Thanks Gerry. Ok, so that is what I do - the z=0 is the top surface of my part and in CamBam I set the clearance plane to say .25". That works fine EXCEPT, at the end of the operation, the tool returns to x=y=z=0, which would break the bit (1/16" end mill).
I'll take a look at the Safe Z again. Maybe I misunderstood it when I looked at it earlier. I thought it would just raise the bit to the safe z height first, move x & y and then lower z to 0? If so, that would collide with the fixture screw. See what I mean?
cheers,
Michael