Drilling through hardened steel is one of the toughest challenges for any DIY enthusiast or professional tradesperson. Standard drill bits simply won’t cut it, often dulling quickly or breaking under the extreme stress and heat generated. To achieve clean, precise holes without damaging your tools or material, you need specialized drill bits engineered for superior hardness, heat resistance, and durability. This guide delves into the best drill bits for drilling hardened steel, exploring top-performing options that utilize advanced materials and coatings like cobalt (M35, M42), Titanium Nitride (TiN), and Titanium Aluminum Nitride (TiAlN) to tackle the most demanding metalworking tasks effectively.
Quick Product Comparison
Our Top 5 Best Drill Bit For Drilling Hardened Steel Reviews – Expert Tested & Recommended
1. toolant Cobalt Drill Bit Set, Titanium Aluminum Nitride Coated, for Hardened Steel, Metal, Stainless Steel
The toolant Cobalt Drill Bit Set is an outstanding choice for tackling hardened steel, offering a robust collection of bits designed for demanding metalworking tasks. This 21-piece set combines premium M35 cobalt high-speed steel with a specialized Titanium Aluminum Nitride (TiAlN) coating, ensuring unparalleled durability and heat resistance.
Key Features That Stand Out
- ✓ 21-piece set for a comprehensive range of sizes.
- ✓ M35 Cobalt High-Speed Steel for enhanced strength and heat resistance.
- ✓ Titanium Aluminum Nitride (TiAlN) coating increases surface hardness to 89HRC and provides superior heat dissipation.
- ✓ Designed for fast cutting and prolonged sharpness, even in tough materials.
- ✓ Suitable for hardened steel, stainless steel, cast iron, and various metals.
Why We Recommend It
We recommend the toolant Cobalt Drill Bit Set for its exceptional blend of material science and practical design. The TiAlN coating is a game-changer, allowing these bits to maintain their edge and integrity under extreme temperatures and friction, making them ideal for materials that would quickly destroy lesser bits. The extensive size range ensures you have the right tool for almost any job.
Best For
This set is best for professionals and serious DIYers who frequently work with hardened steel, stainless steel, and other challenging metals, requiring a durable, high-performance solution.
Pros and Cons
Pros:
- Exceptional durability due to M35 Cobalt and TiAlN coating.
- High heat resistance prevents premature dulling.
- Comprehensive 21-piece set covers many drilling needs.
- Cuts quickly and efficiently through tough materials.
Cons:
- Higher initial cost compared to standard HSS sets.
- Requires proper technique and coolant for maximum lifespan.
Customer Reviews
Customer Review: “I’ve struggled with hardened bolts before, but these toolant bits cut through them like butter. The TiAlN coating really makes a difference; they don’t even get hot.”
Customer Review: “Fantastic set for the price. I’ve used them on several stainless steel projects and they hold up incredibly well. Very impressed with the sharpness.”
2. M35 Cobalt Drill Bit with TiAlN Coating for Hardened Steel and Stainless Steel
This M35 Cobalt Drill Bit with TiAlN Coating is engineered for extreme performance, especially when facing challenging materials like hardened steel and stainless steel. Its advanced design incorporates industry-leading durability features to ensure faster, cleaner, and more efficient drilling.
Key Features That Stand Out
- ✓ M35 Cobalt High-Speed Steel with 5% Cobalt core for superior heat resistance (up to 1200°F).
- ✓ TiAlN Nano-coating (89HRC hardness) provides extreme surface protection and reduces friction.
- ✓ Unique triple-flute design for 40% better chip removal, preventing clogging and breakage.
- ✓ 135° self-centering tip allows for precision drilling without walking.
- ✓ Tested to bore through 1/4″ stainless steel in just 8 seconds.
Why We Recommend It
This drill bit stands out for its innovative triple-flute design, which significantly improves chip evacuation and reduces heat buildup – critical factors when drilling hardened materials. Coupled with the M35 cobalt and TiAlN coating, it delivers a combination of speed, precision, and longevity that few other bits can match, making it an excellent investment for tough jobs.
Best For
Ideal for metal fabrication professionals, mechanics, and advanced DIYers who regularly work with hardened steel, thick stainless steel, and other challenging alloys where speed and precision are paramount.
Pros and Cons
Pros:
- Exceptional durability and heat resistance (5X longer life than standard bits).
- Rapid drilling performance even on tough materials.
- Triple-flute design enhances chip removal and prevents clogging.
- 135° self-centering tip ensures accurate starts.
Cons:
- Potentially higher cost for individual bits or sets.
- Optimal performance requires correct drilling speed and pressure.
