Patent ID: 8898880

Claim:
A method for forming a joint in at least one high strength sheet steel having a UTS (Ultimate Tensile Strength) in the range 200 to 1400 MPa using a self-piercing rivet comprising the steps of: positioning the sheet steel over a die; providing a rivet having a substantially cylindrical shank and a head, the shank having a central blind bore and an annular piercing end spaced from said head, the ratio of the difference between the outside and inside diameters of the shank in the region around the bore to the outside diameter of the shank is in the range 0.47 to 0.52; positioning a rivet over the sheet steel at a position opposite the die; using a punch to set the rivet and force the rivet into the sheet steel such that the rivet pierces an upper surface thereof and such that the shank deforms outwardly to interlock with the material but without penetration to the die side of the material.