Ron Steele Mini Lathe CNC Conversion - Z Axis Leadscrew?

Could anyone in the UK using the Ron Steele plans for a mini lathe conversion tell me what Z-axis lead screw they're using, and where they got it.

The plans quote a high-lead (1/2 inch, I think) Acme leadscrew which allows the machine's original leadscrew, and manual carriage wheel, to still be used by "back-driving" the CNC lead screw.

Marchant Dice have already told me they can't supply such a high lead.
Any other ideas?

BTW, I want to maintain the original lead screw for use in manually-turned spring-making.

I've got this link marked as 'leadscrews' in my bookmarks:
http://www.kingston-engineering.co.uk/data/frame3.htm
I know of them only from an ML7 refurb blog.
Worth a ring, maybe?
HTH
John

Thanks for that, John. I've added them to my bookmarks.

Having now received the motors, I'm not so sure I'd want to back-drive them. Turning the shaft by hand is a tad stiff.
Are all steppers like that?

Yup.......

.

Yes they are like that, if you give it a good go you should be able to make the shaft turn a little bit, then try it again when they turned on....no chance !

I wouldn't describe it as stiff...they should turn OK but with a notchy or coggy feel - the bigger the motor the worse it is. That certainly doesnt make for a smooth hand-drive and, as Lee says, when powered on, you won't be able to move them at all until you overcome the holding torque.

Hmm.
I think I'll disengage the motor and leadscrew when I want to work manually.