Siemens SINUMERIK 840DE Programming Manual page 23

Milling:
Turning:
The third coordinate axis is perpendicular to this plane and determines the infeed direction of
the tool (e.g., for 2½ D machining).
Working planes
The working planes are specified as follows in the NC program with G17, G18 and G19:
Plane
X/Y
Z/X
Y/Z
Fundamentals
Programming Manual, 10.2004 Edition, 6FC5 298-7AB00-0BP1
Designation
G17
G18
G19
Fundamental Geometrical Principles
1.1 Description of workpiece points
Infeed direction
Z
Y
X
1-9