Not all drill bits are created equal, and understanding the different drill bit materials and the relative hardness of your drill bits compared to the material you’re drilling can make a significant difference in your drilling efficiency and results. In this article, we’ll explore the best drill bit material for hardened/stainless steel and discuss what makes the hardest drill bits, also highlight the best drill bits in 2024.
Strongest Drill Bits – Which Drill Bit Material Is Hardest?
There are a few different materials that drill bits can be made of, with varying levels of hardness. The carbide drill bits that are made of tungsten carbide are the strongest drill bits and can work with almost any steel, and tungsten carbide is by far considered the hardest material used for drill bits. Three types of carbide bits are commonly used.
– Solid carbide bits: made entirely of tungsten carbide and are the most durable and long-lasting option.
– Carbide-tipped bits: have a tungsten carbide tip or edge, but the rest of the bit is made of a different material, such as steel.
– Carbide-coated bits: These bits have a thin layer of tungsten carbide coating on the cutting edge, but the rest of the bit is made of a different material.
Cobalt or carbide, which is harder?
On the Mohs hardness scale, which is a relative scale used to define mineral hardness, tungsten carbide ranges from 9 to 9.5. Tungsten carbide is often considered one of the hardest materials available for tooling applications. Cobalt on its own has a Mohs hardness of 5. However, cobalt is often alloyed with other metals like steel to improve hardness. While cobalt alloys can achieve high hardness through heat treatment and composition tuning, they are not able to match the inherent hardness of tungsten carbide’s carbide bonds.
Best Drill Bit Material for Hardened Steel
When it comes to drilling hardened steel, carbide-tipped drill bits emerge as the top choice due to their exceptional properties. Carbide drill bits offer unparalleled hardness and durability, making them ideal for penetrating the tough surface of hardened steel. Their superior heat resistance allows them to withstand the high temperatures generated during drilling, while their efficient heat dissipation design helps prevent damage to both the bit and the workpiece. Carbide bits also excel in chip resistance, ensuring cleaner and more precise holes. Although alternatives like cobalt and titanium-coated bits can be used, they don’t quite match the performance of carbide when tackling hardened steel. Cobalt bits, while offering good heat resistance and the ability to be resharpened, lack the extreme hardness of carbide. Titanium-coated bits provide improved wear resistance initially, but their effectiveness diminishes as the coating wears off.
Best Drill Bit Material for Stainless Steel
The selection of the drill bit for stainless steel will be different according to your budget, production scale, and hardness requirement.
Common leaf spring steel and chisels, often require drill bits that can handle hardness levels in the range of 58 to 62 on the Rockwell hardness scale (HRC). Stainless steel, known for its toughness, also falls within this hardness range. High-speed steel (HSS) bits, while adequate for softer metals, often ceased cutting when faced with harder materials like hardened plates designed to resist drilling, which requires a minimum of 60 HRC in security applications. The standout performer is the carbide drill bit (tungsten carbide), which not only drilled through high-speed steel but also exhibited superior capability in penetrating materials that stopped other bits. Carbide bits, often sharpened to enhance their cutting ability, performed exceptionally well as long as they were used in controlled conditions with proper lubrication and even pressure, proving to be the best choice for drilling through stainless steel and similar hard materials. Carbide-tipped and solid carbide drill bits both offer excellent wear resistance and can maintain their cutting edge for a long time. Carbide bits are ideal for high-volume production environments where maximum tool life is crucial. However, they are more brittle than cobalt bits and can chip or break if not used properly. They’re also the most expensive option, which may not be cost-effective for occasional use.
Cobalt bits maintain their sharp edge longer and can withstand higher temperatures without losing their temper. They’re particularly effective for drilling through thick stainless steel or when many holes need to be drilled. However, they are more brittle than standard HSS bits and can be more expensive.
Titanium-coated HSS are high-speed steel bits coated with titanium nitride. The coating reduces friction and increases the bit’s lifespan. While not as durable as cobalt or carbide for stainless steel, they are a good middle-ground option. They perform better than standard HSS bits and are less expensive than cobalt or carbide options. They’re suitable for occasional use or when drilling thinner stainless steel.
Black oxide-coated HSS bits are treated with a black oxide finish that provides some heat resistance and lubricity. While not as effective as cobalt or titanium-coated bits for stainless steel, they can be a budget-friendly option for light-duty work or occasional use.
Cobalt steel bits are generally the best all-around choice for drilling stainless steel. For professional or mass production, carbide bits might be worth the investment, while titanium-coated HSS bits could be suitable for occasional DIY projects.
Top 5 Best Drill Bits 2024 for Stainless Steel
1. COMOWARE Cobalt Drill Bit Set
This set offers excellent performance for drilling through tough materials. Cobalt-infused high-speed steel provides increased hardness and heat resistance, allowing these bits to maintain their cutting edge longer than standard HSS bits. They are ideal for drilling through hardened steel, stainless steel, and other challenging metals.
2. BOSCH CO14B 14-Piece Cobalt M42 Metal Drill Bit
Bosch’s M42 cobalt steel composition makes these bits exceptionally durable and heat-resistant. With 8% cobalt content, they outperform standard cobalt bits in terms of longevity and cutting speed. The 135-degree split point tip ensures precise starts without walking, making them perfect for professional metalworking applications.
3. M42 8% Cobalt Twist Drill Bits Set
This set features M42 high-speed steel with 8% cobalt content, offering superior wear resistance and the ability to maintain sharpness at high temperatures. The metric sizing makes them ideal for precision work in various industries. These bits excel at drilling through stainless steel, hardened steel, cast iron, and other abrasive materials.
4. DEWALT Cobalt Alloy Steel Drill Bit Set with Pilot Point
DeWalt’s cobalt alloy steel bits offer a great balance of performance and affordability. The cobalt blend provides increased heat and abrasion resistance compared to standard HSS bits. Their pilot point tip design reduces walking and allows for faster, cleaner holes in metal surfaces, making them a versatile choice for both professionals and DIY enthusiasts.
5. Drill America D/A29J-CO-PC 29 Piece M42 Cobalt Drill Bit Set
This set from Drill America features premium cobalt steel bits known for their exceptional durability and performance. The high cobalt content allows these bits to maintain their edge even when drilling through the toughest materials. Their precision ground points ensure accurate starts and smooth cutting, making them a top choice for demanding metalworking applications in industrial settings.
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