Top Cobalt and High-Speed Steel Drill Bits for Hardened Steel Projects
Selecting the right drill bit material is critical when working with hardened steel, as standard bits often fail to maintain their edge under high heat and pressure. M35 and M42 cobalt alloys are widely recognized for their ability to withstand the extreme temperatures generated during metal fabrication. These specialized materials offer superior hardness compared to standard high-speed steel, making them the preferred choice for drilling through stainless steel, cast iron, and other abrasive surfaces. Understanding the specific design features, such as split points and shank styles, helps ensure your equipment remains stable and precise throughout demanding workshop applications.
Beyond material composition, structural design plays a significant role in tool longevity and performance. Features like 135-degree split points prevent walking on hard surfaces, while coatings like TiAlN can provide additional thermal protection. Whether you require a single industrial-grade bit for heavy-duty drilling or a comprehensive set for versatile workshop tasks, evaluating the shank type and shank compatibility is essential for preventing slippage in your drill chuck. This comparison highlights key options ranging from single industrial bits to multi-piece sets to help you match the right tool to your specific metalworking requirements.
1. 5/8 Inch Industrial Grade M35 Cobalt Drill Bit, Reduced Shank,TiAlN Coating | Total Length of 6", 135 Degree Split Point, 3-Flat 1/2" Shank, Cobalt Drill Bit for Metal, Hardened Steel, Stainless Steel
This 5/8-inch industrial-grade bit is constructed from M35 cobalt, a material specifically engineered for the high-friction demands of drilling into hardened steel and stainless steel. It features a 135-degree split point, which is designed to reduce bit walking upon initial contact with the metal surface. The inclusion of a TiAlN coating suggests an emphasis on heat resistance, which is vital when working with tempered metals. With a 3-flat 1/2-inch reduced shank, this tool is intended to provide a secure grip in standard drill chucks, minimizing the risk of slippage during operation. At a 6-inch total length, it offers the reach required for deeper drilling tasks in industrial settings.
Best for: Heavy-duty drilling in hardened and stainless steel.
Check on AmazonHighlights
- M35 cobalt alloy for heat resistance
- 135-degree split point prevents walking
- TiAlN coating for increased durability
- 3-flat shank ensures secure chuck grip
Keep in mind
- Limited to a single 5/8-inch size
- May require specific chuck capacity
2. DEWALT Cobalt Alloy Steel Drill Bit Set with Pilot Point, 14-Piece (DWA1240)
The DEWALT 14-piece set utilizes a cobalt alloy steel composition, providing the robustness needed for drilling into stainless steel and other hard metals. A defining characteristic of this set is the Pilot Point design, which is intended to help the bits start holes on contact and reduce the likelihood of burr formation. This set is structured to offer a range of sizes, making it a versatile choice for mechanics or metalworkers who frequently swap between hole diameters. As a cobalt-based product, these bits are built to maintain their structural integrity at the elevated temperatures typically encountered when cutting through dense, hardened steel materials.
Best for: Versatile metalworking and stainless steel applications.
Check on AmazonHighlights
- Cobalt alloy steel construction
- Pilot Point tip for precise starts
- 14-piece set for size variety
- Designed for high-heat performance
Keep in mind
- No explicit mention of a split point
- May lack specialized coatings found in industrial bits
3. 8 Pack Titanium Coated HSS Twist Drill Bits, 3-10mm Serrated Side Cutting Drill Bit, Hex Shank Serrated Cutting Drill Bits, Drill Bit Woodworking Tools, Hole Holesaw Tool for Plastic Metal Wood Hole
This 8-piece set features titanium-coated high-speed steel (HSS) bits, which offer a different approach to metal drilling compared to cobalt options. These bits are uniquely designed with a serrated side-cutting edge, allowing for hole-saw functionality in addition to standard twist drilling. The hex shank design ensures compatibility with impact drivers and quick-change chucks, making them highly convenient for rapid changes. While titanium coating can improve surface hardness and reduce friction in wood and plastic, users should be cautious when applying these to extremely hard, tempered steel, as HSS may not retain its edge as effectively as cobalt under extreme thermal stress.
Best for: Multi-material use including plastic, wood, and light metal.
Check on AmazonHighlights
- Titanium coating for friction reduction
- Serrated side-cutting edges
- Hex shank for quick-change compatibility
- Versatile 3-10mm size range
Keep in mind
- HSS may be less durable than cobalt for hardened steel
- Serrated design may not be ideal for precision drilling
4. HIDOTOL Cobalt Drill Bit Set 29 PCS - M35 High Speed Steel Twist Jobber Drill Bits for Hardened Metal, Stainless Steel, Cast Iron, Plastic and Wood with Indexed Round Case,1/16"-1/2" by 1/64" THS.
