Another possibility is the drill rod is used as a low cost extender. Most ACME leadscrew is sold in 3 or 6 ft lengths... perhaps to save from buying a 6 ft leadscrew for use on say... a 42" axis where the actual travel may be say... 34 inches or so... a 36" leadscrew would suffice with the drill rod extending the mechanical length of a 36" screw.
Senna |