I am working on the Z studding idlers. I was about to put the bed corners on when I looked at the springs I had ordered from the RepRap parts lister. They have an outside diameter of .281 or 9/32. Is this the right size. If I read the instructions correctly the spring should go around the M8 threaded rod. It seems too small for that. Appreciate any help!

I ran into the same thing. Ended up using springs picked up at the hardware store. The ones I got were compression springs for screen doors: 2-1/8" long, 7/16" dia and .031" wire. Currently, though, I'm working without backlash springs. The weight of the bed seems to be sufficient to prevent backlash.