[alain aleman]

Hi guys,
Here a program for 3" NPT pin.
%
O0002
(PROGRAM NAME - 3 NPT PIN)
(DATE=DD-MM-YY - 08-06-15 TIME=HH:MM - 10:40)
(MCX FILE - D:\HAVEN\O0002.MCX)
(NC FILE - D:\HAVEN CNC\3 NPT PIN.NC)
(MATERIAL - STEEL INCH - 1030 - 200 BHN)
G20
(TOOL - 1 OFFSET - 1)
(DESBASTE PDJNR 2525 M15 INSERT - DNMG 120408)
( REFRENTADO 0.020 )
G0 T0101
G18
G97 S413 M03
G0 G54 X3.7 Z0. M8
G50 S1000
G96 S400
G99 G1 X2.9375 F.01
G0 Z.1
( DESBASTE D0.060 )
X3.6202
Z.11
G1 X3.4202 F.012
Z-.2706
X3.4488 Z-.3013
G18 G3 X3.4564 Z-.3174 R.0412
G1 X3.54 Z-1.655
X3.74
G0 Z.11
X3.5004
G1 X3.3004
Z-.1422
X3.4402 Z-.2921
X3.6402
G0 Z.11
X3.3807
G1 X3.1807
Z-.0138
X3.3204 Z-.1637
X3.5204
( ACABADO )
G18
G0 Z-.018
X3.3426
G1 X3.1426 F.01
X3.4106 Z-.3055
G18 G3 X3.4164 Z-.3177 R.0312
G1 X3.5 Z-1.6553
X3.7
M9
G28 U0. V0. W0. M05
T0100
M01
(TOOL - 7 OFFSET - 7)
(ROSCA EXTERIOR 10-11.5NPT INSERT - TNMA 43 11.5 NPT EXT)
( ROSCA 3 NPT-8 TPI )
G0 T0707
G18
G97 S400 M03
G0 G54 X3.7 Z.2481 M8
G76 P010029 Q0. R0.
G76 X3.310 Z-1.625 P0950 Q0068 R-.057 F.125
M9
G28 U0. V0. W0. M05
T0700
M30
%

I checked the toolpath on CIMCO edit and look the threading process, attached files. I can`t found my mistake (see tool retract).

[fordav11]

Your Q and R should not be 0 (in real life machining situation).
Regardless it doesn't work in the simulation even with Q and R set to some amount.
I tested a proven program that works on real CNC lathe in Cimco Edit 7 (build 7.55.08 the latest release)
and it doesn't work so threading in Cimco Edit 7 is borked.
Report the problem to Cimco and they will hopefully fix it.