Deviation from roundness

Japanese: 真円度 - しんえんど（英語表記）deviation from roundness

Circularity is the amount of deviation of a circular feature from a geometrically correct circle. Its amount is expressed as the difference in radius between two concentric, geometrically correct circles when the circular feature is sandwiched between them and the distance between the two concentric circles is the smallest (Figure 1a). In addition, it can be expressed as the difference in radius between two geometric circles that are concentric with the center of the average circle of the circular feature obtained by the least squares method (Figure b), as the difference in radius between the center of a circle circumscribing the circular feature and a concentric inscribed circle (Figure c), or as the difference in radius between the center of a circle inscribed in the circular feature and a concentric circumscribing circle (Figure d), and the method is selected according to the conditions of use of the circular feature.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

真円度は円形形体の幾何学的に正しい円からの狂いの大きさである。その大きさは円形形体を二つの同心の幾何学的に正しい円で挟んだとき，同心2円の間隔が最小となるときの2円の半径差をもって表す(図1のa)。このほか，円形形体の最小二乗法で求めた平均円の中心と同心の二つの幾何学的円で挟んだ半径差で表す場合(図のb)，円形形体に外接する円の中心と同心の内接円との半径差で表す場合(図のc)，円形形体に内接する円の中心と同心の外接との半径差で表す場合(図のd)があり，円形形体の使用条件で選択される。

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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