I highly,
HIGHLY recommend you go to
Nook Industries to look at leadscrew options before you select a particular screw. They have a a LOT of free online information about lead screws and the selection process for them. You should particularly educate yourself about the different end conditions and the definition of critical speed. I had a sub-team that didn't believe me about the need to support both ends of the lead screws for our tote lift, and the screws nearly shook the system to pieces when they test ran it. After which they sheepishly admitted they needed to support both ends and started working on that.