The false bottom furnishes the lower grinding surface of the machine .
On the inside of the pan is fixed a false bottom of iron, cast either in sections, called " dies," or in one piece which has a diameter somewhat less than that of the pan ; this has an aperture through which rises the central pillar.  The false bottom furnishes the lower grinding surface of the machine .  The muller, forming the upper grinding-surface, is a circular plate of cast-iron, corresponding in size with the false bottom, and having a fiat, conical, or conoidal surface, according to the shape of the pan bottom.