What is a Thin-Walled Four-Point Contact Ball Bearing

What is Thin-Walled Four-Point Contact Ball Bearing

Four-point contact ball bearings are a kind of separable bearings, which can also be said to be a set of foot contact ball bearings that can bear bidirectional axial loads. The inner and outer ring raceways are peach-shaped cross-sections, and when there is no load or pure radial load, the steel ball and the ferrule are in four-point contact, which is also the origin of this name. When only the pure axial load is acted, the steel ball and the ferrule become two points of contact, which can withstand the axial load in both directions. Four-point contact ball bearings can also withstand moment loads and function as both single-row angular contact ball bearings and double-row angular contact ball bearings. A bearing series is based on a single cross-section that remains constant as the bore diameter increases, resulting in significant space and weight savings. Bearings are available in metric or imperial main sizes. Depending on the design and series, bearings can be chemically and corrosion-resistant.

Features of Thin-Walled Four-Point Contact Ball Bearings

Due to its unique design and performance advantages, thin-walled four-point contact ball bearings are widely used in high-precision, lightweight and complex load scenarios. The following is a detailed analysis of its characteristics from multiple dimensions such as structure, mechanical properties, and material technology:

1. Thin-walled design: lightweight and compact

Structural features:

The inner and outer rings are designed with extremely thin sections, and the cross-sectional height is usually only 20%~50% of the standard bearing (for example, the cross-sectional height of thin-walled bearings with an inner diameter of 30mm may only be 3~5mm).

By optimizing the wall thickness distribution, such as asymmetrical trench design, the structural strength is maintained while reducing weight.

Advantage:

Lightweight: The weight is reduced by 30%~60% compared with standard bearings, and it is suitable for weight-sensitive equipment such as robot joints and drones.

Space-saving: The thin-walled design can be embedded in tight installation spaces, such as inside medical instruments or in the precision adjustment mechanism of optical devices.

Material Compensation:

High-strength materials, such as aerospace-grade stainless steel or carburized steel, are used to compensate for the strength loss of thin-walled structures and ensure load-bearing capacity.

2. Four-point contact structure: multi-directional load carrying capacity

Contact angle and load distribution:

The contact point between the steel ball and the inner and outer ring grooves is symmetrically distributed at four points (the contact angle is usually 30°~45°), forming a two-way axial load channel.

Each steel ball is in contact with the inner and outer rings at two points at the same time, and can bear the combined effect of two-way axial load, radial load and overturning moment.

Mechanical advantages:

Two-way axial loading: It can withstand positive and negative axial forces without pairing installation, simplifying the structural design.

Anti-overturning ability: Four-point contact forms a torque support, which is suitable for scenarios that are prone to overturning moment, such as turntables and the end of the robotic arm.

Compared with ordinary bearings:

Single-row angular contact ball bearings can only withstand one-way axial forces, while four-point contact bearings can replace "back-to-back" mating bearings, saving more than 50% of space.

3. High load-bearing capacity and rigidity

Load Type:

Axial load: The four-point contact design increases the axial load capacity to 2~3 times that of ordinary deep groove ball bearings.

Radial load: By optimizing the radius of curvature of the groove, the radial load carrying capacity is close to the level of deep groove ball bearings.

Moment load: Able to withstand overturning moments (e.g., torsional forces when the robot's wrist rotates).

Stiffness Enhancement:

Groove geometry optimization: Ellipse or arc groove design increases the contact area and reduces stress concentration.

Preload design: Some models are preset with a slight negative clearance (preload) at the factory to improve rigidity and reduce operating vibration.

4. Low friction and high speed performance

Friction Control:

The steel ball adopts high-precision G5 grade (diameter tolerance± 0.5μm), and the surface roughness Ra≤0.02μm reduces rolling resistance.

The cage material can be nylon (PA66), copper alloy or phenolic resin to reduce sliding friction with the steel ball.

High-speed adaptability:

The ultimate speed can be up to 1.5 times that of ordinary bearings (e.g. 8000 rpm for 50mm inner diameter bearings).

The temperature rise is low at high speed, and it is suitable for long-term operation equipment such as CT machine rotating bracket.

5. Ease of installation and maintenance

Simplified Installation:

The four-point contact structure comes with preload, so there is no need to adjust the clearance on site (contrast angular contact bearings need to be mated and preloaded).

The flatness of the mounting surface (recommended ≤ 0.02mm) should be strictly controlled for thin-walled design to avoid bearing jamming caused by deformation.

Lubrication & Sealing:

Lubricating grease (such as Krytox fluorogrease for high-speed, temperature resistance -50°C~200°C) or optional lifetime maintenance-free design.

