We need to mill a 19mm slot in a block. The mill starts vertically and remains so in the "A" part of the block. Then it rotates 30 degrees as it transitions through the "B" part. It remains rotated in the "C" section. 

The problem I'm having is the bottom of the mill's path is curved in the "A" and "C" parts of the block. I want them straight; only curving in the "B" area.