Siemens SINUMERIK 808D ADVANCED Programming And Operating Manual page 157

Explanation of the parameters
SPD and SPL (starting point)
Use the parameter SPD to specify the finished part diameter for the undercut. The SPL parameter defines the finished
dimension in the longitudinal axis.
If a final diameter of <3 mm results for the value programmed for SPD, the cycle is canceled, and alarm 61601 "Finished
part diameter too small" is issued.
FORM (definition)
Form E and form F are fixed in DIN509 and must be defined using this parameter.
If the parameter has a value other than E or F, the cycle aborts and creates alarm 61609 "Form defined incorrectly".
See the following illustration for Form E and Form F:
VARI (undercut position)
The position of the undercut can be either specified directly or derived from the tool point direction with the _VARI
parameter.
VARI=0: According to tool point direction
The tool point direction is determined by the cycle automatically from the active tool compensation. The cycle can operate
with the tool point directions 1 ... 4.
Programming and Operating Manual (Turning)
157
6FC5398-5DP10-0BA2, 06/2015