Patent ID: 7658581

Claim:
A joining assembly comprising: a support member of plastic material, said support member having a receiving bore defined by a bore wall, and a threaded element of plastic material and having a central axis (M), said threaded element comprising a core and an external threaded portion which, when the threaded element is threaded into the wall of said receiving bore of the support member, forms an internal threaded portion in said receiving bore by a cutting and/or deforming operation, said threaded element comprising a plurality of angular segments which, in radial planes, are of arcuate peripheries having centers of curvature (Ma, Mb) radially offset with respect to said central axis (M) such that adjacent angular segments are offset at their peripheries by steps so as to provide cutting edges to perform a cutting operation when said threaded element is threaded into the receiving bore of the support member, wherein the centers of curvature (Ma, Mb) of the arcuate peripheries of the angular segments are offset to the central axis (M) of the threaded element in opposite radial directions by an amount X as follows: X=0.10 mm for D Nenn ≦8 mm X=0.15 mm for D Nenn <8 mm and D Nenn ≦12 mm X=0.20 mm for D Nenn <12 mm wherein D Nenn is twice the radius of curvature (R) of the arcuate peripheries of the thread of the angular segments.