Has anyone had a go at machining a two or more start internal thread using the thread milling cycle to produce a threaded nut in the region of 1 1/2'' diameter if so how succesful was it and how did you command the tool to start in the other helix lead-in positions. cheers Colin

Can you do the first 'start' then Rotate 180 deg (for 2 start) and repeat.
On a Fagor I would use G49 or G73.

You can either start the second cut at the same Z position as the first but on the opposite side of the circle or on the same side as the first but with the starting Z half a pitch (or is it half a lead?) above or below the first.