Preload Grade of the Ball Nut

Ball screws are a type of high-precision screw known for their high accuracy, low noise, high transmission efficiency, and small axial backlash, making them suitable for applications with demanding precision requirements.

To further minimize the axial backlash of a ball screw, it is common practice to increase the preload grade of the ball nut.

Preload refers to the adjustment of the ball size within the nut to eliminate or reduce the axial backlash in the ball screw. Preload is typically categorized into four grades: P0, P1, P2, and P3. The following table details the corresponding axial backlash and preload force for each grade.

As shown in the table, the preload force increases with a higher preload grade. Since an increased preload force can reduce the motor's service life, it is crucial to select the appropriate preload grade based on the screw's actual application requirements, thereby striking a balance between acceptable axial backlash and operational lifespan.

Furthermore, the precision grade of the screw must also be considered when selecting a preload grade. Different precision grades correspond to different recommended preload grades. The following are the recommended preload grades for screws of various precision classes:

The following are the screw accuracy and preload grades of conventional ball screw products provided by StepperOnline:

Updated on: 23/09/2025