It…depends
- what material ?
- what DOC/max stepdown on which machine ? There is always a balance between using a large stepover and shallow DOC, and using a lower stepover but deeper DOC. A standard Shapeoko3/4 will like shallow DOC better, while a Pro will allow to push DOC further.
For the sake of illustration, in this 3D roughing adaptive toolpath in bamboo, on a SO3, I used a 0.8mm optimal load on a 6mm (~1/4") 2 flute endmill, at 10mm DOC, 24000RPM, and 120ipm. A much larger optimal load can be used, but you may then need to lower the max stepdown (or not so much, if you have a Pro)
Tell us more about your project and I think folks will be able to contribute reasonable values they have used successfully in similar situations?