The final steps in finishing an instrument are dressing the frets and then installing the strings and doing the final setup. This entry will cover fret dressing, the point of which is to make sure that all the frets are at the correct height and properly shaped both along the top of the fret and at the ends. The first step actually takes place when the frets are installed. It is important that each fret be pressed into its slot with the same amount of downward force. I do this with a modified arbor press on which the normal handle has been replaced by a click-style torque wrench. A fret is placed in its slot and the torque wrench is used to apply downward pressure until it clicks.
Before working on the frets, it is important to tape off the fretboard to keep it clean and to protect it from damage. Installing all of the frets with uniform force reduces the work required to bring them all to the same height at all places on the fretboard. This is an important step that helps prevent buzzing. On this tenor fretboard, all the frets were very nearly the same height as judged by a small straight edge placed across three frets at a time at both the center and the ends of the frets. If it rocks, there’s a problem that needs to be fixed. Only a few minor adjustments were required.
A variety of tools can be used to level the frets as necessary but, in this case, a small diamond file with a concave surface did the work quickly and easily.
All that was required was a few swipes in a few spots. It is often necessary to restore the rounded crown of a fret that has been filed down. In this case, very little shaping was necessary because very little was removed from the tops.
The ends of the frets are sanded or filed earlier in the process of making the neck so that the ends are canted inward. The final step in shaping the ends is rounding them over a bit with a small and very fine file.
The frets are then sanded with very fine sandpaper to remove any marks left by leveling and shaping. Once the frets are leveled and the ends are shaped properly for comfortable playing, the final step is to polish each fret. I usually do this with a small buffing wheel in a Dremel tool. A thin stainless steel mask is used to protect the fretboard. Of course, when I buff frets, I am holding the mask with one hand rather than holding a camera!
The fretboard is cleaned to remove dust that accumulates in the pores and then oiled or waxed. The final “quality control” step is to verify the "relief" that is built into the top surface of the neck before the fretboard is glued in place. This shop-made device shows that the fretboard is very slightly bowed by about three one-thousandths of an inch. It is expected that this will increase slightly under string tension but the carbon fiber rod that is buried in the neck will resist further bending. In the setup process that is done after the strings are installed, this tiny amount of relief allows the strings to be a bit lower than would otherwise be possible. When a string vibrates, the greatest amount of movement occurs at the center of the string and the relief helps to avoid contact between a vibrating string and a fret, which would produce unwanted "buzz”.
