During the grinding process there frequently occurs a lateral vibration of the rotating wheel. In this experiment that vibration was magnified under the microscope and measured on a rotating film. Many modes of vibration were ascertained experimentally, produced by irregularity of the journal of the main spindle; peripheral irregularity of the grinding wheel; a flexible main spindle; clearance in the main bearing; the driving-belt seam and the flapping vibration of the driving belt on the main spindle; a flexible workpiece; the deflection of a grinding machine, and so on. The causes and the characters of these vibrations and some preventative methods were investigated. It has been found that a plain bearing used as the main bearing of a grinder is superior to a ball bearing in so far as prevention of vibration of the wheel is concerned.