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Note: This article is fully rewritten for web publication and synthesizes real-world cobalt drill bit testing, tool specs, and metal-drilling best practices. Product availability, prices, and model names may change, but the buying principles below remain useful for choosing cobalt drill bits for stainless steel, cast iron, mild steel, aluminum, and general shop work.
Drilling into metal is one of those jobs that looks simple until the bit squeals, smokes, skates across the surface, and leaves you wondering whether your drill has filed for early retirement. That is where cobalt drill bits earn their tiny, twisty reputation. Unlike ordinary high-speed steel bits, cobalt bits are made with a cobalt steel alloyusually M35 with 5 percent cobalt or M42 with 8 percent cobaltthat helps the cutting edge survive heat, abrasion, and repeated work in hard materials.
The best cobalt drill bits are not just “harder.” They start cleanly, resist walking, stay sharp after multiple holes, clear chips efficiently, and can usually be resharpened. In testing-style comparisons from Bob Vila and other respected tool reviewers, the strongest performers shared several traits: 135-degree split-point tips, durable storage cases, high-quality cobalt alloy, and shanks that grip securely in a drill chuck.
For homeowners, mechanics, metalworkers, and serious DIYers, a good cobalt set can be the difference between “nice clean hole” and “why is this bit glowing like a toaster coil?” Below is a practical, SEO-friendly guide to the best cobalt drill bits, how they compare, and how to use them without accidentally turning expensive bits into modern art.
Why Cobalt Drill Bits Are Different
Cobalt drill bits are designed for metal first. They can often cut wood, plastic, and PVC, but buying cobalt bits only for soft materials is like hiring a bulldozer to plant tulips. Their real value appears when drilling stainless steel, cast iron, hardened steel, titanium alloy, and other materials that generate enough heat to punish cheaper bits.
The cobalt is not just a coating. In quality cobalt bits, it is part of the steel alloy itself. That matters because coatings can wear away, while cobalt alloy remains useful even after sharpening. This is one of the biggest advantages cobalt has over many titanium-coated bits. Titanium bits can be great for soft metals and general use, but once the coating is worn or ground off, the original benefit declines. Cobalt bits keep their heat resistance deeper into the material.
Best Overall: DeWalt Industrial Cobalt Alloy Steel Drill Bit Set
The DeWalt Industrial Cobalt Alloy Steel Set is a strong all-around pick for users who want clean starts, dependable drilling, and a practical range of sizes. In Bob Vila’s cobalt drill bit testing, this set stood out because the pilot-style point helped the bits start without slipping, and the set created clean holes through multiple test metals.
This is the kind of kit that makes sense for homeowners who work on metal brackets, automotive parts, garage projects, stainless hardware, and repair jobs where a basic black oxide bit feels underpowered. The set includes common small-to-medium sizes, which covers most household and shop needs. It is not the largest set, but that can actually be a benefit. You are not paying for dozens of sizes you may never use.
Why it works well
The main advantage is control. Cobalt drill bits are only useful if they start where you want them to start. A bit that wanders across metal like a caffeinated squirrel creates scratches, crooked holes, and colorful language. The DeWalt set is good for users who want predictable performance without overthinking every hole.
Runner-Up: Irwin 29-Piece Cobalt Alloy Steel M35 Drill Bit Set
The Irwin 29-piece M35 cobalt set is a favorite for anyone who wants a broad size range. With sizes from 1/16 inch to 1/2 inch in 1/64-inch increments, it is built for precision work. That makes it useful for mechanics, fabricators, installers, and DIYers who do not want to “make do” with a bit that is almost the right size.
Irwin’s M35 cobalt alloy offers a practical blend of toughness, heat resistance, and usability. It is not as hard as M42, but it is less brittle and more forgiving in handheld drills. The 135-degree split point helps the bit start on contact with less walking, while the indexed case keeps the sizes organized. That case matters more than people think. Loose drill bits have a mysterious ability to disappear into the same dimension as missing socks and 10mm sockets.
Best for
This set is ideal for users who drill metal regularly and need many fractional sizes. It is especially useful in workshops where accuracy matters, such as tapping holes, matching fasteners, or repairing metal fixtures.
Best Budget Pick: Amoolo 13-Piece Cobalt Drill Bit Set
The Amoolo 13-piece cobalt set proves that not every good cobalt drill bit kit has to cost like a car payment. It typically includes common small sizes and uses M35 cobalt alloy, making it a strong starter set for occasional metal drilling.
The biggest trade-off is storage. Budget sets often save money on the case, and that can make organization less pleasant. Still, if the actual bits cut cleanly and resist heat, many DIYers will happily tolerate a less glamorous case. After all, the hole does not care whether the bit arrived in a luxury apartment or a plastic motel.
Best for
Choose this type of budget cobalt drill bit set if you drill metal occasionally, mostly need smaller holes, and want better performance than standard HSS bits without buying a professional 29-piece index.
