A ball bearing adapted for axial movement on a shaft is comprised of a cage having guideways defining endless paths having axially extending portions for loaded and unloaded balls, and semicircular end portions. An outer sleeve surrounds the central portion of the bearing and defines races for balls in the endless paths. End rings on the axial ends of the bearing radially outwardly cover the semicircular quideway portions. The semicircular guideway portions have outwardly convex bottoms, and the end rings have concave recesses in their inner surfaces aligned with the semicircular guideways. The convex portions of the guideways and the concave portions of the recesses have common centers of curvature extending parallel to the bearing axis and displaced outwardly therefrom.