What would you choose

Because I cannot get any of my projects working I decided to start another in the hope I would succeed and get my inspiration back for my other projects, so naturally I am now stuck, a common theme :heart-borken:

My new plan is to build a leadscrew controller based on the Clough 42 project:

https://youtu.be/FTs9GygRQ-U

I have bought a good few bits but I am now stuck on my choice of Servo/Stepper to drive the leadscrew, my plan is to drive the leadscrew from the tailstock end thus getting around any gearbox issues, the lathe is a Harrison M300 so not Chinese Micro Lathe territory.
I would be very grateful for any and all suggestions as to what size/make/power of Servo or stepper motor I should be looking at, it is going to need to be of a decent spec because the leadscrew is 28mm diameter and 6mm pitch, so not lightweight.

Have you also watched the whole Clough42 YouTube series? From memory, his lathe is roughly the same size as a M300 so I would use that as a guide. I would guess something like a 3Nm NEMA23 would be about right and run off 60-70V to get max torque. This is a lathe leadscrew, not a ballscrew driving a router, so it's torque rather than speed that's needed. So gear down ("belt down" doesn't sound right but I would use a toothed belt) from motor to leadscrew. While the leadscrew is pretty chunky so a fair bit of rotational inertia, the saddle is a heavy old lump as well with relatively high friction sliding surfaces and you have to get that moving.

For this job, I would go stepper not servo. Closed-loop stepper, maybe, as they are not that much dearer than a plain stepper these days, but wouldn't go servo. Costs more, you don't really need the extra torque or resolution, and in fact the higher resolution of the servo might be a problem as you need a higher pulse rate out of the controller module which might push it a bit. Not done the sums to check that, though.

I keep thinking about doing the same for my lathe but it would need a bit of modification to get the drive to the leadscrew and I haven't worked up the energy yet - or needed to prioritise this over the rest of the project list! - to figure out the details. Nice project, though.

I used the same servo as James and it has been fine so far
My video adventure is here!
https://m.youtube.com/playlist?list=...lETQnF_qg-mzh0

It was the isv57t integrated servo geared down 3:1.

I’ve just seen James had a problem with his but maybe that was chance or it overheated being tucked away in the casting.