滚动轴承的理论旋转轴心线，对向心轴承即内圈轴心线，对推力轴承则指轴圈轴心线。
Rolling theoretical rotation axis line of the inner ring to the center axis line of bearings, thrust bearings on the shaft circle refers to the axis line.
圆锥滚子轴承内圈(外圈)的轴心线。
Tapered roller bearing inner ring (outer ring) of the axis line.
轴承内圈(轴圈)的基本圆柱孔或圆锥孔的内接圆柱体或内接圆锥体的轴心线。
Bearing inner ring (shaft circle) of the basic cylindrical hole or holes in the internal tapered cylinder or cone in the axis line access.
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