Im planning on using acme threaded rod in my cnc machine design and was trying to think of a way to reduce the friction and improve the efficiency of the nuts and came up with this (sorry my 3d skills are not good so all I have is a 2d drawing) The green is the block would consist of 3 or 4 around the threaded rod and each side would have to be offset but the thread pitch amount, the blue is normal skate bearings and the red is the bolt that holds the bearing into the block, might be kind of hard to make, was alto thinking if you had a thick pipe can tapered the edges at 45 degrees you could tap that to hold the bearings, but the ends of the pipe would have to follow the thread, instead of just being flat so that would make it much harder to make, but it seems like it would be much more efficient, and should last a lot longer then the nylon nuts

Have a look at the thread here; http://www.cnczone.com/forums/showthread.php?t=13593&highlight=planetary

Your idea is similar.

I assume you have the acme thread, and the loads on the assembly are not so great that 'wear' occurs rapidly.
If this is the case, would a way of trying out your idea be to rig up the bearings with their bolts in the correct positons round the screw, then cast epoxy onto it.
This way you would avoid the complications of the machining, but it would give you something to test the idea.