Sealing options include rubber contact seals (dustproof) or non-contact labyrinth seals (low friction).

6. Materials and manufacturing processes

Material Selection:

Stainless steel: 440C (HRC58~62) is used in corrosive environments (such as medical, food equipment).

High-carbon chromium steel: GCr15 (HRC60~64) is suitable for high-load scenarios, and the surface needs to be galvanized or phosphated to prevent rust.

Precision machining:

The inner and outer rings are processed by CNC grinding machine, and the groove profile error is ≤2μm.

Heat treatment processes (e.g. vacuum quenching) ensure material homogeneity and avoid deformation of thin walls.

7. Application Adaptability

Extreme Environment Adaptability:

Vacuum environment: non-volatile grease is used to avoid contamination (e.g. satellite antenna drive mechanism).

High Temperature/Low Temperature: Ceramic ball (Si3N4) replaces steel ball, and the temperature resistance range is extended to -150°C~300°C.

Industry Customization:

Medical grade: ISO 13485 certified, biocompatible material.

Military-grade: redundant design to withstand shock loads (e.g. drone landing gear).

8. Other key features

Lifetime & Reliability:

The calculated life of dynamic load (L10) can reach tens of thousands of hours (e.g. 50,000 hours @3000rpm).

The failure mode is mainly fatigue spalling, and there is no risk of sudden fracture under non-extreme working conditions.

Noise Control:

The operating noise is ≤ 45dB (A-weighted), making it suitable for quiet environments such as optical inspection equipment.

Thin-walled four-point contact ball bearings achieve a balance between multi-directional load bearing, high-speed operation and compact installation through four-point contact design, thin-walled lightweight structure and high-precision manufacturing process. The core benefits are simplifying system design (replacing multi-bearing combinations) and improving machine performance (e.g. flexibility and precision of robot joints). Consideration should be given to the type of load, environmental compatibility and the technical support capabilities of the supplier to ensure the best fit and application life.

Applications for Thin-Walled Four-Point Contact Ball Bearings

Industrial automation

Robotic joint drives, such as robotic arm rotary joints, enable flexible movements in tight spaces due to their high precision and light weight.

Hollow rotating platform, direct drive turntable and other equipment support high-speed rotation and high rigidity requirements.

Medical equipment

Medical CT machines rotate frames and surgical robots to withstand compound loads and maintain stable operation.

Dental equipment, such as high-speed dental drills, requires low friction and high precision.

Aerospace

The aircraft flap retraction system and radar antenna rotation mechanism meet the requirements of light weight and high reliability.

Guidance systems and drone components need to adapt to stable operation in extreme environments.

Precision instruments and optical equipment

Optical imaging equipment and rotary encoders ensure high-precision positioning and low vibration.

Cylinder support of testing instruments and printing machinery to balance load and space constraints.

Semiconductor manufacturing

The precision transmission of equipment such as IC manufacturing equipment and lithography machines is subject to small vibrations and high rotational speeds.

Price Range and Influencing Factors

The price of thin-walled four-point contact ball bearings is greatly affected by the model, size, accuracy grade and material, and the general range is as follows:

Micro/small models (such as inner diameter 10-50mm): the unit price is about 100-500 yuan, suitable for instrumentation and office equipment.

Medium-sized models (such as inner diameter 60-200mm): the unit price is about 500-3000 yuan, which is commonly used in robot joints and medical equipment.

Large/customized models (such as inner diameter of more than 200mm): The unit price can reach 5,000 yuan to tens of thousands of yuan, which is used in aerospace and industrial heavy machinery.

Bulk purchase discount: Some manufacturers offer a 10%-30% discount to customers with orders of more than 100 sets (for example, a single set of a model is 1688 yuan, and a batch of more than 99 sets is reduced to 168 yuan).

Additional Costs for Special Requirements:

20%-50% price increase for high-precision grades (e.g., P4/P2 grades);

30%-80% increase in cost of ceramic ball or stainless steel bearings;

Custom seal constructions, such as lip seals, are available for an additional 10%-20% fee.

The actual price needs to be negotiated and confirmed with the manufacturer according to the specific parameters.

Supplier of Thin-Walled Four-Point Contact Ball Bearings

LTZC is a high-tech enterprise focusing on the R&D, production and sales of thin-walled four-point contact ball bearings, relying on advanced manufacturing technology and strict quality control system to provide high-precision and lightweight bearing solutions for global customers. Our products are widely used in robots, medical equipment, aerospace and precision instruments and other fields, and are committed to creating value for customers.