Ball and Roller bearings are both rolling bearings and are designed to operate by rotating and supporting loads with minimal friction (fig. 1). Bearings are mounted on shafts or in housings to facilitate rotation and load transfer between machine components wheels as well as transfer loads between machine components. Ball and roller bearings provide precision operation with low friction while maintaining high speeds, reducing noise, heat, energy consumption and wear.
This article demonstrates the different types of roller bearings and their specific applications. Types of roller bearings are cylindrical, needle, barrel, tapered, carb toroidal, cylindrical roller thrust, needle roller thrust, tapered roller thrust and spherical roller thrust.
Rolling bearings have either a round ball or a long roller as the rolling element.
Balls and rollers exhibit different contact points in the raceway. Balls make point contact with the ring raceways (fig. 2). As the loads increase on the ball the point contact becomes elliptical in shape. Due to this feature ball bearings can run at high speeds but consequently have smaller load carrying capacities as compared to rollers.
While balls make a point contact Rollers make line contact with the ring raceways (fig. 3). As the load increases on the roller the contact line becomes slightly rectangular in shape. Due to the larger contact area and more friction a roller bearing will accommodate heavier loads, but lower speeds somewhat the opposite of a similar sized ball bearing.
Roller bearings characterized by their capacity to carry load and to facilitate smooth and controlled movement are specified in an array of applications. Roller bearings are specified anywhere from automotive and aerospace to heavy machinery and various precision industrial equipment.
Cylindrical Roller Bearings
Single-row cylindrical roller bearings are manufactured with a cage or as a full complement of rollers. The bearings will have solid inner and outer rings and cylindrical rollers. The outer rings have rigid ribs on both sides or no ribs, and the inner rings have one or two rigid ribs or are designed without ribs. When designed with a cage the cylindrical rollers are controlled from coming into contact with each other as well producing less friction.
Standard cylindrical roller bearings have extremely high rigidity and radial load-carrying capacity. Cylindrical roller bearings support axial loads when they are used as semi-locating or locating bearings. Radial loads are transmitted through the raceways and axial loads are transmitted through the rolling element end faces and ribs consequently limiting the axial load.
Barrel Roller Bearings
Barrel roller bearings are single-row, self-aligning roller bearings. Barrel roller bearings have solid outer rings with a concave raceway, solid inner rings with two ribs and a cylindrical or tapered bore. Barrel rollers are separated by cages. This type of roller bearing cannot be dismantled.
Barrel roller bearings are used for high radial shock type loads. Barrel roller bearings allow for misalignment. They have low axial load-carrying capacity.
Tapered Roller Bearings
SKF single row tapered roller bearings are designed to accommodate combined loads. Combined loads are radial and axial loads acting at the same time in a bearing application. The SKF tapered roller bearings include matched single row tapered roller bearings. Depending on application requirements, matched tapered roller bearings are available in different designs. They can be supplied as matched bearings arranged face-to-face, matched bearings arranged back-to-back or matched bearings arranged in tandem.
Features and benefits
Matched single row tapered roller bearings have a high-load carrying capacity.
SKF matched tapered roller bearings are often suitable for extremely heavy radial and axial loads. The axial load carrying capacity of tapered roller bearings increases by increasing the contact angle α. The size of the contact angle which is usually between 10° and 30° is related to the calculation factor e (from the product tables). The larger the value of e, the larger the contact angle. Reference product tables found in the SKF catalog or contact us for assistance.
Also depending on the design, matched tapered roller bearings can locate the shaft axially in both directions with a specific axial clearance or preload. Matched bearings can provide a relatively stiff bearing arrangement and when delivered as a set the bearings and ring spacer(s) are matched during production. These bearings are ready for mounting right out of the box as matched.
Additionally because the projection lines of the raceways for each single bearing meet at a common point on the bearing axis (apex point A, fig. 4) they provide a true rolling action and therefore lower operating frictional moments.
The optimized roller end design and surface finish on the flange (fig. 5) of each single bearing promotes lubricant film formation resulting in lower friction. This also reduces frictional heat and flange wear. In addition, the bearings can better maintain preload and run at reduced noise levels.
The crowned raceway profiles of basic design bearings and the logarithmic raceway profiles of SKF bearings improve the load distribution along the contact surfaces, reduce stress peaks at the roller ends (fig. 6), and reduce the sensitivity to misalignment and shaft deflection compared with conventional straight raceway profiles (fig. 7).
