Went back and used a standard key cutter and everything works great. Thanks

This seems to be the way to go. But i can only cut with leading edge of cutter, and when I try using cutter that I defined so that it will use trailing edge it doesnt work. There is no tool path preview.

I have a boss extruding from a wall. It is down inside a part no other way to get to it but with a key cutter style tool. I need to profile a concave radius on the underside of the boss. Mastercam wants to machine a convex radius, putting the cutter on the wrong side of radius, coming thru part not on the inside.