Fastener

摘要

The rotatably driven fastener is for fastening a facing plate to a tapping plate. The fastener has a shank (12) including a tapered tip (22). The shank defines an axis of the fastener and has a thread extending along and around it. The fastener has a head (20) unitary with the shank, the head having a driving portion and a bearing portion adjoining the shank. The driving portion (60) is adapted to be rotatably driven so as to drive the fastener rotatably about the axis defined by the shank. The bearing portion (70) has a peripheral edge and a clamping surface facing the shank, the peripheral edge being annular. The clamping surface flares outwardly from the shank, toward the tapered tip, the clamping surface being frusto-conical and defining a conical angle of about 5[deg] relative to a plane perpendicular to the axis defined by the shank. The head has torque-absorbing ribs (80) projecting from the clamping surface of the bearing portion and spaced at regular intervals about the axis defined by the shank. Each rib has a leading flank and a trailing flank with the leading and trailing flanks defining a flank angle of about 90[deg] and with the leading and trailing flanks defining a ridge. The ridges of the ribs lie on an imaginary, frusto-conical surface flaring outwardly toward the shank at a conical angle of about 1[deg] relative to a plane perpendicular to the axis defined by the shank and at a conical angle of about 4[deg] relative to the clamping surface of the bearing portion. Each rib has a depth not less than about 0.0001 inch when measured from the clamping surface of the bearing portion to the ridge of said rib, in a plane comprising the axis defined by the shank, at the peripheral edge of the bearing portion.