The hardness of the grinding wheel refers to the difficulty of the abrasive grains on the surface of the grinding wheel falling off under the action of the grinding force. A softer grinding wheel hardness means that the grinding wheel abrasive grains are easy to fall off, and a harder grinding wheel hardness means that the grinding wheel abrasive grains are not easy to fall off. Grinding wheel hardness and abrasive hardness are two different concepts. The same abrasive can be made into grinding wheels of different hardness, which mainly depends on the properties and dosage of the binder and the manufacturing process of the grinding wheel. The significant difference between grinding and cutting is that the grinding wheel has the "self-grinding" function. Choosing the hardness of the grinding wheel is actually choosing the self-grinding of the grinding wheel. It is hoped that the abrasive will not fall off or become dull prematurely.
The general principle for selecting the hardness of the white aluminum oxide grinding wheel and brown aluminum oxide grinding wheel is: when processing soft metals, in order to prevent the abrasive from falling off prematurely, a hard wheel is selected. When processing hard metals, in order to make the blunt surface abrasive grains fall off in time and expose new abrasive grains with sharp edges (i.e. self-grinding grains), a soft grinding wheel is selected. The former is because when grinding soft materials, the working abrasive of the white aluminum oxide grinding wheel and brown aluminum oxide grinding wheelwears slowly and does not need to fall off prematurely; the latter is because when grinding hard materials, the working abrasive of the white aluminum oxide grinding wheel and brown aluminum oxide grinding wheel wears faster and needs to be quickly updated. In precision grinding, in order to ensure grinding accuracy and roughness, a slightly harder white aluminum oxide grinding wheel and brown aluminum oxide grinding wheel should be selected. The workpiece material has poor thermal conductivity and is prone to burns and cracks (such as grinding carbide, etc.), the white aluminum oxide grinding wheel and brown aluminum oxide grinding wheel should be soft.
