Please DO NOT run it empty to avoid metal friction. .This grinder is perfect for grinding your coarse spice powder or other coarse soft powder into a fine powder. Top piece has a hand mill, which you can also use to press the spice down, please DO NOT run it empty since the grinding plate and mesh are metal causing friction and get worn, also not suitable for combustible or explosive material. Middle piece has a built in metal mesh screen. Manufactured by TitanOwl team