I have a similar question/situation. I currently have an outlet connected to my table saw switch so that my shop vac comes on simultaneously. Both are 110v. I’m considering converting my saw motor to 220 and I want to keep the same setup. If I run 12/3 and connect one of the switch poles to the outlet, it can be done. However, the “neutral” for 220 operation is the other hot leg. Therefore I’m worried that the saw motor may back feed the outlet which could damage my vac. I reached out to an electrical engineer friend just now. Will advise later what he says.
Losing fingers since 1969