Meta Description:​ Learn the correct methods for fixing DB (back-to-back) and DF (face-to-face) paired bearings. Explore mounting techniques, preload considerations, and best practices for machine tool spindles. Introduction In high-precision machinery such as CNC machine tools​ and industrial gearboxes, single angular contact ball bearings often fall short. Due to their design, they can only handle axial loads in one direction. To manage complex combined loads, engineers frequently use paired angular contact ball bearings​ in DB (back-to-back) or DF (face-to-face) configurations. However, proper performance relies heavily on how these bearings are fixed and secured to the spindle. Incorrect mounting can lead to vibration, overheating, or premature failure. This guide covers the standard fixing methods and critical precautions for DB and DF arrangements. Common Methods for Fixing Paired Bearings (DB & DF) The goal of fixing a paired bearing set is to provide rigid axial location while maintaining the correct preload. Here are four widely used methods: 1. Shaft Shoulder and Housing Abutment (Locating) This is the most fundamental method. In both DB and DF setups: The inner ring is positioned against a shaft shoulder. The outer ring is supported by a housing shoulder. This ensures stable installation and prevents axial movement during operation. 2. Lock Nut Fixation Commonly found in spindle designs, one side of the bearing pair is located by the shaft shoulder, while the other side uses a lock nut. Benefit:​ It provides strong clamping force to secure the bearing and allows for precise adjustment of the preload​ to eliminate internal clearance. 3. Spacer Ring Fixation Used primarily in high-speed precision spindles, spacers are placed between or adjacent to the bearing rings. Function:​ By controlling the exact dimension of the spacer, you limit the bearing position and achieve the required pre-tension. Note:​ The machining accuracy of the spacer is critical; any error can cause noise and vibration. 4. Spring Preload Mechanism For high-speed motorized spindles, springs or disc springs (Belleville washers)​ are often used. Advantage:​ They compensate for thermal expansion of the spindle. Even if the shaft elongates due to heat, the spring maintains a relatively constant preload, reducing the risk of bearing seizure or overheating. Key Precautions When Mounting DB/DF Paired Bearings To ensure reliability, follow these technical guidelines: Consideration Technical Requirement Orientation Check​ DB​ means back-to-back (spreading contact lines); DF​ means face-to-face (converging contact lines). Ensure the contact angle direction matches the load requirements. Reversing them will compromise rigidity and load capacity. Preload Control​ Preload increases spindle rigidity but generates heat. The optimal preload varies by application. Always verify the specification through testing or manufacturer data. Cleanliness​ The mounting environment must be clean. Inspect shaft shoulders, housing bores, and spacers for burrs, chips, or nicks. Contamination will destroy running accuracy and surface finish. Conclusion Whether you choose a DB or DF configuration depends on your equipment's structural design and load profile. Correct fixation—whether via lock nuts, spacers, or spring systems—is essential for longevity. At Beining Technology, we specialize in manufacturing high-precision machine tool spindle bearings. If you encounter challenges with pairing, preload, or mounting, our engineering team is ready to assist. Need help selecting the right paired bearing? Contact Beining Technology  for expert support.

