Bearing bracket for Z-posts

This is a RepRap part for the Darwin design that I couldn't find, so I designed one. It will allow you to use common 608 skate bearings. This obsoletes the Z-Studding tie bracket, which require more material than this object, but needs no bearing (does need an M5 bolt and two nuts).

For other bearings, simply adjust "bearing_OD" and export the model with OpenSCAD.

The parametric model also includes a corner bracket based on accurate measurements of the STL file. This might be useful to som