Hood,
Ah ...as noted in the first posting....
I never did any testing with the SS and haven't used mine in a long time. So additional electronics are involved.
If we just forget about the actual threading then there seems to be a timing issue. ie.The G95 informs Mach that the index was seen x amount of times and
based on an average of the rpm the axis is then instructed to move / accelerate over some linear distance. So the index trigger point,
acceleration value, current rpm of the spindle in a time frame, and actual movement of the axis needs to be consistant to arrive at an exact location.
If one were to use a thin disc ( btw ....the bigger the disc diameter the better one would see any timing issues ) you can get a flavor of magnitude since the cut marks would be off by a greater amount.
If we assume that there is no backlash, the starting point is exactly the same location, and the system can respond to the requested motion,
but, and i say but , the instructions are not the same as the PP, then there could be something wrong in MACH. But before one guesses at that they need to verify that the system is all correct and that is hard to pin point a possible problem.
He is using a max velocity of 190 with accel around 4. So even though his kernel frequency is high that dosen't mean he can use that high velocity in a repeatable
accurate way. The max values are used during the move from standstill to the start of the threading and not the 65ipm he notes.
Maybe try a reduction in spindle rpm and velocity to say 1/2 the currrent velocity value and do some testing to "scribe" marks on the edge of a disc.
I will note to use the wizard since it will check that the spindle rpm and current tuning settings are adequate for the threading to be done.
Not sure what else to say at the moment.....
RICH