A disk refiner consists of two vertical disks with serrated or otherwise contoured surfaces. One disk rotates clockwise, while the other either remains stationary or rotates counterclockwise. The fiber slurry is pumped between the disks through an inlet in the center of one disk. As centrifugal force pushes the fibers out toward the perimeter of the disks, the abrasion experienced by the fibers cuts, softens, rubs, and disperses them to the degree desired. The space between the disks can be widened or shortened, depending on the extent of refining appropriate to the end-use of the paper to be produced.
The disk refining system has replaced the beater in many larger papermills. The advantages it has over the older system include the fact that it is a continuous system, rather than a batch system, meaning that pulp qualities and degree of refining can be altered at will, depending on the grade and type of paper to be produced. (See Refining.)