Abstract: A method of forming blind hole rivets by displacing metal from a relatively thick base metal includes positioning a die against one side of the base metal having a cavity mating with the projection. A tool having a reduced diameter forward portion is pressed into the base metal from the side opposite the die to forward extrude metal into the die cavity during an initial portion of tool penetration. The end portion has a diameter substantially less than the diameter of the die cavity. Rearwardly of the end portion, the tool provides a cylindrical rearward portion having a diameter substantially equal to the diameter of the die cavity. After the forward portion penetrates into the base metal, the rearward portion penetrates the base metal and completes the displacement of material into the die cavity. The height of the rivet or projection can be at least about equal to the original thickness of the base metal without producing cracks or fractures.

Abstract: A method and apparatus for producing a disc structure. The disc provides a radially extending annular wall formed by pressing a workpiece against a contoured tool with a pressure roll. The contoured tool and workpiece move relative to the pressure roll about a first axis while the tool and pressure roll move toward each other in the direction of the first axis. The pressure roll rotates about a second axis perpendicularly intersecting the first axis and provides a cylindrical working surface. The tooling is arranged to radially confine the workpiece. In one embodiment, the tool is formed with a plurality of ribs extending in the direction of the first axis. These ribs cooperate to produce annular grooves in the workpiece along the surface thereof remote from the pressure roll. One embodiment provides a disc particularly suited for use in electromagnetic clutches. The other embodiment may be used to produce wheels, pulleys, and the like.