Material and Hardness of Twist Drill Bits: A Comprehensive Analysis of Brands and Models

Twist drill bits are indispensable tools in machining, construction, and DIY projects, designed to create cylindrical holes in diverse materials such as metals, wood, plastics, and composites. Their performance hinges on material composition and hardness, which directly influence cutting efficiency, tool life, and dimensional accuracy. This article delves into the materials and hardness of twist drill bits, with a focus on leading brands and models, providing a detailed reference for professionals and enthusiasts alike.

1. Material Composition of Twist Drill Bits

The material of a twist drill bit determines its cutting ability, wear resistance, and suitability for specific applications. Common materials include high-speed steel (HSS), cobalt-alloyed high-speed steel (HSS-Co), carbide, and specialized coatings. Each material offers distinct advantages and trade-offs.

1.1 High-Speed Steel (HSS)

High-speed steel is the most widely used material for twist drill bits due to its balanced performance and cost-effectiveness. HSS drill bits are capable of cutting at high speeds and temperatures, making them suitable for drilling steel, cast iron, aluminum, and non-ferrous metals. The hardness of HSS typically ranges from HRC 61 to 66, ensuring durability and resistance to deformation.

Brands and Models:

• DANYANG DAMING TOOLS CO., LTD. DM-DS005 HSS Twist Drill Bit Set
  This set includes 115 pieces of HSS twist drill bits ranging from 1/16″ to 1/2″ in size. The bits are fully ground and feature a black or white finish, with point angles of 118° or 135°. They are designed for metal drilling and are suitable for applications requiring high precision and durability.
• Ningbo T-WIN IMP.&EXP. CO., LTD. TG HSS Twist Drill Bit Set
  The TG HSS drill bits are known for their improved efficiency and long lifespan, offering up to 12 times the durability of ordinary HSS bits. They are available in various sizes and are suitable for drilling hard metals (below HRC38°), wood, and plastics. The straight shank design ensures firm holding and accurate centering.
• Hangzhou Fanxi Tools Co., Ltd. FANXI HSS Twist Drill Bit Set
  Fanxi offers a range of HSS twist drill bits with different point angles (118° and 135° split point) and finishes (black oxide, bright, titanium-coated). These bits are ideal for drilling steel, stainless steel, and other metals, providing excellent performance in both handheld and drill press applications.

1.2 Cobalt-Alloyed High-Speed Steel (HSS-Co)

Cobalt-alloyed high-speed steel (HSS-Co) is a premium material that enhances the performance of HSS drill bits by increasing their hardness and heat resistance. HSS-Co drill bits are typically harder than standard HSS, with hardness values ranging from HRC 67 to 70. They are ideal for drilling hardened steels, stainless steels, and other tough materials.

Brands and Models:

• Hangzhou Fanxi Tools Co., Ltd. FANXI HSS-Co5 Twist Drill Bit Set
  These drill bits contain 5% cobalt, significantly improving their hardness and wear resistance. They are suitable for drilling high-hardness materials such as heat-treated steels and nickel-based alloys. The 135° split point design ensures quick starts and reduces walking.
• Gasttools Ergaster HSS-Co Twist Drill Bit Set
  Gasttools offers HSS-Co drill bits with cobalt content ranging from 5% to 8%. These bits are designed for high-performance drilling applications, providing superior durability and cutting efficiency in challenging materials. The fully ground process ensures precise dimensions and smooth finishes.

1.3 Carbide (Solid Carbide and Carbide-Tipped)

Carbide drill bits are the hardest and most wear-resistant option available, with hardness values exceeding HRC 85. They are typically used for high-speed drilling of hard materials such as hardened steels, cast iron, and composites. Carbide drill bits can be solid carbide or carbide-tipped, with the latter being more cost-effective for general-purpose applications.

