CNC Banjo Fretboard with Mother of Pearl

I just finished this CNC Banjo Fretboard with Mother of Pearl Inlay for my banjo project. This Padauk fretboard uses laser engraved mother of pearl for the inlay and I’m putting it on my next banjo – a 5-string open-back with a custom-designed Walnut rim. The nameplate was engraved with an Omtech Polar CO2 laser. The fretboard is a compound radius design (7.5″ at the nut to 11″ at the end) with hidden-tang fret slots all cut on my Shapeoko 5 Pro.

I used the following router bits:

• 1″ carbide insert facing bit (for flattening)
• 1/4″ ball nose (for the compound radius surface),
• 1/16″ downcut for the inlay slots and 5th string guide hole
• 0.5mm carbide bit (for the fret slots – no breakages!)
• 1mm carbide bit for the inlay cutting

The standard blue tape + super glue + accelerator method holds down the workpiece while the Shapeoko cuts it. I’m using Solidworks for Makers (Cockrum Studios is non-commercial) with SolidCAM to generate the g-code for this and it works well now. There were issues finding a SolidCAM post-processor that works without having to modify the gcode manually. When I tried the free one from Hawk Ridge Systems, it kept generating a G2 P2 command that is known not to be supported by GRBL so I had to delete that line each time. I tried this one from msbealo on GitHub but it kept sending the machine to Z -2 (maybe for some tool change for their particular machine). I went ahead and used the UPG-2 from Camworks to generate my own post processor that seems to work well so far. I posted it on GitHub here in case someone else can make use of it.

I glued in the inlay pieces and used a sanding beam to match them to the compound radius. This went much faster than expected.

For the name block, I used the 1/4″ ball nose bit to cut the compound radius then lasered the engraving into it. I filled it with black CA glue and then installed it into the fretboard. Unfortunately, I then sanded through part of the engraving and attempted to re-laser it but it just didn’t look good. Removing it was less difficult that I expected. A new piece of CNC cut mother of pearl was install and I shaped it with a sanding beam. I then lasered the engraving into it by putting the entire fretboard into the laser. I framed it and ran some tests about 10 times before hitting go and it turned out well.

Along the way, I laser cut a radius gauge to check that I wasn’t affecting the compound radius when I sanded it.

This is sanded to 2500 grit with no finish applied. I’m expecting that the Padauk + Mother of Pearl will look amazing when I get the frets in and put some finish on it.