Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 612)

Thread Cutting
Chapter 25
25-12
The G34 code programs the variable lead thread cutting mode. It is
programmed almost identically to the G33 thread cutting mode with the
addition of a K-word used to program the amount of lead variation per
revolution.
Figure 25.9
Variable Lead Thread
Important: Do not re-program the G34 command in consecutive threading
blocks. Doing so will cause the control to pause axis motion (possibly
damaging the thread) while the axis re--synchronizes with the spindle.
The format for the G34 threading mode is:
Parallel thread G34Z__ F__ Q__K__;
E
Tapered thread G34X__Z__ F__ Q__K__;
E
Face thread G34X__ F__ Q__K__;
E
Where : Is :
X This parameter is the end-point of the thread cutting move in the X axis. This
parameter may be an incremental or absolute and radius or diameter value. If
not present, there must be a Z parameter. If an X parameter is present, it
indicates either a face, tapered, or lead-in thread. When used in a G34 block
without a Z parameter, a facing thread is made parallel to the X-axis at the Z axis
position prior to the G34 block.
The initial minor diameter of any straight or tapered thread is determined by the
position of the X axis prior to the G34 block.
Z This parameter is the end-point of the thread cutting move in the Z axis. This
parameter may be an incremental or absolute value. If not present, there must
be an X parameter. When a Z parameter is used in a G34 block without an X
parameter, the threading pass is made parallel to the Z-axis at whatever X
position the tool tip was at prior to the G34 block.
25.4
Single Pass Variable Lead
Thread Cutting (G34)