Your only choices would be:
- Three phase transformer
One may. It is not an "only". A 1-P transformer 220 <=> 440 into a 440 idler works, too.
- VFD - A 2 or 3 HP model
Not "A". Possibly THREE. He has more than one load motor. Not economically attractive, accordingly. Potential future maintenance headache, if not also problematic at initial installation and commissioning.
MAJOR revision of the controls. ALL of them, or near-as-dammit as well, VFD require. Why go there, when one need not?
- RPC - Needs a 440V idler motor and deal with the controls for it.
A 220 VAC idler on the utility main side of a 220 <=> 440 3-P step-up transformer works also. It could be the preferred solution, depending on what current costs of the major components are. Use of an RPC also means little or no alteration to the controls. Avoidance of controls being assigned to the generated leg is the key. Not at all hard. Not, in fact, any form of disaster, if it DID occur. The "generated" leg is just not so imperfect as all that. The controls draw very little power.
Last place "winner" due to use of dual-speed final-drive motor, OTHER 440 VAC 3-P motors, plus Hardinge intensive optimizations, whole "system". That level of "goodness" is a significant part of what makes a Hardinge desireable. It would be counter-productive to piss it away.
This is not news, here. It has been covered on other 440 V Hardinge. It is not that hard.