PURPOSE: To prevent the contact of the outer periphery of an auger shaft with the inner peripheral face of a feed cylinder by eliminating the deviation of the auger shaft during the rotation and prevent powdered materials from entering the bearing and also prevent oil leakage from the bearing.

CONSTITUTION: The lower end peripheral edge 2d of a protrusive bearing means 2 by which the lower end B2 of an auger shaft B is supported, is closely positioned to the middle 1b of the upper face of an inner chip washer 1 and a labyrinth seal clearance 4 composed of a circular protruded piece 4a and a circular recessed groove 4b which are mutually fitted, is circularly formed to the rotary direction of the auger shaft B, between these opposite faces. In this way, the radial passage of the auger shaft B is divided into two or more and the gas pressure in the passage is gradually lowered and the powdered material and the oil are cut off.