After lots of experimenting trying to get feeds and speeds just right I finally have my first usable fretboard.
I snapped 5 bits before I got the speeds right.
Well, I snapped one when I dropped it on the ground. The tip of these are just 0.61mm thick. Very easy to break. I think especially on the mpcnc as it is not the stiffest design. Even the tiniest amount of chatter will snap it very quickly.
For those interested:
3mm/s feed rate
2mm/s plunge rate
1.8mm depth of cut
The wood is hard maple. The depth of the slot is 2mm.
It is actually much quicker and easier to cut these on the table saw. But this is the only way to get “blind fret slots”. Meaning that they don’t go to the end of the board. They stop before the end so you can’t see them from the sides.
My next step is to try this on much denser wood. Maple is as soft as you want to go for a fretboard. It has a janka of 1450. My preferred fretboard material is African Blackwood with a janka of 3750. Wish me luck!