Hood,
It is interesting, and you need to remember that this is three computers, before with the Dell and the Sherline i never got good threading past say 1" with the SS, then you have a borrowed computer and my new one. Now i just got a replacement opto so i can do index and timing now if i want. But the tests we just did with a friends equipment kind of rules the pulse out. His instrument can actualy pick up the difference in a timing belt timing riding up in the timing pulleys or not seating properly, but, that is "very small" contributor to rpm or feedrate varience to the "lathe system". He can also identify the effect it has on an encoder. You can actualy measure the effect of say not using an idler on the belt. We didn't do all that but he knows his "stuiff" and has folled with his owne setup.
There are four of us here that all see the same effect of the threading, granted, i'm somewhat different in the sense that i am trying to put data against it.
You would certainly see and can measure the effect on a long thread of 200mm / 4" . If a single point tool is used
the pitch diameter would decrease, the nut would become loose, and you would see the difference in outside diameter also / tapering in.
If you use a tool / chaser insert the lead will be more constant per grouping of threads, but, the lead would also decrease overall. Likewise on the outside diamter, if your using one of those inserts which shaves the thread OD as it cuts the v , you would not visualy see it as compared to a single pointed tool.
There is a big difference as i think you are using servos and encoders with your lathe. I am not putting my pulse into the SS board, but rather into the PP. Not sure what you have there in terms of a PLC and what it's doing.
So the "lathe systems" are quite different.
The code is generated by the threading wizard.
I like to have the M1076 .MIS generate the code as G32 since i can relate to a pass number what i see visualy as threading progresses. Very small passes .0001" cuts and a lot of them ( 40 ) as i figure if something is going to get screwy over time it will happen over that manny passes and most folks won't do that manny in practice. The depth then is limited to .004" which saves time. The angle is set to 30 degrees so it radial cutting / no z offsets occuring. That reduces the trigger/acceleration/feedrate to the equivilant of a commanded move to point as you did.
G01 Z-1.0 F1.0 equivilant to G32 Z-1.0 F1.0 ( it just adds the triggering ) but in terms of distance actauly moved there should be none fom a common start point. It's also a good comparitive test to do if your going to try picking up a thread.The rpm used is always the same ( ie; DRO says 402 i use 402, if you use something higher like 404, if that was a high seen in the diagnostics, i still use the DRO as didn't see any change in the resulting scribe lines. That's the logic i have used.
RICH