Siemens sinumerik 840D sl Operating Manual page 105

See also
Thread turning (CYCLE99) (Page 291)
Turning
Operating Manual, 07/2010, 6FC5398-8CP40-0BA0
Note:
The thread synchronization is activated by teaching in a spindle. In
this case, the synchronizing positions of axes X and Z and the
synchronizing angle of spindle (Sn) are saved in the Machine and
displayed in the screen form.
The selection boxes for main spindle and counterspindle indicate
whether thread synchronization is active for the particular spindle (yes
= active / no = not active).
5. Now carry out the "thread turning" machining step.
6. For the main spindle or counterspindle, select the "no" entry to
deactivate thread synchronization.
Working in manual mode
3.6 Thread synchronizing
105