Abstract: A device for indicating the touching of a grinding wheel and a workpiece. On a shaft connected to a spindle of a grinding wheel there is fixed a radially slotted or gear wheel. On the shaft there is also rotatably mounted another identical slotted wheel, which is connected by means of a spring to the shaft, and a stable supporting plate provided with magnetic scanning heads situated over the respective gear wheels. The thus mounted slotted wheels, which are made of magnetic metal, such as steel, the scanning heads, and the phase meter function to detect changes in speed of the grinding wheel. The outputs of the scanning heads are connected to a phase meter, the output of which, after being amplified, controls the in-feed speed of the grinding wheel.

Abstract: A variable range gauge follower apparatus for measuring the diameter of work pieces comprising a pair of pivotable arms each having a contact at one end adapted to engage the surface of the work piece. Each of the arms has fixed to it for conjoint movement a segment member having an angular position Inductosyn at its circumferential edge. Associated with each Inductosyn is a magnet sensing head stationarily fixed so as to be able to sense the induced current as a function of the angular displacement of the segment. Means are provided for phase measurement of the two signals which when compared with a predetermined starting signal determines the angular change of the arms and thus the diameter of the work piece. The two arms are each mounted in a shaft journaled in a frame-like body and are coupled for conjoint rotation by a pair of meshing gears to establish an initial spacing or opening between the two arms. The gears are provided with means for their uncoupling during actual operation.