I agree, just did that a couple of weeks ago making a new part for a pressure washer pump manifold. The thread was 3/8-18 npt but the stock could only be .65" instead of .675". Thread milled fine.

But Mike's situation is a bit tougher, picking up an internal thread in the nut would be hard, and making a new vise nut evener harder, at least for me.

Terry