Abrasives are made from natural and synthetic abrasives abrasive composition, commonly used natural abrasives are corundum, emery. Artificial abrasives are ordinary alumina, white aluminum oxide, black silicon carbide, green silicon carbide. The size of the abrasive particles  metal grinding wheel called wheel size. Particles in the work surface of the grinding wheel and cutting due to friction, wear and tear will gradually become dull, the grinding resistance when the particles and the binding agent exceeds the adhesive force between the particles began to fall off, and replaced by a new sharp particles. So wheel with automatic sharpening performance. But the combination of agents should not be too strong adhesive force, such as the solid particles become too blunt still attached to the wheel surface, the wheel will lose the grinding action. Further, since the grinding wheel and the 4 inch circular saw blade  workpiece to be ground with great friction heat, binders easily softened. By grinding metal material end with adhesive binder filled in the gap between the sand where the grinding wheel stopper reality. If you use this plug real wheel continues to work, not only efficiency is quite low, grinding and cutting tools can also be caused by annealing becomes blue. The other hand, if the bond is not firmly bonded particles, then the particle hole saw blades  has not yet become pure grinding between them will also fall off, so that the transmission line sand abrasion fast, easy deformation, need regular trimming. There are three commonly used binders wheel: vitrified (clay binding agent), the rubber binder resin binding agent.