You are missing the point entirely. Are the components in a machine rated for 220v 20amps capable of handling 50 amps when connected to a 50 amp circuit? Why even bother to specify the circuit for the machine at 220 20 amps, heck connect it to a 100 amp circuit by your logic. Just run some 00 wire in the shop and connect all the machines to a 100 amp circuit breaker, the wire is protected.