Basic knowledge of cutting tools, just read this article!( 一）

A good horse with a good saddle. Using advanced CNC machining equipment, if you use the wrong tool, it is useless! The selection of suitable tool materials has a great impact on tool life, processing efficiency, processing quality, and processing costs. This article provides real talent about cutting tool knowledge, follow and forward, let’s learn together.
Tool material should have basic properties
The choice of tool material has a great influence on tool life, processing efficiency, processing quality, and processing cost. When cutting tools are machining, they have to withstand high pressure, high temperature, friction, impact, and vibration. So, the tool material should have the following basic properties:

• Hardness and wear resistance. The hardness of the tool material must be higher than the hardness of the workpiece material, and it is generally required to be above 60HRC. The higher the hardness of the tool material, the better the wear resistance.

(2) Strength and toughness. The tool material should have high strength and toughness to withstand cutting force, impact, and vibration, and prevent brittle fracture and chipping of the tool.
(3) Heat resistance. The tool material has good heat resistance, can withstand high cutting temperatures, and has good oxidation resistance.
(4) Process performance and economy. The tool material should have good forging performance, heat treatment performance, welding performance; grinding performance, etc., and a high cost-performance ratio should be pursued.
Types, performance, characteristics, and applications of tool materials
1. Diamond tool material
Diamond is an allotrope of carbon. It is the hardest material found in nature. Diamond cutting tools have high hardness, high wear resistance, and high thermal conductivity, and are used in the processing of non-ferrous metals and non-metallic materials. Especially in the high-speed cutting of aluminum and silicon-aluminum alloys, diamond tools are the main types of cutting tools that are difficult to replace. Diamond tools that can achieve high efficiency, high stability, and long-life machining are indispensable and important tools in modern CNC machining.
⑴ Types of diamond tools
① Natural diamond tool: Natural diamond has been used as a cutting tool for hundreds of years. A natural single crystal diamond tool has been ground, the cutting edge can be sharpened, and the cutting edge radius can reach 0.002μm, which can realize ultra-thin cutting. It is a recognized, ideal, and irreplaceable ultra-precision machining tool to process high workpiece accuracy and low surface roughness.
② PCD diamond tools: Natural diamonds are expensive, and diamonds are used in cutting and processing are polycrystalline diamonds (PCD). Since the early 1970s, polycrystalline diamonds (PCD for short) prepared by high temperature and high-pressure synthesis technology have been developed After its success, natural diamond tools have been replaced by synthetic polycrystalline diamonds on many occasions. PCD has a rich source of raw materials, and its price is only one-tenth to one-tenth of that of natural diamond. PCD tools cannot produce sharp The cutting edge and the surface quality of processed workpieces are not as good as natural diamonds. It is not convenient to manufacture PCD blades with chip breakers in the industry. Thus, PCD can only be used for fine cutting of non-ferrous metals and non-metals, and it is difficult to achieve super Precision mirror cutting.
③ CVD diamond tools: Since the late 1970s to the early 1980s, CVD diamond technology has appeared in Japan. CVD diamond refers to the use of chemical vapor deposition (CVD) to synthesize a diamond film on a heterogeneous matrix (such as cemented carbide, ceramic, etc.). CVD diamond has the same structure and characteristics as natural diamond. Compared with natural diamonds, the performance of CVD diamonds is very close. It has the advantages of natural single crystal diamond and polycrystalline diamond (PCD), and overcomes their shortcomings to a certain extent.
⑵ Performance characteristics of diamond tools
① Very high hardness and wear resistance: Natural diamond is the hardest substance found in nature. Diamond has high wear resistance. When processing high-hardness materials, the life of diamond tools is 10-100 times that of cemented carbide tools or even hundreds of times.
② Has a very low coefficient of friction: The coefficient of friction between diamond and some non-ferrous metals is lower than that of other tools, the friction coefficient is low, the deformation is small during processing, and the cutting force can be reduced.
③ The cutting edge is very sharp: the cutting edge of the diamond tool can be sharpened, and the natural single crystal diamond tool can be as high as 0.002～0.008μm, which can perform ultra-thin cutting and ultra-precision machining.
④ It has high thermal conductivity: diamond has high thermal conductivity and thermal diffusivity, cutting heat is dissipated, and the temperature of the cutting part of the tool is low.
