Angular contact ball bearings are capable of withstanding both radial and axial loads.
This content appears to be related to bearings and their properties. Here’s a revised version with some minor changes for clarity:
- Capability to operate at high speeds.
- The axial load carrying capacity increases with a larger contact angle.
- High precision and high-speed bearings usually have a contact angle of 15 degrees.
- The contact angle will increase under axial force.
Angular contact ball bearings have various accuracy grades that involve both dimensional tolerances and rotational accuracy. These grades are expressed from the lowest to the highest level as P0 (normal), P6 (P6X), P5, P4, and P2 according to the ISO and JIS standards.
However, European and American brands utilize additional grades to indicate the level of accuracy. For instance, they use P3, P7, and P9 to indicate the accuracy level, with P3 being equivalent to the P6 level of the ISO and JIS standards, P7 being equivalent to the P4 level, and P9 being equivalent to the P2 level.
1. Universal Matching Bearings
Universal matching bearings are designed to achieve a defined internal clearance or preload and an average load distribution when mounted against each other. This is achieved without the need for gaskets or similar devices, making them suitable for a range of applications.
Paired bearings are typically used when a single bearing has insufficient load carrying capacity in a coupling configuration, or when subjected to a combined load or an axial load acting in both directions using a back-to-back or face-to-face configuration.
2. Basic Bearing Design (Not Suitable for Universal Matching)
The basic design of a bearing is not intended for universal matching. Instead, it is designed to support a radial load, axial load or a combination of both, depending on the type of bearing. Its internal clearance and preload are fixed and cannot be adjusted to match another bearing.
Configuration for a single bearing
The single row angular contact ball bearings are primarily designed to be used with only one bearing in each position. Their width and amount of protrusion are within normal tolerances. Therefore, installing two single-row angular contact ball bearings is not recommended.
Angular Contact Bearing Type
Angular contact ball bearings come in three types: 7000C (∝=15°), 7000AC (∝=25°), and 7000B (∝=40°). The locking mechanism for this type of bearing is on the outer ring.
Typically, the inner and outer rings cannot be separated, but can withstand combined loads in both radial and axial directions, as well as axial loads in one direction. The ability to handle axial loads is determined by the contact angle. The higher the contact angle, the greater the bearing’s ability to handle axial loads.
These bearings limit the axial displacement of the shaft or housing in one direction. They also have a high limit speed and can handle both radial and axial loads, as well as pure axial loads. The axial load capacity is determined by the contact angle, which increases as the angle becomes greater.
Single row angular contact ball bearing
Single-row angular contact ball bearings are designed to withstand axial loads in only one direction. When radial loads are applied, they generate additional axial forces, which necessitate the application of an opposite load to compensate.
Therefore, single-row bearings are typically used in pairs.
In contrast, double-row angular contact ball bearings can handle significant bidirectional combined loads, both radial and axial, as well as moment loads, with a contact angle of 30 degrees. They are primarily intended to limit the axial displacement of the shaft or casing, with radial loads being their main function.
Bearing code: 7
Paired angular contact ball bearings
Paired mounted angular contact ball bearings can withstand both radial and axial bidirectional combined loads with radial loads, as well as pure radial loads.
The series configuration can only withstand axial loads in one direction, while the other two configurations can withstand axial loads in either direction.
Manufacturers typically select this type of bearing and combine them into a pair for users. Once installed, there is preloading and interference, and the ferrule and steel ball are in an axial preload state, thus improving the rigidity and rotation accuracy of the entire set of bearings as a single support.
The back-to-back configuration uses the post code DB (e.g., 70000/DB). Load lines of the back-to-back matched bearings are separated from the bearing shaft, enabling them to withstand axial loads in both directions. However, the load in each direction can only be absorbed by one bearing. Back-to-back mounted bearings provide a relatively rigid bearing configuration and can withstand overturning moments.
For face-to-face configuration, the rear code is DF (e.g., 70,000/DF). The load lines of the face-to-face matched bearings converge toward the bearing shaft.
This bearing can endure axial loads acting in both directions, but each direction’s load can only be absorbed by one bearing. However, this configuration is less stiff than the back-to-back pairing and is not suitable to bear overturning moments.
Compared to the DB configuration, the rigidity and ability to withstand overturning moments are not as good for this configuration, but it can handle bi-axial axial loads.
In a series configuration, the post code is DT (e.g., 70000/DT). Load lines are parallel, and bearings evenly share radial and axial loads. However, the bearing set can only endure axial loads in one direction. If the axial load acts in the opposite direction or if there is a composite load, a third bearing that is adjusted relative to the series-matched bearing must be added.
This configuration also allows connecting three or more bearings in series at the same support, but it can only withstand axial loads in one direction. Typically, to balance and limit the axial displacement of the shaft, the other bearing needs to be fitted with a bearing that can bear the axial load in the opposite direction.
Bearing code: 0
The following is only for the load capacity of the mating bearing, and the basic load rating and fatigue limit load given in the product table apply only to a single bearing.
*Basic dynamic load rating, standard bearings for any configuration and SKF Explorer bearings in back-to-back or face-to-face configurations
C=1, 62xC single bearing
*Basic dynamic load rating, SKF explorer bearings for series configuration
C=2xC single bearing
*Basic rated static load
Co=2xCo single bearing
*Fatigue limit load
Pu=2xPu single bearing
Structural deformation type
Double-row angular contact ball bearings have the ability to support both radial and axial loads simultaneously, while limiting axial displacement on both sides of the shaft.
Compared to two-way thrust ball bearings, this type of bearing has a higher limit speed, a contact angle of 32 degrees, good rigidity, and the ability to withstand large overturning moments.
These bearings are commonly used in the front wheel hub of a car (with some models also using the same size double-row tapered roller bearings).
Double row angular contact ball bearings exhibit four types of structural deformations:
Type A: This is the standard design for bearings with an outer diameter of 90 mm or less. This type does not have a ball gap and can therefore withstand equal bidirectional axial loads. It has a lightweight fiberglass reinforced nylon 66 cage that results in low bearing temperature rise.
Type A: This is also the standard design for bearings with an outer diameter greater than 90 mm. However, this type has a ball gap on one side and is equipped with a z-steel stamping cage or a brass solid cage.
Type E: This type of bearing is a reinforced structure with a ball gap on one side. It can accommodate more steel balls, thereby increasing its carrying capacity. Both sides of the bearing are dust-proof and double-sided with seals.
Both the A-type design and the E-type double-row angular contact ball bearings can be equipped with a dust cover (non-contact) or a seal (contact) on both sides.
The sealed bearing is filled with rust-proof lithium-based grease inside, and it can operate within a temperature range of -30 to 110 degrees Celsius.
No lubrication is needed during use, and there is no need for preheating before installation.
When installing, double-row angular contact ball bearings should be used, even though the bearing can withstand two-way axial loads.
However, if there is a ball gap on one side, caution should be exercised to prevent the primary axial load from passing through the notched side of the groove.