I've had a couple of flea market dish actuators around for a while, and cut one apart to get an idea of the usefulness of the screw. I'll put together some pics shortly, but my initial assessment is that these satellite dish movers would have some good machine applications. Not neccessarily for high precision CNC tables, but other feed or lifting/moving applications. Some of the larger actuator models have 18" of travel and are rated for 600 pound loads.
The screw appears to have been hard surfaced (chrome sprayed?), but I'm not sure of the actual process used. Some of the units I've seen are branded Thomson/Saginaw, so I suppose the quality of the materials is fairly good. The thread definitely appears to have been rolled (not precision ground), and I'm fairly sure it's drill rod.
There are also a nice set of thrust bearings, although they're a little crappy in this old used one that I disassembled. The great thing about this flea market actuator is that it came with a control box for the 36V DC motor drive. The drive has a feedback pot, and the control box has a digital readout (for dish positioning). The 3-digit display reads 0-180 for an 18" screw.. pretty cool for $5.
WB