Expansion dowel with friction reducing coating

Expansion dowel comprising an axially extending anchor bolt having a first end and a second end with the first end leading in the insertion direction when the dowel is inserted into a borehole, said bolt comprises an axially extending cylindrical shank having a first diameter and extending from the second end toward the first end, an axially extending expansion part having a conically shaped outside surface converging toward the second end is located adjacent the first end, means at the second end of said bolt for securing a member to a structure into which the dowel is anchored, an axially extending shank section having a second diameter smaller than the first diameter is located between the cylindrical shank and the expansion part, said shank section has an outer surface, the expansion part has a smaller diameter end with approximately the same diameter as the second diameter, an expansion sleeve positioned on and laterally enclosing the shank section between the cylindrical shank and the expansion part, said expansion sleeve has a first end closer to the first end of said bolt and a second end closer to the second end of said bolt, said expansion sleeve being axially displaceable relative to said anchor bolt, said expansion sleeve has at least one axially extending slot therein open at the first end thereof, radially projecting protrusions on said expansion sleeve, said expansion sleeve having an axially extending inside surface and an axially extending outside surface, wherein the improvement comprises that said protrusions are arranged in a pair spaced apart in the axial direction and projecting radially outwardly from the outside surface of said expansion sleeve, the inside surface of said sleeve and the outside surface of said expansion part are coacting contacting surfaces and at least one of the inside surface of said sleeve and the outside surface of said expansion part has a friction reducing coating thereon.