A dusty 2k (aka “two-component”) acrylic clear coat has been applied (top), then sanded (middle), and finally polished (bottom). Photos courtesy of basslab.de

In my previous column [“DIY Fretless Conversion,” February 2015], I described the process for carefully removing frets from a standard bass to convert it into a fretless instrument. Some of you have asked for more details on reassembly and setup, so let’s take a closer look at what’s required to get your converted fretless into top playing condition after you’ve done the heavy lifting of fret removal. (If you missed the previous installment, take a moment to read it before diving into the following material.)

Installing the nut. Once you’ve sanded and leveled the fretboard, it’s time to reinstall the nut. With the frets removed, you’ll want to lower the string height at the nut. Instead of filing down each individual string slot, it’s far easier to sand down the nut’s base. If the previous setup was good—in other words, the open strings sat as low as possible without rattling on the first fret—you should sand off the exact height of the fret from the bottom of the nut.

This isn’t as easy as it sounds. For one thing, if you have a curved nut slot, you need to maintain the fretboard radius. Conversely, if the slot is flat, you need to keep the nut bottom dead level as you sand it. Also, you’ll want to be very careful not to sand too much off the base. The operation takes time and patience, and you’ll probably need to restring, retune, and check the action of the two outer strings several times.

Yikes! What happens if you end up just a tiny bit too low? An easy way to incrementally regain height is to use paper and superglue (this also works when adjusting a nut on a fretted bass). Here’s the trick: Apply superglue to the base of the nut and press it onto the paper. Once the glue has dried, use a cutter knife to trim off the paper surrounding the nut. The superglue soaks into the paper, stabilizing it so it won’t compress. The key is to use enough glue to impregnate the paper and not so much that the nut adheres to the workbench. (Tip: acetone works well for removing superglue.) Once you’ve found the ideal height for the nut, use a lighter glue to attach the nut to the neck. Any all-purpose adhesive will do the job.

Finishing the fingerboard. Once the nut is installed, it’s time to choose a finish for your fingerboard. You shouldn’t leave the fingerboard without any treatment or protective coating because any change in humidity will cause it to shrink or swell. Thus the neck with its glued-on fingerboard and oiled or lacquered back will behave much like bimetal. That’s not what you want on a stringed instrument that’s so dependent on setup for its tone.

You shouldn’t leave the fingerboard without any treatment or protective coating because any change in humidity will cause it to shrink or swell.

Here you have two choices: You can use oil that soaks into the wood or a hard sealant that stays on top of it. Your decision also depends on your skills, tools, and how you want to use your new fretless. Another consideration is your preferred tone, and whether you’re going to string up with flatwounds or the more popular roundwound strings.

If you opt for flats, then oiling the fingerboard is the easiest and fastest way to go, but even though these strings offer reduced wear, they’ll ultimately eat up your fingerboard. Sonically, choosing flats means your fretless tone will be closer to an upright. Furthermore, the softer oiled surface will suck up even more of the higher frequencies and upper harmonics. Of course, this also depends on the hardness of the fingerboard wood. The softer and less dense, the muddier the tone. That’s not a judgment—some songs require a darker sound, but that effect is often easier to get with EQ.

But over time roundwounds will nibble even the harder woods and create little trenches at your favorite positions. This negatively impacts the characteristic “mwah” sound that comes from the strings gently buzzing against the fingerboard.

To protect the playing surface, you can follow Jaco’s lead and use a marine sealer or another lacquer finish. A hard surface also preserves the trebly parts of your tone. The downside? Any lacquer finish requires more effort to apply than simply pouring some oil over the fingerboard. It’s also more expensive. So this goes back to your original plan, i.e., whether you converted a cheap instrument to tentatively explore the fretless world, or if you know what to expect and are serious about taking the plunge.

One more thought: The huge amount of available epoxies, polyesters, glues, and one- or two-component polyurethane- or acrylic-based lacquers can be confusing. The options outnumber the available wood species! The easiest sealants to apply start with brushing several layers of superglue onto the fingerboard and then sanding it again, while the elaborate ones require a spray gun for a two-component clear coat.

Photo 1 illustrates an interim clear coat solution that almost anyone can manage at home. Carefully tape all around the fretboard area to build up a small basin to hold the clear coat. Beware: Basins leak easily and clear coat loves to seep. It’s safer to first brush a thin layer of clear coat into the edges of the tape and fretboard, and then let that dry to seal these areas before you add the final amount. After that, it’s time to get back to sanding and finally polishing! Even with a lot of dust in the initial clear coat, the final result can look almost professional.