Display of tools for metal cutting

Metal cutting tools: definition, classification, structure and application

In the field of mechanical manufacturing, metal cutting is a crucial process, and metal cutting tools are the core tools of this process. It directly affects the precision, efficiency and quality of processing, and plays a key role in the development of the manufacturing industry. This article will give a detailed introduction to the definition, classification, structure, application and development trend of metal cutting tools.

1. Definition and core role of mtal cutting tools

Metal cutting tools are mechanical processing tools that remove excess material from the workpiece through cutting motion to obtain the required shape, size and surface quality. It is the core equipment in the field of mechanical manufacturing and directly affects the processing efficiency, precision and cost. The cutting process depends on the relative motion between the tool and the workpiece, including the main motion (such as the rotation of the lathe workpiece) and the feed motion (such as the linear movement of the tool). The combined motion of the two determines the cutting trajectory and processing effect.

2. Classification of metal cutting tools

(1) Classification by processing technology

1) Turning tools:

Used for turning processing, they can be divided into external turning tools, end turning tools, internal turning tools, cutting turning tools, etc. External cylindrical turning tools are mainly used to process the outer cylindrical surface and outer conical surface of the workpiece; end turning tools are used to process the end surface of the workpiece; internal turning tools are used to process the inner hole of the workpiece; and cutting turning tools are used to cut or cut grooves out of the workpiece.

Different types of turning tools

2) Milling cutter:

It is suitable for milling processing, and there are many types, including end mills, face mills, slot mills, forming mills, thread mills, etc. End mills are mainly used to process planes, grooves and step surfaces; face mills are used to process larger planes; slot mills are used to process grooves of various shapes; forming mills are used to process forming surfaces, such as gear teeth, etc.; thread mills are used to process the thread shape of parts.

Different types of milling cutters

3) Drills:

It is mainly used for drilling processing, and common ones are twist drills, center drills, deep hole drills, etc. Twist drills are the most commonly used drills, used to process general holes; center drills are used to process the center holes of workpieces to provide positioning references for subsequent processing; deep hole drills are used to process holes with greater depth.

4) Reamer:

Used for reaming to improve the dimensional accuracy and surface quality of holes. Reamers are divided into hand reamers and machine reamers. Hand reamers are used for manual reaming, while machine reamers are installed on the spindle of the machine tool for reaming.

5) Broach:

Used for broaching, it can process through holes, planes and formed surfaces of various shapes. Broaches have high precision and efficiency, but their structure is complex and the cost is high.

6) Gear tools:

Specially used for processing gears, including gear milling cutters, gear hobs, gear shaping cutters, etc. Gear milling cutters are used to process spur gears and helical gears; gear hobs are used to process gears and worm gears; gear shaping cutters are used to process internal gears and duplex gears, etc.

(2) Classification by tool material

1) High-speed steel tools:

High-speed steel is a high-alloy tool steel containing alloy elements such as tungsten, molybdenum, chromium, and vanadium. It has high hardness, wear resistance and heat resistance, and can maintain good cutting performance when the cutting speed is not too high. High-speed steel tools have a simple manufacturing process, are easy to sharpen, and are relatively cheap. They are widely used in the processing of various small and medium-sized parts.

2) Carbide tools: 

Carbide is made of refractory metal carbides (such as tungsten carbide, titanium carbide, etc.) and metal binders (such as cobalt, nickel, etc.) through powder metallurgy. Carbide tools have high hardness, high wear resistance, and high heat resistance. The cutting speed is much higher than that of high-speed steel tools. They are suitable for processing materials with higher hardness and high-speed cutting.

The head part of the carbide tool

3) Ceramic tools: 

Ceramic tools are made of alumina, silicon nitride, etc. as the main raw materials, and are pressed and sintered. Ceramic tools have extremely high hardness and wear resistance, and are also very heat-resistant. They can be cut at high temperatures and are suitable for processing high-hardness materials such as hardened steel, high-speed steel, etc.

4) Superhard tools: 

Superhard tools include diamond tools and cubic boron nitride (CBN) tools. Diamond tools have extremely high hardness and wear resistance, and are mainly used for processing non-metallic materials and non-ferrous metals and their alloys; the hardness of cubic boron nitride tools is second only to diamond, and they have good heat resistance and chemical stability. They are suitable for processing hard steel, chilled cast iron and high-temperature alloys.

(3) Classification by tool structure

1) Integral tools:

The cutting part and the clamping part of the tool are integrated, usually made of high-speed steel or cemented carbide. The integral tool has a simple structure and is easy to manufacture, but the material utilization rate is low and the cost is high. It is suitable for small tools and tools with complex shapes.

