18 years into cnc and I have still yet to calculate a feed.
use your ears
most mid size end mills [the 1/4 to 3/4 sizish] you can start at 2000 rpm and 10 ipm and your chicken switch will keep it sane. Find a spot that sounds right
then 4000 and 20
8000 and 40
12000 and 60
most manual machinists go way too slow