Depends heavily on the alloy you will use.... For a 1/8" bit, depending on the alloy, I run between 1.1/.23 to 1.37/.39.

I never set up for more than .02 depth.

I almost always use an upcut spiral O Flute bit made for aluminum. My fave is Onsrud 63 series bits.

My "cheapie" .25 bit is from Hartlauer. It is the 52-180h.

You can PROBABLY run a little faster with a 1/4" bit, but I tend to keep it slow and steady, so I get a good quality cut.

I ALWAYS SPIRAL RAMP my cuts. I often use either WD 40 or Isopropyl Alcohol dribbled on the cut line as a coolant. (Small quantities of either)

FOr THIN aluminum, I use 16500RPM. For thicker and harder aluminums, I listen to the cutting and look at the chips and adjust until the machine does not sound like it is fighting to make the cut (and make sure the substrate, bit and spindle are all "cool". I do this between cuts, of course)

Best of luck with your project