Various abrasives

　　Grinding tools are used for grinding, polishing, and finishing. Most grinding tools are artificial grinding tools made of abrasives and binders, while some are natural grinding tools made directly from natural minerals. In addition to being widely used in mechanical manufacturing and other metal processing industries, grinding tools are also used in food processing, papermaking, and the processing of non-metallic materials such as ceramics, glass, stone, plastics, rubber, and wood.

　　Grinding tool structures are roughly divided into three categories: dense, medium, and loose. Each category can be further subdivided into several grades, distinguished by a structure number. The larger the grinding tool structure number, the smaller the volume percentage of abrasives in the tool, and the wider the gap between the abrasive grains, indicating a looser structure. Conversely, a smaller structure number indicates a tighter structure. Tools with a looser structure are less prone to dulling during use, generate less heat during grinding, and can reduce workpiece heat deformation and burning. Tools with a tighter structure have abrasive grains that are less likely to fall off, which helps maintain the geometric shape of the tool.

　　During use, when the abrasive grains become dull, the abrasive grains partially fracture or the binder breaks, causing the abrasive grains to partially or completely fall off the tool. However, new cutting edges constantly appear on the working surface of the tool, or new sharp abrasive grains are constantly exposed, allowing the tool to maintain its cutting performance for a certain period of time. This self-sharpening property of grinding tools is a prominent feature compared to general cutting tools.

　　According to their raw material sources, grinding tools are divided into two categories: natural grinding tools and artificial grinding tools. The only natural grinding tool commonly used in the mechanical industry is oilstone. Artificial grinding tools are classified according to their basic shape and structural characteristics into five categories: grinding wheels, grinding heads, oilstones, and abrasive bricks (the latter three are collectively referred to as bonded abrasives) and coated abrasives. In addition, abrasives are also customarily classified as a type of grinding tool.