Abstract: An annular workpiece having an inner peripheral surface and an outer peripheral surface at least one of which is centered on a workpiece axis is ground by supporting the workpiece hydraulically on a liquid layer in a support for rotation about the axis, rotating the workpiece about the axis, and engaging a grinding tool radially against the one surface and thereby removing material from the one surface. A plurality of measuring shoes are supported at angularly equispaced locations about the axis and are urged radially toward the one surface. A jet of liquid is projected from each of the shoes against the one surface such that the liquid forms a layer supporting the shoes on the one surface and merges with the liquid supporting the workpiece. The radial positions of the shoes are monitored relative to the axis and the removal of material from the one surface by the grinding tool is controlled, either by varying grinding force or stopping grinding altogether, in accordance with the monitored radial positions.

Abstract: A method of grinding an annular workpiece having an inner peripheral surface and an outer peripheral surface at least one of which is centered on a workpiece axis comprises the steps of holding the workpiece in a chuck rotatable about the axis and rotating the chuck and workpiece about the axis. A grinding tool is pressed radially against the one surface to remove material from the one surface and a cutting liquid is fed to the one surface to form thereon a liquid layer. A plurality of measuring shoes supported at angularly equispaced locations about the axis are urged radially toward the one surface. A jet of liquid is projected from each of the shoes against the one surface that forms a layer supporting the shoes on the one surface and merges with the layer of cutting liquid.

Abstract: A workpiece having a generally cylindrical outer surface centered on an axis is machined by first closing a pair of journal halves having generally semicylindrical inner surfaces of slightly greater diameter than the outer workpiece surface around the workpiece. Then a fluid is pumped under superatmospheric pressure into the space between the journal inner surface and the workpiece outer surface so as to support the workpiece in the journal halves on the liquid generally out of contact with the inner surfaces thereof. The thus supported workpiece is rotated about its axis and a finishing tool is engaged radially against it. The average radial distance between the journal inner surface and workpiece outer surface when the journal halves are closed on the workpiece is equal to more than the sum of the radial deviations of these surfaces from a perfect cylinder. The workpiece is rotated by axially engaging it between a pair of rotatable elements and rotating at least one of the elements.