⑤ It has a low coefficient of thermal expansion: the coefficient of thermal expansion of diamond is several times smaller than that of cemented carbide. The tool size change caused by cutting heat is very small, which is especially important for precision and ultra-precision machining that requires high dimensional accuracy.
⑶ Application of diamond tools
Diamond tools are used for fine cutting and boring non-ferrous metals and non-metal materials at high speeds. Suitable for processing various wear-resistant non-metals, such as glass fiber reinforced plastic powder metallurgy blanks, ceramic materials, etc.; various wear-resistant non-ferrous metals, such as various silicon aluminum alloys; various non-ferrous metals finishing.
The disadvantage of diamond tools is poor thermal stability. When the cutting temperature exceeds 700℃～800℃, it will completely lose its hardness; besides, it is not suitable for cutting ferrous metals, because diamond (carbon) interacts with iron at high temperatures. Atomic action transforms carbon atoms into graphite structures, and the tool is damaged.
2. Cubic Boron Nitride (CBN) Tool Material
The second superhard material, cubic boron nitride (CBN), synthesized by a method like the diamond manufacturing method, is second only to diamond hardness and thermal conductivity. It has excellent thermal stability and can be heated to 10000C in the atmosphere. No oxidation occurs. CBN has stable chemical properties for ferrous metals and can be used in the processing of steel products
⑴ Types of Cubic Boron Nitride tools
Cubic boron nitride (CBN) is a substance that does not exist in nature. It is divided into single crystal and polycrystal, CBN single crystal and polycrystalline cubic born nitride (PCBN). CBN is one of the allotropes of boron nitride (BN), and its structure is like diamond.
PCBN (Polycrystalline Cubic Boron Nitride) is a polycrystalline material made by sintering fine CBN materials through bonding phases (TiC, TiN, Al, Ti, etc.) under high temperature and high pressure. It is currently the second only to synthesized hardness Diamond tool materials, which are referred to as superhard tool materials with diamond. PCBN is used to make knives or other tools.
PCBN cutting tools can be divided into integral PCBN Inserts and PCBN composite inserts sintered with cemented carbide.
The PCBN composite blade is made by sintering a layer of 0.5～1.0mm thick PCBN on a cemented carbide with better strength and toughness. Its performance has both better toughness and higher hardness and wears resistance. Solved the problems of low bending strength and welding difficulties of CBN blades.
⑵ The main properties and characteristics of CBN
Although the hardness of cubic boron nitride is inferior to diamond, it is much higher than other high hardness materials. The outstanding advantage of CBN is that the thermal stability is much higher than that of diamond, which can reach above 1200℃ (diamond is 700～800℃). Another outstanding advantage is that it is inert and does not react with iron at 1200～1300℃. The main performance characteristics of cubic boron nitride are as follows.
① High hardness and wear resistance: The crystal structure of CBN is like that of diamond, and the hardness and strength are like that of a diamond. PCBN is particularly suitable for processing high-hardness materials that could only be ground before and can get a better surface quality of the workpiece.
② It has high thermal stability: the heat resistance of CBN can reach 1400～1500℃, which is almost 1 times higher than the heat resistance of diamond (700～800℃). PCBN tools can cut high-temperature alloys and hardened steel at a speed 3 to 5 times higher than that of cemented carbide tools.
③ Excellent chemical stability: it does not have a chemical effect when it reaches 1200-1300℃ with iron-based materials, and will not wear as as diamond. Now, it can still maintain the hardness of cemented carbide; PCBN tools are suitable for cutting hardened steel Parts and chilled cast iron can be used in the high-speed cutting of cast iron.
④ Good thermal conductivity: Although the thermal conductivity of CBN is not as good as that of diamond, the thermal conductivity of PCBN is second only to diamond in various tool materials, and is much higher than that of high-speed steel and cemented carbide.
⑤ Has a low coefficient of friction: a low coefficient of friction can lead to a reduction in cutting force during cutting, lower cutting temperature, and improved surface quality.
⑶ Application of CBN
Cubic boron nitride is suitable for finishing various hard-to-cut materials such as hardened steel, hard cast iron, high-temperature alloys, hard alloys, and surface spraying materials. The machining accuracy can reach IT5 (hole is IT6), and the surface roughness value can be as small as Ra1.25～0.20μm.
Cubic boron nitride tool materials have poor toughness and bending strength. Therefore, cubic boron nitride turning tools are not suitable for rough machining at low speeds and large impact loads; at the same time, they are not suitable for cutting materials with high plasticity (such as aluminum alloys, copper alloys, nickel-based alloys, steel with high plasticity, etc.). Because cutting these metals will produce a serious built-up edge, which will deteriorate the machined surface.

