Insert

An insert comprising an exterior part thereof having a series of annular peripheral taper portions, each having the same diameter and each of which tapers down from a rear shoulder thereof in a direction towards the leading end of the insert so that said taper portions are in barb-like formation, each said taper portion being longitudinally serrated with serrations of V-form at its rear part to provide a plurality of projections for retention of the insert in a hole therefor in a parent material, the serrations running out with forward reduction of each taper portion;

• a reduced diameter cylindrical pilot portion at the leading end of the insert;
• an external annular lip about the pilot portion closely adjacent the leading end of said pilot portion and axially spaced along the pilot portion from the adjacent taper portion, which lip is of taper form tapering down towards the leading end of said pilot portion and is of substantially smaller diameter than that of the said series of serrated annular peripheral taper portions for wall engagement in a said hole in order to assist in maintaining initial axial alignment and contact of the insert with the hole at the commencement of and during installation of the insert therein;
• and a rear plain external annular peripheral taper portion behind the rearmost serrated taper portion and of substantially the same diameter thereof and also tapering down in a direction towards the leading end of the insert in order to close a said hole and retain parent material therein on complete installation of the insert.