Assembling the Y axis. Pretty simple and didn't really have any issues here other than some confusion from the instructions. They have already been updated now and are much more clear.
Rail. By now attaching things to the extrusions with the t-nuts is cake.
Cars. They slide right on and don't need broken in like the bushings for the z-axis.
Y plate. I'm not sure if it matters, but in this picture it's upside down- the two empty holes are supposed to be facing the other direction. Haven't figured out what the holes are for yet, so it may not matter. Wasn't hard to get the cars to slide freely- lightly tighten them up and then tighten them all.
Printed part. The print quality seems pretty poor... easy to attach. This piece is what the belt from the y axis stepper motor attaches to so the y plate moves.
Motor. Can't use a screw in the top hole when mounting the stepper motor because it interferes with the slot in the extrusion.
Pretty simple step. Almost looks like a printer!
Time Spent on this step: 30 min.
Total time so far: 5hrs 20 min.