Thanks, John! I think i'm getting a bit better understanding now thanks to your description. So it sounds to me like the biggest 3-phase motor you can run is about 2/3 of your 220v 2-phase capacity, right? Running a 3-phase motor essentially draws about 30% higher current than it's 220v 2-phase counterpart of equal HP rating? (2hp 3-phase would draw about the same as a 1.5hp 2-phase?)
You have some terminology wrong, possibly, as I don't believe there is such thing as a 2-phase, it's really 1-phase. A single phase (1 phase) 220v circuit has 2 x 120v hot lines, and to make it 3 phase, you produce the 3rd 120v line. A 3 phase circuit will at any time produce 240v by using any 2 of the 3 hot lines, hence 120v+120v give you the 2 needed hots for 240v.
Some type of motors require more to start, such as a bandsaw, but typically a table saw and/or jointer, or even planer will not. Compressors require more to start up also, along with band saws that are the most common for woodworkers.
It does require more AMPs than needed for the motor to start from a 1-phase circuit, and I have heard 37% higher in the past, but that number could be wrong. In general, most people plan to have 50% more HP than the largest motor on the circuit, and for a 5HP machine would have a 7.5HP RPC (this is what I run). Once the largest motor is started, you can start 3x the rated HP, so a 7.5HP RPC would be rated to start a 5HP motor, and you could have 15HP of machines running on the 7.5HP RPC at any given time.
There is grey area since some motors do not require as much to start, and you might be able to start a 7.5HP table saw on a 7.5HP RPC for instance, but the general rule of thumb is that you need aprox 50% more HP and 37% higher amps than the 3 phase idler motor will require (23 amps is typical for an average 5HP 3 phase motor, hence you need about 31.5 AMPs to run them). I have also heard that you do not want this number to go over 80% of the rated circuit, but that is for all circuits in general and not sure RPCs. I have an idler that only sucks 19.2 amps, and run it on a 30amp 1 phase 220 circuit with no problems. My RPC is rated to require a 30 amp, but again, the amps are less for the motor and it was sold with those requirements. Do your homework, it's easy to burn a house down.
My motor has the arbor cut off. It's not a big deal to get another arbor if one wants to use the motor for something else, those are available. I believe it is safer to have it cut, although Steve's solution of building a box around it adds the same safety.
3 phase is a PITA and requires some cost up front, but once you solve it at your home, it opens up the world of 3 phase machines, and most of them are in another class of workload than the 1 phase counter parts, but not always. Much of the industrial machines are 3 phase. Having a 5HP 3 phase industrial table saw in your garage is something that most would have scoffed at when some of the machines were built, but it is reality today. Some people like that class of machine, and others shy away from them. It opens up some real possibilities on woodworking machines.
In addition, 3 phase motors are sold for pennies on the dollar since most folks getting rid of them can't use them and many production shops will not buy used motors, and specificially require a new one to replace any old motors. Truth be told, it's not too often these more industrial 3 phase motors have problems, although some occasionally do.
Good luck on your RPC build. I have one and wouldn't want to be without it, because I wouldn't be able to use either my table saw or jointer, and soon to be DC that I will build with a 3 phase motor.