When tackling challenging drilling tasks, especially with tough materials like stainless steel, cast iron, or hardened alloys, standard drill bits often fall short. This is where the superior performance of M42 cobalt drill bits becomes indispensable. Engineered with an 8% cobalt alloy, these bits are renowned for their exceptional heat resistance and hardness, allowing them to maintain their cutting edge even under extreme conditions. Whether you’re a professional tradesperson or a serious DIY enthusiast, investing in a high-quality set of best M42 cobalt drill bits can significantly improve efficiency, reduce wear, and deliver cleaner, more precise holes. Our comprehensive guide reviews the top options available, helping you choose the perfect set for your demanding projects.
Quick Product Comparison
Our Top 5 Best M42 Cobalt Drill Bits Reviews – Expert Tested & Recommended
1. Best 29 Piece M42 Cobalt Drill Bit Set in Round Case, 1/16″ to 1/2″ Range
This comprehensive 29-piece M42 cobalt drill bit set is an excellent choice for professionals and serious DIYers who frequently work with tough materials. Housed in a durable round case, it offers a wide range of sizes from 1/16″ to 1/2″ in 1/64″ increments, ensuring you have the right bit for almost any task. These cobalt drill bits are specifically designed for drilling into high tensile strength materials such as stainless steel, Inconel, and titanium, providing exceptional wear resistance and longevity.
Key Features That Stand Out
- ✓ Contains 29 M42 Cobalt Drill Bits in common sizes (1/16″ – 1/2″ x 1/64″).
- ✓ Made from 8% cobalt alloy, offering superior heat resistance and durability for tough materials.
- ✓ Features a 135° split point for accurate self-centering and minimal walking.
- ✓ Gold oxide finish acts as a lubricant and enhances wear resistance.
- ✓ Ideal for drilling through stainless steel, titanium, and other high-strength alloys.
Why We Recommend It
We highly recommend this set for its versatility and robust construction. The inclusion of 29 different sizes makes it a truly all-encompassing solution, and the M42 cobalt alloy ensures these bits can withstand the rigors of heavy-duty drilling. The 135° split point is a crucial feature that enhances precision and ease of use, making it a reliable choice for demanding projects.
Best For
This set is best for professional machinists, fabricators, and dedicated hobbyists who regularly work with challenging metals like stainless steel, cast iron, and exotic alloys, requiring a wide range of bit sizes.
Pros and Cons
Pros:
- Excellent durability and heat resistance due to 8% cobalt content.
- Wide range of 29 sizes covers most drilling needs.
- 135° split point prevents bit walking and ensures quick starts.
- Gold oxide finish provides added wear resistance and lubrication.
Cons:
- Can be more expensive than standard HSS sets.
- Round shanks might occasionally slip in some drill chucks without proper tightening.
Customer Reviews
Customer Review: “Great bits for hard metals and 135 degree point makes the need for a center punch obsolete. Bits will definitely last long if you use cutting oil and the appropriate drill speed. Just wish they had a hex or square shank for no slippage in a chuck.” – Verified Purchaser
Customer Review: “Great bits for hard metals and 135 degree point makes the need for a center punch obsolete. Bits will definitely last long if you use cutting oil and the appropriate drill speed. Just wish they had a hex or square shank for no slippage in a chuck.Read more” – Verified Purchaser
2. BOSCH Best 14-Piece M42 Cobalt Drill Bits, Three-Flat Shank for Tough Metals
The BOSCH 14-Piece M42 Cobalt Drill Bits set is designed for those who demand precision and longevity when working with challenging materials. Featuring an enhanced M42 alloy with 8% cobalt, these jobber-length bits offer superior durability and exceptional heat resistance. The innovative three-flat shank design helps prevent bit slippage in the drill chuck, making it an ideal choice for sustained, high-torque drilling into tough metals like stainless steel and cast iron.
Key Features That Stand Out
- ✓ Upgraded M42 Cobalt jobber-length bits for excellent durability and heat resistance.
- ✓ Enhanced M42 alloy material contains 8% cobalt, extending tool life up to 10x vs. standard bits.
- ✓ Three-flat shank design provides a secure grip in the chuck, preventing slippage.
- ✓ Withstands high-temperature applications, perfect for drilling hardened steel and stainless steel.
