10 Best Drill Bits For Hardened Steel in 2026

An 8% cobalt M42 alloy gives these bits high heat resistance, so they can drill stainless steel or cast iron without immediately dulling. Features like anti-skid split points on bits 1/8 inch and larger prevent skating for easier starts, while three-flat shanks on bits 3/16 inch and larger provide a better grip in the chuck. This combination tackles common frustrations when drilling hardened metals.

Expert mentions note these bits are a popular, affordable choice for hardened steel, delivering solid performance on a budget. The same research indicates they can wear out more quickly when used on work-hardened steel or without cutting fluid. For occasional tough jobs, they are a reliable option.

Offering a full spectrum from 1/16 inch to 1/2 inch in precise 1/64-inch increments, this set means you’ll almost never need a separate bit for a standard job. The 5% cobalt alloy is the key for drilling hardened steel, as it holds its edge under the high heat generated. That, combined with the heavy-duty web and 135-degree split point, makes this a comprehensive kit for a shop that tackles a wide variety of metalworking tasks and values having the exact size on hand.

The trade-off for that completeness is bulk; the case is over a foot wide, which eats up more drawer space than a compact set. For the most demanding, continuous drilling in stainless or titanium, a set with an M42 cobalt formula, like the Bosch CO21B, or a TiAlN coating might offer a slight edge in longevity. But for general shop use where you need to reach for a specific drill bit without a second thought, this Irwin set’s range is hard to beat.

The TiAlN coating’s ability to withstand 1472°F is the key here. When you’re pushing through hardened steel, heat is the enemy that dulls edges and ruins temper. This set is built for the jobs where friction is unavoidable, letting you maintain cutting pressure longer without degrading the bit. It’s for the fabricator or mechanic who regularly drills stainless or hardened plate and needs a bit that won’t quit when the chips start glowing.

Crosstar’s smallest bits, from 1/16″ through 7/64″, use a conventional two-flute design for delicate work, so the triple-flute benefits like improved chip ejection and hole finish apply only to sizes 3/32″ and larger. This means the set’s headline feature is reserved for its mid-range and larger bits. If your projects frequently require drilling pilot holes smaller than 3/32″, you won’t experience the enhanced performance there.

A 15-piece set built from M35 cobalt steel delivers the essential toughness needed for punching through hardened steel without immediately dulling. The 135-degree split points are the key here, biting in cleanly to stop the bit from skating on curved surfaces. This is a straightforward, no-frills kit for the occasional metal project or the DIYer building a basic toolbox who needs reliable performance without a complex feature set. You get a solid core range of sizes and the inherent durability of cobalt in a simple indexed case.

Round straight shanks fit a standard drill chuck, but unlike the Bosch CO21B’s three-flat shank design, they lack an anti-slip feature. Drilling into materials like stainless steel requires more diligent use of cutting fluid, as the bits lack a friction-reducing coating. This set covers fundamental drilling needs well, positioning it as a sensible starting point before more specialized options.

A 29-piece cobalt set gives you the breadth to tackle almost any hole size in hardened steel, from fine pilot holes to larger fasteners. For a professional or serious home shop that encounters a wide variety of materials and tasks, this comprehensive collection means you’re less likely to be caught without the right bit. The substantial case organizes everything, though its size is better suited for a stationary toolbox than a lightweight service bag.

With its extensive range comes considerable bulk. The set’s case occupies a significant footprint, so it’s not the grab-and-go option for quick jobs away from the bench. If your primary need is drilling thick, hardened steel in a fixed workshop, this Milwaukee set covers the bases. For a more compact kit focused on the most common sizes, the 21-piece Bosch CO21B set with its three-flat shank would be a direct, space-saving alternative.

A set length between 1.83 and 2.32 inches is the whole point here, letting you sneak into corners and clearances where a standard drill bit simply won’t fit. This makes the NordWolf set a perfect match for anyone wrestling with a cramped engine bay, a dense machinery frame, or any project where your swing space is measured in fractions of an inch. The 1/4-inch hex shank locks securely into an impact driver or quick-change chuck, so you can drive these bits hard without worrying about slippage.