In the field of robotics, every gram of weight reduction and every millimeter of space saved directly impacts performance. As robots evolve toward lighter weight, higher precision, and greater flexibility, thin-walled angular contact ball bearings​ have become one of the standard core components in industrial robot and humanoid robot joint transmission systems. What Are Thin-Walled Angular Contact Ball Bearings? Thin-walled angular contact ball bearings are a specialized branch of thin-walled bearings, characterized by small cross-sectional dimensions, thin walls, and light weight. For bearings with the same inner diameter, the cross-sectional area of thin-walled series is only about 20% of that of standard bearings, and their weight is reduced by approximately 50% or more. Common series include 718, 719, and customized non-standard designs. Why Are They Ideal for Robots? Robots—whether collaborative robots, handling robots, or humanoid robots—require compact structures, high precision, and reliable load capacity. Thin-walled angular contact ball bearings offer four key advantages: 1. Lightweight Structure Joint weight directly affects servo motor load and energy consumption. These bearings reduce overall weight while maintaining load-bearing capacity, helping robots operate more efficiently. 2. Space-Saving Design Robot interiors are extremely compact. With thin sections and small outer dimensions, these bearings meet the miniaturization demands of modern robotic systems. 3. High Running Accuracy With an optimized contact angle design, manufacturing accuracy can reach P5 and P4 grades, ensuring repeat positioning accuracy and stable operation while minimizing errors during work cycles. 4. Composite Load Capacity Robot joints must simultaneously withstand radial forces, axial forces, and overturning moments. When properly paired, thin-walled angular contact ball bearings handle composite loads effectively. Combined with preload adjustment to minimize internal clearance, they enhance system rigidity—allowing robot arms to maintain micron-level repeat positioning accuracy even during high-speed movement. Typical Applications in Robotics Beyond use in robot reducers​ as high-precision transmission devices, thin-walled angular contact ball bearings are widely used in: Drive motors Robot joints End effectors They reliably handle complex working loads, reduce heat generation, and meet strict repeat positioning requirements across various robotic applications. Selection Considerations Although thin-walled angular contact ball bearings are suitable for most robots, careful evaluation of dimensional constraints, precision levels, and operating conditions is essential. Whether designing collaborative robots, palletizing robots, or humanoid robots, selecting the correct bearing model ensures optimal performance and long-term reliability. About Beining Technology​ Beining Technology specializes in the production of precision machine tool spindle bearings​ and high-performance thin-walled bearing solutions. We provide customized bearing products to meet the demanding needs of robotics, CNC machinery, and advanced automation systems.

Learn what bearing preload is, why it's critical for angular contact bearings, and the difference between factory and spring preload. Discover how to select the right preload for optimal rigidity and performance.  What is Bearing Preload? Bearing preload​ is a predetermined axial or radial force applied to eliminate internal clearance, creating a state of controlled "negative clearance." This intentional stress elastically deforms the raceways and rolling elements, locking them together to enhance performance. While standard radial bearings often operate with clearance, angular contact bearings​ require preload to maintain constant contact between the balls and raceway. Why Use Preload? Key Benefits Applying the correct preload optimizes bearing performance by: 1.Increasing Rigidity:​ Eliminates play, making assemblies stiffer for machine tool spindles. 2.Improving Accuracy:​ Ensures high running precision, even with changing loads. 3.Reducing Noise & Vibration:​ Prevents axial resonance, especially in small electric motors. 4.Preventing Skidding:​ Optimizes ball spin to reduce sliding friction and wear. Types of Bearing Preload: Factory vs. SpringChoosing the right preload method depends on your application's need for stiffness versus thermal stability. 1. Factory Preload (Built-in)Applied during manufacturing via a calculated axial offset between rings, labeled as Light, Medium, or Heavy. Pros:​ Extremely high rigidity; ideal for stable operating conditions.Cons:​ Sensitive to thermal expansion; requires precise mounting.Example:​ A GMN S6005 C bearing requires 130 N of force to achieve its Medium preload. 2. Spring Preload (External)Uses components like wavy washers or Belleville springs to apply continuous force. Pros:​ Excellent thermal compensation (force stays constant during shaft elongation); allows for looser housing tolerances.Cons:​ Less rigid than factory preload.Best For:​ Applications with significant temperature changes or where cost-effective housing machining is a priority. Feature Factory Preload Spring Preload Rigidity​ Very High Moderate / Flexible Thermal Compensation​ Poor Excellent Mounting Complexity​ High Precision Required More Forgiving How to Select the Right PreloadFollow these steps to choose the optimal preload for your application: 1.Define Requirements:​ Do you need maximum stiffness (e.g., grinding spindles) or precise positioning under light/variable loads? If yes, preload is necessary.2.Analyze Conditions: Temperature:​ If the shaft runs hotter than the housing, a back-to-back (DB)​ arrangement is less sensitive to thermal growth than a face-to-face (DF) setup.Speed:​ Spring preload is common for high speeds but verify it meets stiffness needs.3.Calculate Force (for Springs): Use the empirical formula to estimate the required preload force: F = k × d Where: F​ = Force (kN), d​ = Bore Diameter (mm), k​ = Factor (0.005–0.01 for motors; 0.02 for anti-vibration). Conclusion Proper bearing preload is essential for high-precision performance. Use Factory Preload​ for maximum rigidity and Spring Preload​ for superior thermal stability. Always validate your selection through testing to account for real-world operating conditions.