I did just cut it. Looks like shit. I'm not happy with shit. Now what?
I only have one to make. But I've made two now and I'm running out of aluminum that size. I have never had much luck making a radius x with a 2x diameter end mill no matter what the depth, but certainly with a DOC at 5x the diameter, there are problems. Doesn't sound good, doesn't look good. It doesn't take much force to deflect 2.5 inches stickout on a 1/2 end mill.
I'm the engineer, the radius isn't there out of whim. It really should be 3/8, but I gave that up early on. I tried arcing a larger radius by 0.005, thinking that would keep it from engaging 90 degrees, also pulling off the floor a few thousands. Still no joy, the EM is deflecting more than that as it approaches the corner I guess, still leaves marks around the radius. I don't know how far I need to be away, if had a thousand to do I would experiment more. The 12mm EM is a good idea, don't have one that length on hand (nor do my normal suppliers). Maybe pecking with the reduced shank EM would work - I tried pecking with the long .5, it gets a ways and then its rubbing on the wall too much and goes unstable. I haven't tried lowering the RPM a lot, may give that a go. These are 38 deg EMs I am using.