A method for forming a joint using a self-piercing rivet includes the steps of: positioning the sheet material over a die and 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. The method also includes positioning a rivet over the sheet material at a position opposite the die and using a punch to set the rivet and force it into the sheet material such that it pierces the 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.