Roller bearing is a kind of bearing product which uses rollers to reduce friction between machine parts. It is also known as the rolling-element bearing. Basically, the rolling elements can be classified into two types, i.e. balls and rollers. The latter ones can be further divided into four types: cylindrical, needle, tapered, and spherical. There are also many different kinds of cages such as the pressed cages, machined cages and formed cages. They can prevent the rolling elements from falling out.

The contact surface can support the load that is placed on the bearing. It is common that the inner ring and outer ring are placed at different places. Generally, the inner ring fits on the axle or shaft, whereas the outer ring will be placed on the housing.

The first type is the spherical roller bearing which has a very high radial load capacity. They have a moderate lateral or thrust capacity. It used to be popular for railroad journal applications, but the popularity has been on a steady decline because of its high costs. However, they still have many advantages when compared to many other types. For example, they can tolerate high misalignment which means that they are easier to install in trains and can last longer before they need to be replaced or serviced.

The next type is the tapered roller bearing. They are less expensive than the first one. It was first designed especially for railroad use. They have a high radial load capacity, which means that their capacity to bear loads perpendicular to an axis is high. Moreover, they also have a moderate lateral or thrust capacity, thus, they can bear loads perpendicular to the axis.

The third type is the cylindrical roller bearing which has high radial load capacities due to line contact. They have low lateral or thrust capacity. When compared to the second type, they are cheaper to manufacture and install. However, they require more maintenance which can result in more costs to operate in the long run.