TOOLS FOR TURNING, BORING AND ABRASIVE WHEEL DRESSING EACH CONSISTING OF A METAL SHANK AND AN INSERT OF POLYCRYSTALLINE DIAMOND OR CUBIC BORON NITRIDE BRAZED TO THE SHANK AND PROVIDING A CUTTING EDGE, AND POLYCRYSTALLINE DIAMOND AND CUBIC BORON NITRIDE INSERTS SOLD SEPARATELY FOR USE AS PARTS OF SUCH TOOLS