The best hardened steel drill bits are designed to cut through stainless steel, cast iron, and other hard metals with less wandering and more precise holes. This guide highlights five top-rated options, each suited to different users—from DIY enthusiasts to professional metalworkers. You’ll find bits optimized for heat resistance, long life, and easier chip ejection, plus clear reasons to choose one over another based on your project needs.
| Product | Brand | Type | Best For |
|---|---|---|---|
| Crosstar M35 Cobalt Drill Bit Set | Crosstar | 3-flute TiAlN-coated M35 HSS | Tough metals and long life in stainless steel and hardened alloys |
| BOSCH CO14B 14-Piece Set | Bosch | M42 cobalt, 8% cobalt | Durable, high-heat applications in stainless steel and titanium |
| SEDIANAS 29Pcs M35 Cobalt Set | SEDIANAS | M35 HSS twist drill bits | Extensive size range for varied metal projects |
| SEDIANAS 15Pcs M35 HSS Set | SEDIANAS | M35 HSS twist drill bits | Compact set with strong performance in hardened metals |
| NordWolf 5-Piece M35 Cobalt Stubby Set | NordWolf | Stubby 1/4″ hex shank | Hard-to-reach spaces and quick-chuck use |
Crosstar M35 Cobalt Drill Bit Set for Hardened Metal
Best for heavy-duty metalworking tasks. These bits are crafted from M35 cobalt steel (5% cobalt), enabling drilling through stainless steel, hardened cast iron, high-carbon steel, and titanium alloys with improved hardness up to 60 HRC. A TiAlN coating helps withstand high temperatures, reducing heat buildup and extending life. The three-flute design improves chip ejection and gives a smoother finish than standard two-flute bits. Choose this if you work with very hard metals and need longer tool life in demanding conditions. Caution: TiAlN coatings can wear over extremely long cycles, and feeding speed should be controlled to avoid workpiece deformation.
Best for: Professional metal shops and serious DIYers drilling hardened alloys, where wear resistance and heat management matter most.
BOSCH CO14B 14-Piece Cobalt Drill Bit Set
Best for longevity and frequent use on hard metals. This set uses M42 cobalt with an 8% cobalt composition, offering extended life and excellent heat resistance for drilling stainless steel, cast iron, titanium, and similar metals. The surface-hardened tip aids penetration into tough materials, while the jobber-length bits provide sturdy reach. Best for users who need durable bits that can handle repeated drilling in hard metals without frequent replacements. Limitation: higher cost per bit compared to lower-cobalt options—worth it for longevity in demanding jobs.
Best for: Professionals and serious hobbyists drilling hardened metals regularly, who value durability and heat resistance.
SEDIANAS 29Pcs M35 Cobalt Drill Bit Set
Best for versatile projects requiring a broad size range. The M35 cobalt composition delivers strong heat resistance and longer life than standard HSS bits, and the 135° split point helps with self-centering and faster drilling. Fully ground twist design clears chips efficiently, lowering heat and friction. This set is ideal for those who encounter many different hole sizes in hardened materials and want a comprehensive, portable kit. Caution: Some users may find the larger 1/2″ sizes less forgiving for delicate work without proper clamping.
Best for: Makers and technicians who need a wide variety of sizes for hard metals and plastics in one box.
SEDIANAS 15Pcs M35 HSS Twist Drill Bit Set
Best for compact carrier and solid performance. This 15-piece set features M35 cobalt drill bits with a 135° split point, designed to prevent walk-off and improve speed and precision when drilling hardened metals, stainless steel, cast iron, and plastics. The straight shank supports reliable clamping in standard chucks. Ideal for users who want a portable, dependable selection of hardened-metal drill bits without large hardware. Limitation: fewer sizes than larger sets, so some hole sizes may require alternative tools.
Best for: Homeowners, makers, and technicians who need a reliable, smaller set for occasional work on hard metals.
NordWolf 5-Piece M35 Cobalt Stubby Set
Best for tight spaces and quick-change setups. These stubby drill bits use M35 cobalt steel for enhanced heat resistance and hardness, paired with a 1/4″ hex shank compatible with quick-change chucks and impact drivers. The short length improves rigidity and reduces flex, making them suitable for work in confined areas and on hardened metals like stainless steel and titanium. Caution: shorter length limits depth of hole and can be less effective for deep drilling tasks.
Best for: Pros using impact drivers and working in cramped spaces where long bits are impractical.
Buying Guide
- Material and hardness: Look for M35 cobalt or M42 cobalt formulas for better heat resistance and longer life when drilling hardened metals. Cobalt content correlates with wear resistance and high-temperature performance.
- Coating: TiAlN coatings minimize heat buildup, extending bit life in high-temperature environments. Coatings can affect cost; weigh longevity against price.
- Flute design: Three-flute designs improve chip clearance and reduce workpiece heat, while 135° split points enhance self-centering and reduce walking on tough materials.
- Shank style: Hex shanks provide quick-change compatibility with many chucks and drivers, while straight shanks may require standard chucks. Stubby bits are better for access in tight spaces but limit drilling depth.
- Set size: Choose a set that covers the common hole sizes you encounter. Larger sets offer flexibility but may be heavier and more expensive.
- Workpiece material: For stainless steel and titanium, prioritize higher cobalt content and a robust coating. For softer metals, a more economical option may suffice.
- Application tips: Use appropriate drill speeds, feed rates, and lubrication to maximize tip life and minimize chatter. Secure the workpiece firmly to prevent bit wandering.
Frequently Asked Questions
- What is M35 cobalt drill bit best used for? They excel in drilling hardened metals like stainless steel, cast iron, and titanium alloys due to higher heat resistance and hardness.
- Do cobalt bits require special drills? They work with standard power drills and compatible chucks, but low-speed settings and steady feeds help extend life.
- What’s the difference between M35 and M42 cobalt bits? M42 bits generally have higher cobalt content and offer greater heat resistance and life in very hard metals, often at a higher price.
- When should I choose a stubby bit? Choose stubby bits for tight spaces or quick-chuck setups where extended reach isn’t needed.
- Can I use cobalt bits on wood? Yes, but they are optimized for metals; for wood, standard high-speed steel bits are typically sufficient and more economical.
- How do I maximize drill bit life? Use proper lubrication, feed rate, and cool-down breaks, and avoid excessive pressure that can dull the bit.