Siemens SINUMERIK 840DE Programming Manual page 324

Tool offsets
8.8 Tool radius compensation (G40, G41, G42)
Direction of machining G41, G42
From this information, the control detects the direction, in which the tool path is to be
displaced.
Note
A negative offset value is the same as a change of offset side (G41, G42).
You can generate equidistant paths with OFFN, e.g., for rough-finishing.
Working plane G17 toG19
From this information, the control detects the plane and therefore the axis directions for
compensation.
Example of milling cutters
N10 G17 G41 ...
The tool radius compensation is performed in the X/Y plane, the tool length compensation is
performed in the Z direction.
Note
On 2-axis machines, the tool radius compensation is only possible in "real" planes, in
general with G18 (see tool length compensation table).
8-28
Programming Manual, 10.2004 Edition, 6FC5 298-7AB00-0BP1
Fundamentals