left hand tapping on lathe

TLDR; just use conversational to program the thread then edit g code to change M3 to M4 and it works. G74 might be broken PP 2.8.0 and/or Tormch's instruction are incomplete or possibly wrong. Also I may be an idiot.

This is for anyone else that needs to tap left hand threads. Here are my attempts:
(hand edit lh tap)
(----- Start of G-code -----)
(<cv1>)


G7 (Dia. Mode)
G18 (XZ Plane)
G90 (Absolute Distance Mode)
G40 (Turn Cutter Compensation Off)
G20 (units in inches)
G54 (Work Offset)


G30 (Park Tool)
T1212
G97 (RPM Mode On, CSS Off)
S 216


M8 (Flood Coolant ON)
M4 (Spindle ON, reverse)


G0 X 0.0000
G0 Z 0.2000
g98 G74 x0. z-1.0000 r.2 k.05556
g80
M9 (All Coolant Off)
M5 (Spindle OFF)


G30 (Park Tool)
(</cv1>)
(----- End of Tap -----)

this results in peck drilling i.e. spindle does not reverse, and I don't want to peck. K is supposed to be thread pitch in units per thread according to the programming. 18tpi in this case
Also tried g98 G74 x0. z-1.0000 r.2 F12.0 this either rapids or is 12" per rev
g98 G74 x0. z-1.0000 r.2 F.05556 looks mostly correct but does not change spindle direction at bottom of hole, just rapids out.
g33 x0. z-1.0000 r.2 k.05556 same as above.


But, this worked:

(hand edit lh tap)
(----- Start of G-code -----)
(<cv1>)


G7 (Dia. Mode)
G18 (XZ Plane)
G90 (Absolute Distance Mode)
G40 (Turn Cutter Compensation Off)
G20 (units in inches)
G54 (Work Offset)


G30 (Park Tool)
T1212
G97 (RPM Mode On, CSS Off)
S 216


M8 (Flood Coolant ON)
M4 (Spindle ON, reverse)


G0 X 0.0000
G0 Z 0.2000
g33.1 z-1.0000 r.2 k.05556
g80
M9 (All Coolant Off)
M5 (Spindle OFF)


G30 (Park Tool)
(</cv1>)
(----- End of Tap -----)