Self-aligning ball bearings are particularly suitable:
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Self-aligning ball bearings:
speed comparison with barrel roller bearings, compensation of misalignments
nG = limiting speed
Design variants
Self-aligning ball bearings are available as:
The outer ring has a curved raceway
Self-aligning ball bearings are double row, self-retaining radial ball bearings, which are part of the group of self-aligning bearings. The outer ring has a single concave raceway for the two rows of balls. As a result, the bearings permit the compensation of static and dynamic angular misalignments (skewing between the inner and outer ring) within certain limits ➤ section. The inner ring has two formed raceway grooves in which the rolling elements run. Solid cages made from polyamide PA66 or brass are used ➤ Table.
The bore is cylindrical or tapered
Bearings of basic design are supplied with a cylindrical bore; self-aligning ball bearings of series 12, 13, 22 and 23 are also available with a tapered bore ➤ Figure.
Bearings with a tapered bore have a bore taper of 1:12 and the suffix K ➤ Table.
Suitable for simple bearing arrangements
Self-aligning ball bearings of series 112 have an extended inner ring with cylindrical bore on both sides and a slot on one side of the inner ring ➤ Figure. These bearings are particularly suitable for simple bearing arrangements with conventional shafts. Due to the bearing bore tolerance J7, mounting and dismounting of this type is very simple. The slot is used to locate the bearings in an axial direction by means of a grub screw; ➤ Figure.
Ready-to-fit bearing mounting kits facilitate the ordering and mounting of self-aligning ball bearings
Complete bearing mounting kits are also available for use in locating self-aligning ball bearings with a tapered bore onto a cylindrical shaft journal. These units comprise the bearing, slotted adapter sleeve, tab washer and locknut (series 12..-K + H, 13..-K + H, 22..-K + H, 23..-K + H, 22..-K-2RS + H) ➤ Figure. Adapter sleeves allow bearings to be located on smooth and stepped shafts. The adapter sleeves must also be stated when placing the order. Ordering example ➤ Figure.
The dimension C1 must be observed
In some self-aligning ball bearings with a brass cage (bearings with the suffix M), the balls project to a certain extent at the sides ➤ Figure.
The projection is marked C1 in the product tables. This must be taken into consideration when defining the dimensions for the adjacent parts.
Suitable for high radial and low axial loads
In addition to high radial forces, self-aligning ball bearings also support low axial forces from both directions ➤ Figure to ➤ Figure. Due to the point contact with which the rolling bearings are in contact with the raceways, the radial load carrying capacity of the bearings is lower than for barrel roller bearings with line contact.
Where bearings with adapter sleeves are located on a smooth shaft without a fixed stop (e. g. rigid shoulder), their axial load carrying capacity is dependent on the friction between the shaft and the sleeve.
If there is any doubt about the axial load carrying capacity of the location method, please consult Schaeffler.
Self-aligning ball bearings compensate dynamic and static angular misalignments
Due to the concave rolling element raceway in the outer ring, self-aligning ball bearings are capable of angular adjustment. As a result, they permit skewing between the outer and inner ring within certain limits, without causing damage to the bearings, and can thus compensate misalignments, shaft deflections and housing deformations.
With a rotating inner ring, self-aligning ball bearings can swivel up to 4° from their central position
Under normal operating conditions and with a rotating inner ring, self‑aligning ball bearings can swivel up to 4° from their central position, whereas sealed bearings can swivel up to 1,5°. The extent to which these values can be used in practice is, however, essentially dependent on the design of the bearing arrangement.
If the outer ring rotates or the inner ring undergoes tumbling motion, the angular adjustment facility is considerably smaller. In such cases, please consult Schaeffler.
Greased bearings are maintenance-free
Sealed self-aligning ball bearings are lubricated with a high quality lithium soap grease with a mineral oil base, which has good anti-corrosion characteristics. The grease filling is measured so that it is sufficient for the entire life of the bearing. As a result, these bearings are maintenance‑free.
Do not wash greased bearings out prior to mounting. If mounting is carried out using thermal tools, the bearings should not be heated to a temperature in excess of +80 °C, taking account of the grease filling and seal material. If higher heating temperatures are required, it must be ensured that the permissible upper temperature limits for grease and seals are not exceeded. Schaeffler recommends the use of induction heating devices for heating purposes ➤ link.
