Tackling hardened steel requires specialized tools, and when it comes to drilling, ordinary drill bits simply won’t cut it. That’s where cobalt drill bits shine. Engineered with an alloy of steel and 5-8% cobalt, these bits boast superior heat resistance and increased hardness, making them the ultimate choice for penetrating tough materials like stainless steel, cast iron, and, of course, hardened steel. Selecting the best cobalt drill bits for hardened steel can make all the difference in your project’s efficiency and the longevity of your tools. We’ve rigorously tested and reviewed the top contenders to help you find the perfect set that combines durability, precision, and performance for your most demanding tasks.
Quick Product Comparison
Our Top 5 Best Cobalt Drill Bits For Hardened Steel Reviews – Expert Tested & Recommended
1. Cobalt M35 HSS Twist Drill Bit Set for Hardened Metal and Stainless Steel
The Cobalt M35 HSS Twist Drill Bit Set is an exceptional choice for anyone needing to drill through demanding materials. Crafted from premium M35 High-Speed Steel with 5% cobalt, these bits offer superior heat resistance and impressive hardness compared to standard drill bits. Their robust construction ensures consistent performance and reliability, even under strenuous conditions.
Key Features That Stand Out
- ✓ M35 Cobalt (5%) Composition: Provides enhanced heat resistance and hardness for tackling tough metals.
- ✓ 135° Split Point Design: Allows for quick starts without walking and efficient drilling through various materials.
- ✓ Fully Ground Twist Design: Optimizes chip evacuation, reduces friction and heat build-up for cooler, smoother drilling.
- ✓ Versatile Application: Effectively drills through hardened steel, stainless steel, and other hard objects.
Why We Recommend It
We highly recommend this set for its outstanding balance of durability and cutting performance. The M35 cobalt alloy ensures a prolonged lifespan, while the split point design eliminates the need for a pilot hole, saving time and effort. Its ability to maintain sharpness under high temperatures makes it a reliable tool for continuous, demanding work.
Best For
This set is ideal for professional tradespeople and serious DIY enthusiasts working with hardened metals, stainless steel, and other challenging alloys that require precision and sustained bit integrity.
Pros and Cons
Pros:
- Excellent heat resistance due to 5% cobalt content.
- Superior hardness for drilling through tough materials.
- 135° split point prevents walking and allows for quick, accurate starts.
- Fully ground design ensures efficient chip removal and reduces heat.
Cons:
- May have slightly less durability for extremely heavy, prolonged use compared to M42.
- Individual bits might wear faster if not used with proper cooling.
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”
2. Durable 1/4 Hex Shank Cobalt Twist Drill Bit Set for Hardened Steel
This Durable 1/4 Hex Shank Cobalt Twist Drill Bit Set stands out for its robust construction and innovative design. Utilizing Cobalt M35 material, these bits offer an impressive hardness of up to 67 HRC, superior heat resistance, and a significantly extended lifespan, potentially up to 12 times longer than average HSS bits. The solid bonding hex shank ensures maximum power transfer and prevents slippage, making it an excellent choice for demanding drilling applications.
Key Features That Stand Out
- ✓ Cobalt M35 Material: Provides extreme hardness (up to 67 HRC) and superior heat resistance for cutting hardened steel.
- ✓ Solid Bonding Hex Shank: Prevents bits from breaking loose from the shank base, enhancing durability and power transfer.
- ✓ Enhanced Torque and Concentricity: Offers 5 times higher torque compared to older hex shanks, eliminating radial runout and improving drilling accuracy.
- ✓ Extended Lifespan: Designed for exceptional longevity, cutting faster and lasting significantly longer than standard bits.
Why We Recommend It
The innovative solid bonding hex shank design combined with the high-quality M35 cobalt material makes this set incredibly efficient and reliable. It addresses common issues like bit slippage and breakage, delivering a smooth, precise, and powerful drilling experience every time. The enhanced impact resistance further solidifies its position as a top performer.
Best For
This set is perfect for professionals and serious DIYers who frequently work with hardened steel, needing a drill bit that won’t slip, will maintain its edge, and can withstand high-torque applications with impact drivers.
