About this 3D model

I've found it useful in terms of modularity, to be able to insert a capture nut in the place where a 608 ball bearing might be. This thing is a very simple cylinder with a capture nut indent. Otherwise, there is a thru hole the allow 5/16" rod to pass all the way through. It mates nicely with this thing: http://www.thingiverse.com/thing:5679 Depending on your printer, it could be a very tight fit. I heat the receiver with a heat gun, and then press fit the captured nut bearing into the receiving hole.