US Patent 7195321 Wear ring for a rotatable tool

A tool has a tapered forward cutting end behind which is a cylindrical shank. A rearwardly facing annular flange separates the forward cutting end from the shank. The shank is received in a tool holder having a planar forward surface, and fitted around the shank of the tool and resting on the forward surface of the tool holder is an annular wear ring. The wear ring has a small outer diameter portion that is less than the outer diameter of the radial flange and less than the diameter of the forward end of the tool holder, thereby allowing a gap between those parts to receive an extraction tool. The wear ring also has a large outer diameter portion at least equal to the diameter of the forward surface of the tool holder.