What does your code look like? Are you using G101 with tool comp? If yes,
you may have your nose comp wrong which gives your flats a concave or convex surface depending on your comp value direction error. If I'm not understanding your description, then you may have your turning tool clipping the sharp corners thus rounding them out.
Your code, comp values would be helpful.
Your feedrate will need to be calculated using the formula in your programming book for "C" milling. (yes I too really wish the Okuma control would calculate this for you automatically - isn't that what a computer is for?!)