In this video I use my Stepcraft 2/840 CNC machine and a Kyocera 0.6 mm diameter two flute solid carbide end mill to cut 1.5 mm deep fret slots in 0.25 mm increments in a guitar fretboard. See the following section of my website for further details:
dsgb.net/projects/redspecial/...
I cut the fretboard from spruce (this was a test or validation run) and radiused it to 1/4” (6.35 mm) thick at the crown with a 7 1/4” radius using a 6 mm diameter two flute solid carbide ball nose end mill with a 0.5 mm stepover.
I used the G18 command to cut arcs in the XZ plane with G02 and G03 commands to specify clockwise and counter-clockwise directions. I wrote the full GCode manually rather than using CAM software. The spindle speed is 10,000 rpm, the XY feed rate is 600 mm/min and the Z plunge rate is 120 mm/min.