Cutter radius compensation (G40/G41/G42)

G40                                           Deselect SRK                                          (modal, initial state)

G41                                           SRK left of contour                                                                (modal)

G42                                           SRK right of contour                                                              (modal)

Tool tip radius compensation (SRK) acts in the machining plane selected using G17, G18, G19. In this plane, one of the axes must be operated in "face turning” mode and the other in "longitudinal turning” mode. ( axis mode: P-AXIS-00015)

The data records stored in the D words are used as tool compensation values. For turning tools, the orientation of the cutter edge relative to the machining plane (face/longitudinal turning axis) must be specified in the parameter P-TOOL-00002 by an additional identifier 1...9 (see figure).

Orientation of cutter edge to machining plane.
Orientation of cutter edge to machining plane.

A typical turning tool is characterised by the following values/parameters:

  • Tool type

1 (turning tool)

  • SRK orientation


  • Tool radius

Tool tip radius

  • Tool length


  • Tool offset (see figure below)


Tool gauging for tool offset compensation.
Tool gauging for tool offset compensation.

When specifying tool axis offsets, their mathematical sign should be noted since it refers to components of the tool offset vector in the machining plane. In the example of a turning tool shown in the above figure, the offsets in the direction of the X and Y axis both have negative (mathematical) signs.

Tool offsets must be specified up to the theoretical tool top (point P).

A change between turning tool and milling tool is permitted when G41 or G42 is selected. With absolute programming (G90) the current axis offset values of the new tool are included in the calculation for the next motion block depending on the tool type.