A fastener includes a threaded circular ring half divided along a plane intersecting a central longitudinal axis. One of the end walls is formed with a truncated conical load-bearing surface that is seated on a truncated conical thrust surface formed on a circular ring of a stress generator. The load bearing and thrust generating surfaces are arranged to present a conjugate pair of truncated conical surfaces to provide a favorable resolution of forces developed by torque applied to jack bolts distributed about an outwardly surrounding cylindrical stress generator body section.