Siemens SINUMERIK 840D, Operating Manual, Page: 362 / 610

Programming technological functions (cycles)
8.4 Turning - only for G code programs
Milling
362
Operating Manual, 03/2010, 6FC5398-7CP20-1BA0
Parameters Description Unit
Position Form F machining position:
Undercut size according to DIN table:
e.g.: F0.6 x 0.3 (undercut form F)
X0 Reference point X ∅ mm
Z0 Reference point Z mm
X1 Allowance in X ∅ (abs) or allowance in X (inc) mm
Z1 Allowance in Z (abs) or allowance in Z (inc) – (for undercut form F only) mm
VX Cross feed ∅ (abs) or cross feed (inc) mm
8.4.5 Thread undercut (CYCLE940)
Function
You can use the "Thread undercut DIN" or "Thread undercut" cycle to program thread
undercuts to DIN 76 for workpieces with a metric ISO thread, or freely definable thread
undercuts.
Approach/retraction
1. The tool first moves to the starting point calculated internally in the cycle at rapid traverse.
2. The first cut is made at the machining feedrate, starting from the flank and traveling along
the shape of the thread undercut as far as the safety distance.
3. The tool moves to the next starting position at rapid traverse.
4. Steps 2 and 3 are repeated until the thread undercut is finished.
5. The tool moves back to the starting point at rapid traverse.
During finishing, the tool travels as far as cross-feed VX.