Siemens SINUMERIK 828D Operating Manual page 564

Programming technology functions (cycles)
9.6 Further cycles and functions
Initial state of the machine kinematics
The tool axis is aligned in the Z direction.
β=90° represents a rotation of the cutting plate by +Y.
Mirroring
A mirroring of the Z axis (e.g. on the counter-spindle) for β=0° / γ=0° causes the same
machining in the mirrored coordinate system.
The mirroring of the Z axis must be permanently activated in a work offset.
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Operating Manual, 01/2015, 6FC5398-8CP40-5BA2
Turning