Following on from John's advice, how's this for an idea?
The leadscrew is already threaded M6 ( probably not big enough, could go to M10 ? ) so take a piece of bar greater than 16mm in dia, machine a 10 mm threaded stub, screw into existing hole.
Now, the brass bevel has a 1/8" keyway machined into it, I could then machine a similar size keyway in the extension piece to match.....then machine the o/d back to match the leadscrew.....
The thread section provides longitudinal support, while the keyway provides the torque.....
Sound good?