Diablo Stepped Drill Bit Review

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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.

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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.

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.

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:

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.

Brad Ford has spent most of his life using tools to fix, build, or make things. Growing up he worked on a farm, where he learned to weld, repair, and paint equipment. From the farm he went to work at a classic car dealer, repairing and servicing Rolls Royces, Bentleys, and Jaguars. Today, when he's not testing tools or writing for Popular Mechanics, he's busy keeping up with the projects at his old farmhouse in eastern Pennsylvania.

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