Lubrication for ungreased bearings
Open bearings are not greased. They can be lubricated from the end faces using oil or grease.
Compatibility with plastic cages
When using bearings with plastic cages, compatibility between the lubricant and the cage material must be ensured if synthetic oils, lubricating greases with a synthetic oil base or lubricants containing a high proportion of EP additives are used.
Observe oil change intervals
Aged oil and additives in the oil can impair the operating life of plastics at high temperatures. As a result, stipulated oil change intervals must be strictly observed.
Also available with lip seals
Self-aligning ball bearings of series 22 and 23 are also available with contact seals on both sides of the bearing ➤ Figure. The integration of such seals into the bearing provides a compact, economical and reliable solution for the sealing of bearing arrangements. In order that the highest possible sealing effect can still be achieved with minimum friction, the seal lips are in contact with the ground opposing running surface of the inner ring under light pressure. The sealing material used is the proven, oil-resistant and wear-resistant elastomer material NBR. Sealed self-aligning ball bearings have the suffix 2RS ➤ link.
Sealing can be achieved in the adjacent construction, if the bearings are open
In the case of unsealed bearings, sealing of the bearing position must be carried out in the adjacent construction. The sealing system should reliably prevent:
Speeds in the product tables
The product tables give two speeds for most bearings:
The limiting speed nG is the kinematically permissible speed of the bearing. Even under favourable mounting and operating conditions, this value should not be exceeded without prior consultation with Schaeffler ➤ link.
The values given in the product tables are valid for oil lubrication in the case of bearings without seals and for grease lubrication where bearings are supplied greased and with seals.
Values for grease lubrication
For grease lubrication, 85% of the value stated in the product tables is permissible in each case.
nϑr is used to calculate nϑ
The thermal speed rating nϑr is not an application-oriented speed limit, but is a calculated ancillary value for determining the thermally safe operating speed nϑ ➤ link.
Bearings with contact seals
For bearings with contact seals, no speed ratings are defined in accordance with DIN ISO :. As a result, only the limiting speed nG is given in the product tables for these bearings.
The Schaeffler Noise Index (SGI) is not yet available for this bearing type ➤ link. The data for these bearing series will be introduced and updated in stages.
Limiting values
The operating temperature of the bearings is limited by:
Possible operating temperatures of self-aligning ball bearings ➤ link.
Permissible temperature ranges
The main dimensions of self-aligning ball bearings correspond to DIN 630:, with the exception of bearing series 112. Nominal dimensions of self-aligning ball bearings ➤ link.
Series 112
The dimensions of self-aligning ball bearings with extended inner ring (bearing series 112) correspond to DIN 630-2, which was withdrawn in . Nominal dimensions of bearings ➤ link.
The limiting dimensions for chamfer dimensions correspond to DIN 620‑6:. Overview and limiting values ➤ section. Nominal value of chamfer dimension ➤ link.
The tolerances for the dimensional and running accuracy of self-aligning ball bearings correspond to tolerance class Normal in accordance with ISO 492:, except for the bearing bore of bearing series 112, which is manufactured to tolerance class J7. Tolerance values in accordance with ISO 492 ➤ link.
For a description of the suffixes used in this chapter see ➤ link and medias interchange http://www.schaeffler.de/std/1B69.
Suffixes and corresponding descriptions
Suffix
Description of suffix
Examples of composition of bearing designation
The designation of bearings follows a set model. Examples ➤ Figure and ➤ Figure. The composition of designations is subject to DIN 623-1 ➤ link.
Self-aligning ball bearing with tapered bore: designation structure
Self-aligning ball bearing with tapered bore and adapter sleeve: designation structure
P = Fr under purely radial load of constant magnitude and direction
The basic rating life equation L = (Cr/P)p used in the dimensioning of bearings under dynamic load assumes a load of constant magnitude and direction. In radial bearings, this is a purely radial load Fr. If this condition is met, the bearing load Fr is used in the rating life equation for P (P = Fr).
