
The apparatus comprises a bifurcated head rotatably mounted upon a spring loaded arm. The head has two edge plates which can be brought into tangential contact with the periphery of a rotating object. When the head is brought into contact with objects of different diameters, the points of contact with the edge plates progress along location locus lines which, when produced, intersect an an apex. A displacement transducer mounted upon the head has a spring loaded plunger with a probe which is con...











