INSTRUMENT FOR MEASURING DEVIATION VALUE OF CENTROID POSITION IN RADIUS DIRECTION OF ROTARY CENTER AXIS OF CYLINDRICAL BODY

PURPOSE:To measure the deviation value of a centroid position in the radius direction of the rotary center axis of a cylindrical body by finding out the coordinates of the rotary centroid of the cylindrical body. CONSTITUTION:Driving chucks 2, 3 are fitted to both the ends of the thin cylindrical body 1 and supported by two rollers each. The center of the chuck 2 is coupled with a driving device 6 through a universal joint 4, an angle detector 7 for measuring the turning angle of the cylindrical body 1 is fitted to the device and a thickness measuring sensor 9 is fitted to the external surface of the cylindrical body 1. The deviation delta and thickness (t) of the external size between a reference circle 12 and the cylindrical body 1 which corresponds to the positional angle theta measured by the angle detector 7 are measured by a deviation measuring device 8 having a sensor contacted with the external surface of the cylindrical body 1 and to be reciprocated in accordance with the deviation of the centroid position based upon the shape error and positional shift of the cylindrical body 1 at respective measuring point (i) obtained by dividing the outer periphery of the cylindrical body 1 into n parts and the coordinates Zo, Yo of the centroid G to the center B of the reference circle 12 are calculated. Consequently, the deviation of the radius direction from the rotary center shaft at an optional position in a longitudinal direction can be found out.