本文用《结构力学》中“影响系数”的概念来列写三支承主轴组件在外力作用下,引起的轴端径向位移和前轴承处转角的计算公式;论正了三支承影响系数小于二支承影响系数,从而说明三支承主轴组件的刚度大于两支承;文章还对中支承设在何处为合理,进行了初步的探讨. 目前随着对主轴组件精度和刚度要求的提高,三支承结构的主轴组件逐渐得到应用,如CA6140车床主轴组件便是三支承的一个实例. In this paper, the concept of “influence coefficient” in “structural mechanics” is used to list the formulas for calculating the radial displacement of shaft end and the corner of front bearing under the action of external force. Bearing coefficient of influence, so that the stiffness of the three support shaft assembly is greater than two bearings; article also on the middle support is reasonable, conducted a preliminary discussion.At present with the spindle assembly accuracy and stiffness requirements increased, the three support structure Of the spindle assembly has gradually been applied, such as CA6140 lathe spindle assembly is an example of three bearings.