Originally Posted by
g-codeguy
I noticed 2 things right away. R0005 should be R.0005 P's & Q's have no decimal points. R's do. The 2nd thing was thread height. P0373 is way too small. I've never done a pipe thread that large so I had to look it up. Thread height should be P1000 and I would increase Q0030 (2nd block which is amount of 1st pass) to Q0120 minimum.
BTW, leading zeros can be omitted. Control reads from right to left which is probably why R0005 works. I use to program lathes that didn't use decimal points at all.
So it can be written as
G76 P020060 Q30 R.0005
G76 X3.341 Z-1.2 P1000 Q120 R-.0437 F.125
Also Z.2 gives 1.6 revolutions for acceleration before cutting if the thread starts at Z0. You may want to back up a bit. You do realize that P020060 will keep the threading insert in the part at Z-1.2 for one revolution before withdrawing. P020160 will cause the insert to withdraw in the shortest possible distance (along Z-axis).
Should you go to something like G76 X3.341 Z-1.2 P1000 Q200 R-.0437 F.125 in order to get the number of passes within reason, but have trouble with the insert chipping...lie. Increase P1000. It will make the first cutting depth lighter, but not give as many extra passes than decreasing Q200 to Q150 would.
Also P020060 only cuts on one side of the insert. I only use it when chatter is giving me a problem even after slowing RPM. Consider using P020029 or P020055