M556 - complex macro for different measurement
M557 - simple macro for measurement of left bottom corner in Z, X and Y axes
M558 - simple macro for measurement of hole center
M650 - macro for surface scanning. See dedicated description

Do not forget to set "Edge finder dia." in MACH3 "Offsets!" tab. Even if tip dia is 3mm,
there has to be set bit lower value, alows small movement of the tip before a sensor is triggered.  