Thanks for the replies. I am running a Haas mini-mill, not a lathe. The "G00 G17 G20 G40 G49" etc. safety line does appear at the beginning of every program but not at every tool change.

Well, I don't know how to edit the post processor to do this so I'll just create a manual toolpath entry with "G17" (as code) whenever I have a drill toolpath follow a surfacing toolpath. This will inject "G17" in there before the drill cycle without fail.

I too have this problem. A surfacing toolpath invokes G18. Next comes a drill cycle and no G17 is called. The hole gets drilled in the wrong spot. The post is completely unmodified, generic haas 3 axis mill, inch, from mcam 2017. If anyone can offer advice about how to make G17 be reinstated I would appreciate it.

Are you using transform?

Some kind of a bug I guess. I changed the op1 toolpaths parameters to match op 2, (from OD thread to ID, different depth, different thread diameter) but didn't change the plane, and it put out the bad code. I then changed all parameters one by one to find the cause. It seemed related to the depth. I then changed the depth over and over, incrementally moving towards the depth of the original op 1 toolpath to see where the change occurred. I got within .003" of the op 1 depth and then it put out IJK code, so then I put in a higher value again expecting to see bad code, but now no matter what depth I put in, or if I changed the plane, or if I select the point that the op2 toolpath is based on, or whatever, it puts out the good code. So I just copy pasted that toolpath into op2 and my problem is solved....

Of what?

Greetings, I am using the generic Haas mill posts. When I thread mill, sometimes mcam 2017 puts out code like this: N730 T6 M6 N740 G0 G90 G55 X0. Y0. A0. S6000 M3 N750 G43 H6 Z.1 N760 M8 N770 G1 Z-.27 F40. N780 X.0887 F24. N790 G41 D6 X0. Y-.3415 N800 G3 X.4415 Y0. I.0887 J.3415 N810 Z-.2283 I-.4415 J0. N820 Z-.1867 I-.4415 J0. N830 Z-.145 I-.4415 J0. N840 Z-.1033 I-.4415 J0. N850 Z-.0617 I-.4415 J0. N860 G1 X.4396 Y.0413 Z-.0611 N870 X.4338 Y.0823 Z-.0605 N880 X.4241 Y.1226 Z-.0598 N890 X.4108 Y.1618 Z-.0592 N900 X.3939 Y.1995 Z-.0586 N910 X.3734 Y.2355 Z-.058 N920 X.3497 Y.2694 Z-.0573 N930 X.323 Y.301 Z-.0567 N940 X.2934 Y.3299 Z-.0561 N950 X.2612 Y.356 Z-.0555 N960 X.2267 Y.3788 Z-.0549 N970 X.1902 Y.3984 Z-.0542 N980 X.1521 Y.4145 Z-.0536 N990 X.1126 Y.4269 Z-.053 N1000 X.0722 Y.4356 Z-.0524 N1010 X.0311 Y.4404 Z-.0517 N1020 X-.0103 Y.4414 Z-.0511 N1030 X-.0516 Y.4385 Z-.0505...... The resulting thread looks faceted, as though "linearize helixes" were enabled, though it is not. Sometimes it will put out code with I, J, K instead, and these threads come out perfectly smooth: N1910 T6 M6 N1920 G0 G90 G54 X.0119 Y.9853 S6000 M3 N1930 G43 H6 Z.1 N1940 M8 N1950 G1 Z-.02 F40. N1960 G41 D6 X0. Y.886 F24. N1970 G2 X.786 Y0. I-.1064 J-.886 N1980 Z-.0617 I-.786 J0. N1990 Z-.1033 I-.786 J0. N2000 Z-.145 I-.786 J0. N2010 Z-.1867 I-.786 J0. N2020 Z-.2283 I-.786 J0. N2030 Z-.27 I-.786 J0. N2040 Z-.3117 I-.786 J0. N2050 X.7701 Y.1573 Z-.352 I-.786 J0. N2060 X.1773 Y-.8681 I-.8743 J-.1786 N2070 G1 G40 X.2088 Y-.963 N2080 G0 Z.1 N2090 M5 N2100 G91 G28 Z0. M9 The good IJK code is Op 1, G54 with the default work offset and top plane. The non IJK code is Op 2, the back side of the part, G55 with a custom plane, work offset #1. In machine control settings, helix support is set to all planes. How to get the good IJK code with non default planes?