Methods of applying a nanocrystalline diamond film to a cutting tool are provided. In the methods, the cutting tool comprises tungsten carbide and has a cutting edge with a radius of curvature of no more than about 1 μm. The methods can comprise seeding a cutting surface of the cutting tool with a diamond nanopowder, the cutting surface having a reduced cobalt content, and depositing a nanocrystalline diamond film having a thickness of no more than about 1 μm onto the seeded cutting surface. The methods can also comprise implanting carbon ions into a cutting surface of the cutting tool to provide a carbide rich cutting surface and depositing a nanocrystalline diamond film having a thickness of no more than about 1 μm onto the carbide-rich cutting surface.