Customer Reviews
Customer Review: “The half inch bit I used yesterday on soft iron hinges and 2 inch angle iron. Amazed how sharp these bits are! Never seen the most perfect curly shavings as it cut through the metal with ease. Don’t know how long these will last but boy am I impressed so far. These were used in a cordless drill.”
Customer Review: “The half inch bit I used yesterday on soft iron hinges and 2 inch angle iron. Amazed how sharp these bits are! Never seen the most perfect curly shavings as it cut through the metal with ease. Don’t know how long these will last but boy am I impressed so far. These were used in a cordless drill.”
3. Cobalt M35 HSS Drill Bit Set: Best for Hardened Steel, Stainless Steel, Cast Iron.
For those seeking a cost-effective yet capable solution for drilling tough materials, the Cobalt M35 HSS Drill Bit Set is an excellent choice. Featuring premium M35 Cobalt High-Speed Steel, these bits offer significantly improved heat resistance and hardness over standard HSS bits, making them suitable for hardened steel, stainless steel, and cast iron.
Key Features That Stand Out
- ✓ Premium M35 Cobalt High-Speed Steel (5% Cobalt) for superior heat and abrasion resistance.
- ✓ 135° Split Point Design for precise, non-walking starts and reduced effort.
- ✓ Fully Ground twist design promotes faster particle clearing and reduces friction/heat.
- ✓ Effective on a wide range of soft and hard materials, including alloys.
- ✓ Offers greater hardness compared to ordinary drill bits.
Why We Recommend It
This set proves that you don’t always have to break the bank to get reliable performance on hardened materials. The M35 cobalt composition ensures these bits can withstand higher temperatures and retain their sharpness longer than standard HSS. The 135° split point is a crucial feature for accurate drilling, especially on slick surfaces like hardened steel.
Best For
Perfect for budget-conscious hobbyists, DIYers, or occasional users who need a reliable set of bits for drilling through various challenging metals, including light to moderately hardened steel, without a significant investment.
Pros and Cons
Pros:
- Excellent value for a cobalt drill bit set.
- Good heat resistance and durability for the price point.
- 135° split point ensures accurate and easy starts.
- Efficient chip removal reduces friction and heat.
Cons:
- May not offer the same longevity as higher-end M42 cobalt or TiAlN coated bits for heavy industrial use.
- Durability could be slightly improved, as noted by some users.
Customer Reviews
Customer Review: “Great value. Used a bit to drill a starter hole in a 1/8th inch thick metal frame and it worked well.”
Customer Review: “Work well, could be slightly more durable but for price not a bad value”
4. DEWALT 21-Piece Titanium Nitride Coated Pilot Point Drill Bit Set for Hardened Steel
The DEWALT 21-Piece Titanium Nitride Coated Pilot Point Drill Bit Set delivers the reliability and performance expected from a top brand when drilling through various metals, including hardened steel. These bits feature a Titanium Nitride (TiN) coating, which enhances hardness and reduces friction, extending their lifespan and improving cutting efficiency.
Key Features That Stand Out
- ✓ Titanium Nitride (TiN) coating for increased surface hardness and reduced friction.
- ✓ Pilot Point tip design ensures clean, accurate starts on contact, preventing bit walking.
- ✓ Long-life design for extended use in demanding applications.
- ✓ Comprehensive 21-piece set covers a wide array of drilling needs.
- ✓ Designed for use with both corded and cordless drills.
Why We Recommend It
DEWALT is a trusted name in tools, and this drill bit set lives up to that reputation. The combination of the TiN coating and the innovative Pilot Point tip makes these bits incredibly effective for accurate, clean holes in tough materials. The Pilot Point ensures that even on slick surfaces like hardened steel, your bit won’t wander, leading to fewer errors and less material waste.
Best For
Excellent for general contractors, metal fabricators, and serious DIYers who need a reliable and durable set of drill bits for consistent performance on a variety of materials, including moderately hardened steel and stainless steel.
Pros and Cons
Pros:
- Trusted brand name with quality assurance.
- TiN coating significantly extends bit life and improves cutting.
- Pilot Point tip offers precise, clean hole starts.
- Versatile set for multiple applications.
Cons:
- TiN coating, while good, may not match the extreme heat resistance of TiAlN or M42 cobalt for severely hardened steel.
- Individual bits can be prone to breaking if excessive force is used.
Customer Reviews
Customer Review: “This is an excellent drill bit set from DeWalt. I’d been eyeing it for a long time, waiting for the price to drop, and it was definitely worth the wait. Once it went on sale, I picked it up, and I’m glad I finally did—great quality and performance.”
