Sheet-metal member and a fastening screw

Claim 1

A sheet-metal member that includes an open-bottom socket formed from the sheet metal, the wall of the socket being an endless band of sheet metal which extends circumferentially of the socket axis with the thickness of the sheet metal disposed radially of the socket axis, the sheet metal extending inwardly at the bottom of the socket and being formed into a female thread for receiving and mating with a screw that is of smaller diameter than the socket and is disposed with its axis coincident with the axis of the female thread, and a fastening screw to mate with the female thread, the crest diameter of the thread of the screw being somewhat less than the internal diameter of the socketwherein the improvement comprises: protuberances which extend inwardly of the wall of the socket and which are located at the same level adjacent to the mouth of the socket, the protuberances being formed from the metal of the sheet-metal member by metal displaced from the thickness of the metal without cutting through the metal, the protuberances extending far enough toward the axis of the female thread to be frictionally engaged by the crest of the screw thread when the screw is in mating relation with the female thread, and the protuberances being spaced circumferentially about the axis of the female thread.