HEIDENHAIN TNC 320 User Manual page 104

Danger of collision!
Always program the same algebraic sign for the infeeds:
Cycles comprise several sequences of operation that are
independent of each other. The order of precedence
according to which the work direction is determined is
described with the individual cycles. For example, if you
only want to repeat the countersinking process of a cycle,
enter 0 for the thread depth. The work direction will then
be determined from the countersinking depth.
Procedure in case of a tool break
If a tool break occurs during thread cutting, stop program
run, change to the Positioning with MDI operating mode
and move the tool on a linear path to the hole center. You
can then retract the tool in the infeed axis and replace it.
104 Fixed Cycles: Tapping / Thread Milling