[DonRotolo]

If you actualy have the device, it is easy to estimate the torque requirements empirically - remove the motors and twist the threaded rod. Easy to turn, tens of in-oz, hard to turn but can be done with fingers, several tens of in-oz. Can't turn it by hand, then measure it: Attach something to the rod (like a handle), and use a small weight scale to pull the end of the handle and read the ounces (pounds?) until it starts to turn. Multiply the inches away from the axis by the ounces of force, and then multiply by 1.5 or 2 to get the desired motor rating.

ON THE Other hand, this was probably a machining center first, and as such needed robust motors to push the work tool through the material. Now there is virtually no push needed, aside from overcoming the friction of the mechanism. Likely smaller motors(20-40 in-oz) will be fine.

Don