Customer Review: “This is an excellent drill bit set from DeWalt. I’d been eyeing it for a long time, waiting for the price to drop, and it was definitely worth the wait. Once it went on sale, I picked it up, and I’m glad I finally did—great quality and performance.Read more”
5. Bosch 14-Piece Cobalt M42 Metal Drill Bits with Three-Flat Shank for Hardened Steel
The Bosch 14-Piece Cobalt M42 Metal Drill Bits represent the pinnacle of performance for drilling through the toughest materials, including severely hardened steel. Featuring an upgraded M42 cobalt alloy, these bits are specifically designed for extreme durability and exceptional heat resistance, providing up to 10 times the life of standard bits.
Key Features That Stand Out
- ✓ Enhanced M42 Cobalt alloy (8% Cobalt) offers superior hardness and heat resistance.
- ✓ Provides 10X life compared to standard HSS bits, ideal for continuous heavy-duty use.
- ✓ Withstands high-temperature applications for extended drilling periods.
- ✓ Three-flat shank design prevents slippage in the drill chuck, ensuring stable and efficient drilling.
- ✓ Jobber-length bits suitable for general-purpose drilling in various depths.
Why We Recommend It
Bosch is synonymous with quality, and their M42 Cobalt bits exemplify this. The 8% cobalt content makes these bits incredibly resilient against the heat and abrasion generated when drilling hardened steel. The three-flat shank is a practical feature, preventing frustrating slippage and allowing for maximum torque transfer, making tough jobs much easier and safer.
Best For
This set is indispensable for industrial professionals, serious metalworkers, and anyone who regularly needs to drill into extremely tough and hardened steel, requiring maximum durability and bit lifespan.
Pros and Cons
Pros:
- Superior M42 Cobalt composition for extreme durability.
- Exceptional heat resistance, vital for hardened materials.
- 10X longer life expectancy than standard bits.
- Three-flat shank prevents slippage, ensuring secure drilling.
Cons:
- Higher price point due to premium materials and performance.
- Requires precise drilling practices to maximize longevity.
Customer Reviews
Customer Review: “Anything bosch makes is good, but i feel like they have it down pat when it comes to stuff like twist drills and bits.The M42 cobalt keeps the drill from getting too hot and also acts as a “lubricant”, both contributing to keeping a sharp cutting edge, giving it quality and ease of use.These factors”
Customer Review: “This is a great drill bit set. The reason I purchased this set is because I needed to drill and tap a hole in the end of a lawnmower engine crankshaft. Rather than buying just that drill bit I decided to get a whole set, because I knew I would need drill bits again. I decided to go with this set ove”
Complete Buying Guide for Best Drill Bit For Drilling Hardened Steel
Choosing the best drill bit for drilling hardened steel isn’t just about picking the first set you see. It requires understanding the specific properties that allow a drill bit to withstand the immense heat and abrasion generated by such a demanding task. This buying guide will walk you through the essential factors to consider to ensure your investment is worthwhile and your drilling projects are successful.
Essential Factors We Consider
- Material Composition: For hardened steel, you absolutely need more than standard HSS (High-Speed Steel). Look for bits made from:
- Cobalt (M35 or M42): These bits contain 5% (M35) or 8% (M42) cobalt alloy, which significantly increases their heat resistance and hardness compared to regular HSS. M42 is generally considered superior for extreme hardness.
- Carbide: While less common for general-purpose drilling due to their brittleness, solid carbide or carbide-tipped bits are extremely hard and can be effective, especially at high speeds, but require very stable drilling conditions.
- Coatings: Advanced coatings enhance the bit’s performance and lifespan:
- Titanium Nitride (TiN): A golden coating that adds surface hardness, reduces friction, and improves heat resistance. Good for moderately hardened steel.
- Titanium Aluminum Nitride (TiAlN): A dark gray/black coating that offers even higher hardness and exceptional heat resistance, often outperforming TiN, making it ideal for severely hardened materials without coolant.
- AlCrN (Aluminum Chromium Nitride): Another excellent coating for high-temperature applications, offering superior wear resistance.
- Point Angle and Geometry:
- 135-Degree Split Point: This is crucial. It prevents the bit from “walking” on hard surfaces, allowing for accurate self-centering without a pilot hole. It also creates smaller chips, which helps with heat dissipation.
- Flute Design: Deeper, wider flutes facilitate better chip evacuation, reducing heat buildup and preventing clogging, especially important with hardened metals.
- Shank Type:
- Round Shank: Common but can slip in chucks under high torque.
- Three-Flat Shank: Provides a more secure grip in the chuck, preventing slippage.
- Hex Shank: Offers excellent grip and quick change compatibility.
- Set vs. Individual Bits: Consider whether you need a full set of various sizes or just a few specific sizes for a particular project. Sets often offer better value per bit.
