Hi fellas,
Hey, I thank Jim and Delraydella for their helpful responses. I'm going to copy and paste some the details of my situation that I've already written out to a couple of vendors on Ebay --if something is repeated or incongruent, it's because I didn't edit them properly. But they will probably answer any questions you have and give you a clearer picture of my plan.
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I picked up a couple of plasma cutters that are pretty hefty--Hyperptherm 85 and Hypertherm 1650. The 85 will configure itself to electrical source, 1-phase, 3-phase, 200-600volt. The 1650 is similar, but 3-phase only. For 3-phase Hypertherm recommends a 60amp circuit for the 85, and an 80amp for the 1650. I have 220volt, 3-phase power in my shop. I will probably sell the 1650 so I can get by with just 60amps. It's my understanding that these machines only draw these high amps during a brief spike when starting the arc. The cutting amperage is far less. If I run the 85 model on 1-phase, a 100amp circuit is recommended, so I decided against that, at least for now. A safety switch that can be turned off is required, such as the kind with the typical up-down lever. Fuseable isn't required but desirable--I'm willing to pay a little more for that option.
I'm setting up a little metal-working area in one end of my shop. I acquired a plasma cutter that requires a circuit of at least 60amp capacity if it's 3-phase, 220-240volt. The machine will also work on single phase, but it would require a 100amp circuit and components for that. I originally decided that I'd run both a single-phase, 100amp and a 3-phase, 60amp (or bigger) circuit to accommodate both immediate and future needs. Well, the prices for all that became too much, so I decided to just install the bare minimum for my immediate need---60amp, 3-phase, 220-240volt. The circuit will run about 30ft and terminate on my shop's wall, first going through a safety switch. Two receptacles will come out of that--one on the inside of the shop, and one on the outside. I also want an extension cord about 25-30 feet long that will plug into the outlets and the machine's power cord--and, finally, a male plug installed on the machine's power cord. This arrangement will allow me to use this machine both inside and outside, and gives me the reach to handle most any job I encounter. My materials list follows:
---1 Square D circuit breaker 60amp, 3-phase (I have a 220v, 3-phase service panel already).
---Enough #6AWG wire to make a 30 foot long circuit (~100 feet) and 30 feet of ground wire;
---Enough 1" metal conduit to make a 30 foot circuit;
---1 safety switch (fuseable would be nice, but not essential);
---2 female wall-mounted receptacles.
For the extension cord and power cord I need:
---1 female plug;
---2 male plugs that will fit the receptacles and female plug;
---25-30 feet of #8AWG 4-wire cable.
I'm trying to save some money on Ebay buying a little here and there, but I'm not sure what fits with what.
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Well, that's about it fellas--hope it's all clear.
Hey Jim, I grew up not terribly far from your neck of the woods in the northern panhandle of West Virginia near to Weirton. Everyone around there worked for the steel mills when I was young including my dad and uncles. It's nearly all shut down now.

Most everybody in that area has a heavy "western Pennsylvania" accent, even in Youngstown. I always used to laugh when I heard Dan Marino or Jim Kelly talk on TV--I'd say to myself, "Yeh, they're from the 'area' ". We're all "valley boys" I guess--Ohio River valley that is.
Thanks, Charley