Abstract: A worm mixer is disclosed in which a cover is mounted to a substantially conically shaped vessel with a vertical axis defining a chamber for the mixing of materials. The cover is mounted on the vessel so as to allow rotation of the cover and vessel relative to each other. An elongated mixing worm is mounted to the cover at an off center location and extends within the chamber. The drive while rotating the worm about its axis is connected to an upper end of the worm which extends through the cover. The lead through of the worm through the cover is sealed and at least one bearing is provided rotatably journalling the worm about its axis near the upper end of the worm. The worm bearing and drive means are mounted exclusively outside of the chamber.