Patent ID: 8317079

Claim:
A clinching method, comprising: establishing a first layer on a second layer, the first layer having an aperture formed therein and being thinner than the second layer; engaging a rotating punch with the second layer through the aperture in the first layer, thereby generating frictional heat and softening the second layer, the rotating punch configured with at least a first diameter, a shoulder, a second diameter that is larger than the first diameter, a third diameter that is smaller than both the first and second diameters, and a second shoulder extending from the first diameter to the third diameter, an end of the third diameter initially contacting the second layer; and pressing the rotating punch into the softened second layer, thereby causing at least some of the second layer to: back extrude through an annulus defined by the aperture in the first layer and a section of the punch having at least one of the diameters; contact the shoulder of the rotating punch; and extend onto a surface of the first layer adjacent the aperture.