Standard drill bits often fail when they meet hardened steel or cast iron. They smoke, dull, and eventually snap. If you plan to drill through tough metals, you need the heat resistance and durability of cobalt.
High-quality cobalt bits cut through iron, stainless steel, and titanium without losing their edge. However, not all cobalt bits are the same. Grades differ, and specific tip designs work better for different materials.
We analyzed the market to find the best options for your toolbox. We reviewed these five top-rated cobalt drill bits based on material grade, tip geometry, size range, and overall value.
- 135-degree split point tip
- Self-centering
- Gold oxide coating
- Pilot point design
- No need for pilot holes
- M35 grade
- Engineered for professionals
- Split-point tip
- M42 grade
- For heavy-duty use
- 135-degree tip
- Includes professional carry-case
- 13-piece set
- Split point tips
- M35 grade
What Is a Cobalt Drill Bit?
Cobalt drill bits are not just coated in metal. They are made from a solid steel alloy that contains a specific percentage of cobalt throughout the entire bit. Manufacturers grade these bits as either M35 or M42 based on the concentration of cobalt. M35 contains 5% cobalt, while M42 holds 8%.
The primary advantage of cobalt is heat resistance. Friction generates massive heat when you drill through hard metals like stainless steel. This heat kills standard bits. Cobalt retains its hardness even at high temperatures (known as red hardness).
However, there is a trade-off. Cobalt makes the bit harder but also more brittle. These bits can snap if you apply uneven pressure or let the drill walk. Shorter bits tend to be more durable because they flex less than longer ones.
Types of Cobalt Drill Bits
While the material remains consistent, the shape and application of the bits vary. Here are the four common types:
Twist Bit
Twist bits are the standard image of a drill bit. They feature a cylindrical shaft with helical flutes to remove debris. This is the most versatile type of cobalt bit. You will use these for 90% of your metal drilling tasks. Look for split-point tips, which prevent walking on smooth surfaces.
Step Bit
Step bits look like a cone with stair-stepped ridges. A single bit can drill holes of various diameters depending on how deep you push it. These are excellent for drilling clean holes in thin sheet metal. They eliminate the need to change bits constantly when you need different hole sizes.
Countersink
Countersink bits create a conical hole that allows the head of a screw to sit flush with or below the surface of the material. While more common in woodworking, cobalt countersinks are essential when you need to fasten screws into metal plates without the heads sticking out.
Counterbore
Counterbore bits create a flat-bottomed hole. This allows a fastener with a flat underside, like a socket head cap screw, to sit flush. You will typically see these used in machinery assembly or automotive work where flush mounting is critical for moving parts.
How to Choose
Selecting the right set involves more than just picking a brand. You need to match the bit specifications to your specific project. Consider these factors before you buy:
Length
Length dictates reach and stability. Longer bits can drill deeper holes, but they are prone to wobbling and snapping due to the brittle nature of cobalt. Shorter bits (often called “stubby” or “machine screw” lengths) are much more rigid. Use the shortest bit possible for the job to reduce breakage.
Sizes
Most DIYers benefit from a standard index set that ranges from 1/16-inch to 1/2-inch. If you work on engines or precision machinery, look for sets that include wire gauge or letter sizes for tighter tolerances. A larger set offers versatility, but ensure it includes the specific sizes you use most often.
Material Grade
Check the “M” rating. M35 (5% cobalt) is the industry standard for general hardened steel and is easier to sharpen. M42 (8% cobalt) is harder and handles super-alloys and titanium better. However, M42 is also more brittle and sensitive to shock. For hand-held drills, M35 is usually the safer choice.
Price
Cobalt costs significantly more than black oxide or titanium-coated bits. Expect to pay a premium. Cheap cobalt sets often cut corners on manufacturing quality or heat treatment. Invest in a reputable brand if you plan to drill hard metals frequently, as cheap bits will dull quickly or shatter.
Product Reviews
We selected these products based on their alloy composition, tip geometry, and real-world performance. Whether you are a professional fabricator or a garage hobbyist, there is a set here for your needs.
Drill America 29-Piece M35 Cobalt Drill Bit Set
Best Cobalt Drill Bits For Hardened Steel
Drill America offers a robust solution for machinists and serious DIYers with this 29-piece M35 set. The standout feature is the 135-degree split point tip. Unlike standard 118-degree tips, these bite into the metal immediately without walking, which makes them ideal for drilling without a pilot hole.