Its compact profile means you get a limited selection of just five common sizes. For a big fabrication job requiring dozens of precise holes, you’ll be reaching for a more comprehensive kit like the 29-piece Bosch CO21B set. But when the task calls for getting into a tight spot without sacrificing the ability to cut through hardened steel, these stubby M35 cobalt bits deliver exactly what their design promises: no-nonsense access and bite.

A sharp, self-centering bullet point tip defines this set, reducing wandering on curved or hardened surfaces to help start a hole precisely where you want. Combined with a 135° split point, the design enables faster penetration with less pressure, which provides better control when drilling thin or gummy metals. The feature set is engineered for stainless steel, hardened metal, and similar tough materials where drilling accuracy matters.

The trade-off is in the progression. You get a solid range from 1/16″ to 1/2″, but with only fourteen pieces, you’ll have larger jumps between some sizes compared to a more comprehensive set like the 29-piece Drill America. For general shop work drilling various thicknesses, that’s fine. But if your projects consistently require drilling to specific tap drill sizes, you might find yourself missing the exact bit you need. The TiAlN coating and cobalt construction, however, ensure the bits you do have will last significantly longer than standard options.

The Bosch TI9IM’s impact-rated hex shank is the key feature for anyone using a high-torque impact driver on tough materials. This shank is built to handle the hammering action without slipping or breaking, a common failure point for standard bits. The no-skate tip design and titanium nitride coating are specifically called out for hardened and high-carbon steel, meaning they engineered these bits to bite in and stay cool. For a contractor or serious DIYer who reaches for an impact driver as their primary tool, this set is purpose-built to match that tool’s aggressive power. It’s a focused kit for a specific, demanding job.

This set focuses on durability and impact driver compatibility rather than size variety. Its nine pieces form a curated selection for specific tasks, not a comprehensive workshop assortment. For a wider range of hole sizes, you would need a larger set like the 21-piece Bosch CO21B. The Bosch TI9IM is designed for heavy-gauge and high-carbon steel, with an impact-rated shank to handle the higher torque of a drill/driver. Its construction directly addresses the unique stresses of that tool, while for a drill press, a traditional cobalt bit set remains the conventional choice.

Its TiAlN coating withstands temperatures over 1,472°F, forming a heat shield that keeps the M35 cobalt core sharp far longer. This is the critical performance differentiator for drilling thin, hard metals that generate intense localized heat. The geometry is optimized to cut cleanly without excessive force, which prevents distortion in thin material. A self-centering Pilot Point tip eliminates bit walk on curved or hard surfaces for perfectly placed holes.

The geometry and coating are specifically engineered for thin, hard, and gummy metals like stainless steel and titanium. This focus on thin sheet metal means the set is not a general-purpose option for all materials. Among other products, the Bosch CO21B set is also made from cobalt and includes a three-flat shank, but its performance characteristics for different material thicknesses are not detailed in the available facts.

Meeting ANSI specifications means these bits are built to a consistent, professional-grade standard, so you can trust their sizing and performance match the blueprint. This 29-piece set covers the essential fractional sizes in precise 1/64-inch increments, making it a reliable shop staple for anyone who needs repeatable results on hardened steel and other tough metals. The M35 cobalt construction and gold oxide finish are built for the heat and abrasion of hard materials, while the split point design bites in quickly to prevent walking.

Cobalt bits offer great durability, but research indicates carbide bits last even longer on the toughest jobs. Those, however, demand more careful handling to avoid chipping. Compared to a set like the Bosch CO21B with its three-flat shank, these have a standard round shank. This is perfectly fine for most chucks, but it doesn’t provide the same absolute anti-slip security in high-torque applications. For general shop work on hardened steel where certified consistency is key, this set lays a solid foundation.