Setting zero fret height. With the new zero fret installed, restring the guitar and tune it to pitch. Using an action gauge, measure the action at the 1st fret. Keep in mind we’re measuring from the top of the 1st fret to the bottom of the strings. The action should measure 1/64" for the high E string and 2/64" for the low E.
Occasionally the action will be perfect, but this was not one of those occasions. After installing the new zero fret on the Teisco, the action measured 2/64" for both E strings. This meant I needed to lower the zero fret under the treble strings so they’d have the correct height.
Fortunately, there’s an accurate way to do this using a set of gauged nut files. Choose the appropriate file for each string and cut slots into the zero fret until the action at the 1st fret is correct for every one (Photo 6). When the slots are cut, remove the strings and file the top of the zero fret until the string slots—the cuts you just made—almost disappear (Photo 7). It’s okay to leave very shallow slots on the zero fret to guide each string to the nut.
Filing down the zero fret gives it a flat top, so the next step is to re-crown the zero fret using a fret-crowning file (Photo 8). This will give the fret a rounded top, which helps the guitar’s intonation by insuring that all the strings make contact along the peak of the zero fret. If the fret’s top is flat or inconsistent, the intonation will vary from string to string.
Final steps. To remove any glue or tool marks left by your re-crowning file, carefully scrape the fretboard with a razor blade. Use caution here: Hold the razor blade firmly and scrape the board gently.
With the tool marks removed, you’re ready to burnish the fret with 0000 steel wool or fret polishing paper to make it look flawless. Now install a new set of strings, adjust the intonation at the bridge saddles, and take a step back to admire your work—you’re done!