Step drills are the only drills you can sharpen yourself (both tip and flute). Exlusive single radial concave flute crates perfectly round holes in metal, plastic wood and other thin materials without center punching. Contructed of industrial grade high-speed molybdenum steel, heat-treated and temperature for long life. Slef-stating tip. No center punching needed. Automatically deburrs top side of hole. copper, aluminum and other thin meterials