a rotary polishing disc for dental grinding and polishing includes a disc - shaped piece of sheet of abrasive material fixed to a hub . in one embodiment , the hub is a hollow cylinder which is received onto a rotatable arbor . in another embodiment , the hub has a first end fixed to the sheet material , and has a second end that is received by a socketed end of the arbor . to fix the disc - shaped piece of sheet material more securely to the hub , a retainer plug may pass through a central aperture in the sheet material and enter into the hub . the retainer plug has a flat cap which becomes juxtaposed with the sheet material furthest from the hub . in another aspect , an improved arbor for the first type of hub includes protruding barbs which spear the hub when its hollow interior is disposed on the arbor .