Manual

Thread Cutting
Chapter 25
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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 isthe start-point of thethread cuttingmove in the X axis. This
parameter maybe anincremental or absoluteand radiusor diameter value. This
is thedepth that theX axismoves tobefore startingthe threadcutting pass. This
value may be replacedin anyblock followingthe G21block whilethe G21cycle
is active. X mayalso beprogrammed asan incrementalor absolute value.
Z This parameter isthe end-point of thethread cuttingpass inthe Zaxis. This
parameter maybe anincremental or absolutevalue. Z parametersare always
entered as a radiusvalues regardlessof the current mode.
E F This parametermay beentered byusing either an E- or F-word. It represents the
thread lead along the axis withthe largest programmed distance to travel to
make the thread cut. It is mandatory whencutting any threads.
If the E-word is programmed, itsvalue (signignored) isequal to the number of
threads perinch orinches perthread (determinedin AMP)regardless of whether
inch or metric mode is active at the time.
If the F-word is programmed, itsvalue (signignored) isthe threadlead ininches
per revolutionor millimeters per revolution, dependingon themode inwhich the
control isoperating.
25.5
Single Pass Threading Cycle
(G21)