Expansion core anchor

Claim 1

In an expansion core anchor of the type adapted to be anchored in a predrilled hole in a receiving material, comprising a right-circular cylindrical body formed with a head and a crural end, said head being provided with an external peripheral thread and a circular bore in which is lodged in a nail-like expansion core, said crural end being divided by at least one slot into a plurality of deformable legs, said legs being adapted to be forced radially outwardly to grip the surface of the hole upon driving of said core toward said end; the improvement comprising: at least two pairs of axially limited internal projections, the ones of each pair being disposed adjacent longitudinal edges of said slot and situated one on either side of the axial plane perpendicular to the median plane of said slot, both of each pair of projections lying in a plane perpendicular to the axis of said body, one of said projections being disposed adjacent each edge of said slot, said projections each including a surface curved to conform to the shank of said expansion core, whereby said projections are adapted for guiding said expansion core during driving thereof.