• Ceramic tool materials

Ceramic tools have the characteristics of high hardness, good wear resistance, excellent heat resistance, and chemical stability, and are not easy to bond with metals. Ceramic tools occupy a very important position in CNC machining. Ceramic tools have become one of the main tools for high-speed cutting and processing of difficult-to-machine materials. Ceramic tools are used in high-speed cutting, dry cutting, hard cutting, and cutting of difficult-to-machine materials. Ceramic tools can process high-hard materials that cannot be processed by traditional tools at all, realizing “turning instead of grinding”; the optimal cutting speed of ceramic tools can be 2 to 10 times higher than that of cemented carbide tools, which improves the cutting production efficiency; The main raw materials used in ceramic tool materials are the most abundant elements in the earth’s crust. So, the promotion and application of ceramic tools is of great significance to increase productivity, reduce processing costs, and save strategic precious metals, and will also promote the development of cutting technology. progress.
⑴ Types of ceramic tool materials
The types of ceramic tool materials can generally be divided into three categories: alumina-based ceramics, silicon nitride-based ceramics, and composite silicon nitride-alumina-based ceramics. Among them, alumina-based and silicon nitride-based ceramic tool materials are the most used. The performance of silicon nitride-based ceramics is superior to that of alumina-based ceramics.
⑵ Performance and characteristics of ceramic tools
① High hardness and good wear resistance: Although the hardness of ceramic tools is not as high as that of PCD and PCBN, it is much higher than that of cemented carbide and high-speed steel tools, reaching 93-95HRA. Ceramic tools can process high-hard materials that are difficult to process with traditional tools and are suitable for high-speed cutting and hard cutting.
② Good high-temperature resistance and heat resistance: ceramic tools can still be cut at a high temperature above 1200°C. Ceramic tools have good high-temperature mechanical properties. A12O3 ceramic tools have particularly good oxidation resistance. The cutting edge can be used even if it is in a state of red heat. Thus, ceramic tools can achieve dry cutting, which can save cutting fluid.
③ Good chemical stability: Ceramic tools are not easy to bond with metal, and have good corrosion resistance and chemical stability, which can reduce the bonding wear of the tools.
④ Low coefficient of friction: The affinity of ceramic tools with metal is small, and the coefficient of friction is low, which can reduce cutting force and cutting temperature.
⑶ Application of Ceramic Cutting tools
Ceramics is one of the tool materials used for high-speed finishing and semi-finishing. Ceramic tools are suitable for cutting various cast irons (gray cast iron, ductile iron, malleable cast iron, chilled cast iron, high-alloy wear-resistant cast iron) and steel (carbon structural steel, alloy structural steel, high-strength steel, high-manganese steel, quenched steel) Etc.), can also be used to cut copper alloys, graphite, engineering plastics, and composite materials.
Ceramic tool materials have the problems of low bending strength and poor impact toughness, and they are not suitable for cutting at low speeds and impact loads.