Klein Tools 59014, Unibit High-Speed Steel Step-Drill Bit -Inch. 3/16" -  7/8" Hole Size 

• Perfect for drilling multiple-size holes in thin sections of metal, plastic and wood using a single bit.
• Each Klein-Unibit does the work of many drill-bit sizes.
• Drills round holes in most metals (steel, brass, aluminum, copper) up to 1/8" (3.2 mm) thick as well as in plastic and wood.
• No center punching or pilot hole drilling is required on most sizes.
• The bits are easy to keep sharp.. and the hole size is easily determined by the diameter markings that are permanently laser-etched in the flute areas.
• Fabricated of rugged, high-speed steel in sizes to fit 1/4", 3/8" or 1/2" chuck of portable electric drills and drill presses.
  Unlike standard-point twist drills with two cutting surfaces, the single-flute design of the Klein-Unibit drill bit eliminates skidding. Single cutting-edge design assures penetration of softer materials at the proper speed, stops "hogging-in", helps to eliminate chatter and vibration. Hole is de-burred automatically by the next succeeding size. You can feel and see each step as the bit penetrates. Hole-size diameters are permanently laser-etched in the flute area of each bit, and offer quick and positive identification of each hole-size step to help eliminate user errors.
  Klein-Unibit drill bits are real time savers in electrical work. Rugged, high-speed steel drills steel, brass, aluminum, and copper sheet with ease. No center punch or pilot holes required for most sizes.