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Lets 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, toachieve 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

resolved.

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 relief".

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 thepurpose of this article we are only addressing those guitars with adjustable tension rods.

Here is an easy way to check the curve of the fret board in the playing area: With theguitar 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 than1/64th inch, maximum). You can evaluate the fret board 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 fret board, 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 directiondepending 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

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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 whats called string rattle or

fret buzz from the middle frets up the neck. A back bow can cause fret buzz in the firstfive frets or so.

All too often, a guitar with high or low action has the neck adjusted by a well-meaningperson - 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, andsometimes 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 hasbeen performed. The exposed wood of the fret board 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 hasbeen 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 inthe 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 neckcurvature, 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 thenut, 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 to depress.

If the height of the 1st fret above the fret board is known, a metal gauge (such as an automechanics "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

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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 discernthis gap.

If the string sits on the first fret, while the position between the second and third frets isbeing held down, the slot is probably too low and the string will probably buzz if plucked

open.

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 byfiling or sanding the saddle piece to give the desired height for each string. There is no

correct height of the strings over the fret board. Playing style determines theappropriate setting. A light finger-stylist can get away with very low action, whereas ablue 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 alower 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 flatand 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 tobuzz at a given string height over the frets, ( I suppose you could set the strings extremely

high over the fret board by raising the saddle way up). Playing style is the key.

Ultimately, how you pluck/drive/attack the strings is the biggest determining factor inwhether 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 thetachometer is redlining (reflecting overly high engine rpms) for a long enough periodof time, the engine will likely fail. But this is not a reflection of the quality of the engine

or its 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 cant abide by it, just keep raising the string

height at the saddle. Eventually, it will go away. Whether the guitar will still be

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comfortable to play is another story. Ultimately, as with many things in life, compromises

must sometimes be made.

Which reminds me of the time renowned Telecaster playing guitar-genius Bill Kirchencame 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 andpitted to what had finally reached (beyond) a critical stage. When I asked why he hadnt

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 guitar.

CONCLUSION

Thats it. Three basic steps in the set-up of an acoustic guitar. They must be done in thisorder: neck then nut then saddle. If the neck curvature is off, it wont 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,saddle..