MRR = feed rate x WoC (width) x DoC (Depth) => a volume per minute.
I use ACME and running aluminium with a 1/8" bit I could get good result with 2.5cm^3 per minute. I could go harder but rigidity issues started to show / consistency dropped.
For harder materials rigidity is a major factor because any vibration/runout add to the “bite variation per tooth” which is slim to begin with. For a 1/8" 1F end mill you should be able to do 400mm/min (16IPM) at 16k RPM with a depth per cut = 1mm. Plunge rates must be low unless one can ramp/helix in.
With a 6mm 1F I have done full width cut and 1mm depth at 900mm/min with great success.
MRR = 900 x 6 x 1 = 5,4cm^3/minute
I have also briefly tested same but with 3mm DoC, no complaints.