Siemens SINUMERIK 808D Programming And Operating Manual page 52

Straight cutting cycle:
The sign before the address character R depends on point A' of the viewing direction from point B.
Straight cutting cycle (G code system A):
● When the cycle with G90 (G77, G20) is executed with activated single-block mode, the cycle is not terminated in the
middle, but stops after the end of the cycle, which comprises of the sequence 1-4.
● The functions S, T and M, which are used as cutting conditions for the execution of G90 (G77, G20), are to be specified
in the blocks before the block G90 (G77, G20). When these functions are specified in a block with the travel of axes, then
the functions act only when the block is specified in the range of the operation with G90 (G77, G20).
The operation with G90 (G77, G20) then remains active till the block where a G function of the group 01 is specified.
Thread cutting cycle
There are three kinds of thread cutting operations: cycles for cutting cylindrical threads, cycles for cutting taper threads, and
transverse-taper turning cycles.
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Programming and Operating Manual (ISO Turning/Milling)
01/2017