I noticed that there is a trend to build bigger and bigger CNC's and that sometimes in machines with leadscrews at around 36" and longer the leadscrew sometimes whips when spun fast.
1. My first thought was, build it backwards. That's to say, fix the leadscrew and spin the nut. No whip!. The following drawing shows a hollow shaft supported by two bearings, spaced apart and locked in place with a nut. At the other end is a large diameter section that is machined as a timing belt pulley. Attached to the face of this is a CNC Dumpster anti backlash nut. The whole unit is driven by the stepper mounded above with a 1:1 ratio belt drive.
2. Second thought. If you take a section of leadscrew and cut lengthwise grooves in the thread and then give it some heat treatment you basically get a tap. Mount this in a lathe between centers and then feed the edge of a freewheeling disk into the tap and the disk will start turning, taking on the reverse shape of the tap, like an inside out nut. If you then mount some of the same threaded rod in a C channel and clamp onto the channel/thread combination with your new disk and a bearing under the channel you have a rack and pinion drive. No whip!