I have seen several products on the internet marketed as 'ball screws' that have both the screw itself and the special ball bearing nut. They are intended to have a motor mounted on one end of the screw to rotates it, causing the nut to be moved.
However, I'm looking for the particular kind of ball screw where the nut is part of a gear, and mounted via axial bearings, so that as it is rotated it remains stationary and the screw is extended.
Are these things sold in complete units without any machining necessary? What are they called/where can I find one?