This is almost to depth, after which it'll need a bit of deburring & stoning on the edge to make it razor sharp. This is a .250 dia. two flute HSS end mill. The only reason I used a two flute was because it is so much easier to sharpen the faces by hand than on a three or four flute cutter. I usually use 50 surface feet per minute (SFM) for milling O-1, which works out to about 800 rpm.

RPM = 12 X SFM divided by Pi X Dia....usually abbreviated to 4 X SFM divided by Dia.