HEIDENHAIN TNC 320 User's Manual For Cycle Programming page 105

4
Fundamentals of Thread Milling 4.5
The TNC references the programmed feed rate
during thread milling to the tool cutting edge. Since
the TNC, however, always displays the feed rate
relative to the path of the tool tip, the displayed value
does not match the programmed value.
The machining direction of the thread changes if you
execute a thread milling cycle in connection with
Cycle 8 MIRROR IMAGE in only one axis.
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.
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HEIDENHAIN | TNC 320 | User's manual for cycle programming | 9/2016