How to Adjust a Mandolin Truss Rod
- 1). Place a microphonic tuner within 12 inches of the mandolin. Since a typical mandolin is totally acoustic, you can’t connect them to electronic tuners. The truss rod applies tension to the inside of the neck to compensate for the tension applied to the outside of the neck by the strings. This is why it’s essential that your mandolin is correctly tuned before you begin truss rod adjustments. If you have an electric mandolin, you can use a microphonic or electronic tuner.
- 2). Play string 8, which is the nearest string to you as you hold the mandolin, and monitor the tuner display. Correct the tuning according to the monitor display. If the tuner display points left, the string is flat. If it points right, the string is sharp. Correct sharp notes by loosening the tuning peg. Correct flat notes by tightening it.
- 3). Put a capo on fret one. Put a second capo on fret 11.
- 4). Observe the angle of the first string relative to the fingerboard, between the two capos. If the string slopes down toward the second capo, the neck is forward-bowed. If it slopes up, the neck is back-bowed.
- 5). Unfasten the three screws attaching the truss rod cover to the headstock. This exposes the truss rod adjustment nut.
- 6). Fit a 2.5-mm hex key to the adjustment nut. Rotate the nut 90 degrees. Turn counter-clockwise to correct a back-bow and clockwise to correct a forward-bow.
- 7). Reinspect the angle of the string relative to the fretboard. If it appears parallel, make no further adjustments. If the the angle is less intense, make further small adjustments in the same direction. If the angle is larger, it’s possible that you’ve turned the truss rod in the wrong direction. Try rotating the hex key 180 degrees in the opposite direction.
- 8). Replace the truss rod cover and screw it back in.
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