Abstract: A refiner plate for a rotary disk refiner that is adjustable. The refiner plate has a portion of its refining surface that is adjustable relative to some other part. In one preferred embodiment, the refiner plate has a part of its refining surface that can be angularly adjusted relative to some other part of the refining surface. In another preferred embodiment, at least a part of its refining surface is axially displaceable to accommodate changes in the refining gap. To permit a plate to be quickly changed, guides or pistons with generally J-shaped grooves can be used to attach the plate to its mounting surface.