Brands and Models:

• Jiangsu Goldmoon Industry Co., Ltd. GOLDMOON Carbide-Tipped Twist Drill Bit Set
  While not purely solid carbide, these carbide-tipped drill bits offer excellent performance in drilling hard materials. The carbide tip provides superior hardness and wear resistance, while the HSS shank ensures compatibility with standard drill chucks. These bits are suitable for aluminum alloy, iron plate, and thin steel plate drilling.
• Specialized Carbide Drill Bits for Aircraft Applications
  Some manufacturers, such as Hangzhou Fanxi Tools Co., Ltd., offer extra-long carbide drill bits designed for aircraft maintenance and repair. These bits are manufactured to NAS 907 standards and feature a 135° split point for quick starts and reduced walking. They are ideal for drilling holes in hard-to-reach places.

1.4 Coated Drill Bits

Coatings are applied to drill bits to enhance their performance by reducing friction, improving chip evacuation, and protecting against corrosion. Common coatings include titanium nitride (TiN), titanium aluminum nitride (TiAlN), and black oxide. Coated drill bits typically have higher hardness and longer tool life compared to uncoated bits.

Brands and Models:

• Behappy Crafts (Suzhou) Co., Ltd. BEHAPPY Titanium-Coated HSS Twist Drill Bit Set
  This 99-piece set features titanium-coated HSS drill bits with hardness values up to HRC 66. The titanium coating reduces friction and heat buildup, extending tool life and improving cutting efficiency. These bits are suitable for drilling aluminum alloy, iron plate, and thin steel plate.
• Ningbo T-WIN IMP.&EXP. CO., LTD. TG Titanium-Coated HSS Twist Drill Bit Set
  TG offers titanium-coated HSS drill bits with a gold-colored finish. The coating provides excellent corrosion resistance and enhances the bit’s appearance. These bits are suitable for a wide range of materials, including metals, wood, and plastics.

2. Hardness of Twist Drill Bits and Its Impact on Performance

Hardness is a critical parameter that determines the cutting ability and durability of twist drill bits. It is typically measured using the Rockwell C scale (HRC), with higher values indicating greater hardness. The hardness of a drill bit influences its resistance to wear, deformation, and fracture during drilling operations.

2.1 Hardness and Wear Resistance

Harder drill bits exhibit higher wear resistance, allowing them to maintain their cutting edges for longer periods. This is particularly important when drilling hard materials such as stainless steel and hardened steels, where soft drill bits would quickly dull and lose effectiveness. For example, HSS-Co drill bits with hardness values of HRC 67 to 70 can drill hardened steels with minimal wear, while standard HSS bits (HRC 61 to 66) may struggle.

2.2 Hardness and Toughness

While hardness is desirable for wear resistance, excessive hardness can reduce the toughness of a drill bit, making it more prone to fracture under impact or high-stress conditions. Therefore, drill bit manufacturers must strike a balance between hardness and toughness to ensure optimal performance. Carbide drill bits, while extremely hard, are also brittle and require careful handling to avoid breakage. In contrast, HSS and HSS-Co drill bits offer a better combination of hardness and toughness for general-purpose applications.

2.3 Hardness and Cutting Efficiency

Harder drill bits can cut through materials more efficiently, reducing drilling time and energy consumption. This is because harder bits can maintain a sharper cutting edge, resulting in cleaner holes and less material deformation. Coated drill bits further enhance cutting efficiency by reducing friction and heat buildup, allowing for higher drilling speeds and feeds.

3. Detailed Analysis of Leading Brands and Models

To provide a more comprehensive understanding of twist drill bit materials and hardness, let’s examine some leading brands and their flagship models in detail.

3.1 DANYANG DAMING TOOLS CO., LTD.

DANYANG DAMING TOOLS is a renowned manufacturer of drilling tools, offering a wide range of HSS twist drill bits for various applications. Their DM-DS005 set is a popular choice among professionals and DIY enthusiasts, featuring 115 pieces of fully ground HSS drill bits with sizes ranging from 1/16″ to 1/2″.

Key Features:

• Material: High-speed steel (HSS 4241, HSS 4341, HSS 6542)
• Hardness: HRC 61 to 66
• Point Angle: 118° or 135°
• Finish: Black, white, rainbow, or coffee color
• Shank Type: Straight shank
• Application: Metal drilling, including steel, cast steel, grey cast iron, and malleable iron

The DM-DS005 set is known for its precision and durability, making it suitable for both handheld and drill press applications. The fully ground process ensures consistent dimensions and smooth finishes, while the variety of point angles allows for optimal performance in different materials.

