As a bearing application engineer, one of the most common questions I receive from end users and distributors is: What types of bearings are used for ball screws, and how should they be configured? In this guide, I’ll walk you through the essential bearing types used in ball screw support, the logic behind bearing configuration at each end of the screw, and the practical selection guidelines that I’ve developed over years of field application and failure analysis.

Why Bearing Selection Matters in Ball Screw Systems

Ball screws are designed to convert rotary motion into linear movement with exceptional accuracy and efficiency. However, if the screw is not supported correctly at both ends, issues such as vibration, backlash, poor repeatability, and even mechanical failure can occur. Bearings must not only carry the loads applied to the system but also maintain alignment, compensate for thermal expansion, and provide the correct level of axial stiffness.

Common Bearing Types for Ball Screws

Here are the four primary bearing types used in ball screw assemblies, each with its functional advantages and ideal use cases:

1. Angular Contact Ball Bearings (ACBBs)

• Purpose: Carry axial loads in one direction and high radial loads.
• Configurations: Often used in back-to-back (DB) or face-to-face (DF) pairs, or in a tandem (DT) set when heavy axial load support is needed in one direction.
• Typical Position: Fixed end (drive end) of the screw.

I often specify matched angular contact bearings with 15°–30° contact angles. The higher the angle, the better the axial load capacity. Preloaded ACBB pairs increase system rigidity and reduce axial play.

2. Deep Groove Ball Bearings (DGBBs)

• Function: Handle radial loads and moderate axial loads in both directions.
• Advantages: Economical, compact, quiet, and suitable for higher speeds.
• Application: Ideal for the floating (non-drive) end to allow axial expansion. Also used at both ends in lightweight, low-cost systems.

I often use DGBBs in automation equipment, light-duty ball screw stages, or where cost efficiency and simplicity are critical.

3. Thrust Ball Bearings

• Purpose: Handle axial loads only; not ideal for radial loads.
• Limitations: Not suitable for high-speed or high-radial-load applications.
• Use Case: Low-cost applications where axial loads are dominant, and speed is low.

I rarely recommend these in precision ball screw systems unless cost and simplicity override all other design concerns.

4. Tapered Roller Bearings

• Purpose: High axial and radial load capacity; very rigid.
• Use Case: Heavy-duty machine tools and large ball screw assemblies.

Tapered rollers are ideal for systems that experience high impact loads or need maximum stiffness. However, they come with larger space requirements and more complex preload adjustments.

Ball Screw Bearing Configurations: Fixed vs Floating

To ensure stable axial positioning and thermal compensation, both ends of the ball screw must be supported with specific bearing configurations. I generally divide them into fixed end and floating end.

Fixed Support (Drive End)

This end secures both axial and radial movement. It ensures positioning accuracy and absorbs the primary loads from the nut and motor drive.

Recommended bearing setups:

• Duplex or triplex ACBBs (DB, DF, or DT arrangements)
• Preloaded pairs for zero axial play
• Alternatively: DGBBs for simple or light-load designs

For critical machines like CNC lathes or milling machines, I usually use high-precision P4/P2 class ACBBs with a back-to-back configuration for enhanced moment load resistance.

Floating Support (Opposite End)

The floating end accommodates thermal expansion along the ball screw shaft during operation. It must not resist axial growth.

Recommended bearing setups:

• Single deep groove ball bearing
• Cylindrical roller bearing with loose axial fit
• Single angular contact bearing without preload

The goal is to allow free axial movement while maintaining radial support. For compact equipment or general automation, deep groove ball bearings are often my go-to choice due to their low friction and simplicity.

Application Examples

My Best Practices and Selection Tips

• Use high-contact-angle ACBBs where high axial load or stiffness is required.
• Avoid double-fixed ends—always designate one end as floating to prevent thermal stress.
• Deep groove bearings are reliable, low-cost options for floating ends and general automation.
• Preload is essential—the right preload ensures rigidity and eliminates backlash, but excessive preload reduces bearing life.
• Bearing precision matters—match the bearing grade (P4 or P2) with the accuracy of the ball screw and the application’s requirements.

Final Thoughts

Choosing the right bearing type and configuration for a ball screw is not a one-size-fits-all decision. It depends on your machine’s load requirements, accuracy needs, operating speed, and even environmental conditions. As a bearing application engineer, I’ve seen firsthand how a properly designed support system can dramatically improve machine performance—and how a poor one can quickly lead to costly downtime.

If you’re a distributor or end user unsure about how to configure your system, consult with your bearing supplier’s technical team. Proper bearing selection is an investment in long-term reliability.