The mò reading is the mill-apparatus word — refers to the physical millstone or the act of grinding grain in a mill. Key compounds:
石磨 (stone mill),
磨坊 (flour mill),
推磨 (push / turn the millstone),
水磨 (water mill),
磨豆机 (bean/coffee grinder). The bound colloquialism
磨叽 (to dilly-dally, northern dialect) also uses mò.