Preload Grades of the Ball Nut

Ball screws are high-precision transmission components known for their low noise, high transmission efficiency, and minimal 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 intentional application of an internal force within the ball nut—typically by selecting oversized balls or using spacers—to eliminate or reduce axial backlash in the ball screw assembly. 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 raises friction and heat generation—thereby reducing the ball screw assembly's service life and potentially increasing motor load—it is crucial to select the appropriate preload grade based on the application's actual 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 table lists the recommended preload grades for screws of various precision classes:

The following table lists the screw precision grades and preload grades of standard ball screw products offered by StepperOnline: