A three-piece fastener includes a bolt with a shank having a concentric opening in its threaded end, a nut adapted to fit over the threaded end of the bolt, and a wedge member which is insertable into the end opening of the bolt for expanding and thereby securing it. The threaded end of the bolt is axially slotted to facilitate its expansion.The outer diameter of the wedge member is smaller than the outer diameter of the threaded end of the bolt. When the bolt is to be inserted into an opening of a structure in order to accomplish a fastening action, the wedge member is first loosely inserted into the end opening of the bolt. Then when the bolt and wedge are passed through the opening, the nut is applied to the end of the bolt and is tightened. Thereafter, the wedge is tightened in order to expand the end of the bolt.The end opening of the bolt has interior threads, and is threadedly engaged by the wedge member, but in an opposite rotational sense to that in which the nut is applied to the bolt. The wedge member has a driving portion on its outer end, and a weakened circumferential wall which fractures and shears off when a predetermined torque is applied for tightening the wedge member. After this shearing action takes place, the remaining part of the wedge member is wholly contained within the end of the bolt.