P is a substitute force for combined load and various load cases
If this condition is not met, a constant radial force must first be determined for the rating life calculation that (in relation to the rating life) represents an equivalent load. This force is known as the equivalent dynamic bearing load P.
Fa/Fr ≦ e or Fa/Fr ＞ e
The calculation of P is dependent on the load ratio Fa/Fr and the calculation factor e ➤ Equation and ➤ Equation.
Equivalent dynamic load
Equivalent dynamic load
Legend
P NEquivalent dynamic bearing load
Fr NRadial load
Fa NAxial load
e, Y1, Y2 -Factors ➤ link
For self-aligning ball bearings subjected to static load ➤ Equation.
Equivalent static bearing load
Legend
P0 NEquivalent static bearing load
F0r, F0a NLargest radial or axial load present (maximum load)
Y0 -Axial load factor ➤ link
In addition to the basic rating life L (L10h), it is also always necessary to check the static load safety factor S0 ➤ Equation.
Static load safety factor
Legend
S0 -Static load safety factor
C0 NBasic static load rating
P0 NEquivalent static bearing load
In order to prevent damage due to slippage, a minimum radial load of P ＞ C0r/100 is required
In order that no slippage occurs between the contact partners, the self-aligning ball bearings must be constantly subjected to a sufficiently high load. Based on experience, a minimum radial load of the order of P ＞ C0r/100 is thus necessary. In most cases, however, the radial load is already higher than the requisite minimum load due to the weight of the supported parts and the external forces.
Link to Rimao
If the minimum radial load is lower than indicated above, please consult Schaeffler.
Support bearing rings over their entire circumference and width
In order to allow full utilisation of the load carrying capacity of the bearings and thus also achieve the requisite rating life, the bearing rings must be rigidly and uniformly supported by means of contact surfaces over their entire circumference and over the entire width of the raceway. Support can be provided by means of a cylindrical or tapered seating surface ➤ Figure to ➤ Figure. The seating and contact surfaces should not be interrupted by grooves, holes or other recesses. The accuracy of mating parts must meet specific requirements ➤ Table to ➤ Table.
For secure radial location, tight fits are necessary
In addition to supporting the rings adequately, the bearings must also be securely located in a radial direction, to prevent creep of the bearing rings on the mating parts under load. This is generally achieved by means of tight fits between the bearing rings and the mating parts. If the rings are not secured adequately or correctly, this can cause severe damage to the bearings and adjacent machine parts. Influencing factors, such as the conditions of rotation, magnitude of the load, internal clearance, temperature conditions, design of the mating parts and the mounting and dismounting options must be taken into consideration in the selection of fits.
If shock type loads occur, tight fits (transition fit or interference fit) are required to prevent the rings from coming loose at any point. Clearance, transition or interference fits ➤ link.
The following information provided in Technical principles must be taken into consideration in the design of bearing arrangements:
The bearings must also be securely located in an axial direction
As a tight fit alone is not normally sufficient to also locate the bearing rings securely on the shaft and in the housing bore in an axial direction, this must usually be achieved by means of an additional axial location or retention method. The axial location of the bearing rings must be matched to the type of bearing arrangement. Shaft and housing shoulders, housing covers, nuts, spacer rings, retaining rings, adapter and withdrawal sleeves etc. are generally suitable.
Simple location by means of a grub screw
Bearings of series 112 are axially located by means of a grub screw, which engages in the slot in the bearing inner ring ➤ Figure. The grub screw also prevents the inner ring creeping on the shaft.
If a shaft is to be supported by two bearings, the slots in the inner ring must either be arranged on the sides of the bearing facing towards or away from each other ➤ Figure.
Location by means of locknut and tab washer
If a bearing with a tapered bore is mounted directly on a tapered journal the bearing can be axially located with ease using an axial locknut and tab washer ➤ Figure.
Mounting can be carried out quickly and reliably by means of wrench sets from Schaeffler
Self-aligning ball bearings with a tapered bore can be located easily and reliably on smooth or stepped cylindrical shafts by means of an adapter sleeve ➤ Figure. The adapter sleeve does not need to be secured on the shaft by any additional means. The bearings can be positioned at any point on smooth shafts. Axial load carrying capacity of bearing arrangements by means of adapter sleeve connection ➤ section.
