Roller Bearings vs Ball Bearings: What is The Difference?
A roller bearing is a cylindrical device that facilitates low-friction movement between two elements, and ball bearings serve pretty much the same purpose. The actual distinction between the two is in the contact surface area between the rolling elements and the inner and outer races.
In this article, we'll dive deep into the difference between roller and ball bearings by explaining what each type is in greater detail, as well as how they perform their functions differently. So, without further ado, let's dive right in.
What is a Ball Bearing?
A typical ball bearing, also known as a spherical roller bearing, is a device that consists of rolling elements — spheres made of hardened steel — and outer and inner rings, as well as the retainer. The inner and outer rings have machined grooves called raceways, which "encapsulate" the rolling elements individually separated by a retainer.
When installed, the outer ring is frequently kept in housing, while the inner race is highly forced onto the rotating shaft. When subjected to a load, the rolling elements transfer the load inputted by the inner race and output it to the outer race, thus creating rotational movement. Heavy radial loads, lighter axial loads, as well as combinations of both, can be handled by certain designs.
Point contact is the term used to describe how each spherical ball interacts with the raceway in a relatively small patch known as a point in ball bearings. The unloaded ball springs back to its original shape because bearings are made to ensure that the little deformation the spherical element experiences as it enters and exits the load zone doesn't surpass the material's yield point.
However, this type of bearing has a finite lifespan, and it'll eventually stop working due to wear and tear, spalling, and/or various other factors. As such, ball bearings have a defined number of predicted revolutions before failure and are built with a lifespan based on statistics.
Bearing life is significantly influenced by shaft and bearing alignment. Self-aligning ball bearings are employed because they have a higher misalignment capacity.
What is a Roller Bearing?
Cylindrical roller bearings are made similarly to ball bearings; however, they feature a line contact area instead of point contact, which increases their load capacity and shock resistance. There are various different types of rollers, including tapered roller bearings, cylindrical roller bearings, and needle roller bearings.
This type of bearing can manage smaller thrust loads, but tapered roller bearings can manage thrust loads that are significantly higher. Needle bearings, a type of cylindrical bearing, can be produced as needle roller thrust bearings and have a high radial load capacity for their size. Overall, roller bearings are more commonly seen in industrial equipment, as they're better suited for heavier loads.
Roller Bearings vs Ball Bearings: Pros and Cons
Ball bearings are often utilized at higher speed applications and lighter weights than roller bearings, which typically perform better under impact and shock loading. Here are the advantages and drawbacks of both types:
Speed
Single-row ball bearings are typically used in applications with higher revolutions per minute, and lighter loads, due to smaller contact points and generally lower friction. This also means that the rotation of the components is very smooth. Ball bearings are quite simple assemblies that are simply replaced as whole units. This makes them perfect for high-speed applications in which speed and maneuverability matter.
Likewise, roller bearings have a much larger contact surface, which produces more friction. This is why they're not as well-suited for high RPMs as ball bearings are. They're also more susceptible to angular misalignment, but in turn, they can withstand massive loads.
Weight
Roller bearings can sustain heavier loads without bending or breaking due to their huge contact surfaces. Because of this, roller bearings are the best option for industrial machinery intended to support enormous loads or for other applications with a little margin for error. The same can't be said for typical ball bearings, with a single notable exception — a full complement ball bearing.
A full-complement ball bearing is one form of ball bearing that crams as many balls as it can into the gap between the inner and outer raceways. This kind of bearing can support bigger loads since the loads are split among a greater number of rolling elements.
However, due to more frequent contact between nearby rolling elements, a full-complement ball bearing is also more vulnerable to wear and strain.
Shock and Impact Loading
Roller bearings can withstand greater shock and impact even though ball bearings handle misalignment better. Each roller bearing shape has specific benefits and is designed to be used with bigger weights and lower speeds because of its wider contact area.
For example, the ideal bearings for controlling mixed radial and thrust loads are tapered and spherical roller bearings. In general, roller bearings are the recommended option for industrial applications with large loads.
Price
One has to consider the cost of maintenance when designing equipment, and this is what makes ball bearings a pricier option. They're not serviceable as easily as roller bearings, which are typically easier to disassemble and reassemble for cleaning and lubrication, which adds to their overall lifespan.
Lubrication
Ball bearings are typically the easiest to lubricate unless they feature a shield or a seal that would prevent dust and debris from entering the bearing and lubricant from leaking out. However, you can always remove the seal and try to reapply it.
Roller bearings aren't really maintenance-friendly, but their design allows easier disassembly and maintenance.
Applications Of Roller Bearings and Ball Bearings
Depending on the conditions and load, both roller and ball bearings have their appropriate applications. Ball bearings are designed to rotate in radial acts, higher speeds, and lighter loads. Generating less friction is another benefit, as it implies a longer lifespan.
Roller bearings, on the other hand, are designed for heavier loads, as they distribute the load more evenly among the rolling elements. The downside is heat generation due to friction, which is why they're used in slower, more controlled conditions.
Summary
In the industrial, commercial, and residential contexts, bearings are, without a doubt, one of the most crucial technical components. They offer a reliable rotational motion that is smooth and steady, preventing friction-related wear and strain.
If you want to learn more about ball or roller bearings, visit Reid Supply, or download their professional literature.