Abstract: Parts having centered spherical surfaces are produced by a method and by a tool which seats an inner spherical end of each part on a very accurately generated spherical surface of the tool while a spherical surface is ground and polished on an outer end of each part. The ground and polished surface is formed concentric with the underlying precisely formed spherical surface of the tool or block. The seating of a part against the spherical surface eliminates problems of tilting of the optical axis of the part.A shell is attached to the spherical surface of the block, and a plurality of openings are drilled through the shell. The sidewalls of the parts are located and supported by the side surfaces of these openings so that the shell holds the parts against any lateral movement during the grinding and polishing operation. As a result the parts can be vigorously ground and polished while being held firmly in a fixed position. A single tool has a large number of openings in the shell.