110 of the hollow shell 102 is provided by the exterior surface 108 thereof having a plurality of corners 112 which twist or turn to form spirals about the shell axis a u2032 between the head 106 and the point 104 the number of corners is preferably related to that of a symmetrically balanced geometrical object having corners such as a square having 4 corners or a hexagon having 6 corners wherein the number of corners may be other than those exemplified the corners 112 may be radiused to u201c soften u201d the right angularity of the corners so as to inhibit nonuniform stretch of the rivet during inserting and risk of rivet splitting in operation the spiraled self piercing rivet 100 is placed at the ram of a ram and die mechanism as generally depicted at fig3 and sheets of metal i e aluminum another metal or metal composite 114 116 are stacked at the die and the ram is then stroked fig7 depicts an example of the deformation d u2032 resulting from the ram and die mechanism driving the asymmetric self piercing rivet into the sheets as can be discerned by this exemplification the corners 112 now provide an interference location with respect to at least one of the sheets which resists any force component applied to the sheets in a direction parallel to the shell axis a u2032 which would tend to loosen the rivet with respect to the sheets in order to ensure a tight clamping fit between the spiral feature spirals.