Well, I tried to model it exactly after a normal cube, so the centerpieces will just be held on by screws. They'll be locked into the axes but the centers will be able to rotate freely about them. (If you've never seen the inside of a cube, check out
this article) Also, I'll probably make the axes out of some kind of plastic or even take it from one of my DIY cubes so I won't have to tap the holes.
As for fabrication...not quite sure how to approach all those curved protrusions yet...I have a vague plan involving a mill, plenty of coolant, and
a lot of G coding...
Heh, it might even be easier to just cast it.