Hi, Piet
As far as I now, LazyCam and Mach3, work in UNITS, MM or Inch.
Check your Mach3 is not in Inch. Mode.
In Mach3, goto Config, Select Native Unit's, OK, Set Default Units to MM, then OK.
If it was in Inch mode you will need to adjust your Step's Per settings in Motor Tuning if there setup
Hope this Fixes your Problem.
Thanks, Chip