Best Drill Bits for Steel: Cobalt vs. High-Speed Steel Comparisons
Selecting the correct drill bit for steel requires balancing material hardness with the specific demands of your project. High-speed steel (HSS) serves as a reliable standard for general metal drilling, while cobalt alloys offer superior heat resistance when working with hardened or stainless steel. Titanium nitride (TiN) and titanium aluminum nitride (TiAlN) coatings are frequently applied to these bits to reduce friction and extend tool life during repetitive tasks. Whether you need a singular large-diameter bit for heavy-duty industrial applications or a comprehensive set for versatile workshop utility, choosing bits with appropriate geometry—such as 135-degree split points—can significantly improve centering and reduce bit walking on hard surfaces.
When drilling into steel, the shank design and bit geometry are as critical as the metallurgical composition. Reduced shanks allow larger bits to fit into standard chucks, while hex shanks provide compatibility with impact drivers. For specialized tasks like side cutting or deburring, serrated designs offer added utility. This guide evaluates five distinct options, ranging from individual industrial-grade cobalt bits to multi-piece high-speed steel sets. Each product features specific coatings or material grades engineered to withstand the thermal stress of drilling through dense metals. Reviewing these specifications helps ensure your selection aligns with your specific power tool requirements and the hardness of the material you intend to penetrate.
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 chosen for drilling into hardened and stainless steel. It features a TiAlN coating, which is designed to enhance performance under high-heat conditions. The bit measures 6 inches in total length and utilizes a 135-degree split point to assist with accurate starts without the need for a center punch. Its design includes a reduced 3-flat 1/2-inch shank, which helps prevent slippage in the drill chuck during heavy-duty operation. With a 4.8-star rating, this option is tailored for users who require a robust, singular bit capable of handling demanding metalwork tasks where standard bits might fail due to thermal fatigue or material density.
Best for: Heavy-duty drilling in stainless and hardened steel.
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- M35 cobalt construction for heat resistance
- TiAlN coating for increased durability
- 135-degree split point prevents walking
- 3-flat 1/2-inch shank prevents chuck slippage
Keep in mind
- Limited to a single 5/8-inch size
- May be overkill for soft metal applications
2. Drill America - KFD29J-PC 29 Piece Heavy Duty High Speed Steel Drill Bit Set with Black and Gold Finish in Round Case (1/16" - 1/2" x 64ths), KFD Series
The Drill America KFD29J-PC set includes 29 pieces of heavy-duty high-speed steel bits, providing a comprehensive range of sizes from 1/16 inch to 1/2 inch in 64ths. These bits feature a black and gold finish, which is a standard aesthetic for HSS tools intended for metal drilling. The set is organized within a round case for storage and portability. As a versatile collection, it is positioned for workshop environments where various hole diameters are frequently required. With a 4.5-star rating, this set offers a broad selection for users who need a reliable range of sizes for general-purpose metalworking rather than specialized industrial applications.
Best for: General workshop versatility and broad size range.
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- Comprehensive 29-piece set
- High-speed steel construction
- Range covers 1/16 to 1/2 inch
- Includes convenient round storage case
Keep in mind
- Lacks specialized cobalt heat resistance
- Round cases can be cumbersome to organize
3. Bosch TI5IM 5 Pc. Impact Tough™ Titanium Nitride Coated Drill Bit Set
Bosch’s TI5IM set consists of 5 impact-tough drill bits featuring a titanium nitride coating. These bits are engineered specifically for use with impact drivers, a feature that distinguishes them from standard rotary bits. The titanium coating is intended to reduce friction, which can help prolong the life of the bit when drilling through metal. Rated at 4.6 stars, this set is designed for users who prioritize compatibility with existing impact tools. Because these bits are built for the higher torque environment of an impact driver, they provide a focused solution for professionals or hobbyists who prefer not to switch between different power tool platforms for their drilling needs.
Best for: Users of impact drivers needing metal-drilling capability.
