Good for you! Far better to ask, than to assume and do it wrong. The bottom
line is, neither your plasma cutter nor your compressor requires a *neutral*.
They both require a *ground*. So in the receptacles for both of them, you
connect the ground. There is no place to connect the neutral, so you don't
need to run four wires to the receps -- three will do.

At this point, you're probably wondering why you bothered running four wires
to the subpanel, if all you're going to need is three. The answer is, so that
you can run 120V circuits off that subpanel, too -- they need the neutral,
even though the 240V circuits don't. Maybe you don't ever plan on putting any
120V circuits in that panel... but the next guy to own your home might.

Excellent. Thanks very much for your response. You really made it
clear for me.

And i do plan to run several 120 circuits of the panel too.

Again, thanks a lot.
Tim