This Epiphone Broadway had been re-fretted once before, but the frets had not been leveled. The result was nice tall new frets but a wavy fretboard with lots of humps and valleys. The action had to be raised very high so the strings wouldn't buzz. This is a pretty common problem, and the solution is ... level the frets.
I use this jig for a more accurate leveling job. It uses a strap and jack at the peg head to re-create the stresses of string tension after the strings have been removed. I adjust the truss rod to get the neck as straight as possible with the strings on. Then I set the dial indicators to zero, remove the strings, and adjust the strap and jack until the indicators read zero again. Now the neck is straight, and the truss rod is still tightened, so there will be no surprises when the strings go back on later.
The strings are off and the jack, strap, and support rods are set.
I mark the tops of the frets with a festive color so I can see how the sanding is coming along.
I usually start with 220 grit sand paper, on a straight bar. In really rough cases I might use 120 grit, or even a file in some places When all the color is gone the frets are level.
I mark the frets again and use a radius block to make sure each fret has the original radius.
The frets that had to be sanded lower now have flat tops, so it's time to crown them with crowning files and sanding sticks. I mark them again and round the tops until each fret is left with just a thin line of color in the center. If I took off all the color I'd be changing the heights and have to start all over. I have a video of the crowning process posted here:
Nice ... cleaned, oiled, and ready for new strings and a set up.
Now the action can be lowered to a comfortable level ... ready to get back on the bandstand. (This guitar belongs to Matt Trimboli, guitarist and music director for the local big band Swing Shift.)