Problem with rotary tables, no matter where they come from originally, works that is, not reseller, is that they are being dumbed down in an effort to remain competitive.
As far as I can assertain none of the CURRENT crop have bearings on the worm shaft and some like the 8" Vetex only has one thrust bearing so you are suppost to go one way only.
Most are steel into cast iron, no bushes and some are even steel into steel. They have also moved off the envoloping worm wheel and instead have a worm engaging with a helical gear so the worm shaft stays parallel.
SOBA started all this in India and Vertex have had to copy them to remain competitive. You can buy a high end Vertex table but it's out the price range of the home shop guy and because of this not carried by any of our usual suppliers.