Single row ball slewing bearing are four point contact bearing, it has only one row of steel balls. They could bear axial load, radial load and tilting moment at the same time. One row four point contact ball slewing rings are composed of two seat rings, which design in compact structure and light weight, steel ball contact with the circular raceway at four points. There are three types of this kind of single row 4 points contact ball slewing bearing: without gear bearing (non tooth), external gear bearing (external tooth), and Internal gear bearing (internal tooth).