I got to spend a few hours over the weekend and turned down the supported end of the ballscrew (THK BIF 2004 ground ballscrew travel 257mm) as it was 30mm too long. I first attached the ballnut with tape to ensure it would not move and no chips/dust could get in, and then used the bench grinder to remove the hardened layer so I could turn it with a carbide insert. Luckily the screw had originally been turned between centres so it was an easy job to get it centred in the lathe and relatively straight forward to turn a 15mm diameter for mounting the ball bearing.