Common types of cutting knives
In metal cutting, cut-off cutters are essential tools for cutting or grooving workpieces. Their performance directly impacts machining efficiency, cut quality, and tool life. Common cut-off cutters are categorized into various types based on various classification criteria, each with its own unique structural characteristics and application range. Understanding the types and characteristics of these cut-off cutters is crucial for optimal tool selection and optimized machining processes. Whether on lathes, milling machines, or other machining equipment, cut-off cutters play an indispensable role. Their design and selection require comprehensive consideration of multiple factors, including the workpiece material, shape, size, and machining requirements.
Common cut-off knives, categorized by tool material, include high-speed steel (HSS), carbide, and ceramic. High-speed steel (HSS) cut-off knives offer high strength and toughness, can withstand significant impact loads, are easy to sharpen, and maintain a sharp edge. They are suitable for lower cutting speeds and softer workpieces, such as mild steel and non-ferrous metals. However, their disadvantage is their poor heat resistance and prone to wear at high cutting speeds. Therefore, they are typically used on slow-speed manual lathes or in applications where cut quality is less critical. Carbide cut-off knives, on the other hand, are widely used for high-speed cutting and for cutting difficult-to-cut materials, such as high-carbon steel, alloy steel, and cast iron, due to their high hardness, high wear resistance, and excellent heat resistance. They can achieve cutting speeds several times that of HSS, significantly improving machining efficiency. However, they have lower toughness and poor impact resistance, and should be used to avoid severe vibration and shock. Ceramic cut-off knives offer greater hardness and heat resistance, enabling them to operate at extremely high cutting speeds. They are suitable for cutting hard materials and high-temperature alloys, but they are more brittle and are generally used in automated machining where high precision and stable cutting conditions are required.
Based on their structural type, cut-off knives can be categorized as integral, welded, and mechanically clamped. Integral cut-off knives are made from a single piece of high-speed steel or carbide, offering a simple structure, ease of manufacturing, and low cost. They are suitable for cutting or grooving small workpieces. However, due to low tool material utilization and significant dimensional change after sharpening, they are often used in single-piece, small-batch production. Welded cut-off knives, made by welding a carbide blade to a standard structural steel shank, combine the high wear resistance of carbide with the high strength of the steel shank. They are reasonably priced and widely used. However, the welding process can easily generate internal stress, leading to blade cracking and shortening tool life. Furthermore, it is difficult to maintain a consistent blade angle after sharpening. Mechanically clamped cut-off knives use a mechanical device to secure an indexable blade to the shank. When the blade is worn, it can be directly indexed or replaced without resharpening, significantly improving tool replacement efficiency and reducing auxiliary time. Furthermore, the shank is reusable, resulting in high blade material utilization, making it suitable for high-volume production and automated processing. It represents a type of cut-off knife with promising application prospects.
Based on their application, parting knives can be divided into standard parting knives and grooving knives. Standard parting knives are primarily used to separate workpieces from blanks. Their blade width is relatively narrow, typically 2-6mm, and the head length must be slightly larger than the workpiece radius to ensure complete severing. Grooving knives are used to create grooves of various widths and depths on the workpiece surface. Depending on the shape and location of the grooves, they can be categorized as external grooving knives, internal grooving knives, and face grooving knives. External grooving knives are used to cut grooves on the outer surface of a workpiece. Their blade structure is similar to that of standard parting knives, but the blade width is determined by the required groove width. Internal grooving knives, used to cut grooves on the inner surface of a workpiece, have slender toolholders that require sufficient rigidity to prevent vibration during machining. Face grooving knives, used to cut grooves on the end face of a workpiece, have blades oriented perpendicular to the workpiece end face, and the toolholder structure must accommodate the space requirements for end-face machining. These different parting knives have different structural design emphases to meet different processing requirements.
In addition, there are some special types of cutting knives, such as arc-shaped cutting knives and wavy-edge cutting knives. The blade of the arc-shaped cutting knife is arc-shaped. During the cutting process, the contact point between the blade and the workpiece constantly changes, which can reduce the fluctuation of cutting force, reduce vibration, and improve the surface quality of the cut. It is suitable for cutting large-diameter workpieces. The blade of the wavy-edge cutting knife has a wavy chip groove, which can divide the chips into small fragments, facilitate chip removal, and avoid chip blockage and damage to the tool and workpiece. It is suitable for cutting plastic materials. These specially structured cutting knives have excellent performance in specific processing situations by optimizing the blade shape and chip removal performance, providing an effective solution to complex cutting problems. With the continuous development of processing technology, the types of new cutting knives are still increasing, and their performance is also continuously improving to meet increasingly high processing requirements.