Pros and Cons
Pros:
- Exceptional hardness and heat resistance from M35 cobalt.
- Solid bonding hex shank eliminates slippage and improves concentricity.
- Significantly extended tool life, reducing replacement frequency.
- Higher torque resistance, ideal for impact drivers.
Cons:
- Higher initial cost compared to standard HSS bits.
- May require specific adaptors if 1/4″ hex shank isn’t compatible with all drill types.
Customer Reviews
Customer Review: “Excellent product. These are high quality bits that work great”
Customer Review: “These hold up I’m shocked that they are so good and I been light on all my drill bits they all broke within 20 minutes. These are perfect definitely recommend”
3. Best M35 Cobalt Stubby Drill Bit Set for Hardened Steel 1/4″ Hex Shank
The MATEWORK M35 Cobalt Stubby Drill Bit Set is an excellent value for those seeking reliable performance on a budget. Crafted from M35 cobalt high-speed steel and fortified with a protective coating, these stubby bits offer enhanced durability and resistance to wear. Their design ensures efficient chip evacuation and excellent stability, prolonging blade life, even when tackling hardened steel and other challenging materials.
Key Features That Stand Out
- ✓ High-Quality M35 Cobalt Material: Provides superior hardness and heat resistance compared to standard HSS bits.
- ✓ Double Protection Fortification: Enhances bit durability and extends its working life.
- ✓ Efficient Chip Evacuation: Ensures stability during cutting and contributes to a longer blade life.
- ✓ Stubby Design: Ideal for working in tight spaces and provides added rigidity for tough drilling.
- ✓ Versatile Size Range: Includes 5 popular sizes (3/32″, 1/8″, 3/16″, 1/4″, 5/16″) and a larger 3/8″ bit for various applications.
Why We Recommend It
For its price point, this set delivers impressive quality and performance. The M35 cobalt construction ensures it can handle hardened materials effectively, while the stubby design offers better control and reduced bit breakage, especially in compact areas. It’s a versatile set that provides great utility without breaking the bank.
Best For
This set is best for DIYers, hobbyists, and light professional use where drilling in hardened steel or metal in confined spaces is common, offering excellent value for money.
Pros and Cons
Pros:
- Cost-effective solution for cobalt drilling needs.
- M35 cobalt provides good heat and wear resistance.
- Stubby design offers increased rigidity and control in tight spots.
- Efficient chip clearing improves cutting performance and bit longevity.
Cons:
- Limited length due to stubby design may not suit all applications.
- While durable for its class, it may not match the extreme longevity of premium M42 bits.
Customer Reviews
Customer Review: “I was skeptical given the price, but these stubby cobalt bits really chewed through some tough exhaust manifold bolts. Highly impressed with their cutting ability and how they held up.”
Customer Review: “Great little set for my small projects. The 1/4″ hex shank is handy for quick changes, and they drill stainless steel far better than any HSS bit I’ve owned.”
4. M35 Cobalt High-Speed Steel Drill Bit Set for Hardened Steel, Stainless, and Cast Iron
This M35 Cobalt High-Speed Steel Drill Bit Set is meticulously designed to provide extended tool life and superior performance when drilling through challenging materials. Featuring 5% cobalt content, these bits offer significantly enhanced heat resistance and durability compared to standard HSS bits. The 135° split point and fully ground twist design ensure precise, fast drilling without walking, making it an excellent choice for a wide range of tough applications including hardened steel, stainless steel, and cast iron.
Key Features That Stand Out
- ✓ M35 Cobalt (5%) HSS Construction: Ensures extended tool life and excellent performance on hard materials.
- ✓ 135° Split Point Tip: Facilitates self-centering, preventing bit walking and enabling precise, quicker drilling starts.
- ✓ Fully Ground Twist Design: Optimizes chip removal, reduces friction, and minimizes heat buildup for a cooler drilling process.
- ✓ Round Straight Shank: Offers broad compatibility with most drill chucks.
- ✓ Versatile Application: Particularly effective for tough, high tensile strength materials like hardened metals, stainless steel, and cast iron.
