Abstract: A boring block and tool holder is disclosed having an opening therein. The block is made of a thick rectangular plate having inserts set into its front corners and inclined surfaces adjacent its rear edge forming a noncircular tang part having two rearwardly facing shoulders adjacent the tang portion which is received in a slot in a boring bar. The shape of the slot is complimentary to the shape of the tang part of the block. A tapered hole through the tang aligns with a tapered hole in the boring bar and the tapered hole in the block receives a taper pin which forces the block rearward bringing the block into firm rigid relationship with the end of the bar thereby clamping the block in positive rigid relation to the bar. The block has more strength than previous blocks because the block is thicker below the cutting inserts and there is more metal below the cutting insert, yet it can use the same bar and same slot width as rectangular blocks.

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.