Upgrade Pick: Drill America M42 Cobalt Jobber Drill Bit Set
For harder metals and heavier use, the Drill America M42 cobalt jobber set is a serious upgrade. M42 cobalt contains about 8 percent cobalt, giving it higher heat resistance and edge retention than M35. That makes it especially useful for stainless steel, high-tensile steel, titanium, and demanding shop work.
The 29-piece format gives users a wide selection from 1/16 inch to 1/2 inch in 1/64-inch increments. A 135-degree split point helps with self-centering and reduces thrust, meaning the bit can start more accurately and require less force than a traditional 118-degree point.
The trade-off is brittleness. Harder bits can snap if the user wobbles the drill, applies side pressure, or runs the bit too fast. M42 is excellent in a drill press and very capable in a handheld drill, but it rewards steady hands and patient technique.
Best M42 Set: Bosch 14-Piece M42 Cobalt Drill Bit Set
The Bosch 14-piece M42 cobalt set is a compact but high-performing option for hard metal. It uses an upgraded M42 alloy and a thick web-helix design for stability and material removal. Larger bits often include three-flat shanks, which help prevent slipping in the chuck.
This set is especially appealing for users who want premium cobalt performance but do not need a full 29-piece index. The common sizes cover many drilling tasks, and the compact case is easy to store in a tool bag. If the Irwin 29-piece set is the organized workshop librarian, the Bosch M42 set is the compact field kit that says, “I packed light, but I came prepared.”
Best for
Use the Bosch M42 set for stainless steel, cast iron, titanium alloy, and tough repair work where heat resistance matters. It is also a good choice for users who prefer secure shank grip over maximum size selection.
Best Metric Set: Stroton Metric M42 Cobalt Twist Drill Bits
Not every project speaks in fractions. For users working with metric fasteners, imported equipment, motorcycles, bicycles, appliances, or machinery, a metric cobalt set can save time and prevent sloppy hole sizing. The Stroton metric M42 cobalt set is designed for users who want 1 millimeter to 10 millimeter coverage in small increments.
Its M42 alloy helps with heat and edge retention, while the stepped split-point design can improve starting performance. Metric sets are particularly useful in precision repairs where “close enough” can become “why does this bolt rattle?”
Best Cobalt Step Bits: Milwaukee Cobalt Step Drill Bit Set
Step bits are different from standard twist bits. Instead of drilling one fixed diameter, they enlarge holes through a series of stepped sizes. That makes them excellent for sheet metal, electrical boxes, thin steel, panels, and clean hole enlargement.
Milwaukee’s cobalt step bits are designed for sheet metal work and feature details such as three-flat shanks, elongated flutes, and starting tips made for fast penetration. They are not the best choice for thick steel plate, but they are fantastic when you need clean, round holes in thinner metal without constantly changing bits.
M35 vs. M42 Cobalt Drill Bits
The simplest explanation is this: M35 is the practical everyday choice, while M42 is the premium hard-metal choice. M35 cobalt bits usually contain 5 percent cobalt. They are durable, heat resistant, and less brittle than M42. They are great for general steel, stainless steel, cast iron, and repeated DIY use.
M42 cobalt bits usually contain 8 percent cobalt. They handle heat better, hold an edge longer, and perform well in harder metals. However, they are more expensive and can be more brittle. If you use a drill press, M42 can be a beautiful thing. If you use a handheld drill while standing on a ladder, leaning sideways, and thinking about lunch, M35 may forgive you more.
What to Look for in the Best Cobalt Drill Bits
135-Degree Split Point
A 135-degree split point reduces walking and helps the bit start faster on metal. This is especially useful on stainless steel and curved surfaces. A center punch still helps, but a good split point makes the job easier.
Quality Alloy
Look for M35 or M42 cobalt alloy. Avoid vague listings that say “cobalt coating” without explaining the material. True cobalt alloy bits remain useful after sharpening because the cobalt is part of the bit, not just a surface treatment.
Good Case Design
A sturdy case keeps sizes organized and protects cutting edges. Metal index cases, rubber overmolded cases, and clearly labeled holders are worth paying for if you use bits often.
Shank Grip
Round shanks work, but they can slip under load. Three-flat, hex, or no-spin shanks help the chuck hold better, especially when drilling larger holes or tougher metal.
Sharpenability
One big advantage of cobalt bits is that they can often be resharpened. Split points are easier to align on a grinder or sharpening tool, but sharpening takes practice. A badly sharpened expensive bit is still a sad little sculpture.
How to Use Cobalt Drill Bits Correctly
The best cobalt drill bits can still fail if used incorrectly. Metal drilling is about speed, pressure, lubrication, and patience. Start by clamping the workpiece securely. Metal should not spin, bounce, or vibrate under the drill. Use safety glasses because metal chips are small, sharp, and extremely uninterested in your comfort.
