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17 Canned Cycles for Drilling
142
Fig. 17.1.2-1
17.1.2 Counter Tapping Cycle (G74)
This cycle can be used only with a spring tap. The variables used in the cycle are
G17 G74 X
p
__ Y
p
__ Z
p
__ R__ (P__) F__ L__
G18 G74 Z
p
__ X
p
__ Y
p
__ R__ (P__) F__ L__
G19 G74 Y
p
__ Z
p
__ X
p
__ R__ (P__) F__ L__
Prior to start the cycle, the spindle has to be started or programmed to rotate in the direction of M4
(counter-clockwise).
The value of feed has to be specified in conformity with the thread pitch of the tapper.
– In state G94 (feed per minute):
where P is the thread pitch in mm/rev or inches/rev,
S is the spindle speed in rpm
– In state G95 (feed per revolution):
where P is the thread pitch in mm/rev or inches/rev.
The operations of the cycle:
1.
rapid-traverse positioning in the selected plane
2.
-
3.
rapid-traverse movement as far as point R
4.
-
5.
drilling as far as thebottom point, with feed F (override and stop inhibited)
6.
dwell with the value specified at address P, provided parameter TAPDWELL is
enabled (=1) spindle direction reversal (M3)
7.
retraction as far as point R with feed F (override and stop inhibited)
8.
spindle direction reversal (M4)
9.
with G98, rapid-traverse retraction to the initial point
10.
-