- ✓ Hardened surface for superior performance in tough metal applications.
Why We Recommend It
Bosch is a name synonymous with quality, and this M42 cobalt drill bit set lives up to that reputation. The three-flat shank is a significant advantage, eliminating common frustrations with bit slippage. Its high cobalt content and heat resistance ensure that these bits cut efficiently and last considerably longer, offering great value for money for those working with difficult materials.
Best For
This set is best for professionals needing reliable, slip-resistant bits for frequent drilling in stainless steel, cast iron, and other hard metals, where precision and bit longevity are paramount.
Pros and Cons
Pros:
- Exceptional durability and 10x longer life due to 8% cobalt.
- Three-flat shank eliminates bit slippage in drill chucks.
- High heat resistance maintains sharpness under heavy use.
- Ideal for a variety of tough metals including stainless steel.
Cons:
- Fewer bits (14 pieces) compared to some other sets.
- Higher initial cost than basic HSS drill bits.
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” – Verified Purchaser
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” – Verified Purchaser
3. Best M42 Cobalt Drill Bit Set for Hardened Metal, Stainless Steel, and Cast Iron
This M42 Cobalt Drill Bit Set offers an excellent balance of performance and affordability, making it our top budget pick for tackling demanding materials. Crafted from 8% cobalt high-speed steel (M42 HSS), these bits are specifically engineered for drilling into hardened metal, stainless steel, and cast iron. Their precise 135° split point and gold oxide finish contribute to faster chip clearance and reduced walking, delivering consistent results for a variety of challenging applications.
Key Features That Stand Out
- ✓ High-quality 8% M42 Cobalt High-Speed Steel for extended tool life.
- ✓ Precise 135° split point ensures self-centering and prevents bit walking.
- ✓ Gold oxide finish reduces friction, acts as a lubricant, and enhances wear resistance.
- ✓ Round straight shanks for compatibility with most drill chucks.
- ✓ Optimized for professional use in cutting through hardened metals like stainless steel and cast iron.
Why We Recommend It
For those seeking robust performance without breaking the bank, this M42 cobalt drill bit set is an outstanding choice. Its construction with 8% cobalt and specific design features like the 135° split point ensure effective drilling through tough materials at a competitive price point. It’s a great entry into the world of cobalt bits for users needing reliable, durable tools.
Best For
This set is best for budget-conscious DIYers and professionals who need effective and durable drill bits for occasional to moderate use on hardened metals, stainless steel, and cast iron projects.
Pros and Cons
Pros:
- Excellent performance on hard metals for its price point.
- 8% cobalt content provides good heat and wear resistance.
- 135° split point for accurate, fast drilling starts.
- Gold oxide finish adds durability and reduces heat buildup.
Cons:
- May not match the extreme longevity of premium, higher-priced sets under continuous heavy use.
- Customer reviews mention some inconsistency in durability over time.
Customer Reviews
Customer Review: “**UPDATE**Well unfortunately I have to amend my review after using these bits a little more and especially after my last experience with them. At first I thought they were decent quality for the price. I wasn’t expecting the performance or durability of a $200 set but they are supposed to be cobalt ” – Verified Purchaser
Customer Review: “I needed these to remove some heavy duty carbon steel bolts with an extractor set. I went for the M42 due to the hardness of the metal. These will not break off or wear down because they’re made for the same type of hard metals.Time is money and I didn’t feel like spending days on this so I paid a l” – Verified Purchaser
4. High Performance M42 Cobalt Drill Bits for Hardened Metal, Stainless Steel, Cast Iron
This set of high-performance M42 cobalt drill bits is engineered for exceptional cutting power and durability when facing the toughest materials. Featuring 8% cobalt high-speed steel, these bits are ideal for applications involving hardened metal, stainless steel, and cast iron. The precise 135° split point and gold oxide finish work in tandem to prevent walking, facilitate efficient chip removal, and reduce heat buildup, ensuring a smooth and effective drilling experience.
Key Features That Stand Out
- ✓ Constructed from 8% M42 Cobalt High Speed Steel for extended tool life and hardness.
- ✓ Features a 135° split point for quick, accurate starts without pre-punching.
