Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 616)

Thread Cutting
Chapter 25
25-16
The G21 single pass threading cycle can be programmed to cut parallel or
tapered fixed lead threads (variable lead threads may only be cut using a
G34 block). This threading cycle performs a predetermined series of
machining steps designated by a single program block.
The two chamfering features (threading retract and threading chamfer)
described on page 25-4 can also be used with this threading cycle. The
parameter to enable these and determine their angle and length is set in
AMP. The thread chamfer feature must also be enabled through PAL.
This threading cycle repeats automatically after every block that contains
axis words until the cycle is cancelled. These axis words generate rapid
moves. A G21 single pass threading cycle is canceled by programming
any other G-code in modal group 1 (this includes G00, G01, etc.).
The conditions to be satisfied to execute this thread cutting cycle are
described on page 25-2, thread cutting considerations.
Before programming the G21 threading cycle, the cutting tool must be
positioned away from the part at a location that allows the control to
execute the cycle correctly.
Straight Thread Cutting
This format is for programming a single pass straight threading cycle:
G21 X__ Z__ {F__};E
Where : Is :
X This parameter is the start-point of the thread cutting move in the X axis. This
parameter may be an incremental or absolute and radius or diameter value. This
is the depth that the X axis moves to before starting the thread cutting pass. This
value may be replaced in any block following the G21 block while the G21 cycle
is active. X may also be programmed as an incremental or absolute value.
Z This parameter is the end-point of the thread cutting pass in the Z axis. This
parameter may be an incremental or absolute value. Z parameters are always
entered as a radius values regardless of the current mode.
E F This parameter may be entered by using either an E- or F-word. It represents the
thread lead along the axis with the largest programmed distance to travel to
make the thread cut. It is mandatory when cutting any threads.
If the E-word is programmed, its value (sign ignored) is equal to the number of
threads per inch or inches per thread (determined in AMP) regardless of whether
inch or metric mode is active at the time.
If the F-word is programmed, its value (sign ignored) is the thread lead in inches
per revolution or millimeters per revolution, depending on the mode in which the
control is operating.
25.5
Single Pass Threading Cycle
(G21)