I don't see any reason for you to use EITHER a G100 or a Smooth Stepper. Unless you are planning to run more than 4 Axes, or do not HAVE a parallel port on your computer.
A pair of ordinary Break out boards should do. You could then simply run the parallel cable from your computer to a DB-25 A-B switch. From that would exit TWO parallel cables, one to the mill and one to the lathe. That would allow switching the COMPUTER from one machine to another. Mach3 would run different profiles for the mill and lathe.
What size mill and lathe are you thinking of? You might even be able to use a G540 for each.
CR. |