FASTENER FOR ROOF ASSEMBLIES AND THE LIKE

A fastener for securing a sheet metal roof panel to a roof frame with a layer of compressible insulation between the two includes an elongated shank with a tip at one end and a driving head at the other. The shank either is inserted tip first through a preformed hole in the sheet or through a hole which the tip drills and the shank is driven through the insulation layer. A first thread on the shank adjacent the tip is driven into the frame and draws a flared portion of the shank through the hole to enlarge the latter and roll over the metal around the edge of the hole. The rolled over edge then is engaged by a second thread on an enlarged portion of the shank under the head and the plate together with a washer are compressed between the second thread and the head so as to prevent overdrive of the fastener and reduce the possibility of the sheet being dimpled. Longitudinally extending beads or a third thread on the flared portion produce a smooth and gradual rolling over of the edge of the hole in the plate.