Thin Section Bearing Application

Thin section bearings are used extensively in applications where space is constrained, weight is restricted or high precision is required. Examples include gimbal mounts, missile tracking systems and robotic arms.

In the coming weeks both Silverthin and Carter will launch a handy selector tool designed to assist design engineers with selecting the correct thin section bearing for their application. It will cover a raft of important factors including:

Radial Loads

A thin section bearing will typically support a large number of radial loads. With this in mind, they can be used in a variety of applications including handling equipment, robotics, aerospace, cameras and optical equipment.

The smaller cross sections of thin section bearings can save space and reduce the weight of a design whilst maintaining high rigidity and rotational accuracy. When combined with a suitable lubrication system these bearings can deliver outstanding performance.

When heavier load capacities are required, Carter Manufacturing recommends an X type or four point contact ball bearing. These feature gothic arch raceways creating four contact points between the balls and the raceways, making them a great solution for moment loading or reversing axial loads.

However, the recommended speed ratings for this type of bearing can be impacted by the application dynamic loading and shaft speeds. Therefore, it is highly recommended that a detailed bearing analysis be undertaken to determine the best option for your application.

Axial Loads

While all radial bearings are capable of accepting some axial loads, thin section bearings are more commonly specified for applications that require both radial and axial load capacity. Carter’s engineering team creates thin section bearing designs by keeping space, load, accuracy and reliability in mind, helping to minimise system cost and build a robust system that delivers results over long periods of time.

A rotary table in semiconductor automated test equipment used a 4-point contact RBC Thin Section Bearing to carry radial, axial and moment loading. The bearing provides stiffness to enable accurate positioning with minimal oscillation.

Axial loading is influenced by shaft and housing fit and limiting speed. A good fit will result in reduced internal clearance of the bearing and improve the performance of the assembly. For more information on selecting the appropriate bearing for an axial/moment application, refer to industry standard data and ABMA or ANSI bearing catalog load capacities.

Moment Loads

As thin section bearings have very small cross-sections in relation to their diameters they can take moment loads that would normally be absorbed by other types of rolling bearing. Moment loads are forces applied along a shaft's rotational axis and can cause the bearing rings to rotate if they don't have adequate support.

A duplex pair of angular contact RBC Thin Section Bearings was used in this airborne radar antenna drive assembly to provide combined radial and axial load carrying capabilities and low torque. The application also required vacuum compatible lubrication and corrosion resistance.

Using standard Celcon (POM) acetal plastic and machined ring construction with 316 stainless steel balls, this thin section angular contact bearing is designed to carry both radial and axial loads. This application also requires high stiffness with minimum deflection resulting in a streamlined and lightweight design. Alternative ball materials and cage designs are available on request. A variety of lubrication choices are also available including vacuum compatible PTFE and molybdenum disulphide.

Internal Clearance

Bearing internal clearance (or play) has a direct impact on the performance and ultimately the life of a bearing. A reduced clearance can increase heat generation and create unwanted vibrations. Conversely, an excessive clearance can lead to increased noise and vibration, misalignment and premature bearing failure.

In thin section bearing applications, the shaft fit and housing fit can dramatically affect the amount of internal clearance remaining during operation. For example, a tight fit on the shaft will cause the inner ring to expand and reduce internal clearance. Similarly, a loose fit in the housing will allow the outer ring to contract, further reducing internal clearance.

For this reason, it is critical that both the shaft and the housing are well-machined and round. In addition, the shaft and housing should be made from a material that will withstand vibration and shock loading. This will help to minimize the effect of vibration and shock on the bearing.