One VFD for both lathe and mill

Perfect except the cost of 3-prong twist lock plugs and receptacles is much more than a switch
 
Even if you are able to come up with a satisfactory switching arrangement, it is not very likely that you will want the same parameters for both machines. A milling machine will typically have an end mill or drill bit mounted in the spindle, so ramping up to full speed in a second or two will be no problem, but if you have a three jaw chuck and a chunk of steel mounted in the lathe, (10-30 lbs) such a fast start or stop could be quite exciting, especially if it is a threaded spindle.
 
Some people think of a VFD as just a power supply to make 1 phase 220 from 3 phase 220 like a rotary phase converter. Just a power source, plug whatever in and it powers all. Rotary phase converter is like that.

But a VFD is specific to each motor it works with and parameters are set for the motor. (Or should be for best functioning). So could use same VFD with two similar motors but be careful with different motors. Could use same VFD and change the parameter set but that takes a little time, not bad if you do it repeatedly.
 
I never use both at the same time so why bother buying another VFD. What type of switch could I used to switch the 3 wires from the lathe to the mill?
After giving this more thought. After its all said and done, you will likely spend over 1/2, if not over the full cost of a second VFD. Consider just buying 2 of the same VFD's. Makes all this mute, and tons easier to wire it all up. Plus, you have a second that can be switched between machines if one goes bad.
 
I agree, good to have a spare, never know how long those chinese VFD's will last.
 
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