A tool is a tool used in machining for machining, also known as a cutting tool. Most of the tools are machine-made, but they are also used by hand. Since the tools used in mechanical manufacturing are basically used to cut metal materials, the term "tool" is generally understood to mean a metal cutting tool. The tool used to cut wood is called a woodworking tool. There is also a special type of tool for geological exploration, well drilling, and mine drilling, called mining tools.
The development of cutting tools plays an important role in the history of human progress. As early as 28 BC to 20 BC, copper knives such as cones, drills, and knives of brass cones and copper had appeared. In the late Warring States period (3rd century BC), copper cutters were made due to the mastery of carburizing technology. The drill bits and saws at the time were somewhat similar to modern flat drills and saws. However, the rapid development of the tool was developed in the late 18th century with the development of machines such as steam engines. In 1783, France's Rene first produced a milling cutter. In 1792, the British Mozley made taps and dies. The earliest literature on the invention of twist drills was recorded in 1822, but it was not produced until 1864. The tool at that time was made of integral high carbon tool steel with a cutting speed of about 5 m/min. In 1868, the British Mussett made alloy tool steel containing tungsten. In 1898, Taylor and the United States. White invented high speed tool steel. In 1923, Schletel of Germany invented cemented carbide. When using alloy tool steel, the cutting speed of the tool is increased to about 8 m/min, and when using high-speed steel, it is more than doubled. When using hard alloy, it is more than twice as high as that of high-speed steel. The surface quality and dimensional accuracy of the workpiece are also greatly improved. Due to the high price of high speed steel and hard alloy, the tool has a welded and mechanically clamped structure. Between 1949 and 1950, the United States began using indexable inserts on turning tools, and soon applied to milling cutters and other tools. In 1938, the German company Degussa obtained a patent on ceramic knives. In 1972, General Electric Company of the United States produced polycrystalline synthetic diamond and polycrystalline cubic boron nitride inserts. These non-metallic tool materials allow the tool to cut at higher speeds. In 1969, the Swedish Sandvik Steel Plant patented the production of titanium carbide coated carbide inserts by chemical vapor deposition. In 1972, Bangsa and Lagrange in the United States developed physical vapor deposition to coat hard surfaces of titanium carbide or titanium nitride on the surface of cemented carbide or high speed steel tools. The surface coating method combines the high strength and toughness of the base material with the high hardness and wear resistance of the surface layer, so that the composite material has better cutting performance.
The material used to make the tool must have high high temperature hardness and wear resistance, necessary bending strength, impact toughness and chemical inertness, good processability (cutting, forging and heat treatment, etc.) and not easily deformed. Generally, when the hardness of the material is high, the wear resistance is also high; when the bending strength is high, the impact toughness is also high. However, the higher the material hardness, the lower the bending strength and impact toughness. Due to its high flexural strength and impact toughness and good machinability, high-speed steel is still the most widely used tool material, followed by hard alloys. Polycrystalline cubic boron nitride is suitable for cutting high hardness hardened steel and hard cast iron; polycrystalline diamond is suitable for cutting iron-free metal, and alloy, plastic and glass steel; carbon tool steel and alloy tool steel are only used Tools such as trowels, dies and taps. Carbide indexable inserts have been coated with titanium carbide, titanium nitride, alumina hard or composite hard layers by chemical vapor deposition. The evolving physical vapor deposition method can be used not only for cemented carbide tools, but also for high speed steel tools such as drills, hobs, taps and milling cutters. As a barrier to chemical diffusion and heat conduction, the hard coating slows the wear of the tool during cutting, and the life of the coated blade is about 1 to 3 times higher than that of the uncoated one.
Choosing the right machining conditions has a considerable impact on the life of the tool. 1. Cutting mode (shun milling and up milling), the cutting vibration during down milling is smaller than the cutting vibration of up milling. The cutting thickness of the tool during down-cutting is reduced from the maximum to zero. After the tool is cut into the workpiece, there is no knives caused by cutting the chips. The rigidity of the process system is good and the cutting vibration is small. When cutting the thickness of the tool during the milling From zero to maximum, the cutting edge will be scratched on the surface of the workpiece due to the thin cutting thickness. At this time, if the cutting edge encounters hard spots in the graphite material or chip particles remaining on the surface of the workpiece, it will cause the tool. The knives or flutter, so the cutting vibration of the up-cut milling is large; 2. Blowing (or vacuuming) and impregnating EDM liquid processing, timely cleaning the graphite dust on the surface of the workpiece, is beneficial to reduce secondary wear of the tool, prolong the service life of the tool, and reduce the influence of graphite dust on the lead screw and guide rail of the machine; . Choose the right high speed and the corresponding large feed. In summary of the above points, the tool material, geometric angle, coating, edge reinforcement and machining conditions play different roles in the life of the tool, and they are indispensable and complementary. A good graphite tool should have a smooth graphite powder chip flute, long service life, deep engraving processing, and can save processing costs.
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