Abstract: An assembly of at least two components joined together by at least one mechanical connection formed in sheet-like portions of the components and in an area of faying contact between the components. The assembly includes an integral collar projecting from one of the components and an outer integral collar projecting from the other components circumscribing the first collar. The inner collar has a cylindrical inner surface portion and a wall of varying thickness. At least a portion of this wall increases in thickness toward the outboard end of the collar to lock the collars together.

Abstract: A method of joining together two or more pieces of malleable material. The method includes the steps of placing thoroughly cleaned surfaces of the pieces in intimate contact with each other and forming a flanged hole through all of them at the same time. This is accomplished by producing a starting hole and then directing a draw punch against the pieces and directing the same into the opening of a die while the material is compressively stressed to a value substantially equal to the yield strength of the material. The punch provides the completed flanges with an hourglass shape, such shape locking the inner and outer flanges together against axial displacement.

Abstract: A method of joining together two or more pieces of malleable material. The method includes the steps of placing thoroughly cleaned surfaces of the pieces in intimate contact with each other and forming a flanged hole through all of them at the same time. This is accomplished by directing a draw punch against the pieces and directing the same into the opening of a die while the material is compressively stressed to a value substantially equal to the yield strength of the material. The punch provides the completed flanges with an hourglass shape, such shape locking the inner and outer flanges together against axial displacement.