Best Drill Bits for Drilling Through Hardened Steel
Harder metals demand tougher drill bits. The following five cobalt-based sets are selected for their performance in hardened steel, stainless alloys, and other hard metals. Each option blends high-speed steel with cobalt alloys to resist heat and wear, while offering practical shank designs and packaged storage. Use the buying guide to compare features such as material, tip design, and storage to pick the best fit for your workshop.
Below is a quick summary table of the chosen products, highlighting the material, shank style, size range, and standout benefits. This helps you compare at a glance before diving into detailed specs for each option.
| Product | Material | Shank | Size Range | Notable Benefit |
|---|---|---|---|---|
| Bosch CO14B | M42 Cobalt | Three-Flat | Assorted (14-piece) | Long life, high heat resistance |
| M35 Cobalt | Standard | 1/16″ – 3/8″ | Wide range, strong wear resistance | |
| NordWolf 5-Piece | M35 Cobalt | 1/4″ Hex | 3/32″ – 5/16″ | Stubby design for tight spaces |
| HIDOTOL 13-Pcs | M35 Cobalt | Round | 1/16″ – 1/4″ | 135° split point for self-centering |
| MACXCOIP 13Pcs | M35 Cobalt | Standard | 1/16″ – 1/4″ | Index storage case included |
Bosch CO14B 14-Piece Cobalt Bits
The Bosch CO14B kit uses M42 cobalt alloy, delivering exceptional heat resistance and extended life in hardened materials. The 8% cobalt composition enhances durability for stainless steel, cast iron, titanium, aluminum, and similar hard metals. A three-flat shank provides secure grip in both standard and quick-change chucks, reducing bit slippage during heavy-duty drilling. This 14-piece assortment comes in a protective case for organized storage and quick access.
Designed for frequent, demanding tasks, these bits offer robust performance in professional work or serious DIY projects. The combination of cobalt strength and precise geometry helps maintain sharpness under high temperatures, enabling cleaner holes and fewer bit changes. They are well-suited to metalworking tasks that involve persistent drilling through hard alloys.
Sinyeenglon 99-Pcs M35 Cobalt Bits
This expansive set leverages M35 cobalt (5%) to deliver hardness up to about 67 HRC, enabling faster cutting and extended life—often up to twelve times that of standard HSS bits. The cobalt full-grinding process enhances wear resistance, helping bits stay sharper longer when working with stainless steel, cast iron, zinc alloys, titanium, aluminum, and other hard metals. The bits arrive in a sturdy plastic box with compartmentalized storage for easy organization and transport.
With such a broad size range (1/16″ through 3/8″), this kit covers many common hole sizes encountered in metal fabrication, automotive work, and metal repair. The comprehensive assortment is particularly useful for shops that need flexibility across multiple materials. While the set’s breadth is beneficial, users should take care to use appropriate speeds and feeds to maximize bit life in tougher alloys.
NordWolf 5-Piece M35 Cobalt Bits
The NordWolf set uses M35 cobalt steel for enhanced durability and longer life, with a design that emphasizes self-centering accuracy. Each bit features a 135-degree split point and a multi-blade tip to improve starting accuracy and reduce walking. The 1/4-inch hex shank is compatible with standard and quick-change chucks, making these bits versatile for drills and impact drivers. The stubby length (ranging from 1.84 to 2.32 inches) allows drilling in tight spaces where longer bits struggle.
Ideal for hard metals such as stainless steel, cast iron, titanium, and aluminum, these bits are well-suited for automotive work, appliance repair, or on-site fabrication where space is limited. While compact, they deliver reliable performance and convenient compatibility with common drilling tools, helping to maintain solid hole quality in challenging materials.
HIDOTOL 13-Piece Cobalt Drill Bit Set
HIDOTOL’s set uses premium M35 cobalt HSS (5%) for extended tool life and high heat resistance. A 135-degree split point with a round, straight shank aids self-centering and reduces walking during initial contact. The fully ground twist design helps clear chips quickly and reduces friction and heat, supporting cooler drilling under load. This set is broadly compatible with stainless steel, cast iron, high-temperature alloys, titanium, hard plastics, and wood, making it a versatile choice for metalworking and mixed-material projects.
Sizes range from 1/16″ to 1/4″, providing solid coverage for common hole sizes in metal fabrication, automotive repair, and home DIY. The cobalt composition and TiAlN-like performance characteristics help maintain sharpness and efficiency over time, though users should still monitor bit temperatures and pause for cooling on particularly tough tasks.
MACXCOIP 13-Piece M35 Cobalt Set
The MACXCOIP set contains 13 bits ranging from 1/16″ to 1/4″, all crafted from M35 cobalt high-speed steel for improved durability and wear resistance. A 135-degree point aids fast, precise drilling with self-centering action to prevent wandering. The bits feature a standard round shank suitable for most drill chucks, and they come in an index storage case for portable organization. This kit is well-suited for stainless steel, cast iron, aluminum, and other hard metals, as well as plastics and wood when needed.
For users seeking a compact yet capable assortment, MACXCOIP offers balanced coverage and solid performance without needing to resort to larger, heavier sets. Proper drilling speed, a sharp point, and adequate coolant or lubrication will maximize the life of these cobalt bits in demanding materials.
Buying Guide
Material And Coating
For drilling hardened steel, cobalt alloys dramatically improve heat resistance and wear life. M35 cobalt (about 5%) blends durability with reasonable cost, while M42 cobalt (about 8%) offers even greater heat tolerance and longer life in the toughest metals. Some high-end bits add TiAlN coatings to further extend life by reducing surface wear and heat buildup. When choosing a kit, consider your typical materials, drilling speeds, and how often you drill through stainless steel, cast iron, or titanium alloys.
Tip Geometry And Performance
A 135-degree split point helps the bit start holes cleanly with minimal walking. This geometry pairs well with hard metals where wandering leads to damaged workpieces. Multi-blade or three-flute designs can improve chip clearance and heat dissipation, which matters when cutting through thick or tough material. If your tasks involve frequent drilling in stainless steel or hardened alloys, prioritize bits with a precise tip and robust flute design.
Shank Type And Compatibility
Shank design affects grip and ease of use. A three-flat shank reduces slipping in chucks and enables smooth, secure engagement with quick-change systems. Hex shanks offer even faster chuck reversals and compatibility with impact drivers, while round shanks are standard for most drill chucks. When buying a kit, match the shank type to your drill setup and your preferred chuck style.
Size Range And Kit Coverage
Choose a kit that covers the hole sizes you encounter most often. Common ranges include 1/16″ to 1/4″ for general metalworking, with some sets extending up to 3/8″ or larger for thicker stock. If you regularly work with a variety of metals, a larger set with many sizes is convenient, but ensure you will use the included bits to justify the purchase.
Storage, Durability, And Value
Storage cases help prevent bit loss and misplacement in busy shops. Hard plastic cases with compartmentalized trays reduce damage and confusion. Durable construction and precise grinding processes contribute to long life and reliable performance, which translates into better value over time despite the upfront cost. Evaluate whether the kit’s size and case meet your workspace needs to optimize overall value.
Usage Tips For Hardened Steel
- Use appropriate speeds: high speeds can generate excess heat; start slower, then increase as needed while lubricating.
- Select sharp bits with a proper point angle and good chip clearance to minimize heat buildup.
- Maintain steady pressure and allow the bit to cut rather than force drilling, which can dull edges quickly.
- Coolant or oil-based lubrication can extend life when drilling through stainless steel or titanium alloys.