Abstract: In a mixing machine having a cylindrical mixing chamber in which a centrifuging agitator coaxially rotates on a horizontal axis, an inlet duct for dry mix material and liquid curves downwardly and towards one end wall of the chamber and an outlet duct for mixture curves downward and away from said end wall. Material to be mixed thus enters the chamber in substantially horizontal flow through an inlet port in said end wall, all portions of said port being spaced radially inwardly from the cylindrical chamber wall and below the level of the chamber axis. Mixture leaves the chamber in substantially horizontal flow through an outlet port wholly spaced below the inlet port and extending down to the level of the bottom of the chamber. Centrifuging action maintains a pressure difference between the ports that assures fast movement of materials through the mixing chamber to prevent plugging of the machine when mashed potato mix is used.