GARY,
The Mach3 mill screen can be used to run the lathe if you rename the screen set to a ".lset" so Mach knows it's a lathe. What are the specifics internaly .....I don't know!
The only thing I did "long time ago" was to use a stepper motor geared downto turn the lathe spindle and it was configured as a rotary and slaved to the Z axis. I also used it to index the spindle but was using live tooling on the carriage for milling and drilling. Intended purpose was for small stuff so one need not remount the piece from the lathe to a milling machine. Was able to do neat stuff but it was limited.
I am not up on Tormach's stuff but The Duality Lathe can not be used with Mach3 and needs Tormach's program.
Simpson did a development on using the Mill spindle to do the equivilant of what you see in the Tormach videos. He uses "swap axis" function but note that swap axis only changes the pin outs,thus, if what your swawping is not the same it won't work and he also learned that a stepper was not good for what he wanted to do.
Save some time and have a look at Simpson's site for what he now does:
www.theInTurn.comhttp://www.theinturn.com/Info on some of Simpson's Macro's.
http://www.machsupport.com/forum/index.php/topic,11422.msg96092.html#msg96092Here is a link to a board created by Simpson so the swap axis is done via hardware and also macro's posted
http://www.machsupport.com/forum/index.php/topic,11422.msg99637.html#msg99637Not sure I can be of much more help,
RICH