G40 G41 G42 Cutter Compensation

Cutter compensation offsets the tool from the programmed path by its radius, so you can program the finished part edge and let the control account for the actual tool size. Change tools or regrind and you only update the offset, not the program.

Code Action
G40 Cancel compensation
G41 Compensate left of the path
G42 Compensate right of the path

How it works

  • G41/G42 reference a diameter or radius offset register, usually called with a D word.
  • Engage and cancel compensation on a straight lead-in or lead-out move, never inside an arc.
  • Left or right is judged looking in the direction of travel.
G41 D01 X0.0 Y0.0 (turn on, comp left)
G40 X-0.5 (cancel on the way out)

Related: plane selection.

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