Thanks guys, that was real quick.
That bushing looks like exactly what I need (there are three screws), because the rods seem to have some 'play' in them when I move them around (they are lubed fine, but there is probably 1-2 cms so they can pop around within the bearing). I'm not sure, though: do I need to purchase two of these per rod, for the inside only? or do I need something on the outside of the table as well?