I picked up some drill rod today at the local Fastenal store and put the X axis together.
We used smooth rods out of various printers and a scanner for the other axes, but we didn't have any rods long enough for the X axis, which needed rods of at least 16.5". So I spent some time looking at drill rod suppliers before I discovered Fastenal. It turns out there is a store here in Omaha, and the company keeps inventory info online so you can see what is available at the stores and what will need to be ordered.
I stopped by after work on the way to the Omaha Maker Group 'space and picked up a 36" piece of 8mm drill rod for $5, and also a couple of scrap pieces of 3/8" threaded rod that I thought might be useful as the Z axis screws.
The drill rod fit perfectly,but the threaded rod was a bit big. to make it work we tapped the holes in the plastic parts out to 3/8" and then dribbled some PLA around the rod to build up the cavity where the nut was intended to go.
Next we need to turn down the ends of the screws for couplers, build the couplers, and get the motors mounted. Then we'll be looking for electronics.