The particle size selection of the resin plate should consider factors such as the size of the workpiece, geometric accuracy, surface roughness, grinding efficiency, and how to avoid certain defects. Generally speaking, it is required to have high efficiency, large surface roughness value, large contact surface between the aluminum flat cutting disc and the workpiece, or grinding of the workpiece to the bevel of the workpiece, high toughness of the workpiece material, large elongation and processing of thin-walled workpieces. Some particle sizes; conversely, processing materials with high hardness, brittleness, and tight structure; when fine grinding, forming polishing, or high-speed grinding, a smaller particle size should be selected. The commonly used particle size is 46-80. The coarse-grained grinding disc is used for coarse grinding, and the fine-grained grinding disc is used for fine grinding. In addition, the end grinding should be coarser than the grinding of the circumferential grinding; the inner grinding should be more than the grinding of the outer grinding The particle size is coarse; the dry grinding should be coarser than the wet grinding wheel. The general principle of hardness selection of grinding discs is: grinding hard materials, soft grinding discs should be used to maintain good "self-sharpness", improve the service life of polishing discs, reduce grinding force and grinding heat; When softening the material, the hard grinding wheel should be used, which can keep the sharp edge of the abrasive grain for a long time, which is good for cutting. Details are as follows: 1. When grinding toughness, such as non-ferrous metal workpieces, high-hardness flat cutting disc on sale, grinding thin-walled parts and materials that have blocked polishing sheets, softer grinding discs should be used; super-soft grinding discs should be selected for mirror grinding. 2, the workpiece material is the same, longitudinal grinding and plunge grinding, peripheral grinding and end grinding, cylindrical grinding and inner circle, plane grinding, wet grinding in dry grinding, fine grinding in rough grinding, intermittent surface grinding For cutting and continuous surface grinding, the former must use a grinding disc that is harder than the latter. 3, high-speed, high-precision grinding, steel blank grinding, workpiece deburring, etc., should choose a harder grinding disc.