G12 Circular Pocket Milling CW / G13 Circular Pocket Milling CCW (Group 00) These two G codes are used to mill circular shapes. They are different only in which direction of rotation is used. Both G codes use the default XY circular plane (G17) and imply the use of G42 (cutter compensation) for G12 and G41 for G13. These two G-codes are non-modal.

D- Tool radius or diameter selection
I- Radius of first circle (or finish if no K)
I value must be greater than Tool Radius, but less than K value.
K- Radius of finished circle (if specified)
L- Loop count for repeating deeper cuts
Q- Radius increment, or stepover (must be used with K)
F- feedrate in inches (mm) per minute
Z- Depth of cut or increment