We have an Okuma captain 3 axis lathe. When setting up a part we indicate across a flat on the part and calculate that as being C0. When we run the part the holes we drill on the on are always shifted about 1/4 degree. This shift varies a bit from part to part. So, I put in a C-axis variable shift in the program (VZSHC)to try to align it better. Does anyone know why we might have this alignment problem? We also have the same issue on a 3 axis Samsung lathe with a fanuc control.