- ✓ Gold oxide coating enhances lubricity and improves wear resistance against abrasive materials.
- ✓ Designed for professional and widespread use in challenging materials like stainless steel and hardened alloys.
- ✓ Round straight shanks offer broad compatibility with various drilling tools.
Why We Recommend It
We recommend these M42 cobalt drill bits for their reliable performance across a spectrum of difficult drilling tasks. The combination of 8% cobalt, a sharp split point, and a durable finish ensures that these bits can handle significant stress and heat, making them a valuable addition to any toolkit. They provide a strong balance between performance and value for tackling tough materials.
Best For
This set is best for tradespeople and serious DIYers who require consistently reliable bits for drilling through various hardened metals, including thicker sections of stainless steel and cast iron, especially where durability is key.
Pros and Cons
Pros:
- Robust 8% cobalt construction for superior heat and abrasion resistance.
- 135° split point for precise drilling and reduced skidding.
- Gold oxide finish extends bit life and drilling efficiency.
- Effective on a wide range of hard and abrasive materials.
Cons:
- Some user feedback suggests varying durability, similar to other budget-friendly cobalt options.
- Requires proper drilling techniques (speed, pressure, coolant) to maximize lifespan.
Customer Reviews
Customer Review: “**UPDATE**Well unfortunately I have to amend my review after using these bits a little more and especially after my last experience with them. At first I thought they were decent quality for the price. I wasn’t expecting the performance or durability of a $200 set but they are supposed to be cobalt ” – Verified Purchaser
Customer Review: “I needed these to remove some heavy duty carbon steel bolts with an extractor set. I went for the M42 due to the hardness of the metal. These will not break off or wear down because they’re made for the same type of hard metals.Time is money and I didn’t feel like spending days on this so I paid a l” – Verified Purchaser
5. Bosch 1/4″ x 4″ M42 Cobalt Drill Bit with Three-Flat Shank for Stainless Steel and Cast Iron
This individual Bosch 1/4″ x 4″ M42 Cobalt Drill Bit is a testament to quality and specialized performance. Designed for exceptional durability and high heat resistance, it’s an ideal choice for specific, challenging drilling tasks in materials like stainless steel and cast iron. The bit features an upgraded M42 cobalt alloy with 8% cobalt content, promising extended life compared to standard bits, and its innovative three-flat shank prevents frustrating slippage in the chuck.
Key Features That Stand Out
- ✓ Individual 1/4″ x 4″ M42 Cobalt Drill Bit for precise, heavy-duty applications.
- ✓ Features an enhanced 8% Cobalt M42 alloy for exceptional durability and heat resistance.
- ✓ Three-flat shank design ensures maximum grip and prevents bit spin-out.
- ✓ Hardened surface specifically engineered for working with stainless steel, cast iron, and other tough metals.
- ✓ Withstands high-temperature drilling applications for prolonged periods.
Why We Recommend It
For those needing a single, highly reliable 1/4″ bit for tough jobs, this Bosch M42 cobalt drill bit is an excellent investment. Its superior material composition and anti-slip shank design make it perfect for demanding tasks where standard bits would quickly fail. It’s particularly recommended for its sustained performance in high-heat environments and its long lifespan.
Best For
This single bit is best for users who frequently need a precise 1/4″ hole in stainless steel, cast iron, or other hard metals and require the utmost reliability and anti-slip performance.
Pros and Cons
Pros:
- Outstanding durability and heat resistance from 8% cobalt.
- Three-flat shank prevents slippage, enhancing safety and efficiency.
- Ideal for persistent drilling in very tough materials like stainless steel.
- Bosch quality ensures reliable performance.
Cons:
- Only a single bit, not a full set, limiting versatility across different sizes.
- Higher price point for an individual bit.
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” – Verified Purchaser
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” – Verified Purchaser
Complete Buying Guide for M42 Cobalt Drill Bits
Essential Factors We Consider
When selecting the best M42 cobalt drill bits, several critical factors come into play to ensure you get the right tool for your specific needs. First and foremost is the cobalt content; M42 bits typically contain 8% cobalt, which dramatically improves heat resistance and hardness compared to M35 (5% cobalt) or standard HSS bits. This higher cobalt percentage is crucial for drilling through challenging materials such as stainless steel, cast iron, and other hardened alloys without losing its cutting edge.
