Size matters. Before you begin grinding on the frets, you need to confirm they’re tall enough to level and recrown. To do this, I use a luthier’s digital caliper. Available from stewmac.com, the tool is designed to let you measure fret height right off the fretboard. On this Manea, the fret height measured .043"—a good height for frets on an acoustic guitar. If the current frets measure less than .038", they’ll be too difficult to recrown after being leveled, and that means new frets are required.
Tap and seal. After removing the strings, place the guitar neck onto a secure platform, and then remove the nut (I demonstrate removing a nut in this PG DIY video, “How to Convert a Flattop into a High-Strung Guitar”).
Next, check the frets to make sure they’re securely seated in the fretboard. Shine a bright light along the fretboard to see if any frets have sprung loose from their slots. The flat bottom of the crown should sit flush to the wood. If you see a fret that’s come up, gently tap it down with a fretting hammer and then run a bead of thin superglue along each side of the fret to hold it in place.
Drop Off and Fall Away
Most acoustic guitars have what’s called a fall away or drop off at the end of the fretboard where it extends over the top. This is a result of the neck angling down very slightly into the guitar to provide room for the strings to vibrate without hitting the frets. If the fretboard doesn’t drop off, it could be a sign of a low neck angle. If you see this on your guitar, I recommend you take it to a qualified luthier for advice. Correcting low neck angle requires major surgery. At the very least, the frets over the fretboard extension may have to be dramatically filed down.
Note: Whenever you have superglue in one hand, always have a Q-tip in the other. The Q-tip lets you quickly soak up any excess glue (Photo 4). Be very sparing when applying glue along the frets. If you use too much, it can spill over onto the neck. Thin superglue travels fast, so be ready with your Q-tip.
Leveling the frets. Once the frets are all seated, it’s time to begin leveling them. Different luthiers have different techniques for doing this. Here’s my approach: Place the leveling bar across the frets and adjust the truss rod until the bar is touching most—if not all—the frets. This process can take several attempts, so be patient.
Once the leveling bar is touching as evenly as possible, attach 400 grit self-adhesive sandpaper to the leveling bar, place it perpendicular to the frets, and then gently begin sliding the leveling bar along the frets. I like to start on the bass side and gradually work my way to the treble side of the fretboard. Don’t press too hard, just skim the surface of the frets with slow, controlled motions.
After a few passes, check the frets for scuff marks. Again, use a bright light to see if you are contacting all the frets evenly. If not, then you may have to readjust the truss rod. Keep using your leveling bar to remove more fret material.
About those last few frets. When the frets are perfectly even, they should all have file marks with the exception of the last five to eight frets (Photo 5). If those last several frets don’t have any file marks, but the rest of the frets do, that’s okay. It just means the fretboard has what’s called a fall away or drop off. For more details, read the “Drop Off and Fall Away” sidebar.
However, if you see you’re filing the last few frets, but not the frets in the middle of the fretboard, there’s a problem. Either the truss rod is too loose, which creates a bow or dip in the middle of the neck, or the fretboard has a “kick-up.” The latter is a condition that requires professional surgery to repair.
Recrowning. To ensure that a guitar intonates correctly and plays comfortably, the newly flattened frets need to be shaped to provide a narrow, precise point of contact for the string. This is called recrowning.