Abstract: A grain mill includes upper and lower supports defining a chamber. An upper mill stone is disposed in the chamber and affixed to the upper support. A lower mill stone is disposed in the chamber beneath the upper mill stone and is driven about a vertical axis of rotation. The upper support cannot rotate relative to the lower support, but can move vertically relative thereto to adjust a grinding gap between the mill stones. Adjustment of the upper support is achieved by a rotatable adjusting ring having right and left-handed screw threads which engage respective threads of the upper and lower supports. The upper support comprises a cover member which carries the upper mill stone and a cover ring which is threadedly connected to the adjustment ring. The cover member is removable from the cover ring while the cover ring remains attached to the adjustment ring.