HEIDENHAIN TNC 640 (34059x-04) Cycle programming - Manual (Page 116)

Fixed Cycles: Tapping / Thread Milling
4.6 THREAD MILLING (Cycle 262, DIN/ISO: G262)
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TNC 640 | User's Manual Cycle Programming | 3/2014
Please note while programming:
Program a positioning block for the starting point
(hole center) in the working plane with radius
compensation
R0.
The algebraic sign for the cycle parameter "thread
depth" determines the working direction.
If you program the thread DEPTH = 0, the cycle will
not be executed.
The nominal thread diameter is approached in a semi-
circle from the center. A pre-positioning movement
to the side is carried out if the pitch of the tool
diameter is four times smaller than the nominal
thread diameter.
Note that the TNC makes a compensation
movement in the tool axis before the approach
movement. The length of the compensation
movement is at most half of the thread pitch. Ensure
sufficient space in the hole!
If you change the thread depth, the TNC
automatically changes the starting point for the
helical movement.
Danger of collision!
Use the machine parameter displayDepthErr to
define whether, if a positive depth is entered, the
TNC should output an error message (on) or not (off).
Keep in mind that the TNC reverses the calculation
for pre-positioning when a
positive depth is
entered . This means that the tool moves at rapid
traverse in the tool axis to set-up clearance below
the workpiece surface!