Mark the hole with a center punch when accuracy matters. Apply cutting oil or drilling lubricant to reduce heat and friction. Use a slower speed than you would use for wood. Large bits need especially slow speeds. Apply steady pressure, but do not force the bit. Let the cutting edges do the work.
If the bit squeals, smokes, or stops producing chips, something is wrong. You may be drilling too fast, pressing too lightly, using no lubricant, or working with a dull bit. In metal drilling, chips are good. Dust or squealing usually means the bit is rubbing instead of cutting.
Cobalt vs. Titanium Drill Bits
Titanium drill bits are usually HSS bits with a titanium nitride or similar coating. They reduce friction and work well in wood, plastic, aluminum, copper, and light metal. They are often cheaper than cobalt bits and are excellent for general-purpose drilling.
Cobalt bits are better for hard metals. They resist heat, can be sharpened, and keep their useful material properties after the edge is refreshed. For stainless steel, cast iron, and repeated metal drilling, cobalt is usually the better investment. For soft metals and occasional household use, titanium may be enough.
Maintenance Tips That Make Cobalt Bits Last Longer
Clean bits after use. Brush metal chips out of the flutes, wipe the bit dry, and add a light coat of oil before storage. This reduces corrosion and keeps the cutting edges ready for the next job. Do not toss cobalt bits loose into a drawer with screws, washers, and whatever that mystery Allen key belongs to. Protect the edges and the bits will reward you.
When a bit dulls, sharpen it instead of pushing harder. More pressure on a dull bit usually creates more heat, more frustration, and possibly a broken bit. If you drill metal often, a drill bit sharpener or bench grinder setup can pay for itself quickly.
Real-World Experience: What Using Cobalt Drill Bits Teaches You
After enough metal-drilling projects, you learn that drill bits have personalities. Cheap bits are optimistic for about twelve seconds. Titanium bits are friendly and useful until the coating wears down. Cobalt bits are the serious ones in the room. They do not need applause, but they expect you to behave properly.
The first lesson is that slow drilling is not lazy drilling. Many beginners assume more speed equals faster holes. In wood, that can be true. In metal, too much speed creates heat, and heat is the villain. A cobalt bit can tolerate heat better than standard HSS, but it is not magic. Run it too fast without oil and it will still dull, discolor, or lose performance.
The second lesson is that pressure matters. Too little pressure causes rubbing. Too much pressure can bind or break the bit. The sweet spot feels steady and deliberate. You should see chips coming out of the hole. Long curls or consistent small chips mean the bit is cutting. Fine powder means the bit is struggling. Smoke means the bit is sending a resignation letter.
The third lesson is that a drill press makes everything easier. Handheld drills are convenient, but a drill press gives better alignment, steadier feed pressure, and more consistent speed. When using M42 cobalt bits, this extra control is especially helpful because the alloy is harder but more brittle. For expensive bits and tough metals, stability is your friend.
The fourth lesson is that the case is not just packaging. A well-labeled index case saves time and protects the bits. When you need a 7/32-inch bit, you do not want to squint at twelve nearly identical pieces of metal like you are solving a tiny silver puzzle. Good storage helps you use the right size and prevents damage.
The fifth lesson is that cutting oil is cheap insurance. A few drops can improve cutting, reduce heat, extend tool life, and produce cleaner holes. People skip lubricant because they are in a hurry. Then they spend more time fighting a dull bit. That is not efficiency; that is comedy with sparks.
The sixth lesson is to match the bit to the material. For thin sheet metal, a cobalt step bit may be cleaner and faster than a twist bit. For stainless steel, M35 or M42 cobalt twist bits are better. For aluminum, cobalt works, but titanium or polished-flute bits may clear chips more smoothly. The best cobalt drill bits are excellent tools, not universal solutions for every hole on Earth.
Finally, cobalt bits reward patience. They are more expensive than basic bits, but they last longer when treated correctly. A good set can survive repeated sharpening, tough metals, and years of careful use. Buy the right grade, use the right speed, add lubricant, clean the bits, and store them properly. Do that, and drilling metal becomes less of a battle and more of a satisfying little victoryone clean hole at a time.
Final Verdict
The best cobalt drill bit set depends on how often you drill metal and what kind of metal you drill. For most DIYers, the DeWalt Industrial Cobalt Alloy Steel Set is a reliable overall choice. For maximum size selection, the Irwin 29-piece M35 set is hard to beat. For tougher metals and longer edge life, Drill America and Bosch M42 sets are excellent upgrades. For sheet metal, Milwaukee cobalt step bits are the smarter tool.
If you remember only one thing, remember this: cobalt bits are made for heat, but they still need respect. Use slow speed, steady pressure, cutting oil, and proper storage. Your reward will be cleaner holes, longer bit life, and fewer moments where your drill sounds like it is auditioning for a horror movie.
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