Abstract: A taper adapter assembly is disclosed for attaching a boring bar or the like to a machine spindle. The adapter is made up of a tapered adapter member and a drive ring. The adapter member has a taper of the ordinary type with a bore in its small end to receive a draw bolt and a cylindrical portion on its large end which receives the drive ring and a cylindrical portion that extends out from the first mentioned cylindrical portion. The adapter is made up by inserting the tapered adapter member in the spindle of a machine, applying an adhesive to the enlarged cylindrical part of the taper adapter member and placing the drive ring over the cylindrical part and forcing the ring into place against the face of the spindle with a bonding clamp. The drive ring is thereby affixed to the taper adapter and the reduced size cylindrical portion inserted into a bore in the end of a tool holder. The flange of the taper adapter is bolted to the clamping ring. The tool holder (boring bar) is then bolted to the drive ring.