A resin molding is made by integrally joining a first resin molded part configured with a concave portion and a second resin molded part configured with a convex portion so that the concave portion and the convex portion are mated together. In a method for grinding center bearings of a crankshaft using the apparatus, the center bearings are simultaneously ground using a multilayer grinding wheel set, and prior to a final grinding of the center bearings to their final dimensions, a bearing seat for a steady is ground on at least one center bearing. An operating system of the Smart Phone may provide an application programming interface to support diverse applications.