A force transducer and circuit are used to detect the edge of a rotating grinding wheel. The force transducer produces an output signal indicative of a force applied thereto. The output signal is filtered by a high pass filter coupled to the output of the transducer. The amplitude of the filtered transducer output signal is compared to a reference value. An output pulse is produced if the amplitude reaches a predetermined level with respect to the reference value. A timer responsive to a first output pulse establishes a fixed interval during which the number of subsequent output pulses is counted. If the number of pulses counted during the fixed interval reaches a predetermined quantity, a control signal indicative of edge contact of the grinding tool with the force transducer is produced.