METAL TO METAL FASTENER
A fastener (100) includes a shank (102) having a diameter (D2) including a helical thread (125) and a cutting tip (116). The fastener (100) includes a head (140) having an integral washer (145) and nut (142). The washer (145) has a diameter (d) and a thickness (t), wherein a relation of the diameter to the thickness is established through a shape factor greater than 0.55, the shape factor for the thickness (t) greater than 0.06 inches being d*(l+2.5t)*t(t"0 06)and for the thickness (t) less than or equal to 0.06 inches being d (1+2.5t) *t(O.06-t). The fastener (100) may be used in a system wherein a thin steel element (210) abuts the washer (145) and the fastener (100) joins the thin steel element (210) to a thick steel element (220).