The HIDOTOL 29-piece set is comprised of M35 high-speed steel containing cobalt, providing a balanced solution for users who need a wide array of jobber-length drill bits. This collection covers sizes from 1/16 inch to 1/2 inch in 1/64-inch increments, ensuring that the correct size is available for almost any standard fastener or hole requirement. The M35 material is specifically chosen for its ability to cut through cast iron, stainless steel, and hardened metal without rapid degradation. The set includes an indexed round case, which assists in keeping the bits organized by size, a necessary feature for maintaining a productive workshop environment.
Best for: Comprehensive metal drilling and workshop organization.
Check on AmazonHighlights
- M35 cobalt-enhanced high-speed steel
- 29-piece set in 1/64-inch increments
- Suitable for cast iron and stainless steel
- Includes indexed storage case
Keep in mind
- Round case may be bulkier than flat sets
- Performance on extremely hardened alloys may vary
5. BOSCH CO14B 14-Piece Cobalt Drill Bit Set with Included Case - M42 Metal Drill Bits with Three-Flat Shank for Drilling Applications in Stainless Steel, Cast Iron, Titanium, and Light-Gauge Metal
The BOSCH CO14B set is manufactured from M42 cobalt, an alloy known for its high cobalt content, which provides exceptional heat and wear resistance. This 14-piece set is specifically optimized for drilling into challenging materials such as titanium, cast iron, and stainless steel. Each bit features a three-flat shank, which is engineered to prevent the bit from spinning in the chuck during high-torque applications. By utilizing M42 grade material, these bits are positioned at the higher end of the spectrum for thermal endurance, making them a reliable choice for professional settings where drilling through light-gauge and hardened metal is a frequent task.
Best for: Professional-grade drilling in titanium and stainless steel.
Check on AmazonHighlights
- M42 cobalt alloy for extreme heat resistance
- Three-flat shank prevents chuck slippage
- Optimized for titanium and cast iron
- Includes protective storage case
Keep in mind
- Higher cost expected for M42 material
- Set size may be limited for some industrial needs
How to choose
Material Composition
When drilling hardened steel, material composition is the most critical factor. M35 cobalt steel, found in the 5/8 Inch Industrial Grade bit and the HIDOTOL 29-piece set, is specifically formulated for high-heat resistance and structural integrity in tough metals. Bosch utilizes M42 cobalt, another high-performance alloy designed for demanding applications like stainless steel and titanium. Conversely, titanium-coated HSS bits, such as the 8-pack serrated set, are better suited for softer materials like wood, plastic, or general metal work rather than hardened steel. Always prioritize cobalt alloy steel over basic HSS or standard titanium coatings to ensure the bit maintains its edge when encountering high-strength, hardened steel surfaces.
Coating Technologies
Coatings significantly impact the longevity and performance of drill bits. The 5/8 Inch Industrial Grade bit features a TiAlN (Titanium Aluminum Nitride) coating, which provides extra hardness and heat shielding, making it ideal for the high-friction environment of drilling hardened steel. While titanium coatings on the serrated 8-pack bits offer surface-level benefits, they do not provide the same thermal protection as the TiAlN coating or the inherent heat-resistant properties of solid cobalt alloy steel. For consistent results in hardened metals, look for bits that prioritize heat management through advanced industrial coatings rather than just surface-level appearance.
Shank Design and Compatibility
The shank design determines how the bit interacts with your power tool's chuck. The 5/8 Inch Industrial Grade bit features a 3-flat 1/2-inch shank to prevent slippage under high torque loads, which is essential when drilling through hardened steel. Similarly, the Bosch CO14B set includes a three-flat shank for improved grip. For smaller projects or variable needs, the HIDOTOL set offers round shanks, while the 8-pack serrated set uses a hex shank for quick-change compatibility. Ensure your drill chuck is compatible with the shank type, especially when using larger diameter bits that require a secure, non-slip connection to handle the stress of hard metal.
Point Geometry
Point geometry determines how effectively a bit initiates a hole. The 135-degree split point on the 5/8 Inch Industrial Grade bit is engineered to prevent walking on hard, slick surfaces, allowing for accurate centering without a pilot hole. DeWalt’s Cobalt Alloy set includes a Pilot Point design, which also assists in starting holes quickly. Proper point angles are vital for hardened steel, as they minimize the time the bit spends rubbing against the surface, which causes heat buildup. Avoid standard point designs if you require precision, as split points or dedicated pilot features significantly improve the initial bite into dense, hardened materials.
