So I had plans to belt drive my z axis but it just wouldn't work. The axis is too heavy and my counterweight plan didn't work because of the weight of the axis and because the pulleys had too much friction. So I'm back to a leadscrew for the z. It is a 1/4-20 all thread studding. I had problems figuring out how to mount it before but last night I got most of it layed out. Before I was trying to put the motor at the top on the front and have the captured nut right next to the platform. Now I cut out a panel in the support and the motor sits on the bottom with the threaded rod pointing up. The captured nut is back behind the z slides and attached to the z sled with some angle iron (actually some rack mount ears from some old router or switch.) This should solve the problem I had before with the support of the far end of the driven rod. When I had leadscrews on the x and y they would bind up because I was supporting the side of the rod away from the motor in makeshift pillowblocks. The three parts weren't in alignment and so would bind up. I figured out that you didn't really need to support the far end anyhow. So with this verticle setup with the motor ar the bottom is easer than the motor at the top since I don't have to worry about support it alignment of a far end point.
Still have to figure out a coupling that works. I've been using tubing but I need proper pipe/tube clamps. I'll pick some up at the hardware store tomorrow. I had made do with zipties connecting things but it would slip if the rod binded. I may do a coupling connector from the hardware store ifit I can drill and tap some grubscrews into them. Well see how it goes tonight