Let me re-phrase the question, as I did a terrible job the first time.
I have a mill that can definitely run at 220v, with two legs of 110v, (split phase, as commenters have informed me). I've run it from both a drier plug (split phase 110v in canada), and a variac (split phase 110v.). The nameplate also says 240v.
I bought a 2kw transformer (perhaps an autotransformer?) that provides 240v, single phase.
Is it safe to connect these?