Manual

Thread Cutting
Chapter 25
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Programming Multipass Thread Cutting
Before programming the G78 threading routine, the cutting tool must be
positioned to the point from which the routine is to be executed. This point
is the end-point of each complete cycle of the threading routine’s
execution.
Use this format to program a multipass thread cutting routine:
G78X__Z__K__D__ F__ A__P__I__;
E
Where : Is :
X: This parameter isthe coordinatevalue of theroot (depth) of the thread. If
programming a tapered thread, it is the coordinatevalue to be attained at theend
of the last threading pass (assumethere isno chamfer cut at the endof the
pass). X values maybe enteredas aradius or adiameter value. X mayalso be
programmed as an incrementalor absolutevalue.
Z: This parameter isthe Zcoordinate valueof the endof the threadcutting pass. Z
parameters arealways enteredas aradius valueregardless of thecurrent mode.
Z may also beprogrammed asan incremental or absolute value.
K: This parameter isan unsignedvalue (alwaysprogrammed aspositive). It
programs thedistance fromthe threadroot (as determinedby theX parameter to
the top of the thread. K is alwaysprogrammed asa radiusvalue.
D: This parameter programsthe depthof cut (designated inradius) for thefirst pass.
It is anunsigned value(always programmedas positive). The depthof following
passes isdetermined bythis valueand thetype of infeedselected withthe P
parameter.
A: This parameter programsthe angleof the tooltip. It must be enteredas an
integer valuefrom 0 to120 (correspondingto 0-120degrees). Not programming
a value for A isthe sameas A0. A0 wouldbe the same as a plungetype infeed.
The value entered here determines theangle that the infeed moves makes,
which also determines thefinal threadangle. See thetool infeedsection that
follows fordetails.
P: This parameter determinesthe toolinfeed. It must be enteredas aninteger
value from one tofour. See thetool infeedsection that followsfor details.
E,F: This parameter maybe enteredby usingeither E or Ffor the threadlead
(as inG33).
If the E-word is programmed, itsvalue (alwaysunsigned) isequal to the number
of threads perinch orinches perthread (determinedin AMP)regardless of
whether inchor metric modeis activeat the time.
If the F-word is programmed, itsvalue (alwaysunsigned) isthe threadlead in
inches perrevolution ormillimeters perrevolution, depending onthe modein
which the control isoperating.
I This isthe changein radiusof the thread(on theX axis) that thethreading pass
makes asit reaches theend-point of the threadcutting pass. The end-point is
the X position programmedwith theX-word. I is anincremental, signed distance
(+ or -) added tothe Xparameter to determinethe start-point of the threading
pass onthe Xaxis. If a chamfer isbeing cut at theend of thethread cutting
pass, it does not affect the value programmed here. This parameter shouldbe
entered as if no chamferwere beingcut. I is always anincremental value
regardless of thecurrent mode. This parameteris alwaysentered asa radius
value regardless of the current mode.