JPH0451761B

PURPOSE: To make remote measurement convenient by measuring the change of the distance between the center of a sphere segment and a conical recessed bottom surface caused by the contact with the conical recessed bottom surface by a length gauge. CONSTITUTION: The gauge S has a sphere segment 70 and the segment 70 is constituted of a part of a sphere formed so as to contain the parts of certain width on both sides of the circular contact line 72 with a conical recessed bottom surface 40. When the gauge S comes into contact with the bottom surface 40 of a control rod driving housing H, the gauge S is rotated up to an azimuth angle position selected for measurement at first and subsequently shaken with respect to the bottom surface as shown by an arrow. The min. dimension reading value of a length gauge 60 during this shaking motion is recorded and the position where this value is obtained is the contact point between a contact circle 72 and the bottom surface 40. When one measurement is completed, the gauge S is rotated to a next new azimuth angle position and, continuously, the segment 70 is shaken within a vertical plane in the same way and, by performing a series of these measurements, the roundness of the recessed bottom surface 40 provided to the top part of the control rod driving housing H can be inspected in detail.