Abstract: A method of and a device for measuring the radius of a grinding wheel during the rotation thereof, said grinding wheel being supported by at least one pivoting arm of predetermined length and urged against an object to be ground having predetermined dimensions, wherein the value of the angle formed between said pivoting arm in relation to a fixed direction is measured, and an electric signal in relation to the value of the measured angle is generated and fed to a computer together with electric signals corresponding to predetermined fixed parameters for generating from said signals an electric signal proportional to the radius of the grinding wheel. This invention is applicable notably to the control of the speed of rotation of the grinding wheel as a function of the radius thereof which decreases as a consequence of the normal wear of the grinding wheel.