High-speed steel drill bits(Hss drill bits) and hard metal drill bits are two common drill bit types.In the fast-paced realm of modern machinery manufacturing, innovation in tool materials marches forward hand in hand with advancements in smelting technology. With each stride, the array of tool materials expands, each imbued with refined properties and enhanced performance. Among the plethora of options, high-speed steel1, cemented carbide2, ceramics, diamond, cubic boron nitride3 (CBN), and polycrystalline cubic boron nitride4 (PCBN) stand as stalwarts in hole processing. In our exploration today, we delve into the enduring efficacy of high-speed steel drill bits and the formidable strength of carbide drill bits.

CategoryDensities/
(g.cm3)
HardnessBending Strength/MPaImpact Toughness/(kj.m2)Elastic ModulusHeat Resistance
Hss8~8.863~70HRC2000~4000100~600200~230600~650
Hard Metal8~1589~93.5HRA1100~260025~60420~630800~1000
Physical and mechanical property parameter ranges of high-speed steel and cemented carbide

Understanding the Basics: what is a high speed drill bit ?

HSS Drill Bits, also known as High-Speed Steel Drill Bits or simply High-Speed Bits, are crafted primarily from high-speed steel.

Understanding the Materials of High Speed Steel Drill Bits.

What is high speed steel?

High-speed steel (HSS) is a high-quality tool steel rich in tungsten (W5), molybdenum6 (Mo), chromium7 (Cr), vanadium (V), cobalt (Co), aluminum (Al) and other alloying elements.

Why do drill bits use high-speed steel?

High speed steel has excellent heat resistance and can withstand cutting temperatures of 500 to 650°C. In addition, they have excellent hardness, toughness and wear resistance. Therefore, high-speed steel is the typical material for manufacturing metal drill bits and remains the cornerstone material for various cutting tools.

How many types of high-speed steel are there?

High-speed steel encompasses three main categories based on cutting performance and manufacturing processes: ordinary high-speed steel (HSS), high-performance high-speed steel (HSS-E), and powder metallurgy high-speed steel (HSS-PM).

  1. Ordinary High-Speed Steel:
    • Tungsten-Based High-Speed Steel: Notable for its composition, typical grades like W18Cr4V (W18) exhibit commendable properties, including good overall performance, low decarburization sensitivity, and strong resistance to plastic deformation. However, challenges such as high carbide content and uneven distribution may limit its utility in certain applications.
    • Tungsten-Molybdenum High-Speed Steel: Exemplified by grades like W6Mo5Cr4V2 (M2), this variant offers improved mechanical properties, including enhanced bending strength and impact toughness. With its excellent thermoplasticity, it finds utility in manufacturing tools for hot forming applications.

    2. High-Performance High-Speed Steel:

      • High-performance high-speed steel incorporates additional elements like carbon (C), vanadium (V), cobalt (Co), and aluminum (Al) to enhance heat resistance and wear resistance. It boasts a service life up to 15 times longer than ordinary HSS, making it ideal for processing challenging materials such as stainless steel, heat-resistant steel, and titanium alloys.

      3.Powder Metallurgy High-Speed Steel:

        • Utilizing advanced powder metallurgy techniques, this category of high-speed steel addresses issues of carbide segregation. By atomizing molten high-speed steel into fine, uniform powder and subsequently sintering it to full density, powder metallurgy HSS achieves superior strength, toughness, and hardness. It finds application in crafting precision tools like drill bits, broaches, and gear shaper cutters.
        Types and main properties of commonly used high-speed steels
        Types and main properties of commonly used high-speed steels

        Understanding the Basics: An Introduction to hard metal drill bits.

        Hard metal drill bits, also known as Carbide Drill Bits or Tungsten Carbide Drill Bits, are crafted primarily from hard metal.

        Understanding the Materials of hard metal drill bits – What is hard metal(carbide)?


        Cemented carbide is made of refractory metal carbide (WC, TiC, TaC or NbC, etc.) powder with high hardness and high melting point as the main component, and is sintered at high temperature with the metal component (Co, Mo or Ni) that acts as a binder. Powder metallurgy products formed.

        Main properties of refractory metal carbides in cemented carbide
        Main properties of refractory metal carbides in cemented carbide

        Cemented carbide, primarily composed of refractory metal carbide, contains a significant proportion of high-temperature carbides. This unique composition grants it remarkable hardness, wear resistance, and red hardness, surpassing high-speed steel by far. With a cutting temperature tolerance of 800~1000°C, cemented carbide drill bits outlast their high-speed steel counterparts by over tenfold. This exceptional durability makes them highly resistant to wear, allowing for operation at elevated speeds and pressures without succumbing to wear.

        However, despite its durability, cemented carbide exhibits relatively low bending strength and impact toughness due to its brittle nature. Additionally, its processing capabilities are somewhat limited. The performance of cemented carbide depends on factors such as carbide content, powder grain size, and sintering process. Higher carbide content and finer grains result in increased hardness but reduced flexural strength, making them suitable for rough applications. Conversely, a higher binder content enhances flexural strength while compromising hardness, making it ideal for finishing tasks.

