HK should be a perforated single-sided sealed needle roller bearing, and the stamping outer ring is open at one end during processing (some companies have mature technology of direct stamping, the accuracy can meet the requirements, while others need to add grinding process to ensure the final processing accuracy). But at the end of the final installation, one end of the opening will be crimped, and the final shape is similar to the short cylindrical bearing with both ends of Nu and NJ. Therefore, during the final assembly, the positioning shoulder is not on the roller pin, but on the outside of the retaining edge of the base surface of the top during the processing. In addition, the shoulder step is generally not a horizontal plane, but an inclined plane that gradually rises from the center to the edge (the step surface of the profile is V-shaped, and the single side is at an angle of about 15 ° with the horizontal plane), and the part in contact with the bearing is rounded, that is to say The real contact with the bearing is the fillet part outside the shoulder step.