Harmonica Workbench: BlueXlab SP20 Comb—The Sequel
by Kinya Pollard
In the 2011 October issue of HarmonicaSessions.com®, I wrote about two extraordinarily good looking BlueXlab combs I had purchased. The quality and craftsmanship of the olive wood and anodized aluminum combs were exquisite. It was love at first site. I even contemplated running off to Vegas with them—and why not? After all, “what happens in Vegas, stays in Vegas!”
My heart was broken, however, the moment I placed the SP20 to my lips. The protruding mouthpiece created an obstacle between me and the “fat tone” embouchure I worked so many years to perfect.
Always the optimist, I was determined to make the BlueXlab combs work for me. Here is how I turned it around:
For this project, I chose the Micro Mark modeler disc sander #80849
(http://www.micromark.com/10-inch-disk-sander,7558.html) with #240 grit sand paper for the olive comb, and a belt sander with #120 grit for the aluminum comb. The Micro Mark sander features a 10″ disc sander, which means you’ll have five inches of down stroke sanding—left of center—for a “swirl free” finish.
I selected the belt sander for two reasons:  an aluminum friendly 100 grit belt was already installed onto the rollers; and  simply for nostalgic reasons—I built this tool 40 years ago and I didn’t want it to feel left out ;o)
In order to avoid chatter scars on the top/bottom of the olive comb, I applied a layer of blue painter’s tape onto the metal table. The table was calibrated at 90° to the disc surface. This will ensure that the face of the mouthpiece will be straight and true.
With a forward/downward pressure onto the comb, I pushed it side-to-side across the left face of the disc.
It was critical to frequently check the mouthpiece to make certain the desired amount of material was removed.
I wanted the comb to be as comfortable in my hands as the mouthpiece would be in my mouth. I shaped the corners for the ideal look and feel.
I found twirling the counter sink bit in-between my thumb, index and middle finger to be a very effective technique for controlling the amount of material removed during the counter sinking/deburring process.
See how nice this olive comb is shaping up?
Preparing for the finishing process, I gently screwed into opposing holes—one per side—# 6×3″ sheet rock screws (a.k.a. cover plates holes) of the comb. While safely holding onto the comb by the screws, I was able to apply two to three light coats of Zinsser Bulls Eye Shellac allowing each coat to dry in-between. Depending on your sheen preference—satin to gloss—gently sand the comb with light grit (+360g) sandpaper on the final coat.
Let it be known that back in the day, I enjoyed my time in metal shop more than wood shop. So for me, I’m saving the best for last… whip’n the BlueXlab aluminum comb into shape.
I removed the radius (extra material) off the mouthpiece with the belt sander. It was a good reminder for me to chant the carpenter’s mantra, “measure twice, cut once.” Without a reference fence or table to guide me, it would have been easy for me to get off course and distort the angle of the mouthpiece. This is why I checked my work frequently with a machinist square.
Here’s a shot of the “rough cut” finish. Notice the circular grinding marks?
Referring to the olive comb above, apply the same procedure for counter sinking and de-burring the mouthpiece holes. By the way, I did not find a meaningful difference between clamping the comb into the soft jaw machinist vise, versus firmly holding the comb in my hands.
Lay a sheet of 360 grit “wet or dry” sandpaper onto a flat surface (a plate of plastic or glass). Sand-polish the mouthpiece until the grinding marks disappear.
Sure it was a lot of (fun) work, but trimming off the extra material from the mouthpiece created two harmonicas that are now compatible with the “fat tone” embouchure I prefer using. Thumbs up!
“Play the notes people want to hear” © 2008
Musician & Harp-Tech
Harmonica Masterclass Workshop Instructor
Mel Bay’s Harmonica Sessions Columnist
www.bluesharmonica.com Harp-Tech Expert