SELF-DRILLING DOWEL WITH DRILL HEAD

摘要

A self-drilling dowel has a drill head extending across its leading end. A bore extending through the dowel from its trailing end is closed at its leading end by the drill head forming a centrally located blind bore. The blind bore is cylindrically shaped for a part of its axial length from the trailing end of the dowel with the remainder of its axial length to its closed end tapering inwardly from the surface of the cylindrically shaped part. A spreader is positionable in the central bore with complementary dimensioned surfaces relative to the cylindrically shaped and tapering parts of the bore. Slots are formed in the dowel and extend from the drill head to approximately the transition plane between the cylindrically shaped and tapering parts of the blind bore. The slots have a dimension extending transversely of the axis of the bore just sufficient to open into the bore at the transition plane. The drill head has a centering point projecting outwardly from the remainder of its surface at the leading end of the dowel. The part of the drill head forming the centering point is shaped so that it can separate from the dowel when the spreader is driven through the central bore toward the leading end of the dowel.