Abstract: A sprocket has a hub with a wide, carefully-machined, convex, outer surface, has a number of circumferentially-spaced, radially-directed, threaded sockets opening to that outer surface, and has a plurality of arcuate segments. Each of those arcuate segments has a wide, concave, carefully-machined, inner surface which is complementary to a portion of the outer surface of the hub, has a convex outer periphery with a plurality of sprocket teeth thereon, has a plurality of radially-directed, shouldered passages therethrough intermediate the teeth thereon to accommodate shouldered screws, and has end faces adjacent the roots of the end teeth which can closely confront the corresponding end faces of an adjacent arcuate segment.