2) Welded tools:

Tools made by welding carbide blades to the tool body. Welded tools have a compact structure and good rigidity, but stress and cracks are easily generated during the welding process, which affects the service life of the tool, and it is difficult to replace the blade after it is worn.

3) Machine clamped tools:

Tools that use mechanical clamping to fix the blade to the tool body. Machine clamped tools avoid the influence of welding stress, and the blade can be replaced after it is worn, which improves the service life and economy of the tool. They are widely used in various turning tools, milling cutters, etc.

4) Indexable tool: 

The indexable insert is mounted on the cutter body by mechanical clamping. When one cutting edge of the insert is worn, the insert can be rotated to an angle and another new cutting edge can be used to continue cutting. Indexable tools have the advantages of convenient insert replacement, saving tool change time, and improving processing efficiency. They are one of the most widely used tools in modern cutting processing.

The most widely used tool: indexable tool

3. Introduction to the structure of metal cutting tools

(1) Structural design

The structural design of metal cutting tools has a decisive influence on cutting performance. Its structure usually consists of two major parts: the cutter head and the tool holder, as follows: ​

Tool structure: tool head + handle

1) Cutting head: 

As the part directly involved in cutting work, it covers key parts such as the front cutting face, main back cutting face, secondary back cutting face, main cutting edge, secondary cutting edge and cutting tip. ​

● Front cutting face: It is the surface that the chips contact when they flow out. Its shape and roughness will affect the formation and discharge of chips. ​

● Main back cutting face and secondary back cutting face: They are opposite to the machining surface and the machined surface of the workpiece respectively, and play a key role in machining accuracy and surface quality.​

● Main cutting edge: undertakes the main cutting task. ​

● Secondary cutting edge: assists the main cutting edge to complete the material removal process. ​

● Tool tip: is the intersection of the main and secondary cutting edges. Its strength and wear resistance are directly related to the service life of the tool. ​

2) Tool holder:

Mainly used to fix the tool on the machine tool to ensure that the tool can stably transmit the cutting force and maintain the correct cutting position during the cutting process. Different types of machine tools need to be adapted to tool holders of different structures, such as common cylindrical shanks, tapered shanks, etc., to meet various processing needs.

(2) Tool clamping part

The tool clamping part is used to install the tool on the machine tool spindle or tool holder, and requires good rigidity and positioning accuracy. Common clamping methods include tapered shank clamping, straight shank clamping and machine clamping.

4. Application of metal cutting tools

Metal cutting tools are widely used in various mechanical manufacturing industries, such as automobile manufacturing, aerospace, shipbuilding, mold manufacturing, etc. In automobile manufacturing, it is necessary to process engine blocks, cylinder heads, crankshafts, gears and other parts. The processing of these parts cannot be separated from various metal cutting tools. In the field of aerospace, it is necessary to process difficult-to-process materials such as high-temperature alloys and titanium alloys, which puts higher requirements on the performance of the tools. In mold manufacturing, it is necessary to process various complex cavities and forming surfaces, which requires the tools to have high precision and high wear resistance.

Tool changes when machining parts

5. Development trend of metal cutting tools

(1) High precision

As the manufacturing industry has higher and higher requirements for processing accuracy, metal cutting tools are also developing in the direction of high precision. High-precision tools can achieve micron-level or even nanometer-level processing accuracy to meet the needs of precision processing.

(2) Efficiency

In order to improve processing efficiency and reduce production costs, metal cutting tools are constantly developing in the direction of high efficiency. The application of new technologies such as high-speed cutting and high-power cutting requires tools to have higher strength, wear resistance and heat resistance.

(3) Automation and intelligence

With the development of intelligent manufacturing, metal cutting tools are also gradually developing in the direction of automation and intelligence. Intelligent tools can monitor tool wear, cutting force and other parameters in real time, and automatically adjust processing parameters according to these parameters to achieve automation and intelligence of the processing process.

(4) Greening

With the increasing awareness of environmental protection, the green development of metal cutting tools has also become an inevitable trend. Green tools use environmentally friendly materials and manufacturing processes to reduce pollution to the environment, while increasing the service life of tools and reducing resource consumption.

6. Summary

In short, metal cutting tools are an indispensable key tool in mechanical manufacturing. With the continuous development of the manufacturing industry, higher requirements are placed on the performance and quality of metal cutting tools. In the future, metal cutting tools will continue to develop in the direction of high precision, high efficiency, automation, intelligence and greening, making greater contributions to the progress of the manufacturing industry.