Eric, those look great, bet you could sell them.
I'd always thought a turners cube, as the English apprentices were taught, had undercuts so that the cubes separated, cube inside a cube that can't come out. Lautard in one of his books walks through how. here's a three cube one i made years ago, its 1" sq. Lot of fun just having it sit on the desk because all the non technical people would pick it up and hurt their brains trying to figure it out. lol. its the machinist's equivalent of worry beads so the edges have long since been rounded.
http://i20.photobucket.com/albums/b2...urnerscube.jpg