D. P. Universal Mill The D.P. Universal Mills find applications in fine and ultra fine size reduction of soft to medium hard products, with an upper hardness limit between 3 and 4 on the Mohs hardness scale for minerals. The D.P. Universal Mill casing and doors that can be closed by screwing down a hand wheel. At the rear side of the case there is a bearing body with the drive shaft that runs on rolling bearing and carries the interchangeable crushing elements.