Siemens SINUMERIK 828D Programming Manual page 167

Further information
General
It is recommended that the working plane G17 to G19 be selected at the start of the
program. In the default setting, the Z/X plane is preset for turning G18.
Turning:
The control requires the specification of the working plane for the calculation of the direction
of rotation (see circular interpolation G2/G3).
Machining on inclined planes
Rotate the coordinate system with
the coordinate axes on the inclined surface. The working planes rotate accordingly.
Tool length compensation on inclined planes
As a general rule, the tool length compensation always refers to the fixed, non-rotated
working plane.
Fundamentals
Programming Manual, 07/2010, 6FC5398-1BP40-0BA0
8.2 Selection of the working plane (G17/G18/G19)
(see Section "Coordinate system offset") to position
ROT
Geometry settings
167