The gold oxide finish adds a layer of lubricity, but the real worker here is the 5% cobalt alloy. It handles heat well, making these bits effective for high-tensile steel and titanium alloys. The set covers all standard fractional sizes from 1/16-inch to 1/2-inch in 1/64-inch increments.
The round shank fits standard drill chucks securely. While the plastic case is basic, the bits themselves offer professional-level performance at a reasonable price point.
Pros
- Tip Design: 135-degree split point prevents walking.
- Alloy: M35 cobalt steel resists high heat.
- Range: Comprehensive 29-piece size collection.
- Finish: Gold oxide aids chip flow.
Cons
- Price: Higher cost than standard steel sets.
- Case: The index case can be fragile.
Product Specs
| Number of pieces | 29 |
| Sizes (inches) | 0.063 to 0.50 |
| Tip | Split-point |
| Grade | M35 |
| Price | $$$ |
Our Ratings
DeWALT Cobalt Pilot Point Drill Bit Set
Best Pilot-Point Cobalt Drill Bits
DeWALT brings a unique geometry to the table with their Pilot Point tip. This design features a small central tip that starts the hole before the full diameter of the bit engages. This results in clean, round holes with minimal burring and zero walking on startup.
These bits perform exceptionally well in stainless steel and angle iron. The set includes sizes from 1/16-inch to 3/8-inch. Note that the largest bit here is 3/8-inch, not the standard 1/2-inch found in larger sets.
The M35 cobalt blend ensures durability, while the Pilot Point design reduces lock-up when the bit breaks through the other side of the material. This is a user-friendly set perfect for hand-drill use.
Pros
- Geometry: Pilot Point tip ensures clean starts.
- Ease of Use: Reduces bit walking significantly.
- Value: Good balance of price and performance.
- Storage: Tough case with rubber bumpers.
Cons
- Size Limit: Maxes out at 3/8-inch.
- Consistency: Smaller bits can be fragile.
Product Specs
| Number of pieces | 14 |
| Sizes (inches) | 0.063 to 0.375 |
| Tip | Pilot point |
| Grade | M35 |
| Price | $$ |
Our Ratings
Bosch 14-Piece Cobalt Metal Drill Bit Set
Best Professional Cobalt Drill Bits
Bosch utilizes an M42 alloy for this set, giving these bits an 8% cobalt content. This higher percentage provides superior heat resistance compared to standard M35 bits. This makes them a top choice for continuous drilling in abrasive metals like cast iron or stainless steel.
The thick web design adds core strength to the bit, which helps resist side-load breakage. They feature a split point tip for accurate starting. The set ranges from 1/16-inch to 1/2-inch, covering the most essential sizes for HVAC, electrical, and plumbing work.
These are hard, professional-grade bits. Because M42 is more brittle, you must hold the drill steady to avoid snapping them.
Pros
- Grade: M42 alloy with 8% cobalt.
- Strength: Thick web design adds rigidity.
- Accuracy: No-skate split point tip.
- Durability: High heat resistance for production work.
Cons
- Brittleness: Can snap if the drill tilts.
- Cost: Premium pricing for M42 grade.
Product Specs
| Number of pieces | 14 |
| Sizes (inches) | 0.063 to 0.50 |
| Tip | Split-point |
| Grade | M42 |
| Price | $$ |
Our Ratings
Irwin Tools M35 Cobalt Drill Bit Set
Best Heavy-Duty Cobalt Drill Bits
Irwin is a staple in many professional toolboxes, and this 29-piece set shows why. These M35 cobalt bits are ground for heavy-duty applications in abrasive metal. The 135-degree split point reduces feed pressure, meaning you don’t have to lean as hard on the drill to get it to cut.
The set is comprehensive, offering every size from 1/16-inch to 1/2-inch. A standout feature is the rubber-lined metal index case. It protects the cutting edges from chipping during transport, a common issue with loose bits.
While the price point is high, the consistency of the grind and the durability of the alloy make this a smart investment for professionals who rely on their tools daily.
Pros
- Quality: Consistent grind and symmetry.
- Protection: Excellent rubber-lined metal case.
- Application: Reduced feed pressure required.
- Variety: Full 29-piece fractional set.
Cons
- Price: Expensive upfront investment.
Product Specs
| Number of pieces | 29 |
| Sizes (inches) | 0.063 to 0.50 |
| Tip | Split-point |
| Grade | M35 |
| Price | $$$ |
Our Ratings
Comoware Cobalt Drill bit Set
Best Budget Cobalt Drill Bit Set
If you need to drill hardened steel occasionally but cannot justify the price of a pro-grade set, Comoware offers a viable alternative. This 13-piece M35 set handles light-to-medium duty work in hard metals surprisingly well for the price.