Enhanced operational reliability is a result of an optimized surface finish on the contact surfaces of the rollers and raceways supporting the formation of a hydrodynamic lubricant film.
SKF provides consistent roller profiles and sizes as the rollers are incorporated into SKF tapered roller bearings and are manufactured to very close dimensional and geometrical tolerances. This attention to precision manufacturing provides better load distribution between rollers.
The matched bearings are manufactured so as to reduce noise and vibration, and enable preload to be set as accurately as possible. Standard tapered roller bearings experience a significant amount of friction resulting in wear during the run in period. With the SKF tapered roller bearing design friction, wear and frictional heat are significantly reduced when the bearings are mounted and lubricated correctly.
The geometry of tapered roller bearings assures precise alignment even under dynamic conditions, ensuring stable and efficient load transmission.
The mechanics behind tapered roller bearings optimize the distribution of both axial and radial loads. The conical arrangement of the raceways ensures that loads are transmitted along the axis of rotation, a property pivotal in resisting axial forces. Additionally, the gradually changing contact angle along the tapered surface distributes radial loads more evenly than other bearing types. Tapered roller bearings axial and radial combined capabilities enable tapered roller bearings to be applied in demanding applications.
Automotive applications like wheel hub assemblies are ideal for controlling axial forces to ensure vehicle stability and safety. In construction machinery, these bearings are often specified in heavy-duty applications, providing robust axial load support in equipment such as cranes and excavators. Their use is equally important and useful in high-speed rail systems contributing to consistent and reliable motion.
Spherical Roller Bearings
Spherical roller bearings are designed for applications where high loads must be supported and shaft flexing and misalignment needs to be mitigated. Spherical bearings deliver extremely high performance and are designed to carry extreme loads. Through years of development SKF spherical bearings are designed to ensure optimal kinematics and provide for longer life.
Spherical bearings are designed to accommodate misalignment inherent in its design (fig. 8).
Spherical bearings have a high-load carrying capacity and have a longer service life than other bearings, spherical bearings are low friction and perform in a robust manner.
These bearings are also available sealed to meet the most demanding circumstances. Spherical bearings perform longer and have Increased service life in most contaminated environments. Spherical bearings may be ordered as pre-lubricated and sealed for easy mounting. Spherical roller bearing applications include wind energy, mining, mineral processing and cement plants, material handling, pulp and paper, industrial transmission, and marine.
Needle Roller Bearings
Needle roller bearings are proven machine elements in the design of compact radial bearing arrangements. Needle bearings have a very high-load carrying capacity. In the INA series X-life configuration, they have an up to 50 % longer service life.
Needle roller and cage assemblies
As self contained SKF and INA needle roller and cage assemblies are manufactured ready-to-mount bearings. Perfect for mounting in minimal radial space situations the shaft and housing bore serve as raceways.
Features and benefits include the lowest cross section among rolling bearings offering a very compact solution. Due to the large number of rollers, needle roller and cage assemblies have a high-load carrying capacity. Also the large number of small-diameter rollers, needle roller and cage assemblies will create high stiffness.
Needle Roller bearings have:
- Higher load capacities than single-row ball or roller bearings of comparable dimensions.
- The ability to handle a larger, more rigid shaft configuration.
- Reliable and good rolling characteristics within their small cross section.
- Lower cost, particularly for the drawn-cup type compared with machined versions.
Applications include automotive , gearboxes, robotics , aerospace, medical and many industrial applications.
SKF Cooper Split Spherical Roller Bearings
SKF Cooper split spherical roller bearings are made up of two rows of symmetrical roller have a common sphered outer ring raceway and two inner ring raceways. The rollers are inclined at an angle to the bearing axis.
SKF Cooper Split Roller bearings are designed to accommodate heavy radial loads, combined with or without axial loads in both directions. The bearings are useful for both locating and non-locating bearing positions of shafts. The split design makes them advantageous within inaccessible applications where mounting, dismounting and maintenance is difficult. The split spherical roller bearings are applied in several heavy-duty industries such as mining, mineral processing and cement.
CARB Toroidal Roller Bearings
CARB toroidal roller bearings are unique in accommodating misalignment and minimizing stress levels. CARB toroidal roller bearings provide frictionless axial movement within the bearing in the non-locating position in self-aligning bearing arrangements. They can handle high loads and are known to have extended service life.
