G41, G42 & G40 Cutter Radius Compensation CNC Programming

G41 (cutter left) and G42 (cutter right) shift the toolpath automatically by the radius stored in the tool geometry register (D-offset), allowing programmed part contours to remain independent of cutter size.

Engineering Specifications & Parameters

G40 Function	Cancel Cutter Compensation
G41 Function	Cutter Radius Compensation Left (Climb Milling)
G42 Function	Cutter Radius Compensation Right (Conventional)
Offset Registry	D-Address in tool offset table
Minimum Lead-in Distance	Must exceed cutter radius

Principles of Cutter Radius Compensation (CRC)

Cutter compensation allows the programmer to code exact part blueprint dimensions. The CNC controller calculates the offset vector perpendicular to the toolpath.

G-Code Definitions

G41: Cutter Left Compensation (Standard for Climb Milling in XY plane).
G42: Cutter Right Compensation (Used for Conventional Milling or OD Lathe Turning).
G40: Cancel Cutter Radius Compensation.

Frequently Asked Questions

What causes the Overcut / Gouge alarm during G41 activation?

Activating G41 on an internal contour with radius smaller than tool radius, or lead-in move distance smaller than cutter radius.

How does wear offset tweaking work with G41/G42?

If a part is measuring 0.02mm oversize on a pocket, simply input -0.01mm into the tool D-wear register to adjust sizing.