Next, consider the bit design. A 135° split point is highly recommended as it prevents “walking” at the start of drilling and allows for self-centering, leading to cleaner, more accurate holes. For larger bits, a three-flat shank or hexagonal shank can significantly reduce slippage in the drill chuck, which is particularly important when applying high torque to tough materials. The finish, such as gold oxide, can also offer additional lubricity and wear resistance, further extending the bit’s life. Finally, evaluate the set composition – do you need a comprehensive 29-piece set for varied tasks, or just a few specific sizes for repetitive work? Matching the set to your common applications will maximize value and efficiency.
Budget Planning
Investing in M42 cobalt drill bits typically means a higher upfront cost than standard high-speed steel (HSS) bits. However, this initial investment is often recouped through superior performance and significantly longer tool life, especially when working with difficult materials. For those on a tighter budget, look for sets that offer a good balance of cobalt content and essential sizes without compromising too much on quality. Individual cobalt bits can also be a cost-effective solution if you only need one or two specific sizes for a particular project. Remember that proper technique, including using appropriate drill speeds and cutting fluids, will extend the life of even the most expensive cobalt bits, ultimately saving you money in the long run by reducing the frequency of replacements.
Final Thoughts
Choosing the right M42 cobalt drill bits is about understanding your material, your frequency of use, and your budget. Prioritize bits with 8% cobalt, a 135° split point, and a secure shank design for the best results. Whether you opt for a versatile large set or a specialized individual bit, the enhanced durability and heat resistance of M42 cobalt will make your drilling tasks on hard metals far more efficient and satisfying. Always remember to use safety gear and appropriate drilling practices to maximize both your safety and the longevity of your new bits.
Frequently Asked Questions
Q: What is the main advantage of M42 cobalt drill bits over standard HSS bits?
A: The primary advantage of M42 cobalt drill bits is their superior heat resistance and hardness, thanks to an 8% cobalt alloy content. This allows them to maintain their cutting edge and integrity even when drilling through very tough and abrasive materials like stainless steel, cast iron, and hardened alloys, where standard HSS bits would quickly dull or overheat.
Q: Can M42 cobalt drill bits be used on regular wood or softer metals?
A: Yes, M42 cobalt drill bits can certainly be used on wood, plastics, and softer metals. However, they are overkill for such applications. Using them on softer materials will still provide excellent results, but their specialized properties are best utilized and most beneficial when drilling tough, high-tensile strength materials that typically cause other bits to fail.
Q: How can I extend the life of my M42 cobalt drill bits?
A: To extend the life of your M42 cobalt drill bits, always use the correct drill speed (lower speeds for harder materials), apply consistent but moderate pressure, and use a suitable cutting fluid or lubricant. Avoid overheating the bit, and allow it to cool down between drilling operations. Proper storage in a designated case also protects the bits from damage and dulling.
Q: What is the significance of a 135° split point on a drill bit?
A: A 135° split point is crucial for improved drilling performance, especially in hard materials. It creates two additional cutting edges at the tip, which helps the bit self-center and prevents it from “walking” or skidding across the workpiece surface. This leads to quicker, more accurate hole starts without the need for a pilot hole or center punch, especially on rounded or uneven surfaces.
Q: Are M42 cobalt drill bits suitable for drilling through hardened tool steel?
A: M42 cobalt drill bits are among the best options available for drilling through hardened tool steel and other extremely tough materials. Their high cobalt content (8%) allows them to resist the high heat generated during such demanding applications and maintain their sharpness, offering significantly better performance and longevity than lower-grade bits.
Choosing the right M42 cobalt drill bits is a crucial decision for anyone serious about tackling tough materials effectively and efficiently. From the comprehensive sets offering a wide array of sizes to specialized individual bits designed for precision, the options reviewed here represent the pinnacle of durability and performance. We encourage you to evaluate your specific project needs against our expert recommendations to find the perfect set that will serve you reliably for years to come. Don’t let challenging materials hold you back – invest in the power of M42 cobalt drill bits today and experience the difference in precision and longevity. Click on the “Check Price on Amazon” buttons above to get your hands on these top-tier drilling solutions!
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.
