Expanding bolt-like fastening means

In combination, bolt fastener means for locking engagement in a socket and a screw threaded means for engaging said fastener means and setting same in the socket, the fastener means comprising an elongated cylinder-like member with a bore and a collar element loosely fitted on said member;

• said member comprising an inner end portion and an outer end portion of equal diameters and a waisted portion formed between said inner end portion and said outer end portion, the waisted portion further comprising a cylindrical portion of lesser diameter than said end portions and an abutting, axially-extending conical portion, the cylindrical portion extending from a radially directed shoulder formed on said outer end portion, the conical portion being convergent in a direction away from said inner end portion and leading to the cylindrical portion;
• said bore being of stepped diameter and extending axially throughout the length of the fastener, said stepped bore comprising a plain bore and of a screw threaded bore of less root diameter than the diameter of the plain bore, the screw threaded bore extending through the inner end portion of the fastener and the plain bore extending through the outer end portion and the waisted portion of the fastener to the region where the conical portion meets the inner end portion;
• said collar element being of one piece and retained loosely on said waisted portion of the fastener between the shoulder and said inner end portion of the fastener and adapted for radially expansion into engagement with the socket by having at the end of the collar which is adjacent to said inner end portion of the fastener at least one slit therein which extends axially from that end of the collar which is adjacent to the conical portion toward the outer end portion of the fastener, the collar further having an inner diameter which, before the radial expansion, is less then the greatest diameter of the conical portion;
• the screw threaded means for engaging and setting the fastener extending through the plain bore and into the screw threaded bore in the inner end portion and making screw thread engagement therewith, the screw threaded means being under tension during the withdrawing movement of the fastener in relation to the collar and setting of the fastener in the socket, the tension in the bolt applying axial compression to the waisted portion of the fastener as the conical portion is drawn into the collar which is expanded against the socket into locking engagement therewith.