The abrasive plays a cutting role in the abrasive tool. Bonding agents are materials that consolidate loose abrasives into abrasive tools, both inorganic and organic. Inorganic binders include ceramics, rhombohedral and sodium silicate; organic resins, rubber and shellac. The most commonly used are ceramic, resin and rubber binders.
The hardness of the abrasive tool mainly depends on the amount of the binder added and the density of the abrasive. The abrasive particles are easy to fall off, indicating that the hardness of the abrasive is low; otherwise, the hardness is high. The hardness grades are generally divided into seven levels: super soft, soft, medium soft, medium, medium hard, hard and super hard. From these levels, several small levels can be subdivided. The method for determining the hardness of the grinding tool is more commonly used by a hand cone method, a mechanical cone method, a Rockwell hardness tester method, and a sand blast hardness tester.
The hardness of the abrasive tool has a corresponding relationship with its dynamic elastic modulus, which is advantageous for determining the dynamic modulus of the abrasive tool by the audio method to indicate the hardness of the abrasive tool. In the grinding process, if the material of the workpiece to be ground is high in hardness, a grinding tool having a low hardness is generally used; and vice versa, a grinding tool having a high hardness is used.