This paper reports the effects of additives or the presence of polar radicals on the grinding ratio and the wearing process of the grinding wheel. Steel specimens were plane, being ground with 12 kinds of grinding fluids of emulsion type. These grinding fluids were prepared from spindle oil as the basic-oil and the activation agent as the emulsifying agent. In addition to these, sulphides, chlorides, and their compounds of polar radicals, as the additives, were respectively used. These experiments have revealed the following : The additives with polar radicals bring about the increase of the grinding ratio, but the deformation in the surface of the grinding wheel caused by cross feeding is independent of the use of them. Additives containing sulpher, on the other hand, cause the decrease of deformation. In the case of light grinding, the presence of polar radicals has nothing to do with avoiding the deformation in the profile of the wheel.