10 Best Cobalt Drill Bits For Hardened Steel in 2026

This 21-piece cobalt set reaches up to a 1/2-inch bit, giving you the range to handle most metal jobs without needing another kit. It’s manufactured from cobalt for drilling hard materials like stainless steel and cast iron, which means it can handle the high temperatures that quickly dull standard bits. The three-flat shank design gives a better grip and guards against slipping in the chuck on bits 3/16 inch and larger, so you get more control during tough jobs. That combination makes it a reliable choice for anyone who regularly drills into metal and wants a complete set ready to go.

The trade-off for that complete size range and sturdy construction is a bit of heft and slower drilling times compared to some specialized bits, as noted in timed tests on thick stainless. For the money, however, you’re getting significantly more bits and a larger maximum size than options like the Spyder Mach Blue set for only a few dollars more. If your focus is strictly on small, precise work in tight spaces, a stubby set like the NordWolf might be more maneuverable. But for a comprehensive, do-it-all set that won’t quit, the Bosch CO21 is the benchmark.

The M42 8% cobalt steel construction is the key here, hitting a Rockwell hardness of 68-70 HRC, which translates directly into a bit that laughs at the heat generated by drilling hardened steel. This set is for the serious metalworker or machinist who demands the longest possible tool life and needs to push feed rates on a drill press or mill. The 135-degree split point and aggressive flute design cut long, curling chips instead of grinding, which means you spend less time drilling and more time building.

M42 cobalt bits are typically recommended for use in a drill press when working with hardened steel or stainless steel, according to expert round-ups. For handheld drilling, the same sources suggest M35 cobalt bits as the more suitable choice. If your workshop includes a stable drill press for regular work on tough alloys, this STROTON M42 set’s composition is designed for that precise application.

With a 5% cobalt alloy, this set is built to handle the heat and wear of stainless steel and cast iron without immediately dulling. The 135-degree split points bite in without walking, a real advantage on curved or hard surfaces. For a home shop or a mechanic who drills a variety of metals but doesn’t need exotic coatings, this 21-piece kit delivers the core cobalt performance in a practical, organized package. It’s the foundational set that covers most common tasks.

The trade-off is in the shank and length. These are standard jobber-length bits with a round shank. That’s fine for a drill press or a steady hand, but it doesn’t offer the anti-slip security of the Bosch CO21’s three-flat shank when you’re really leaning into hardened material. If your projects involve deep holes or exclusively heavy-gauge steel, you’ll want a shorter, stubbier bit like the NordWolf set for rigidity. For general fabrication and repair, however, the COMOWARE set provides excellent coverage without fuss.

The 135-degree stepped point is the key here. That aggressive geometry bites into hard metal without walking, so you spend less time center-punching and more time drilling. For anyone regularly enlarging existing holes or tackling multi-material jobs with acrylic and hardened steel, this set’s design directly addresses the frustration of bit wander. It’s a logical pick for the mechanic or fabricator who needs a bit to start where they aim and produce a clean, sized hole in one go.

Drill America’s gold stepped point design starts easier and drills faster in metal, which means less pressure and heat during tough jobs. You trade some shank consistency for that performance, as bits 11/64-inch and smaller use a round shank instead of the 3-flat type. That round shank works fine in a drill press but can slip more in a hand drill compared to a uniform set like the Bosch CO21.

The TiAlN coating is the standout feature here, pushing surface hardness to a level that significantly outlasts standard coatings. This means the bits stay sharper through more holes in hardened steel or stainless, directly lowering long-term replacement costs. For a professional or serious DIYer who regularly drills into tough alloys, this set is engineered to handle the heat and abrasion that would quickly dull a standard bit. The 135° split point and three-flat shank provide immediate benefits, too, biting in fast without walking and preventing spin-out in the chuck.

