Printed in ABS with 0.2mm layers height. W/T : 2.5The balls are 1/8" (3.175mm) steel balls I salvaged from old bikes when I was a kid, we can source them in bike parts stores. A complete bearing uses 88 balls.The different pieces are drawn in google sketchup but the boolean operations are made with blender after a conversion to .stlThe "springs" put some pressure on the bearing and compensate an eventual wear. The spikes in the spring fit inside small holes printed on the bearing.It's a part of my current project, a self replicable 3D printer/mill/PCB engraver, each axis will be equipped with 4 of these bearings.[edit] Design update with captive M4 nuts[edit] 2nd Design update : track improvement (larger on the outside) must be printed with 0.2mm layer height and W/T=2 because of the thiner outside wall