A cutting tool for woodworking applications has a tungsten carbide substrate and a hard layer bonded to the substrate at high temperature and high pressure, i.e. where diamond or cubic boron nitride is thermodynamically stable. The hard layer comprises polycrystalline diamond or polycrystalline cubic boron nitride, and a supporting cobalt phase including adjuvant alloying materials for providing oxidation and corrosion resistance. Typical alloying elements include nickel, aluminum, silicon, titanium, molybdenum and chromium. Such materials also retard transformation of cobalt from the HCP to the FCC crystal structure at high temperature. The hard layer has an as-pressed surface parallel to the substrate and is only about 0.3 millimeters thick. An additional secondary phase including a carbide, nitride and carbonitride of metals such as titanium may also be present in the PCD or PCBN layer.