3.2 Ningbo T-WIN IMP.&EXP. CO., LTD.

Ningbo T-WIN is a leading supplier of power tool accessories, including high-quality HSS twist drill bits. Their TG series drill bits are designed for improved efficiency and long lifespan, offering up to 12 times the durability of ordinary HSS bits.

Key Features:

• Material: High-speed steel (HSS 4241, HSS 4341, HSS 6542)
• Hardness: HRC 62 to 67
• Point Angle: 118° or 135° split point
• Finish: Black oxide, bright, or titanium-coated
• Shank Type: Straight shank
• Application: Metal drilling (hardness below HRC38°), wood, and plastics

The TG drill bits are known for their self-centering ability, thanks to the 135° split point design. This feature eliminates the need for pre-punching or pilot drilling in materials up to 10mm in diameter, saving time and effort. The titanium-coated finish provides additional protection against corrosion and wear, extending tool life.

3.3 Hangzhou Fanxi Tools Co., Ltd.

Hangzhou Fanxi Tools is a specialized manufacturer of drilling tools, offering a comprehensive range of HSS and HSS-Co twist drill bits. Their products are known for their precision, durability, and versatility, catering to a wide range of applications.

Key Features (HSS Model):

• Material: High-speed steel (HSS 4241, HSS 4341, HSS 6542)
• Hardness: HRC 61 to 66
• Point Angle: 118° or 135° split point
• Finish: Black oxide, bright, or titanium-coated
• Shank Type: Straight shank or hex shank
• Application: Metal drilling, including steel, stainless steel, and heat-resistant steel

Key Features (HSS-Co Model):

• Material: Cobalt-alloyed high-speed steel (HSS-Co5)
• Hardness: HRC 67 to 70
• Point Angle: 135° split point
• Finish: Black oxide or titanium-coated
• Shank Type: Straight shank
• Application: High-hardness materials such as hardened steels and nickel-based alloys

Fanxi’s HSS-Co drill bits are designed for demanding applications where standard HSS bits may fail. The 5% cobalt content significantly improves hardness and wear resistance, allowing these bits to drill through tough materials with ease. The 135° split point design ensures quick starts and reduced walking, enhancing drilling accuracy.

3.4 Behappy Crafts (Suzhou) Co., Ltd.

Behappy Crafts is a manufacturer of high-quality power tool accessories, including a wide range of HSS twist drill bits. Their 99-piece titanium-coated HSS drill bit set is a popular choice among professionals and hobbyists, offering excellent performance and value.

Key Features:

• Material: High-speed steel (HSS 4241, HSS 4341, HSS 6542)
• Hardness: HRC 61 to 66
• Point Angle: 118° or 135°
• Finish: Titanium-coated
• Shank Type: Round shank
• Application: Metal drilling (aluminum alloy, iron plate, thin steel plate), wood, and plastics

The titanium coating on Behappy’s drill bits provides excellent corrosion resistance and reduces friction, extending tool life and improving cutting efficiency. The set includes a wide range of sizes, making it suitable for various drilling tasks. The plastic box packaging ensures easy storage and transportation.

4. Conclusion

The material and hardness of twist drill bits are critical factors that determine their performance, durability, and suitability for specific applications. High-speed steel (HSS) is the most widely used material due to its balanced performance and cost-effectiveness, while cobalt-alloyed high-speed steel (HSS-Co) offers superior hardness and wear resistance for drilling hard materials. Carbide drill bits, although extremely hard, are more brittle and require careful handling. Coated drill bits further enhance performance by reducing friction and improving chip evacuation.

Leading brands such as DANYANG DAMING TOOLS, Ningbo T-WIN, Hangzhou Fanxi Tools, and Behappy Crafts offer a wide range of twist drill bits with varying materials, hardness values, and features to cater to diverse needs. By selecting the appropriate drill bit based on material, hardness, and application requirements, users can achieve optimal drilling results and extend tool life. Whether drilling metals, wood, plastics, or composites, there is a twist drill bit available to meet every challenge.