The Takeaway: Diablo’s Impact Strong Step Drill Bits are a fast, convenient way to drill holes from 3⁄16 of an inch to 1-1⁄8 inches without having to swap bits. While they can drill many different sized holes, they won’t necessarily replace a full drill bit index—they’re best for metal and plastics, up to 5⁄16 of an inch thick. Although they were originally designed for electrical and plumbing work, I find Diablo’s step drill bits are incredibly useful in fabrication, as well as working with or making repairs to metal and plastic equipment.

  • Includes one drill bit with six steps, up to a 1⁄2-inch diameter
  • Includes one drill bit with 12 steps, up to a 7⁄8-inch diameter
  • Includes one drill bit with 17 steps, up to a 1-1⁄8-inch diameter

    Price: $89.99


    Fast and Convenient

    The process of drilling in metal typically involves starting with a small hole and then enlarging it with successively bigger drill bits until you have the size you need. Sometimes, you may have to do this four or more times—removing the drill bit, returning it to the index, selecting the next one, and chucking it up each time. And then, if the edges are sharp or rough, you may need to clean up the hole with a larger drill bit or countersink. Diablo’s Impact Strong Step Drill Bits simplify the process, enabling you to drill small or large holes in metal in one single operation.

    Here’s how they accomplish this. Between each step on Diablo’s drill bits is a beveled transition. The sharpened edge of these bevels remove material up to the size of the next step. So each successive step does the job that would normally occur when switching to a larger bit, saving time in the process. The convenience of this is something I’ve come to appreciate, especially on projects that require multiple holes. That convenience is also accentuated due to the impact-ready, 1⁄4-inch hex shank on each of the drill bits. When I used these with an impact driver, it eliminates fussing with the drill chuck, which has to be tightened to hold the bits—instead, I can just slip them straight in and then pull on the chuck collar to release them.

    diablo step drill bits
    Trevor Raab

    Another thing I like is the ability to finish the rough edges of holes with the same Diablo bit used to drill the hole, saving yet another step. Once I drill a hole to the desired size, for just a moment, I continue drilling with the bevel to the next size. This removes just a little material from the top edge of the hole, chamfering it inward and finishing it nicely.

    The Right Tool for the Right Job

    Diablo originally designed its step drill bits with electricians and plumbers in mind, for jobs like drilling holes in junction boxes or sink flanges. However, these are useful for anyone needing to drill holes in metal and plastic materials up to 5⁄16 of an inch thick. I’ve found step drill bits to be especially useful when fabricating and making repairs or alterations to equipment. At these times, we might be away from our toolbox, working on something that may be difficult to measure precisely. Taking a drill or impact driver with one bit—as opposed to several—simplifies the operation.

    Some examples where we’ve used step drill bits:

    • Making mounting brackets for automotive electrical relays and exhaust systems
    • Making gasket flanges for swimming pool plumbing
    • Fabricating mounts and brackets for Popular Mechanics test equipment
    • Mounting custom signs on sign-posts
    • Drilling holes for grommets when passing wires through sheet metal
    • Drilling holes for conduit fittings and connectors in electrical boxes
      hole drilled in steel bar stock
      Trevor Raab

      About Drilling Holes in Metal

      While Diablo’s stepped drill bits will save time and hassle, they’re not exactly cheap. To get the best performance and life out of them, it’s important to take care of them properly. Using these, or any drill bits, improperly can render them largely useless pretty quickly. There are a couple of things to know about drilling holes in metal.

      • Use a center punch and a hammer to mark the location of the hole and to give the drill bit a place to start without wandering.
      • When drilling steel or other hard metal, use a drop of cutting oil where you’ll start drilling. Stop and add a drop occasionally if it’s a deep hole. If you don’t have cutting oil, 3-In-One oil is a good substitute that works fine. Cutting oil keeps the bit cooler by reducing friction and will help the drill bit stay sharp longer. (Softer metal like aluminum and brass don’t require cutting oil.)
      • Use low to medium speeds when drilling in hard metal. The bit won’t bite any more moving fast—it will just get hotter faster. If the tip overheats, it will lose its sharp edge.
      • When you’re not using them, keep the drill bits in their case or index. Rattling around loose in a tool box or bag is a sure way to dull the cutting edges prematurely.

        Impact Strong Step Drill Bit Set
        Diablo ACME Tools

        • Work with both drills and impact wrenches
        • Drill large holes in metal in one step

        • Only works for materials up to 5/16 of an inch