John - I did something similar years ago to get beneath/remove the hardened threads on the end of a ballscrew. Not wanting to get grinding debris on the mill or lathe, I anchored an XY compound vice alongside a bench grinder and clamped the nut in the vice. Infeed towards the wheel was via the compound table, traverse and covering the circumference was via a cordless drill on the other end of the ballscrew.
Dave