Why We Recommend It
This set offers a fantastic combination of precision and durability. The M35 cobalt alloy, coupled with the self-centering split point, makes drilling into hard materials a much more manageable task. Its fully ground design ensures longevity and consistent performance, solidifying its place as a reliable tool in any workshop.
Best For
This set is ideal for machinists, fabricators, and serious DIYers who frequently encounter a variety of tough metals, including hardened steel, stainless steel, and cast iron, where precision and bit longevity are paramount.
Pros and Cons
Pros:
- Excellent durability and extended tool life for hard materials.
- Self-centering 135° split point for accurate drilling without pre-punching.
- Efficient chip evacuation due to fully ground twist design.
- Versatile for a wide range of tough, high-tensile strength metals.
Cons:
- The range of sizes might not cover every niche requirement.
- Case quality, while strong, may not be as premium as some higher-priced brands.
Customer Reviews
Customer Review: “I drill holes in 1095 carbon steel to attach the knife handle.”
Customer Review: “Have seen similar setups from the high end parts shops stock something very similar. Strong case, and the impressive thing about these is the machinist measurements on the bits. Sharp and runs the job. Did not disappoint. Prompt delivery”
5. Bosch CO14B 14-Piece M42 Cobalt Metal Drill Bit Set for Hardened Steel
The Bosch CO14B 14-Piece M42 Cobalt Metal Drill Bit Set is a premium choice for tackling the toughest drilling applications. Featuring an enhanced M42 alloy material with 8% cobalt, these jobber-length bits deliver exceptional durability and an impressive 10x longer life compared to standard bits. Their high-heat resistant design allows them to withstand rigorous applications over extended periods, making them indispensable for drilling into hardened steel, stainless steel, and other challenging metals.
Key Features That Stand Out
- ✓ M42 Cobalt (8%) Alloy: Provides the highest level of cobalt content for ultimate hardness, durability, and heat resistance.
- ✓ 10x Life vs. Standard Bits: Engineered for superior longevity, drastically reducing the need for frequent replacements.
- ✓ High-Heat Resistant: Designed to perform under high-temperature applications for extended periods without dulling.
- ✓ Hardened Surface: Specifically optimized for cutting through stainless steel and other hardened surfaces.
- ✓ Trusted Bosch Quality: From a renowned brand known for its commitment to tool performance and reliability.
Why We Recommend It
For sheer performance and longevity on extremely hard materials, the Bosch CO14B M42 Cobalt Set is hard to beat. The higher cobalt content translates directly into a bit that can endure immense heat and friction, making quick work of materials that would destroy lesser bits. It’s an investment that pays off in sustained productivity and less downtime.
Best For
This set is ideal for industrial use, heavy-duty fabrication, or any professional application where drilling into extremely hardened steel, thick stainless steel, or exotic alloys is a regular requirement, and maximum tool life is desired.
Pros and Cons
Pros:
- Highest cobalt content (M42, 8%) for extreme hardness and heat resistance.
- Exceptional longevity, providing up to 10 times the life of standard bits.
- Withstands high-temperature applications effectively.
- From a globally trusted brand known for quality power tools.
Cons:
- Higher price point due to premium M42 cobalt material.
- The 14-piece set might not include all possible sizes needed for specialized projects.
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 Cobalt Drill Bits For Hardened Steel
Choosing the right cobalt drill bits for hardened steel is crucial for efficiency, safety, and the longevity of your tools. Here’s a comprehensive guide to help you make an informed decision.
Essential Factors We Consider
When evaluating cobalt drill bits, several key factors come into play:
- Cobalt Content (M35 vs. M42): This is perhaps the most critical distinction. M35 cobalt drill bits contain 5% cobalt, offering excellent heat and abrasion resistance. M42 cobalt drill bits, with 8% cobalt, provide even greater hardness, superior heat resistance, and a longer tool life, making them ideal for the most challenging hardened metals.
- Split Point Tip: A 135-degree split point tip is highly recommended for drilling hardened steel. It’s self-centering, which prevents the bit from “walking” on the workpiece, and allows for faster penetration without the need for a pilot hole.
