All About Radial Ball Bearings

Radial ball bearings are friction reduction components that are equipped with the ability to carry loads radially around their axis. Serving as a subtype of ball bearings, their design consists of lubricated steel balls that are placed between two grooved rings. As such, they are often called deep-groove bearings or Conrad bearings.

While these bearings can support a certain amount of axial thrust, thrust bearings or roller bearings should be used in their place as these are designed to withstand high axial loads. To better understand the working principle of radial ball bearings, we will cover their design and function. First, they contain a specific number of balls within their raceway that is formed by two circular races. It is important to note that a majority of these bearings have balls that are made of carbon steel, stainless steel, ceramic, or glass.

With radial ball bearings, one must ensure that there is no excess grease or oil lubrication as this may reduce friction and produce a dampening effect on the contact between the balls and the raceways. This can be prevented with the use of rubber seals or a metal-faced shield, though the latter does not offer a secure sealing effect. However, either option prevents dirt and dust from affecting bearing rotation.

As radial ball bearings serve a diverse set of industrial applications, they are made available in a variety of styles, including single row bearings, double row bearings, internally self-aligning bearings, externally self-aligning bearings, thin-section bearings, and insert bearings. Each of these bearings is also available in differing configurations, those of which include open bearings, bearings with seals, bearings with shields, and bearings with snap ring grooves.  

Production is an equally important aspect to radial ball bearing construction, most being manufactured as individual components that must be assembled together. This requires accurate measurements and precision, ensuring the smooth and quiet rotation of the final product. Keep in mind that very small deviations may exist among bearings, accommodating for varying application specifications.

Similar to other industrial fasteners, radial ball bearings are subjected to rigorous standards, determining their precision, efficiency, and reliability. For example, high-speed applications benefit from incredibly precise bearings, while low-speed applications can afford less precision in the manufacturing process. That being said, we will provide a brief overview of various radial ball bearing configurations that are widely used by engineers.

Ball Distribution

Conrad bearings require a cage or separator to maintain the balls evenly distributed throughout the bearing. The inner raceway is situated in an eccentric position with relation to the outer raceway. This configuration provides a disproportionate gap where the roller balls are held, producing a concentric bearing. Once the balls have been positioned, the cage can be inserted. Together, these parameters allow Conrad bearings to handle radial and axial loads.

Additionally, they are available with double rows to increase their ability to support radial loads. However, friction between cages may lessen axial capacity. 

Slot-fill or maximum capacity bearings are another type which have raceways filled to the brim with balls. This configuration is called a full complement. These bearings can handle high radial loads and axial loads, but only in one direction. The raceways are designed with small slots so that the balls are in a concentric position. It is important to note that the slots alter the strength of the raceway, and if the balls make contact with the slots while supporting a load, they can become damaged.

Bearing Retainers/Cages

There are a variety of retainers and cages one may procure for their applications, some of which will be outlined in this section.

The first is a two-piece ribbon design of two halves that are held together by folding tabs, and the retainer is guided by the balls. Typically made of stainless steel, carbon steel, or brass, this configuration is ideal for low to moderate speed applications which may be adjusted based on the type of crimping connecting the halves.

For small bearings, a one-piece stainless steel “crown” that snaps in over the balls and is guided by the inner raceway may be used. This type is great for low-speed, low-torque applications.

Lastly, a one-piece cage that is usually machined from brass with holes that hold the balls is the final type. These cages offer more precision, reliability, and durability than their counterparts. 

Bearing Closures

A majority of radial ball bearings will implement seals and shields to protect the balls, cages, and lubricants from contamination and dust. In addition, seals and shields are specifically designed to not affect the efficiency of the bearing. There are a myriad of seal and shield variations, those of which are designated a bearing part-number suffix.

The suffix “R” indicates a single seal that is located on one side of the bearing, while the suffix “RR” indicates a single seal that can be found on both sides of the bearing. Similarly, the suffix “Z” indicates a single shield that is positioned on one size of the bearing, while “ZZ” indicates a double shield that is placed on both sides of the bearing. 

Bearing Lubrication

Another important factor to consider when looking at radial ball bearings for your intended applications is lubrication. The most common lubricating mediums include oil, grease, and dry films.

Synthetic oils are often used for moderate to high speed applications as they typically exhibit enhanced lubrication characteristics. Silicone oils, in particular, offer good heat resistance and do not corrode rubber, and they can be dripped, centrifuged, or impregnated into bearings.

Grease works best for moderate to high rotation applications and offers good heat resistance. It may be applied with a grease pack, but grease plating is also an option.

The last type of bearing lubricant that is used is dry film, but it should only be utilized where wet lubricants are unsuitable. However, they are difficult to apply and may produce wear flakes over time, eventually obstructing bearing operation.


If you find yourself in need of radial ball bearings, thrust bearings, roller bearings, or another specialized type, rely on ASAP Aviation Stock. ASAP Aviation Stock is a one-stop-shop for all your operational needs. Get in contact with a representative today and see how we can fulfill your parts requirements.  


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