M3 & M4
To start the main cutting spindle use the M3 ( clockwise) or M4 (Counter-clockwise) miscellaneous code at any point in the programme. This is normally associated with the S code which define the spindle speed in RPM.
N4 M3 S4500 – Spindle starts in a clockwise direction at 4500RPM
(note to stop the spindle us the M5 code)