I am building a portable saw table/router table and would like to supply power to both motors with one cable. I plan on using 12/4 SJ cord. Since the router and the saw share the same table, they will never be powered at the same time. I would like to wire the saw motor 220 volt and the router table 110 volt. For the 110 circuit I would use one leg of the 220 and the neutral. The circuit would be protected with a 20 amp double pole breaker. Will this work?

Thanks for your respnse

Yes, but why not simply wire both motors 120VAC?

Yes, but why not simply wire both motors 120VAC?
The saw motor draws 12 amps at 230 and 5 amps at 113. I thought the motor would run more efficiently on the 230 with less potential for lugging down an a possible savings on energy. Is this not the case?

While the current draw will be less you will need different wiring sizes, different breakers. All will probably off set any actual savings you might see. Running a single 20 amp circuit is way easier. While your at it, why not put in a receptacle and simply plug in the item you are using at the time? That way there is no possibility of running both at once.
I think you have your amp draws switched too.
220 volts at 5 amps and 120volts at 12 amps

The choice of whether to wire 120 or 240 relates to cost.
More copper is needed for the 120 circuits. There is little to be gained otherwise.

For systems that can be 120 or 240 where the switch isn't changed, then increased reliability of the switch could occur.

Motors 3 HP or more should be wired 240. 1 to 3 HP is gray area.

Thanks 450donn, you convinced me. I think I will keep it 110 and save the extra effort.