Patent ID: 7503106

Claim:
A method of fastening one or more apertured members to an apertured workpiece, an aperture of the or each member being aligned with an aperture in the workpiece, which method comprises the steps of inserting into the aligned apertures a fastener, said fastener being formed of ductile material and having a head, a shank, and an axial bore extending through the shank and into the head, said shank being circumferentially entire and being formed with an external screw-thread, said fastener being inserted so that the head engages a face of the said one member, and the shank extends though the member or members and into the workpiece, and at least a part of the screw-thread being within the workpiece, and then, while supporting the fastener at the head, drawing into and entirely through the bore, in the direction from the tail portion to the head, a tapering, enlarged, mandrel head capable of axially compressing the shank of the fastener between the mandrel head and the support at the fastener head, and of expanding the bore, and thereby enlarging the bore evenly throughout its length and causing ductile radial expansion of the shank sufficient to cause the external screw-thread to embed in the workpiece and the shank of the fastener undergoing ductile axial reduction in length, whereby the diameter of the bore of the fastener, the original diameter of the shank of the fastener, the diameter of the cylindrical portion of the mandrel head, and thereby the expanded diameter of the fastener are such that the depth of penetration is less than half of the thread depth.