hey guys, Keen just posted a new segment of his RapidTurn video's, part 5. If you look at about the 9:15 mark he talks about spindle flex and tightening the draw bar. It looks as if this could have direct bearing on the OP's problem.
Terry
Tim
Tormach 1100-3 mill, Grizzly G0709 lathe, PM935 mill, SolidWorks, HSMWorks.
He is also using a Dixon QCTP which is somewhat more rigid than the Tormach supplied 0XA one.
I have a similar requirement, at least width wise, but not as deep, and I am actually trying to decide between a manual lathe and the RapidTurn, and this thread caught my eye. Out of curiosity, would this operation work better with a 4th axis and an end mill? Or at least the bulk of it and then finish it on the RapidTurn? Are you plunging the parting tool the whole inch in each pass, or working your way down gradually across the entire width?