Abstract: A threaded fastener having a two-piece nut member and a bolt with the nut member having a threaded nut member and a base member is disclosed. The threaded nut member has a body portion and a neck portion, the neck portion engaging with a transition beginning engagement on the base member. The base member includes a transition portion, the diameter of the transition portion increasing radially as it extends axially from the cylindrical through bore portion to an increased diameter at the outer planar surface of the base member. Movement of the neck potion into the based member results in the threaded form having a compressive engagement with engaged threads of the bolt to provide the prevailing torque structure. The threaded nut member and base member may be made of dissimilar materials and is more flexible in use with varying bearing surfaces.