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- Optimized for impact driver use
- Titanium nitride coating reduces friction
- 5-piece set for common hole sizes
- High durability rating for impact tools
Keep in mind
- Small piece count limits overall range
- May wear faster than solid cobalt in steel
4. Bosch CO14 14 pc. Cobalt Metal Drill Bit Set
The Bosch CO14 set features 14 cobalt metal drill bits, offering a higher heat tolerance than standard HSS or titanium-coated alternatives. Cobalt is essential for drilling into abrasive metals, and this set provides a balanced selection of sizes to accommodate standard metalworking projects. Holding a 4.7-star rating, these bits are designed to maintain their edge integrity during prolonged use in dense materials. This set is a practical middle ground for users who need the performance benefits of cobalt but do not require the specialized industrial-sized bits. The selection is geared toward those looking for a durable, reliable set that can handle the rigors of drilling into steel without premature dulling.
Best for: Reliable, durable performance in metal drilling.
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- Cobalt construction for superior heat tolerance
- 14-piece set covers frequent size needs
- Maintains edge integrity in hard materials
- High user satisfaction rating
Keep in mind
- Higher cost relative to standard HSS sets
- Cobalt bits can be brittle if misused
5. 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-pack of titanium-coated HSS bits offers a unique design featuring serrated side-cutting edges. These bits allow for dual-functionality: drilling a hole and then using the side of the bit to enlarge or shape the opening, which is useful for plastic, metal, and wood. The bits utilize a hex shank, making them compatible with quick-change chucks found on many cordless drills and drivers. With a 4.0-star rating, this product is aimed at users who prioritize multifunctionality for light-duty or craft-oriented projects. The serrated design is a specialized feature that provides versatility, though it is intended for specific hole-shaping tasks rather than heavy-duty industrial steel drilling.
Best for: Light-duty projects requiring hole shaping and deburring.
Check on AmazonHighlights
- Serrated edges for side cutting
- Hex shank for quick-change compatibility
- Titanium coating for friction reduction
- 8-piece set offers multiple size options
Keep in mind
- Not designed for heavy industrial steel
- Side-cutting requires careful control
How to choose
Material Composition
When drilling into steel, the material of the drill bit is the primary factor for performance. High-speed steel (HSS) is a standard option for general metalwork, as seen in the Drill America KFD29J-PC set. However, for hardened steel or stainless steel, M35 Cobalt alloy bits like the 5/8 Inch Industrial Grade Cobalt bit provide superior heat resistance and durability. Cobalt bits maintain their cutting edge longer under the intense friction generated by steel. Titanium Nitride coating, featured on the Bosch TI5IM set and the generic 8-pack, adds a layer of hardness to HSS bits, reducing friction and extending the tool's life during repetitive drilling tasks in various metals.
Coating and Finish
Coatings significantly impact how a bit handles heat and wear. Titanium Nitride (TiN) coatings, found on the Bosch TI5IM and the 8-pack serrated bits, offer increased surface hardness to prevent overheating. The 5/8 Inch Industrial Grade bit utilizes a TiAlN coating, which is engineered to perform exceptionally well in high-heat environments like drilling through hardened steel. Alternatively, the black and gold finish on the Drill America set is designed to reduce friction and improve chip ejection. Matching the coating to the specific metal hardness ensures that the bit remains sharp and effective throughout the duration of the drilling project.
Point Geometry
The geometry of the drill tip determines how easily a bit penetrates the steel surface. Many heavy-duty bits for steel feature a 135-degree split point, such as the 5/8 Inch Industrial Grade M35 Cobalt bit. This design prevents the bit from 'walking' or wandering across the surface of the metal when starting a hole. A split point allows for faster penetration without the need for a center punch in many applications. When selecting a bit for steel, prioritize those with precision-ground split points to ensure accurate hole placement and to reduce the physical effort required to initiate the cut.
Shank Design
The shank configuration determines compatibility with your power tool chuck. The 5/8 Inch Industrial Grade M35 Cobalt bit features a 3-flat 1/2-inch reduced shank, which prevents slippage in the drill chuck during high-torque applications. Smaller sets, like the 8-pack, offer hex shanks for quick-change compatibility with impact drivers. Standard round shanks, found in the Drill America KFD29J-PC and Bosch CO14 sets, are traditional for standard drill presses and hand drills. Choosing the correct shank ensures a secure grip, which is essential for maintaining control and preventing damage to both the drill bit and the workpiece when drilling into steel.