Its TiAlN coating is the critical performance differentiator, increasing surface hardness and heat resistance for a multi-fold increase in usable life over uncoated bits. This means the drill bits maintain a sharp cutting edge through demanding jobs on materials like stainless steel and hardened metal, lowering long-term cost. With 14 sizes from 1/16″ to 1/2″, the set covers an essential range for common holes rather than offering extensive gradation. For a shop doing high-volume work on tough materials, the coating provides a premium, long-life foundation to supplement with specific sizes as needed.

The stepped tip design is the standout feature, letting you start a clean hole in hardened steel without the fuss of a pilot bit. This makes the Steel Vision set a serious time-saver for repetitive metal fabrication or repair work. The M35 cobalt construction holds up to the heat, and the stubby mechanics length gives you the rigidity to push hard without the bit flexing and snapping. It’s built for the tradesperson who needs to drill a lot of holes in tight spaces, like inside a machine frame or a crowded electrical panel.

The manufacturer specifically calls for lubrication on metal to prevent heat buildup, so you’ll need to keep the oil can handy for any steel or stainless drilling. That step is essential for bit longevity with this set. Its mechanics length design reduces breakage, which makes it ideal for drilling in tight spaces. For tasks where depth isn’t a constraint, like on an open bench, other products like the COMOWARE M35 set use a standard jobber length. This Steel Vision set is purpose-driven for tough materials in cramped quarters.

The NordWolf M35 Cobalt Stubby Drill Bit Set uses a 1/4-inch hex shank, which allows direct insertion into impact drivers and quick-release chucks for fast bit changes. Its stubby design, with bits as short as 1.83 inches, provides clearance in tight spaces where standard-length bits cannot reach. M35 cobalt steel offers heat resistance for drilling stainless steel and hardened metals like cast iron or titanium.

This set includes only five imperial sizes, from 3/32″ to 5/16″, limiting its scope compared to more comprehensive kits. Its specialized short length and hex shank make it suitable for drilling in confined areas where access is restricted. The bits are stored in a plastic box with imprinted size labels and a sliding clip for pegboard hanging.

A pack of twenty identical 1/8″ bits made from 5% cobalt M35 steel is built for a specific, high-wear scenario. This is for the shop that goes through this particular size regularly when drilling hardened steel or stainless steel, where the extreme hardness of the cobalt alloy is non-negotiable. The 135-degree split point genuinely helps the bit bite and stay centered on a curved or angled surface, reducing skidding and broken bits. You get a straightforward, no-frills bulk supply of a workhorse bit from a factory-focused brand, which is exactly why it stands out for pure volume replacement in a single size.

The obvious trade-off is the lack of size variety. If your project requires stepping up through different drill sizes or you need a comprehensive set for various tasks, this single-diameter pack won’t suffice. For a broader range of sizes in a similar M35 cobalt formulation, the STROTON M35 Cobalt Drill Bit Set offers a 21-piece assortment from 1/16″ to 3/8″.

The claim of up to three times faster speed with a tool life up to three times longer is this set’s core value, which means a lower cost per hole over the set’s lifetime. Research mentions recommend M35 cobalt bits specifically for handheld drills when working with materials like stainless steel. This makes the set a balanced choice for users who need to drill into hard metals without a dedicated drill press.

The alloy choice involves a trade-off. Expert round-ups note M35 is the recommended choice for handheld drilling, while M42 cobalt is better suited for the rigid precision of a drill press. Therefore, if your work primarily uses a drill press, you might consider a set like the STROTON M42. For general handheld drilling applications, this M35 set provides cobalt performance.

This pack contains five identical 3/8-inch bits, which allows you to continue working if one becomes dull during a project. The bits are made from M35 high-speed steel with 5% cobalt, a material chosen for better heat and wear resistance to support a long tool life. Their 135-degree split point design centers itself quickly and penetrates with less pressure, reducing the chance of the bit wandering off your mark. A case is included, making the set easy to carry and store without losing pieces.

The trade-off is a focus on a single size rather than a range. Compared to multi-piece assortments like the Bosch CO21 set, this pack offers multiple copies of one 3/8-inch diameter. This approach is practical when your work regularly requires that specific hole size in materials like stainless steel or cast iron.