My sizes are out

[Doddy]

Random thought and I'd appreciate anyone else explaining if I'm talking balls, If you home to 0,0 and manually drop the Z into a sacrificial board, raise Z, traverse e.g. G0X33 (you mentioned a 33mm circle), the drop the Z into the sacrificial board (spindle running of course) then the distance between the left edge of the hole created by the first drop and the second drop should be 33mm. If it is, then your scaling is correct. If not then either thread pitch or steps. If it is still 33mm, and you have all the evidence of no loss of steps then I'd seriously be looking at your CAM, tool sizes and compensation.