This type of bearing has a contact angle, so it is suitable for bearing axial loads in one direction or combined loads. Structurally, after bearing radial loads, axial separation occurs. Therefore, two bearings are usually used in opposition or two or more bearings are used in pairs. For single-row angular contact ball bearings, the rigidity can be improved by using the preloading method. Thus, it is suitable for the spindles of machine tools with high rotational accuracy. Generally, angular contact ball bearings with a contact angle of 30° (designated as A) and 40° (designated as B) use cages. However, depending on different conditions, synthetic resin cages or polyamide molded cages are also used.