Siemens Sinumerik 840D sl Programming Manual page 215

Note
Technical requirement for thread cutting with G33 is a variable-speed spindle with position
measuring system.
Multiple thread
Multiple thread (thread with offset cuts) can be machined by specifying a starting point offset.
The programming is performed in the G33 block at address SF.
Note
If no starting point offset is specified, the "starting angle for thread" defined in the setting data
is used.
Thread chain
A thread chain can be machined with several G33 blocks programmed in succession:
Fundamentals
Programming Manual, 01/2015, 6FC5398-1BP40-5BA2
Motion commands
10.10 Thread cutting
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