Siemens SINUMERIK 840D sl Programming Manual page 27

Position of the coordinate system in different machine types
The position of the coordinate system resulting from the "three-finger rule" can have a
different orientation for different machine types. Here are a few examples:
Fundamentals
Programming Manual, 09/2011, 6FC5398-1BP40-2BA0
Fundamental Geometrical Principles
1.4 Coordinate systems
27