddle pickup. Changing your saddle could affect
the string-to-string balance.
If you need to lower the height of your saddle, sandpaper attached to
a flat surface works well. Simply slide the saddle back and forth across
the abrasive, being careful to keep the bottom of the saddle flat. It
helps to mark with a pencil how much material you wish to remove and
then sand to that mark.
Setting up your own guitar can be very satisfying. You will be most
successful if you work when you are not in a hurry and if you take extra
care at each step. Good luck.
Magazine, November 1999, No. 83.