Siemens SINUMERIK 840D sl Programming Manual page 285

Change in compensation direction (G41 ↔ G42)
A change in compensation direction (G41 ↔ G42) can be programmed without an
intermediate G40.
Changing the working plane
The working plane (G17/G18/G19) cannot be changed if G41/G42 is active.
Change in tool offset data record (D...)
The tool offset data record can be changed in compensation mode.
A modified tool radius is active with effect from the block, in which the new D number is
programmed.
CAUTION
The radius change or compensation movement is performed across the entire block and only
reaches the new equidistance at the programmed end point.
Fundamentals
Programming Manual, 09/2011, 6FC5398-1BP40-2BA0
10.1 Tool radius compensation (G40, G41, G42, OFFN)
G41
G42
Tool radius compensation
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