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       July 21-26, 2013            Oct. 20-25, 2013

There have been numerous articles written about setting the correct "action" for string musical instruments. "Action" is the description of how high the strings are over the fretboard. High action means that the distance between the strings and the fretboard is great, and low action means that the strings are close to the fretboard. Usually, a description of the action refers to the height of the strings over the 12th fret.

While the "ideal" action depends on the musician's personal preference, there are four important considerations for the "correct" action. These are: 1) action at the first fret; 2) squareness or flatness of the fretboard; 3) action high enough to eliminate buzzes; and 3) limiting excessive action height that causes intonation problems.

Some luthiers measure the correct action at the first fret in terms of fractions of an inch or millimeters, but my objective in setting up an instrument is to make the action at the first fret (i.e., distance between the bottom of string and top of the first fret) the same distance as space between the bottom of the string and the SECOND fret when the string is fretted at the FIRST fret. This, of course, requires that the bridge is first set to the proper height, which is usually determined by the distance between the strings and the 12th fret. A good starting point is .080˝ for the mandolin and .085˝ for the mandola and 5-string banjo. (And, as previously stated, the final height is a matter of the musician's personal preference.)

Some luthiers like to set their fretboard with a slight "hollow" in the center. Hollow refers to a fretboard that has a low area in the center (as opposed to it being perfectly straight or "square"). A neck that has a high spot in the center is said to have a "bow." Necks with a slight hollow have the advantage of the strings being somewhat parallel to the fretboard for the upper portion of the neck, which means that the action is more consistent from about the middle of the neck to the end of the neck than it would be on a square fretboard. A fretboard with a hollow allows the action to be set slightly lower than a straight or "square" fretboard. Further, it is less prone to produce buzzes. A fretboard with a bow is especially prone to produce buzzes.

An action that is set too high will cause intonation (improper noting) problems. This is due to the string(s) being "choked" (bent) excessively as they are drawn to the fretboard. As this happens, the string(s) tension increases and as a result the pitch also increases. So, the less distance the strings have to travel to the fretboard, the truer the noting will be.

Setting proper action is not really difficult; it's just a matter of practice and knowing what the variables are.

For ideal tone and amplitude, it is critically important that the feet of the bridge are perfectly mated to the surface of the soundboard. Securing a two-footed bridge to a fixture in preparation for fitting is rather easy because the bridge's two posts provide a means for attaching the bridge base to the bridge-fitting fixture. However, Gibson's earliest mandolins featured a one-piece, non-adjustable bridge that did not have posts that are common on adjustable bridges, and fitting a one-piece bridge to the soundboard requires a slightly different fixture than the one used for bridges with posts. Page 124 of The Ultimate Bluegrass Mandolin Construction Manual shows photos of the fixture used for adjustable bridges, and the images also show how to place a piece of sandpaper on the soundboard and use the fixture to shape the bottom of the bridge base to the shape of the soundboard.

The process for fitting the bridge to the soundboard is identical for one-piece bridges except that a fixture has to be made that clamps around the entire bridge rather than attaching to the posts of the bridge.

The fixture is rather easy to make. Cut the handle part from a piece of hardwood and attach two 10/32 lag screws into the handle's face. The lag screws should be separated by a distance that allows the bridge to slip between them. Then fashion a simple wood cover, and use two wing nuts to secure the cover and bridge in place.

With the bridge securely fastened to the fixture, hold the fixture steady and move the bridge and fixture back and forth (towards the peghead and then towards the tailpiece) until two dark stripes appear on the sandpaper. This will be an indication that the bridge feet are mated to the shape of the soundboard. Hold the sandpaper securely so that it does not slide around on the face of the soundboard. Also, it is ideal to move the handle of the fixture in a slight arc so that the base of the bridge is fitted to fore and aft curvature of the soundboard.