High-speed steel turning blades
High-speed steel turning tool blades are a common tool material used in machining. Made from high-speed steel, they are rolled, forged, and processed into long, rectangular blanks with defined cross-sections for tool sharpening. Due to their excellent toughness, wear resistance, and sharpening properties, high-speed steel turning tool blades play a crucial role in turning operations, particularly in low-speed cutting, complex tool manufacturing, and other applications requiring high tool toughness. Understanding the material properties, classification, specifications, sharpening methods, and application range of high-speed steel turning tool blades is crucial for the proper selection and use of high-speed steel turning tools.
The material properties of high-speed steel (HSS) turning tool inserts are the basis for their widespread application. High-speed steel (HSS) is a high-alloy tool steel containing tungsten, chromium, vanadium, and molybdenum, resulting in high hardness, wear resistance, and red hardness. At room temperature, HSS can achieve a hardness of HRC62-65, meeting the cutting requirements of general metal materials. At high temperatures (approximately 600°C), its hardness remains above HRC50, demonstrating excellent red hardness and enabling higher cutting speeds (typically 30-50 m/min). Compared to carbide, HSS offers greater toughness, stronger impact resistance, and a low chipping resistance, making it suitable for machining brittle materials or performing interrupted cuts. Furthermore, HSS’s excellent machinability allows for easy sharpening of cutting edges and produces workpieces with low surface roughness. This is a key reason for the widespread use of HSS turning tool inserts in both precision turning and form turning. Commonly used high-speed steel grades are W18Cr4V and W6Mo5Cr4V2. W18Cr4V has higher red hardness and wear resistance, while W6Mo5Cr4V2 has better toughness and grindability.
High-speed steel turning tool blades can be categorized in various ways, including rectangular, square, circular, and diamond-shaped cross-sections. Different cross-sectional shapes are suitable for different types of turning tools. Rectangular turning tool blades are the most widely used, suitable for producing external cylindrical turning tools and facing tools. Their cross-sectional dimensions are typically expressed as width × thickness, such as 12mm × 12mm or 16mm × 16mm. Square turning tool blades are suitable for making parting tools and grooving tools, and offer excellent symmetry and rigidity. Circular turning tool blades are suitable for making internal boring tools or forming tools, facilitating the grinding of complex cutting edge shapes. Diamond-shaped turning tool blades are suitable for angled turning tools, such as threading tools and worm gear tools, and their angles are designed to meet the tool’s geometric parameter requirements. Based on their application, they can be divided into general-purpose and specialized types. General-purpose high-speed steel turning tool blades are suitable for general turning operations, while specialized types are designed for specific processing requirements. For example, high-speed steel turning tool blades for threading have specific cross-sectional angles and dimensions.
High-speed steel turning tool blade specifications primarily include length, cross-sectional dimensions, and hardness. These parameters should be selected based on processing requirements and lathe model. Lengths typically range from 100mm, 150mm, and 200mm. Longer blades are suitable for larger lathes, allowing for greater reach; shorter blades are more rigid for smaller lathes. Cross-sectional dimensions directly impact tool rigidity and strength. For machining large-diameter workpieces or rough turning, blades with larger cross-sectional dimensions, such as 20mm x 20mm, should be selected. For machining small-diameter workpieces or finish turning, blades with smaller cross-sectional dimensions, such as 8mm x 8mm, can be selected. Hardness is a key performance indicator for high-speed steel turning tool blades, generally requiring HRC 62-65. Insufficient hardness will result in rapid tool wear, impacting machining efficiency and surface quality. Excessive hardness will increase tool brittleness and lead to chipping. When selecting high-speed steel turning tool blades, the surface quality should be inspected. The surface should be smooth, crack-free, and free of scale to ensure tool quality after sharpening.
Sharpening high-speed steel turning tool blades is a critical process for achieving the desired tool shape and geometry. The quality of sharpening directly impacts the tool’s cutting performance and machining quality. Sharpening is typically performed on a tool grinder using aluminum oxide or silicon carbide grinding wheels. For rough grinding, a coarser-grit wheel (such as 46#) is used to improve sharpening efficiency; for fine grinding, a finer-grit wheel (such as 80# or 120#) is used to ensure cutting edge sharpness and surface finish. During sharpening, tool geometric parameters, such as rake angle, clearance angle, and lead angle, must meet design requirements. These parameters should be determined based on the material being machined and the processing requirements. For example, when machining plastic materials, a larger rake angle (10°-15°) is recommended to reduce cutting forces and chip deformation; when machining brittle materials, a smaller rake angle (0°-5°) is recommended to increase tool strength. During sharpening, the tool should be continuously cooled to prevent annealing and hardness loss caused by high temperatures. Emulsions or water are typically used for cooling. The cutting edge of the tool after sharpening should be straight and sharp, without chipping or burrs. The sharpening quality can be checked by visual inspection or with a magnifying glass.
High-speed steel (HSS) turning tool inserts have a wide range of applications, suitable for turning a variety of metal materials, including carbon steel, alloy steel, cast iron, and non-ferrous metals. When machining carbon and alloy steels, tools made with HSS blades achieve superior surface quality and efficiency. When machining brittle materials like cast iron, HSS blades offer advantages over carbide tools due to their superior toughness and resistance to chipping. When machining non-ferrous metals such as copper and aluminum, HSS blades prevent tool sticking and maintain surface finish. HSS blades are particularly well-suited for single-piece, low-volume production, repair work, and turning complex formed surfaces, such as threads, worm gears, and profiled surfaces, as they are easily sharpened to create complex cutting edge geometries. However, HSS blades also suffer from the limitation of lower cutting speeds, making them less efficient than carbide tools in high-volume production or high-speed cutting applications. Overall, however, HSS blades, due to their excellent overall performance, continue to play an irreplaceable role in machining.
