Abstract: Hollow ball bearings of improved strength and uniformity are produced by causing identical first and second hemispheric units to rotate at different speeds in facing relationship upon a common axis, and forcing the hemispheres into aligned contact. The frictional heat generated by such contact melts the material adjacent the open rim of each contacting hemisphere. The molten material is distributed by centrifugal force about the interior of the hemispheres. The speeds of the two hemispheres are then equalized with attendant cooling and re-solidification of the molten material, thereby producing a hollow sphere.