Hi,
if I'm not mistaken none of the CNCDrive motion control boards (UC100, UC300,UC400) support single point lathe threading.
In order to synchronise the start of the thread the motion controller must do it. The communication delays (controller to Mach, Mach makes up it mind, Mach to controller plus buffer delay)
are such that Mach is not fast enough to synchronise the start of a thread, whereas the motion controller is.
Mach's parallel port can do it, if somewhat less precise. An Ethernet Smoothstepper, a PoKeys 57CNC, a Vital Systems Hicon or a CSMIO can all do lathe threading. Of them I use
an Ethernet SmoothStepper, although not for lathe threading.
Craig