different string gauges or climatic
conditions.
An adjustable truss rod can correct
any changes in neck curvature. On
a Gibson, the truss rod is adjusted
by turning a nut that is found under
a bell-shaped celluloid piece on the
headstock. A neck with too little
or too much relief can cause string
action to be too low or too high, but
once the neck is properly adjusted
for relief, adjustments to the action
should be made at the bridge.
To assess the neck, hold the guitar
so that you can see from the nut
down the entire length of the neck.
If the fingerboard appears flat, the
truss rod should be loosened by
turning the nut counterclockwise
(no more than one-quarter turn at
a time). If the fingerboard has too
much curvature, the truss rod can
be tightened by turning the nut
clockwise.
THE BRIDGE
The bridge’s purpose is to maintain
intonation and action (string height).
Adjusting the truss rod or changing
string gauge can change intonation
and/or action.
String height should be adjusted
first, raising or lowering the strings
to the desired playing level by
raising or lowering the bridge. Then
string length, which determines
intonation, can be adjusted. With
Gibson’s Tune-o-matic bridge, a
small screw moves the saddle to
lengthen or shorten the string. When
performing the intonation check
described in Rule 12, if the fretted
note is higher than the harmonic
note, then the saddle should be
moved to increase the length of the
string. If the fretted note is lower
than the harmonic note, then the
string length should be shortened.
15