The bits feature a gold oxide finish and the standard 135-degree split point to prevent walking. The size range is limited, topping out at 1/4-inch. This makes the set suitable for pilot holes or small fasteners but not for large-diameter drilling.
The chamfered shank on the larger bits fits securely in drill drivers. While they may not last as long as the Irwin or Drill America bits in a production environment, they are perfect for the home toolbox.
Pros
- Value: Very affordable entry point.
- Performance: M35 grade cuts hard metal.
- Design: 135-degree split point included.
Cons
- Sizes: Limited range (max 1/4-inch).
- Longevity: Dulls faster than premium brands.
Product Specs
| Number of pieces | 13 |
| Sizes (inches) | 0.063 to 0.25 |
| Tip | Split-point |
| Grade | M35 |
| Price | $ |
Our Ratings
| Product | Best | No. of pieces | Sizes | Tip | Grade |
| Drill America M35 Cobalt Drill Bit Set | Hardened Steel | 29 | 0.063 to 0.50″ | Split-point | M35 |
| DeWALT Cobalt Pilot Point Drill Bit Set | Pilot-Point | 14 | 0.063 to 0.375″ | Pilot point | M35 |
| Bosch Cobalt Metal Drill Bit Set | Professional | 14 | 0.063 to 0.50″ | Split-point | M42 |
| Irwin Tools M35 Cobalt Drill Bit Set | Heavy-Duty | 29 | 0.063 to 0.50″ | Split-point | M35 |
| Comoware Cobalt Drill bit Set | Budget Pick | 13 | 0.063 to 0.25″ | Split-point | M35 |
FAQs
Can Cobalt Drill Bits Be Sharpened?
Yes, you can sharpen cobalt drill bits. Because the cobalt alloy runs through the entire bit (unlike a coating), sharpening does not ruin the heat resistance or hardness. You can use a dedicated drill bit sharpener or a bench grinder to restore the cutting edge multiple times.
Are Cobalt Drill Bits Better Than High-Speed Steel (HSS) Bits?
Cobalt bits are superior to standard HSS bits for drilling hard metals. They withstand higher temperatures, which allows them to cut through stainless steel and cast iron without dulling immediately. However, for softer materials like wood or plastic, standard HSS bits are often sufficient and less brittle.
Are Cobalt Drill Bits Better Than Titanium?
It depends on the application. Titanium bits are HSS bits with a surface coating (TiN) that reduces friction and heat. They stay sharp longer than standard HSS but cannot be sharpened without losing the coating. Cobalt bits are a solid alloy, offering higher heat resistance for harder metals, and they can be sharpened. Choose cobalt for hardened steel; choose titanium for general-purpose drilling.
How Long Do Cobalt Drill Bits Last?
Lifespan varies by usage, but cobalt bits generally last significantly longer than HSS bits in metal applications. With proper speed control and lubrication, a high-quality cobalt bit can drill hundreds of holes in stainless steel. If you overheat the bit or apply too much side pressure, it can snap prematurely.
Do Cobalt Drill Bits Break Easily?
Yes, cobalt bits are more brittle than standard HSS bits. The same property that makes them hard also lowers their flexibility. If you tilt the drill while the bit is in the hole or apply sudden shock, they can snap. They require a steady hand or a drill press for the best results.
What Is a Good Speed for Cobalt Drill Bits?
Harder materials require slower speeds. For stainless steel, run your drill between 500 and 1,000 RPM. If you see smoke or the bit changes color, you are drilling too fast. High speed creates friction, which is the primary enemy of drill bit longevity. Always start slow and apply firm, steady pressure.
What Are the Different Grades of Cobalt Drill Bits?
The two primary grades are M35 and M42. M35 contains 5% cobalt and strikes a good balance between hardness and durability. It is the most common grade for general use. M42 contains 8% cobalt, making it harder and more heat resistant, but also more brittle and expensive.
What Are the Best Cobalt Drill Bits?
The IRWIN 3018002 29-piece cobalt drill bit set is widely regarded as a top choice. It offers a complete range of sizes, excellent manufacturing consistency, and a durable case. For specific tasks, DeWALT Pilot Point bits are excellent for clean starts, while Drill America offers great value for bulk drilling.
Should I Use Cutting Fluid With Cobalt Bits?
Yes, you should always use cutting fluid or oil when drilling metal. Even though cobalt resists heat well, lubrication reduces friction and flushes chips away from the hole. This significantly extends the life of the bit and produces a cleaner cut.