Set Versatility
The size and scope of a drill bit set should align with your project requirements. The Drill America KFD29J-PC provides a comprehensive 29-piece range, suitable for users who need various diameters from 1/16 to 1/2 inch. For dedicated metalwork, the Bosch CO14 14-piece Cobalt set offers a specialized selection of sizes. If your project involves unique tasks like side-cutting or hole enlargement, the 8-pack of serrated side-cutting bits provides specialized functionality. Consider whether you need a broad range of standard bit sizes or if your steel drilling tasks require specific features like side-cutting capabilities or industrial-grade durability for larger, single-diameter holes.
Frequently asked questions
Which drill bit is best for hardened steel?
For hardened steel, M35 Cobalt drill bits are the preferred choice. The 5/8 Inch Industrial Grade M35 Cobalt bit is specifically designed for these demanding applications. Cobalt alloy is significantly harder than standard high-speed steel and is formulated to withstand the high temperatures generated when drilling through dense, hardened metal. Combined with a 135-degree split point and TiAlN coating, these bits offer the heat resistance and structural integrity necessary to penetrate hardened steel without dulling or breaking prematurely.
Can I use standard HSS bits on steel?
You can use standard high-speed steel (HSS) bits on softer steel, but they may wear out quickly. The Drill America KFD29J-PC set uses heavy-duty HSS, which is suitable for many general-purpose metal drilling tasks. However, for stainless steel or hardened steel, HSS bits are prone to overheating, which causes the cutting edge to fail. If you are working with tougher materials, upgrading to a Cobalt set like the Bosch CO14 or an industrial-grade M35 bit will provide much better results and longevity.
What does the 135-degree split point do?
The 135-degree split point, found on the 5/8 Inch Industrial Grade M35 Cobalt bit, is a design feature that prevents the drill bit from wandering or 'walking' on the surface of the steel. Because metal is hard and slick, a standard tip can easily slide off the intended mark. The split point geometry bites into the metal immediately upon contact, allowing for a precise start and faster penetration without requiring a center punch in many drilling scenarios.
Why use a 3-flat shank on a drill bit?
The 3-flat shank, featured on the 5/8 Inch Industrial Grade M35 Cobalt bit, is designed to provide a more secure grip in the drill chuck. When drilling into tough materials like steel, the high torque can cause a standard round shank to slip, which damages the chuck and the bit. The flat surfaces on the shank allow the chuck jaws to lock in place firmly, ensuring that the power from the drill is transferred efficiently to the bit without rotation slippage.
Are serrated side-cutting bits suitable for steel?
The 8-pack of titanium-coated serrated side-cutting bits is designed for versatility across materials like plastic, wood, and metal. While the titanium coating adds hardness, these bits are generally intended for lighter-duty tasks or hole enlargement rather than heavy-duty industrial steel drilling. If your primary task is drilling through thick or hardened steel, a dedicated Cobalt drill bit set, such as the Bosch CO14, is a more robust and reliable option for maintaining accuracy and preventing premature tool wear.
Bottom line
For the most demanding applications involving hardened steel or stainless steel, the 5/8 Inch Industrial Grade M35 Cobalt Drill Bit stands out as the strongest fit. Its construction from M35 Cobalt alloy provides the necessary heat resistance to handle dense materials, while the TiAlN coating further protects the cutting edge from thermal degradation. The inclusion of a 135-degree split point ensures immediate, accurate engagement with the steel surface, and the 3-flat 1/2-inch shank provides the high-torque stability required to prevent slippage in the chuck. This bit is clearly engineered for professional-grade performance where durability and precision in tough metal are the highest priorities for the user.
Deciding on the right bit depends on the scope of your work and the hardness of the steel. If you require a broad range of sizes for general-purpose drilling, a high-quality set like the Drill America KFD29J-PC or the Bosch CO14 Cobalt set is the most logical choice. For specialized tasks or occasional repairs, the Bosch TI5IM Titanium Nitride set offers a balance of durability and performance. If your project demands specific hole shaping or side-cutting, the serrated 8-pack provides unique utility. Always match the material rating of the bit to the grade of steel you are drilling to ensure safety and efficiency.
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