Hi,
threading is a function that's largely enacted by the motion controller. In the case of Mach 3 the motion controller is the humble
parallel port. While Art has written a parallel port driver for Mach 4 he hasn't bothered to try to add threading, apparently its quite a mission
and he is of the opinion that most users will be better served with an external controller.
To get the best from Mach4 you really need an external controller, there are a half dozen manufacturers who have a good reputation
and make good gear. None of them are free. The cheapest is about $120 and a full blown HICON from Vital Systems could cost $2000.
A UC100 from CNCDrive, a PMDX-411 from PMDX or a PoKeys u57CNCd25 are all very similar, they plug in to your PC with USB and their
output is a db25 plug just like your parallel port, in fact would plug into you G540 no troubles. You will have to do some research to see if
any or all of them support threading. All of these devices are around $120. Note that they only have one 'ports worth' of IO that is 12 outputs
and 5 inputs. You don't need a very sophisticated machine and you run out of IO.
For a few more bucks you can get an Ethernet Smoothstepper from Warp9 which has three ports worth of IO, a PMDX-426 with two ports
or a PoKeys 57E or 57U with 55 IOs, equivalent to a bit more than three ports. There again you will have to do some research to find out
if any of them support threading. I believe the Smoothstepper has very recently added that function, but I can't tell you for sure yet.
As I've already mentioned the HICON unit from Vital Systems is a very good bit of kit with all sorts of functionality but it starts at $600 and
probably you'll want features which take it up to $1200. Those people who've stumped up for one all say they are very good. Can't afford
one myself.
I use an ESS Smoothstepper, about $190 and its been great.
Beware that there are heaps of Chinese UC100 knock-offs on Ebay at the moment and they're rubbish. If you want a UC100 buy from CNCDrive
or their US distributor.
Craig