Mainly related to surface roughness and productivity during machining. During rough grinding, the grinding allowance is large and the required surface roughness value is large. Therefore, coarser abrasive particles should be selected. Because the abrasive grains are coarse and the pores are large, the grinding depth can be larger, and the grinding wheel is not easily blocked and heated. During precision grinding, the allowance is small and a lower roughness value is required. Finer abrasive particles can be selected. Generally speaking, the finer the abrasive particles, the better the surface roughness during grinding.

Hardness and its selection

The hardness of a grinding wheel refers to the difficulty of the abrasive particles on the surface of the wheel falling off under the action of grinding force. The hardness of the grinding wheel is soft, indicating that the abrasive particles are easy to fall off, while the hardness of the grinding wheel is hard, indicating that the abrasive particles are difficult to fall off. The hardness of grinding wheels and the hardness of abrasives are two different concepts. The same type of abrasive can be made into grinding wheels with different hardness, which mainly depends on the performance and quantity of the binder, as well as the manufacturing process of the grinding wheel. The significant difference between grinding and cutting is that the grinding wheel has "self sharpening". Choosing the hardness of the grinding wheel is actually choosing the self sharpening of the grinding wheel, hoping that even sharp abrasive particles do not fall off too early, nor do they become dull and do not fall off. The general principle for selecting the hardness of grinding wheels is: when processing soft metals, in order to prevent the abrasive from falling off prematurely, a hard grinding wheel is selected. When processing hard metal, in order to timely remove blunt abrasive particles and expose new abrasive particles with sharp edges (i.e. self sharpening), soft grinding wheels are used. The former is because when grinding soft materials, the working abrasive wear of the grinding wheel is slow and does not need to detach too early; The latter is because when grinding hard materials, the working abrasive wear of the grinding wheel is faster and requires faster updates. During precision grinding, slightly harder grinding wheels should be used to ensure grinding accuracy and roughness. When the thermal conductivity of the workpiece material is poor and it is prone to burns and cracks (such as grinding hard alloys), the selected grinding wheel should be softer.

organization

The organization of a grinding wheel refers to the proportional relationship between the volume of the abrasive particles, binder, and pores that make up the grinding wheel. Classification is usually based on the percentage of abrasive particles in the volume of the grinding wheel. Grinding wheels have three organizational states: tight, medium, and loose; Subdivided into rooms 0-14, totaling 15 levels. The smaller the organization number, the larger the proportion of abrasive particles and the tighter the grinding wheel; On the contrary, the larger the organizational number, the smaller the proportion of abrasive particles, and the more loose the grinding wheel.

Shape, size and selection

According to the structure of the machine tool and the needs of grinding processing, grinding wheels are made into various shapes and sizes. Table 6 shows the commonly used shapes, sizes, codes, and uses of grinding wheels. The outer diameter of the grinding wheel should be selected as large as possible to improve the circumferential speed of the grinding wheel, which is beneficial for improving grinding productivity and surface roughness. In addition, under the conditions of allowable machine tool stiffness and power, selecting a wider grinding wheel can also improve productivity and reduce roughness. However, when grinding materials with high thermal sensitivity, to avoid burns and cracks on the surface of the workpiece, the width of the grinding wheel should be appropriately reduced.