Abstract: A centrifugal processing machine for the merchanical processing, for example, grinding, polishing, cleaning and de-burring of workpieces, with a container serving to accommodate the work-pieces and processing agents. The container comprises a substantially cylindrical casing and a rotating bottom, in the form of a plate or similar dished structure, mounted coaxially with the casing. The peripheral edge of the bottom projects towards the cylindrical casing and forms a narrow gap. For adjusting automatically the width of the gap around the entire periphery of the container, as a function of a given or varying gap-width, the casing is adapted to be raised and lowered in relation to the bottom. This is accomplished by means of a measuring device, which measures the width of the gap, and by means of a device for raising and lowering the casing which is adapted to be controlled by the measuring device in such a manner that the width of the gap is adjusted to a specific value and is held at this value.