Sphericity deviation

Japanese: 真球度 - しんきゅうど（英語表記）sphericity deviation

The deviation of a ball from being a perfect sphericity is called sphericity, and is used for steel balls in rolling bearings. The magnitude of deviation is expressed using the same two-point method (diameter method) or three-point method as for roundness. In addition, there are also methods such as the radius method, which estimates the roundness from measurements of multiple cross sections using a roundness measuring instrument, and the method of expressing the deviation range of the top surface by holding the ball on a three-half surface or three-sphere seat. [Sawabe Masaji]

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

玉の真球からの狂いを真球度といい，転がり軸受の鋼球などに用いられている。真円度におけると同様な二点法(直径法)，三点法によって狂いの大きさを表す。このほかに，半径法として真円度測定器で多断面の真円度測定から推定する方法，三半面または三球座上に玉を保持して上面の変動幅で表す方法なども行われることがある。【沢辺雅二】

出典　株式会社平凡社世界大百科事典第２版について　情報

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