- Material and Construction: Look for bits made from High-Speed Steel (HSS) alloyed with cobalt. Fully ground construction ensures consistent quality, precise dimensions, and efficient chip evacuation.
- Shank Type: Most cobalt drill bits feature a round shank. However, hex shanks (1/4″) are becoming popular for use with impact drivers, offering improved grip and preventing slippage.
- Surface Finish/Coating: While cobalt itself offers excellent properties, some bits may have additional coatings (e.g., bronze oxide, black oxide) that can further reduce friction, resist corrosion, and prolong tool life.
- Set Sizes and Organization: Consider the range of sizes included in a set and if they meet your typical project needs. A well-organized case can protect your bits and make selection easier.
- Brand Reputation: Reputable brands like Bosch, DeWalt, and others often provide higher quality control, better performance, and reliable customer support.
Budget Planning
Cobalt drill bits are generally more expensive than standard HSS bits, but their superior performance and longevity on hardened materials often justify the investment. While M35 sets offer a great balance of performance and affordability for most users, M42 sets represent a premium investment for heavy-duty, professional applications where maximum durability and heat resistance are paramount. Consider your frequency of use and the types of materials you’ll be drilling to determine the best price-to-performance ratio for your budget.
Final Thoughts
Investing in the right set of cobalt drill bits for hardened steel will save you time, frustration, and money in the long run. Prioritize bits with higher cobalt content (M42 if possible), a 135° split point, and a sturdy construction. Remember that proper drilling techniques, including using appropriate speeds and cutting fluid, will also significantly extend the life and performance of your cobalt bits.
Frequently Asked Questions
Q: What makes cobalt drill bits better for hardened steel than regular HSS bits?
A: Cobalt drill bits are made from High-Speed Steel (HSS) with an added alloy of 5-8% cobalt. This cobalt content significantly increases the bit’s hardness and, crucially, its heat resistance. When drilling hardened steel, high friction generates intense heat; regular HSS bits will quickly lose their temper and dull, whereas cobalt bits maintain their sharp edge under these demanding conditions.
Q: What’s the difference between M35 and M42 cobalt drill bits?
A: The primary difference lies in their cobalt content. M35 cobalt drill bits contain 5% cobalt, offering excellent heat resistance and hardness suitable for a wide range of tough materials. M42 cobalt drill bits contain 8% cobalt, providing even greater hardness, superior heat dissipation, and an extended tool life, making them ideal for the most extreme applications involving highly hardened or abrasive metals.
Q: Can I use cobalt drill bits on regular steel or softer materials?
A: Yes, absolutely. Cobalt drill bits can be used effectively on regular steel, aluminum, wood, and plastics. However, due to their higher cost, it’s generally more economical to reserve them for tougher materials where their superior properties are truly needed, and use standard HSS bits for softer materials.
Q: How do I prevent cobalt drill bits from breaking or dulling prematurely?
A: To maximize the lifespan of your cobalt drill bits:
- Use a slow drilling speed and apply firm, consistent pressure.
- Always use a cutting fluid or lubricant to dissipate heat and reduce friction.
- Avoid overheating the bit; take breaks to let it cool if necessary.
- Ensure the workpiece is securely clamped to prevent movement.
- Use the correct size bit for the task.
Q: Do I need a special drill or impact driver for cobalt bits?
A: No, cobalt drill bits can be used with standard drills, drill presses, and (if they have a hex shank) impact drivers. However, using a drill press provides more control over speed and pressure, which is beneficial for drilling into hardened steel. When using an impact driver, ensure it’s on a drilling setting and apply appropriate pressure.
When it comes to drilling through the toughest materials like hardened steel, having the right tools is paramount. Our comprehensive review of the best cobalt drill bits for hardened steel highlights options that deliver exceptional durability, heat resistance, and precision, ensuring your projects are completed efficiently and effectively. Whether you opt for the robust M35 options or the ultimate M42 performance, choosing a quality cobalt drill bit will undoubtedly elevate your drilling capabilities. Don’t let hardened steel stand in your way – equip yourself with one of our top recommendations today and experience the difference in performance and longevity. Click on “Check Price on Amazon” to make your selection and power through your next tough project!
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.