- Brand Reputation: Stick with reputable brands known for quality in metalworking tools. Brands like Bosch, DEWALT, and specialized bit manufacturers often use better materials and manufacturing processes.
Budget Planning
When it comes to drilling hardened steel, trying to save money by opting for cheap, standard drill bits will cost you more in the long run through damaged bits, wasted material, and frustration. While cobalt and coated bits are more expensive upfront, their enhanced durability and performance mean they last significantly longer, even when used on demanding materials. Consider it an investment. A good quality set will pay for itself by successfully completing tasks that would otherwise be impossible or incredibly time-consuming with inferior tools. Prioritize bits with M35 or M42 cobalt, and TiN or TiAlN coatings for the best performance-to-cost ratio.
Final Thoughts
Successfully drilling through hardened steel is achievable with the right tools and techniques. The key is to select drill bits specifically designed for the task, focusing on material composition (cobalt), advanced coatings (TiN, TiAlN), and effective tip geometry (135-degree split point). Always use appropriate cutting fluid to reduce heat and friction, and maintain a slow, consistent drill speed with firm pressure. Investing in a high-quality drill bit set tailored for hardened steel will not only make your projects easier but also ensure greater safety and a longer lifespan for your tools. Choose wisely, and you’ll be able to tackle even the most stubborn metal drilling challenges with confidence.
Frequently Asked Questions
Q: Can I use a regular HSS drill bit on hardened steel?
A: No, using a regular HSS (High-Speed Steel) drill bit on hardened steel is highly ineffective and can be dangerous. HSS bits lack the necessary hardness and heat resistance to cut through hardened steel. They will quickly dull, generate excessive heat, and likely break, potentially causing injury or damage to your workpiece.
Q: What makes cobalt drill bits good for hardened steel?
A: Cobalt drill bits (M35 or M42) are made from high-speed steel alloyed with 5% to 8% cobalt. This cobalt content significantly increases the bit’s hardness, abrasion resistance, and, most importantly, its heat resistance. Hardened steel generates intense heat during drilling, and cobalt bits retain their cutting edge even at high temperatures, allowing them to cut effectively where standard HSS bits would fail.
Q: What is the benefit of a 135-degree split point tip?
A: A 135-degree split point tip is highly beneficial for drilling hardened steel because it acts as a self-centering point, preventing the drill bit from “walking” or wandering on the hard, smooth surface. This eliminates the need for a pilot hole and ensures a precise start. Additionally, the split point design helps to break up chips into smaller, more manageable pieces, facilitating better chip evacuation and reducing heat buildup.
Q: What are TiN and TiAlN coatings?
A: TiN (Titanium Nitride) and TiAlN (Titanium Aluminum Nitride) are advanced ceramic coatings applied to drill bits to enhance their performance. TiN (gold color) increases surface hardness, reduces friction, and improves heat resistance, making bits last longer. TiAlN (dark gray/black) offers even greater hardness and superior heat resistance compared to TiN, making it exceptionally effective for drilling very hard or abrasive materials like hardened steel, especially in high-heat, dry cutting applications.
Q: Do I need to use coolant when drilling hardened steel?
A: Yes, using a suitable cutting fluid or coolant is highly recommended when drilling hardened steel. Coolant helps to dissipate the extreme heat generated during drilling, lubricates the cutting edge to reduce friction, and aids in chip removal. This extends the lifespan of your drill bit, improves cutting efficiency, and helps produce a cleaner hole. For some TiAlN coated bits, dry cutting is possible due to their extreme heat resistance, but coolant generally still provides additional benefits.
Selecting the right drill bit is paramount when tackling the challenge of drilling into hardened steel. Our comprehensive review and buying guide highlight that materials like M35 and M42 cobalt, combined with advanced coatings such as TiN and TiAlN, are essential for success. These specialized bits offer the superior hardness, heat resistance, and cutting efficiency required to penetrate tough metals without premature wear or breakage. Whether you opt for the robust toolant Cobalt Drill Bit Set, the precision of the M35 Cobalt Drill Bit with TiAlN Coating, or the premium performance of the Bosch 14-Piece Cobalt M42 Metal Drill Bits, investing in the right tool will save you time, effort, and frustration. Equip yourself with one of our top recommendations, and confidently take on your most demanding metalworking projects. Check out our top picks on Amazon today to upgrade your toolkit!
I’m Darrell Julian, the founder, lead writer, and hands-on welding enthusiast behind ArcWeldingPro.com. With more than 15 years of real-world welding experience, I created this platform to share what I’ve learned in the field, in the shop, and in the heat of the arc.
