There are many different types of bearings available today, with little information on how they differ. Perhaps you have considered which bearing is best for your application. Or how do I select a bearing? This article will assist you in answering those questions.
To begin, most bearings with a rolling element fall into two broad categories:
1. Bearings made of balls
2. Bearings on rollers
There are sub-categories of bearings within these groups that have unique features or optimized designs to improve performance.
In this article, we will go over four things you should know about your application in order to select the right type of bearing.
Determine the Bearing Load and Load Capacity
Bearing loads are generally defined as the reaction force applied to a bearing when it is in use.
When selecting the right bearing for your application, you should first determine the bearing’s load capacity. The load capacity of a bearing is the amount of load it can withstand and is one of the most important factors to consider when selecting a bearing.
Load Distribution by Ball Bearings
Ball bearings use spherical balls to distribute loads over a medium-sized surface area. They are more effective for small-to-medium-sized loads, spreading loads through a single point of contact.
A quick reference for the type of bearing load and the best ball bearing for the job is provided below:
1. Radial (perpendicular to the shaft) and light loads: Radial ball bearings should be used (also known as deep groove ball bearings). Radial bearings are among the most widely used types of bearings on the market.
2. Axial (thrust) loads (parallel to the shaft): Use thrust ball bearings.
3. Choose an angular contact bearing for combined radial and axial loads. The balls make contact with the raceway at an angle that supports combination loads better.
Bearing Load and Roller Bearings
Roller bearings use cylindrical rollers to distribute loads across a larger surface area than ball bearings. They are more suitable for heavy-duty applications.
A quick reference for the type of bearing load and the best roller bearing for the job is provided below:
1. Choose standard cylindrical roller bearings for radial (perpendicular to the shaft) loads.
2. Axial (thrust) loads (parallel to the shaft): Use cylindrical thrust bearings.
3. Choose a taper roller bearing for combined radial and axial loads.
How to Select a Bearing
How to Select the Proper Bearing for Your Application:
1. Determine the Bearing Load and Load Capacity
To begin, determine the type and amount of bearing load that your application will impose on the bearing. Ball bearings are typically best suited for small-to-medium-sized loads. Roller bearings are typically used in high-load applications.
2. Understand Your Application’s Rotational Speed
Determine the rotational speed of your application. Ball bearings work best at high speeds (RPM), while roller bearings work best at low speeds.
3. Consider bearing runout and rigidity.
You should also figure out what kind of runout your application will allow. If the application only allows for minor deviations, a ball bearing is most likely the best option.
4. Find the Best Bearing Lubricant for Your Needs
Calculate your value for high-speed applications; if it is greater than the maximum speed of the grease, the grease will not provide adequate lubrication. Other options include oil misting. An oil bath is a good choice for low-speed applications.
Speed of Rotation
The rotational speed of your application is the next consideration when selecting a bearing. Ball bearings are usually the best choice for applications that require high rotational speeds. They outperform roller bearings at higher speeds and have a wider speed range.
One reason for this is that the contact between the rolling element and the raceways in a ball bearing is a point rather than a line, as in roller bearings. Because rolling elements press into the raceway as they roll over the surface, there is much less surface deformation in ball-bearing point loads.
Bearings and Centrifugal Force
Centrifugal forces are another reason why a ball bearing is better for high-speed applications. Centrifugal force is defined as a force that pushes outward on a moving body that revolves around a center and is caused by the body’s inertia.
Because it generates radial and axial loads on a bearing, centrifugal force is the primary limiting factor to bearing speed. Because roller bearings have more mass than ball bearings, they produce more centrifugal force than ball bearings of the same size.
Ceramic Balls Material Reduces Centrifugal Force
Sometimes the speed of an application exceeds the speed rating of a ball bearing. If this occurs, a simple and common solution is to replace the ball-bearing material with ceramic. This maintains the same bearing size while providing a 25% increase in speed. Ceramic balls produce less centrifugal force for any given speed because they are lighter than steel.