more lm8 bearings

This is my take on a linear bearing, there are better out there. I just wanted to learn polar repetition in #FreeCad and have a bearing that printed under my sloppy tolerances.

So the InnerDiameter in freecad ar 4.1mm radius, which once stuffed through a cura2 slicer produce a nice fit that needs a bit of dry lubricant (for my sloppy tolerance). The ribs would be improved with a helicular pattern, but I haven't learnt that yet.

I have provided stls of lm8uu (24mm) lm8lu (45mm).

The f