为了保证双半外圈双列调心球轴承的预紧效果，对其预紧力的确定和预紧量的大小进行了分析计算。这种轴承结合了成对双联向心推力球轴承和双列向心调心球轴承的优点，既能实现大角度调心，调心角度达3°，又能进行轴向预紧。通过对这类轴承的力学分析，推导了轴向预紧力与轴承支撑负载的关系公式，而预紧量是通过控制两个半外圈之间的隔圈厚度进行调节的。基于弹性接触理论，推导了轴承定位隔圈磨削量大小的公式。将轴承用于LAMOST天文望远镜像场旋转轴中，对内径1 100 mm的轴承现场安装预紧调整后进行实测。测量结果表明，在任意50°范围内(旋转轴工作范围)，轴系径向跳动＜0.02 mm，端面跳动＜0.03 mm，满足了LAMOST对像场旋转轴系刚度和旋转精度的要求。跟星实测像场旋转精度RMS值优于0.3″。

The preload and precompact capacity of a two-piece outer ring self-aligning ball bearing are analyzed in this paper to ensure the preload effectivity. This bearing has the merits both from a double row angular contact ball bearing and a double row self-aligning ball bearing, so it not only can be preloaded to enhance stiffness, but also can self-align to compensate the misalignment. The maximum misalignment angle reaches 3°. In order to be preloaded properly, the outer ring is consisted of two spherical inner face raceways, which forms a spherical surface whose center is common to the bearing center and a in-between spacer. The preload is controlled by adjusting the thickness of the spacer. The relationship between preload and bearing supporting is analysed and formulated with the help of a mechanic theory. Meanwhile, based on the Hertz contact theory, the formula to determine the spacer thickness is given. This kind of bearing is adopted in a LAMOST telescope,test results show that the radial runout is less than 0.02 mm and axial runout is less than 0.03 mm for a φ1 100 mm bearing at an arbitrary angle of 50°. The tracking accuracy of focal rotation is better than 0.3″supported by this kind of bearings.