If very high axial forces are present, a support ring can also be used to provide axial support ➤ Figure. In this instance, the mounting dimensions of the support ring Ba and db in the product tables must be observed ➤ link.
A minimum of IT6 should be provided for the shaft seat and a minimum of IT7 for the housing seat
The accuracy of the cylindrical bearing seat on the shaft and in the housing should correspond to the accuracy of the bearing used. For self-aligning ball bearings with the tolerance class Normal, the shaft seat should correspond to a minimum of standard tolerance grade IT6 and the housing seat to a minimum of IT7. Guide values for the geometrical and positional tolerances of bearing seating surfaces ➤ Table, tolerances t1 to t3 in accordance with ➤ Figure. Numerical values for IT grades ➤ Table.
Guide values for the geometrical and positional tolerances of bearing seating surfaces
Specifications for tapered bearing seats
For bearings located directly on a tapered shaft journal, ➤ Figure, the data are in accordance with ➤ Figure.
The contact surfaces for the rings must be of sufficient height
The mounting dimensions of the shaft and housing shoulders, and spacer rings etc., must ensure that the contact surfaces for the bearing rings are of sufficient height. However, they must also reliably prevent rotating parts of the bearing from grazing stationary parts. Proven mounting dimensions for the radii and diameters of the abutment shoulders ➤ link. These dimensions are limiting dimensions (maximum or minimum dimensions); the actual values should not be higher or lower than specified.
A large range of housings is available
For economical, operationally reliable and easily interchangeable bearing arrangement units, the self-aligning ball bearings can also be combined with Schaeffler bearing housings ➤ Figure. These easy-to-fit units fulfil all of the requirements for modern machine and plant designs with favourable maintenance-related characteristics.
Due to the large number of application areas, an extensive range of bearing housings is available for bearings with cylindrical and tapered bores. These include split and unsplit plummer block housings, take-up housings, flanged housings and housings for specific industrial and railway applications. Detailed information on bearing housings can be found in publication GK 1 http://www.schaeffler.de/std/1B63. This book can be ordered from Schaeffler.
Split plummer block housing with a self-aligning ball bearing
Split plummer block housing SNV
Self-aligning ball bearing
The mounting and dismounting options for self-aligning ball bearings, by thermal, hydraulic or mechanical methods, must be taken into consideration in the design of the bearing position.
Ensure that the bearings are not damaged during mounting
Self-aligning ball bearings are not separable. In the mounting of non‑separable bearings, the mounting forces must always be applied to the bearing ring with a tight fit.
Suitable methods
Bearings with a tapered bore are mounted with a tight fit on the shaft or adapter and withdrawal sleeve. The measurement of the reduction in radial internal clearance or of the axial drive-up distance of the inner ring on the tapered bearing seat serves as an indication of the tight fit.
The measurement is usually carried out with a feeler gauge
The reduction in radial internal clearance is the difference between the radial internal clearance before mounting and the bearing clearance after mounting of the bearing ➤ Figure. The radial internal clearance must be measured first. During pressing on, the radial clearance (bearing clearance) must be checked until the necessary reduction in the radial internal clearance and the required tight fit is achieved.
The axial drive-up distance can also be measured in place of the reduction in radial internal clearance ➤ Figure.
The malfunction-free operation of bearings presupposes that these have been mounted correctly. An insufficient operating clearance or inadequately tight fit on the shaft generally leads to bearing damage.
If there is any uncertainty regarding the practical application of both methods, Schaeffler must always be consulted.
The mounting of self-aligning ball bearings is also described in the Schaeffler publication BA 28. This BA publication can be requested from Schaeffler.
Rolling bearings must be handled with great care
Rolling bearings are well-proven precision machine elements for the design of economical and reliable bearing arrangements, which offer high operational security. In order that these products can function correctly and achieve the envisaged operating life without detrimental effect, they must be handled with care.
The Schaeffler Mounting Handbook MH 1 gives comprehensive information about the correct storage, mounting, dismounting and maintenance of rotary rolling bearings http://www.schaeffler.de/std/1B68. It also provides information which should be observed by the designer, in relation to the mounting, dismounting and maintenance of bearings, in the original design of the bearing position. This book is available from Schaeffler on request.