Set Versatility versus Specialized Tools
Choosing between a single specialized bit and a comprehensive set depends on the scope of your work. The HIDOTOL 29-piece set and the Bosch CO14B 14-piece set provide a wide range of sizes for recurring projects, ensuring you have the right diameter for various metalworking tasks. However, if your work strictly involves large-diameter holes in hardened steel, a dedicated industrial-grade bit like the 5/8 Inch M35 Cobalt bit offers specific features like reduced shanks and advanced coatings tailored for that single purpose. Assess whether you need a broad range of smaller bits for general shop maintenance or a heavy-duty, single-purpose tool for high-torque, large-scale hardened steel drilling.
Frequently asked questions
Can I use titanium-coated HSS bits for hardened steel?
Titanium-coated HSS bits, such as the 8-pack serrated set provided, are generally intended for softer materials like wood, plastic, or light-gauge metal. They lack the heat-resistant cobalt alloys found in the M35 or M42 sets. Hardened steel generates intense friction and heat during the drilling process, which can cause the edge of a standard HSS bit to dull or fail prematurely. For reliable performance in hardened steel, choose cobalt alloy steel bits instead.
What is the difference between M35 and M42 cobalt bits?
Both M35 and M42 are high-speed steel alloys containing cobalt, which provides superior hardness and heat resistance compared to standard steel. The Bosch CO14B set uses M42, while the HIDOTOL set and the 5/8-inch Industrial Grade bit use M35. Both are excellent choices for drilling into tough materials like stainless steel, cast iron, and hardened steel. They are designed to maintain their hardness even when operating at the high temperatures common in metal-drilling applications.
Why do some bits have a 3-flat shank?
A 3-flat shank, found on the Bosch CO14B and the 5/8-inch Industrial Grade bit, is designed to provide a more secure grip in the drill chuck. This prevents the bit from spinning or slipping when you apply high pressure or torque. Because hardened steel requires significant downward force and steady rotation, a 3-flat shank is a valuable feature to ensure the drill bit maintains a firm connection with the power tool throughout the entire operation.
Are serrated side-cutting bits good for hardened steel?
The serrated side-cutting bits in the 8-pack set are primarily marketed for woodworking, plastic, and general metal hole-cutting tasks. They are not engineered with the cobalt alloy composition required to withstand the high-heat and high-stress environment of drilling through hardened steel. Using them on hardened surfaces may lead to rapid dulling or damage to the serrated cutting edges. Stick to cobalt-based jobber bits for high-strength steel projects.
How do I prevent the drill bit from 'walking' on hardened steel?
To prevent a bit from walking, or moving off-center, look for bits with specific tip geometries like the 135-degree split point on the 5/8-inch Industrial Grade bit or the Pilot Point design on the DeWalt set. These features allow the bit to bite into the material immediately upon contact. Using a center punch to create a small indentation before you begin drilling will also provide a secure starting point, further improving precision on hard surfaces.
Bottom line
For the most demanding applications involving hardened steel, the 5/8 Inch Industrial Grade M35 Cobalt Drill Bit stands out as the strongest fit. Its combination of M35 cobalt steel, a high-heat-resistant TiAlN coating, and a 3-flat shank makes it purpose-built for heavy-duty metalwork. The 135-degree split point is specifically designed to handle the difficulty of starting a hole in hardened surfaces without walking. While sets like the Bosch CO14B or the HIDOTOL 29-piece M35 set are excellent for versatility across various hole sizes, the 5/8-inch bit offers the specialized construction necessary to maintain structural integrity and cutting performance when tackling the toughest, high-strength steel projects encountered in professional or industrial workshop environments.
Deciding on the right drill bit depends on your specific project scope and material hardness. If your work involves a wide variety of hole sizes in stainless steel, cast iron, or hardened metal, invest in the Bosch CO14B or HIDOTOL M35 cobalt sets to ensure you have the correct diameter on hand. If you are performing large-diameter drilling in hardened steel, prioritize the singular, industrial-grade cobalt bits with specialized coatings and shank designs. Always avoid using HSS or titanium-coated bits for hardened steel, as they lack the thermal endurance required to prevent premature dulling, ensuring your tools remain effective over the life of your metalworking projects.
More from Power Tools
Top Cobalt and HSS Drill Bit Sets for Drilling 304 Stainless Steel
Explore top-rated drill bit sets for 304 stainless steel, featuring M35 and M42 cobalt options and specialized installation tools for professional workshop need
Read comparison →
Top Cobalt and HSS Drill Bits for Drilling Into Steel Lintels and Hard Metals
Compare top-rated cobalt and HSS drill bits for steel lintels. Find the right bit set for your workshop, from jobber lengths to versatile step drill options.
Read comparison →
Top Cobalt and HSS Drill Bits for Stainless Steel Projects
Compare top-rated drill bits for stainless steel. Evaluate M35 and M42 cobalt sets, hex shank stubby bits, and step bits for your next metalwork project.
Read comparison →