An improved axial-piston energy converting device is provided by utilizing a thin ceramic wear plate insert, having a typical thickness of only about .005 to .040 inches in thickness, as a cam surface secured by atmospheric pressure to an underlying support surface of a steel cam plate support structure. Attachment of the wear plate to the cam plate supporting surface is accomplished by polishing both a supporting surface of the cam plate, and a mating surface of the wear plate to a very smooth finish, and wiping a thin film of a fluid such as oil onto one of the polished surfaces prior to placing the wear plate onto the supporting surface. The highly polished surface, together with the light film of oil, results in a joint that is essentially air tight. Atmospheric pressure acting on the cam surface of the wear plate serves to hold the wear plate tightly in place on the support surface in the same manner that a pair of Johansson blocks are held together if their highly polished surfaces are mated.