        One notable drawback of carbide drill bits compared to high-speed steel counterparts is their brittleness. This means they’re prone to breakage or damage when working with extremely fragile or brittle materials like glass or ceramics. Despite this limitation, the superior wear resistance and longevity of cemented carbide make it a preferred choice for applications demanding high precision and prolonged machining durations.

        Applications and Advantages: When to Choose HSS or Hard Metal Drill Bits.

        When to Choose HSS Drill Bits:

        • For drilling softer materials such as wood, plastic, and non-ferrous metals.
        • For general-purpose drilling tasks in workshops, construction sites, and DIY projects.
        • When cost-effectiveness and ease of sharpening are priorities.

        When to Choose hard metal drill bits:

        • For drilling hard and abrasive materials like stainless steel, cast iron, ceramics, and concrete.
        • For precision drilling tasks that require high accuracy and tight tolerances.
        • When long tool life and durability are essential, even if the initial cost is higher.

        In summary, choosing between HSS and hard metal drill bits depends on the specific material, application requirements, and budget considerations. HSS drill bits are suitable for general-purpose drilling in softer materials, while hard metal drill bits are preferred for drilling hard and abrasive materials where durability and precision are paramount.

        hss drill bit vs hard metal drill bits
        hss drill bit vs hard metal drill bits

        What are the Advantages and Disadvantages of High-Speed Steel (HSS) Drill Bits and hard metal drill bits?

        It is undeniable that each drill bit material has its advantages and disadvantages.

        What are the advantages and disadvantages of High-Speed Steel (HSS) Drill Bits?:

        Advantages:

        1. Cost-Effectiveness: HSS drill bits are relatively inexpensive, making them suitable for applications with budget constraints.
        2. Versatility: They can be used for various materials, including wood, plastic, and softer metals like aluminum and brass.
        3. Ease of Machining: High-speed steel has good toughness and is easy to machine and sharpen.
        4. Suitable for Larger Hole Sizes: They can be used for drilling larger diameter holes.

        Disadvantages:

        1. Lower Wear Resistance: Compared to hard metal drill bits, they have lower wear resistance and are suitable for lighter cutting tasks.
        2. Limited Application Range: Not suitable for processing hard and highly wear-resistant materials such as stainless steel and cast iron.
        advantages-and-disadvantages-of-High-Speed-Steel-HSS-Drill-Bits
        advantages-and-disadvantages-of-High-Speed-Steel-HSS-Drill-Bits

        What are the advantages and disadvantages of hard metal drill bits?:

        Advantages:

        1. Exceptional Wear Resistance: hard metal drill bits have extremely high hardness and wear resistance, suitable for processing hard and highly wear-resistant materials like stainless steel, cast iron, and concrete.
        2. Longer Tool Life: Due to their wear resistance, carbide drill bits have a much longer lifespan than HSS drill bits, reducing replacement frequency and costs.
        3. High Precision: Carbide drill bits provide precise and accurate drilling, suitable for applications requiring high precision and strict requirements.

        Disadvantages:

        1. Higher Cost: The manufacturing cost of hard metal drill bits is higher, resulting in a higher price compared to HSS drill bits.
        2. Greater Brittle: Carbide materials are more brittle, making them prone to breakage under impact, requiring higher operational skills and environmental conditions.
        3. Not Suitable for Some Materials: Due to their brittleness, they are not suitable for processing some very fragile or brittle materials, such as glass and ceramics.
        advantages and disadvantages of hard metal drill bits
        advantages and disadvantages of hard metal drill bits

        In summary, high-speed steel drill bits and carbide drill bits have their own suitable applications. Maximizing Your Drilling Efficiency With The Right Material Selection.HSS drill bits are suitable for general cutting tasks and softer materials, while carbide drill bits are more suitable for processing hard and highly wear-resistant materials, requiring high precision and long tool life applications.

        1. High-speed steel (HSS or HS) is a subset of tool steels, commonly used as cutting tool material. ↩︎
        2. Cemented carbides are a class of hard materials used extensively for cutting tools, as well as in other industrial applications. ↩︎
        3. Cubic boron nitride (CBN or c-BN) is widely used as an abrasive. Its usefulness arises from its insolubility in iron, nickel, and related alloys at high temperatures, whereas diamond is soluble in these metals. ↩︎
        4. PCBN polycrystalline cubic boron nitride is used as a cutting material from which cutting inserts are manufactured for machining. ↩︎
        5. Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. ↩︎
        6. Molybdenum is a chemical element; it has symbol Mo (from Neo-Latin molybdaenum) and atomic number 42. ↩︎
        7. Chromium is a chemical element; it has symbol Cr and atomic number 24. ↩︎

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