[colin1544]

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

[Kiwi]

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

[Geof]

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.

[mikiet]

machine one start then move the threading tool in Z" by the pitch, (distance from one start to the next)

[cncsnw]

I haven't tried this, but I expect if you didn't want to change the starting Z (the usual method), you could apply a Subprogram/Rotate to the Thread Milling cycle. The start angle for the Rotate would be 180 degrees (or 120 degrees for three starts, etc.).

[WayneHill]

I once programmed them for plastic milk bottle blow molds. It was the section where the milk bottle cap fits on the body.

Used a vee cutter. Started at the bottom and profiled up in a helix. The most leads programmed was six. I wrote a program for it. It is posted in a Yahoo group somewhere. I will check.

[WayneHill]

Here it is!