Bringing a Guitar Into Balance
I wrote this description of the repair/maintenance of a guitar, then realized that it might also apply in other areas of endeavor as well. There might be similarities found which might make useful these instructions for other purposes than that solely of the provenance of the luthier.
Part I: The Truss Rod - Tightening the truss rod may be likened to the adjusting of the stays on a sailboat mast. In order for the mast to be straight and vertical, the pressure on the stays, or guy wires, must be equal on all sides.
On a guitar this means that the pressure that the tightened strings pulling the fretboard (or the mast) up is exactly countered by the truss rod on the other side, inside the neck. This is set up in the shop or factory at the time of manufacture, but over time, the wood compresses at the truss rod ends, and the rod needs to be tightened to allow for this. (When tuning up a bicycle, one often has to tighten the nuts clamping the pedal cranks to the crankshaft, in a similar way).
On a guitar, however, over-tightening and pulling the fretboard backwards may occur. A proper adjustment may be made by using one of the stretched strings as a straight edge, holding it against the frets at the first fret and at the highest fret, allowing a slight curve for the strings to vibrate. A good starting place might be to be able to insert a business card between the string and the midpoint fret between the ends of the string (at the first and highest fret).
Part II: The Bridge Saddle - filing down the bottom side of the saddle sometimes needs to be done after adjusting the truss rod, in order to lower the string height at the higher frets. (This also decreases the angle out from the neck, and lowers the outward pressure on the neck from the strings).
Marking a line on the sides of the saddle before filing it helps to gauge how much to take off. Hold the saddle in a vice and file it with a mill file, or sand it against a sandpaper block, with care and attention given to keep the bottom of the saddle straight and square. If too much material is removed, sometimes a shim may be inserted, but often a new saddle must be fabricated. (This can turn into an upgrade, plastic to bone, bone to ivory, etc.).
This is the point where the sound is transmitted from the strings to the soundboard, and also sometimes to an under-saddle pick-up. It requires some expertise and attention to detail.
When the strings are lowered closer to the fretboard, this reduces the pull on the neck and sometimes causes the neck to straighten even more over the next few weeks! This is in addition to the immediate goal of bringing the strings closer to the neck in order to make the guitar easier to play, and may improve the playability even more over time, especially with older instruments!
Part III: Leveling Raised Frets: - When the action is lowered to facilitate very easy fingering, un-even fret height, usually not a problem with slightly higher action, may cause buzzing or may cause the same note to be played when fingering the fret or frets below the raised fret. If the fret above the fingered fret cannot be tapped down into it’s slot, then it may need to be filed down with a fret file, a short file that can rest on several frets in order to lower the one sticking up. This should be practiced on a cheap guitar or two before attempting work on someone else’s guitar!!! It is not for beginners. Dressing the frets afterwards with special files is recommended. (See guitar building instruction books for details).
(Perhaps adjusting dysfunctional behaviors may be likened to this process, and is the subject of a future paper.)
