Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 646)

Milling Fixed Cycles
Chapter 26
26-14
to re-tap a hole, a Q-word must have been programmed when the hole
was originally tapped
block retrace is possible during the tap-in portion of the cycle, but not
during the tap-out
Figure 26.6
G74.1: Left-Hand Solid-Tapping Cycle
Tapping feed
Rapid feed
R point level
initial point
level
R
Z
Hole bottom
Spindle rotation direction is
reversed at hole bottom
1
2
3
4 5
6
7
5
6
G98 G99
In the G74.1 left-hand solid-tapping cycle, the control moves the axes in
this manner:
1. The tool rapids to the tapping position above the hole location.
2. The threading tool then rapids to the R point.
3. The control either orients or stops the spindle.
If a Q-word was programmed: the control:
yes orients the spindle
no stops the spindle
4. Tap-in: The counterclockwise rotation of the spindle ramps up to the
programmed S spindle speed and linear motion of the Z axis moves
synchronously to reach the Z position.