Features and Benefits:
- Accommodate misalignment. CARB bearings are self-aligning similar to spherical roller bearings.
- Accommodate axial displacement. CARB bearings compensate for thermal expansion of the shaft.
- Wide assortment of dimension series. CARB bearings are available with the same boundary dimensions as corresponding spherical roller bearings, self-aligning ball bearings, cylindrical roller bearings and needle roller bearings.
- Long service life. Special roller profiles prevents stress peaks at the roller ends.
- Low friction. Self-guiding rollers maintain friction and frictional heat at low levels.
- Improved wear resistance – Material improvements provide for longer wear resistance.
- Long bearing system life. CARB bearings provide benefits in self-aligning bearing arrangements With a CARB bearing in the non-locating position, there are no internally induced axial forces.
- Less load extends the service life. CARB bearings run cooler, the lubricant lasts longer and maintenance intervals can be increased.
- Noise and vibration levels can be reduced. CARB bearings reduce noise and vibration levels in applications such as paper machines and fans.
Cylindrical Roller Thrust Bearings
SKF cylindrical roller thrust bearings are designed for heavy axial loads and impact loads. Cylindrical roller thrust bearings are not used for radial loads. The bearings are stiff and require very little axial space.
Features and Benefits
- Separable design. They have a separable design with a shaft washer, housing washer, cylindrical roller and the cage thrust assembly can be mounted separately.
- Longer bearing service life. The roller ends are relieved slightly to modify the line contact between the raceway and rollers and prevent stress peaks.
Needle Roller Thrust Bearings
SKF needle roller thrust bearings are designed with a form-stable cage retaining and guiding a large number of needle rollers. Needle roller thrust bearings provide a high degree of stiffness while in a small axial space. In applications the faces of adjacent machine components may serve as raceways, needle roller thrust bearings take up no more space than a standard thrust washer.
Features and Benefits
- Heavy Loads. Needle Bearings can accommodate heavy axial loads and peak loads
- Small Diameter. The small diameter of the rollers within one assembly enables these bearings to accommodate heavy axial loads.
- Extending Life. To prevent stress peaks, the roller ends are relieved slightly to modify the line contact between the raceway and rollers extending bearing service life.
Tapered Roller Thrust Bearings
SKF tapered roller thrust bearings are designed to accommodate peak loads and heavy axial loads. SKF tapered roller thrust bearings are stiff and fit in small axial spaces.
Features and Benefits
- Separable Design. The shaft and housing washers and the roller and cage thrust assemblies of tapered roller thrust bearings with cages can be mounted separately.
- Less Friction. Due to the optimized roller end design and surface finish on the flange it promotes lubricant film formation, resulting in less friction.
- Heavy Loads. Single direction tapered roller thrust bearings are designed for heavy loads.
- Close Tolerances. The rollers incorporated in SKF tapered roller thrust bearings are manufactured to close dimensional and geometrical tolerances. The close tolerances provide for optimal load distribution and enable the bearings to accommodate heavy axial loads.
Spherical roller thrust bearings
SKF spherical roller thrust bearings have specific raceway designs and asymmetrical rollers. The bearings accommodate axial loads acting in one direction and simultaneously acting radial loads. Typically the load is transmitted between the raceways through the rollers at an angle to the bearing axis, where the flange guides the rollers.
Features and Benefits
- Very High-load Carrying Capacity. The large number of rollers have an optimum conformity with the washer raceways, enabling the bearings to accommodate heavy axial and simultaneously acting radial loads.
- Self-Aligning. SKF spherical roller thrust bearings are self-aligning and accommodate misalignment.
- Separable Design. SKF spherical roller thrust bearings are separable, allowing mounting and dismounting of the housing washer from the shaft washer and roller and cage assembly.
- High Speeds. SKF Spherical roller thrust bearings have a high speed capability. The cage designs and conformity of the rollers with the washer raceways make the bearings ideal for relatively high speeds.
- Special Profile.The special roller profile reduces edge stresses at the roller/raceway contact and keeps frictional heat at low level, even at higher speeds.
Rolling bearings provide high precision and low friction and enable high rotational speeds. Rolling bearings reduce noise, heat, energy consumption and wear. Rolling bearings are cost-effective. They support loads with minimal friction and are used for rotating or oscillating machine elements like shafts, axles and wheels.
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