Best Cobalt Drill Bits: The Ultimate Guide for Metal Drilling

When it comes to drilling through tough metals like stainless steel, cast iron, or titanium, regular high-speed steel (HSS) bits often fall short. This is where cobalt drill bits shine. Made with a steel alloy containing 5-8% cobalt, these specialized bits offer superior hardness, heat resistance, and durability that make them the go-to choice for serious metalworking. Whether you’re a professional machinist or a dedicated DIYer tackling demanding projects, investing in quality cobalt drill bits can save you time, frustration, and ultimately money.

In this comprehensive guide, we’ll explore the best cobalt drill bits on the market, their unique advantages, and how to select the right set for your specific needs.

1. What Makes Cobalt Drill Bits Special

Cobalt drill bits are manufactured with a steel alloy containing 5-8% cobalt, which significantly enhances their performance compared to standard bits. The addition of cobalt creates a harder, more heat-resistant bit that can maintain its edge even when drilling through the toughest materials.

Key advantages include:
– Higher heat resistance (up to 1,100°F)
– Superior hardness for maintaining sharp cutting edges
– Excellent wear resistance for longer life
– Ability to drill through hardened steel, stainless steel, cast iron, and titanium
– Less frequent sharpening required

While they cost more than standard HSS bits, their durability and performance in demanding applications make them worth the investment for serious users.

2. M35 vs. M42 Cobalt: Understanding the Difference

Not all cobalt drill bits are created equal. The two most common grades are M35 and M42, referring to the percentage of cobalt in the alloy:

M35 Cobalt Bits

– Contain approximately 5% cobalt
– Good balance of hardness and flexibility
– Less brittle than M42
– More affordable option
– Ideal for general-purpose metal drilling

M42 Cobalt Bits

– Contain approximately 8% cobalt
– Maximum hardness and heat resistance
– Best performance on the toughest materials
– Higher price point
– Preferred for professional and industrial applications

According to experienced users on r/Tools, M42 bits are worth the extra cost when drilling extremely hard metals regularly. As one user noted, “M42 bits worked GREAT! They cut through stainless like butter compared to my old bits.”

3. Drill Hog Cobalt Drill Bit Set

Drill Hog has developed a strong reputation among professionals and hobbyists alike for their M42 cobalt drill bits. Despite being sold on platforms like eBay, these bits consistently receive positive reviews for their performance.

Key features:
– Made from genuine M42 high-speed steel with 8% cobalt content
– 135-degree split point design that prevents walking and reduces thrust
– Gold oxide finish that helps with heat dissipation
– Available in various set configurations
– Lifetime warranty

A discussion on Practical Machinist forums revealed that many professionals have had excellent experiences with Drill Hog bits, with one user stating, “I bought M42 bits from Drill Hog on eBay, and they worked GREAT!”

4. Dewalt DWA1240 Cobalt Drill Bit Set

Dewalt is a trusted name in power tools, and their cobalt drill bits maintain the brand’s reputation for quality and performance.

Key features:
– M35 grade cobalt steel construction
– Pilot point tip design that starts on contact and reduces walking
– No spin shanks on larger bits to prevent slipping in the chuck
– Web taper design that increases strength and reduces breaking
– Available in various set configurations

These bits are particularly well-regarded for their durability and ability to maintain sharpness even after multiple uses on hard metals.

5. Irwin Tools Cobalt M-35 Metal Index Drill Bit Set

Irwin Tools offers a high-quality option with their M-35 cobalt drill bit sets, which provide excellent performance at a competitive price point.

Key features:
– 5% cobalt blend for enhanced durability
– 135-degree split point that starts on contact and reduces walking
– Reduced shank on larger bits for secure chuck grip
– Straight shank design for compatibility with most drill chucks
– Durable metal index case for organization and storage

These bits are particularly popular among DIY enthusiasts who need professional-grade performance without breaking the bank.

6. When to Choose Cobalt Over Carbide Bits

While cobalt bits excel at drilling through tough metals, carbide bits are even harder. However, this doesn’t always make carbide the better choice.

As noted by a user in a Canadian Hobby Metal Workers discussion: “Cobalt is better than HSS but not nearly as good as carbide. I use cobalt for most drilling because carbide is brittle and expensive.”

Consider these factors when choosing between cobalt and carbide:

Choose Cobalt When:

– You need a balance of hardness and flexibility
– Cost is a consideration
– You’re drilling various materials
– You need bits that can be resharpened
– You’re using a hand drill rather than a drill press

Choose Carbide When:

– Maximum hardness is required
– You’re drilling extremely abrasive materials
– Precision and consistent hole size are critical
– You’re using a drill press with stable conditions
– Budget is less of a concern

7. Maintenance and Care Tips for Cobalt Drill Bits

To get the most value from your investment in cobalt drill bits, proper maintenance is essential:

1. Use cutting fluid or oil when drilling to reduce heat and friction
2. Start with slower speeds for harder materials
3. Apply steady, moderate pressure rather than forcing the bit
4. Allow bits to cool between uses on tough materials
5. Store bits in a dry, organized case to prevent damage
6. Sharpen bits at the first sign of dulling using a proper grinding wheel
7. Clean bits after use to remove metal chips and prevent corrosion

Following these practices can significantly extend the life of your cobalt drill bits and maintain their cutting performance.

Conclusion: Investing in Quality Pays Off

When it comes to cobalt drill bits, the consensus among professionals and serious hobbyists is clear: quality matters. While premium cobalt bits represent a higher initial investment, their superior performance and longevity make them more economical in the long run, especially when working with challenging materials.

For occasional DIY use on softer metals, M35 cobalt bits from reputable brands like Dewalt or Irwin provide an excellent balance of performance and value. For professionals or those regularly drilling through stainless steel and other hardened metals, M42 bits from manufacturers like Drill Hog offer the ultimate in durability and cutting ability.

Remember that even the best cobalt bits require proper technique and maintenance to perform at their peak. By following the care tips outlined above and matching the right bit to the job at hand, you’ll enjoy cleaner holes, faster drilling, and fewer frustrations in your metalworking projects.