I frequently use bits smaller than that in ebony. My best guess is a feed around 50 mm,I run feeds of 30 mm for 0.010 bits. Definitely ignore CC’s suggested speed, I usually run about 9000 RPM in wood. I’m on a Nomad, this may vary for you, possible lower feeds due to more deflection from a less precise spindle.
BTW, I’m a guitar maker (retired), I’ve always cut 0.020 fret slots. It seems counter intuitive the fretwire for a uke would have larger tangs so maybe double check, even do a test if you haven’t already.
A little more research brought me here, where he uses .010 DOC 5IPM feed and 9IPM plunge.
Seems like this going to be a multi-day job with speeds this slow.
The cbgitty website has the suggested width as .023 for the fret wire i purchased, so I think it will be ok. If i break the mill, it does look like .020 mills are more available and more economical though.
Interesting, the feed is high and the plunge very high compared to my useage. Still possible, test first.
Suppose your fretboard averages 2" wide with 20 frets. That’s 40" of slot. If your slots are, say, 4 mm deep, that’s 16 passes making a total of 640" to mill. With a 5 IPM feed, that’s about 2 hours. So, no more than three hours with plunge and traverse times.
Are you familar with fretboard compensation? According to common practice you should also mill the “zeroth” fret, where the nut will abutt. Because the nut will then be flush with the edge of the “slot” instead of the center, the first fret length will be slightly smaller than calculations indicate. This makes the pitch slightly higher but that compensates for the fact that pressing the string down at any other fret also raises the pitch due to the added tension. (In fact, I’ve found it necessary to compensate even more for good intonation. Opinions abound on the internet!)
Wish I had the Nomad for the 30 or so guitars I made.