Hello again and welcome to another installment of Luthier's Corner. This month, I’d like to discuss fretless instruments, specifically converting a fretted instrument to fretless. Fretless instruments are nothing new. The orchestral string family, consisting of violin, viola, cello, and upright double bass, as well as instruments like the oud, have been around for centuries. But almost since the invention of the fretted electric bass guitar, back in the 1950’s, it seems that certain bass players were converting those factory fretted instruments to fretless.

Jaco Pastorius is just one example. In recent years, the fretless guitar has been making quite a stir, especially in the hands of monster players like Ron “Bumblefoot” Thal. And on that note, I would like to discuss the process of converting a fretted instrument to fretless, and I will use a recent conversion I did for a client, a neck through body Yamaha TRB 6 string bass, as an example.

First off, when deciding to remove frets from your guitar or bass, the first thing you must do is check the straightness of the neck itself. A warped or twisted neck will only create a headache for you. Once you’ve determined that the neck is straight, check the fretboard itself for any wear due to years of use. Even though the strings mainly touch the frets, wear spots can often develop in the surface of the fretboard itself. OK, you’ve checked the neck and it is straight, and there is no wear to the board. Excellent. Remove the strings and then, using your fret puller, you slowly and carefully “walk” each fret out of their respective slots. Once all the frets are removed, take a fret saw and “clean” up the slots with a couple of passes through the slots.

Don’t worry about sanding the board yet. We’ll do that after we fill the slots. The way I prefer to fill the slots is with wood veneer, and depending on the client’s preference, I can either match the color of the board, so that it looks consistent, or use a different color to create lines. And you can buy wood veneer in thin strips, so you don’t even need to buy a sheet, and cut out the strips. Some people use putty to fill the slots. I’m not a big fan of that approach.

OK, so glue a strip of veneer into the first fret slot, using wood glue, and then use painter’s tape to hold it down tight while the glue dries. Repeat this for each fret. Once the glue is dry, carefully remove the tape. Now it’s time to level the board. Ideally, you want to use a radius block that matches the radius of the board, and medium grit sandpaper, 150 grit is fine. If you don’t have a radius block, use a long block of wood, and wrap the sandpaper around the block tightly. Naturally you want to sand with the grain, not against it, along the length of the board.

Make sure to maintain even pressure the entire length of the board. Once you’ve sanded the board smooth, check it with your straight edge. If you see any gaps of light, continue sanding until the gaps disappear. Don’t forget to first adjust your truss rod to make the neck straight. Often when you remove all the strings, the neck may backbow. So you want to loosen the truss rod accordingly. Always check your work with the straight edge.