The further development of products may also result in technical changes to catalogue products
Of central interest to Schaeffler is the further development and optimisation of its products and the satisfaction of its customers. In order that you, as the customer, can keep yourself optimally informed about the progress that is being made here and with regard to the current technical status of the products, we publish any product changes which differ from the printed version in our electronic product catalogue.
We therefore reserve the right to make changes to the data and illustrations in this catalogue. This catalogue reflects the status at the time of printing. More recent publications released by us (as printed or digital media) will automatically precede this catalogue if they involve the same subject. Therefore, please always use our electronic product catalogue to check whether more up-to-date information or modification notices exist for your desired product.
In addition to the data in this chapter, the following chapters in Technical principles must also be observed in the design of bearing arrangements:
Self-aligning ball bearings are a vital component in many industries due to their unique ability to handle misalignment. In this article, we will cover everything you need to know about self-aligning ball bearings, including what they are, types, advantages, installation, identification, and their applications. Whether you're an engineer, manufacturer, or just curious about these essential bearings, this guide provides a detailed understanding of self-aligning ball bearings and their role in modern machinery, especially BYWB Bearing.
A self-aligning ball bearing is a type of bearing designed to accommodate shaft misalignment. This design consists of two rows of balls that run in circular races, with the inner race slightly tilted relative to the outer race. The key feature that sets self-aligning ball bearings apart from traditional ball bearings is their ability to self-align, which means they can automatically compensate for angular misalignment between the shaft and the housing.
This alignment is made possible because the bearing's outer race has a spherical shape, allowing the inner race to adjust to angular movements. As a result, self-aligning ball bearings are particularly useful in applications where slight misalignments or shaft deflections are inevitable, such as in conveyor belts, motors, and pumps.
In simpler terms, these bearings are designed to handle imperfections in alignment without causing premature wear or failure, which leads to longer service life and enhanced reliability in machinery.
· Two rows of balls: A self-aligning ball bearing features two rows of balls, which helps distribute the load more evenly.
· Spherical outer race: The outer race is spherical, which allows the bearing to accommodate angular misalignment.
· High load capacity: These bearings can handle both radial and axial loads.
· Reduced wear: The ability to self-align reduces friction and wear, leading to a longer lifespan.
Self-aligning ball bearings come in several variations, each designed to handle specific operational conditions and requirements. There are two main types of self-aligning ball bearings: open and sealed.
Open self-aligning ball bearings are designed without any seals or shields. While they are more exposed to contaminants like dirt, dust, and moisture, they allow for easier lubrication and heat dissipation. These bearings are often used in environments where contamination is minimal, or where maintenance is easily accessible.
Common features of open self-aligning ball bearings:
· No seals or shields.
· Require external lubrication.
· Suitable for low to moderate speed applications.
Sealed self-aligning ball bearings feature a protective shield or seal on one or both sides of the bearing. This shield keeps contaminants out and helps retain the lubricant within the bearing. Sealed bearings are more commonly used in applications where exposure to dirt, dust, and moisture is higher.
Common features of sealed self-aligning ball bearings:
· Seals on one or both sides.
· Protection against dirt, moisture, and contaminants.
· Extended lubrication intervals.
· Caged self-aligning ball bearings: These bearings include a cage to separate the balls, reducing friction and enhancing performance, especially in high-speed applications.The choice between steel, brass, and polyamide cages for your Self-aligning ball bearings depends on several factors, including load requirements, speed, temperature conditions, noise sensitivity, and cost considerations. Steel cages are best for heavy-duty applications where high load and speed capacity are needed. Brass cages offer excellent heat resistance and wear durability, making them ideal for industrial machinery and automotive applications. Polyamide cages, on the other hand, are lightweight, cost-effective, and provide low friction and noise reduction, making them perfect for light-to-moderate load applications in household and office equipment.
· Full complement self-aligning ball bearings: These bearings contain the maximum number of balls, providing higher load capacities but at the cost of speed and efficiency.
Self-aligning ball bearings offer several key benefits that make them highly suitable for industrial and mechanical applications. Let’s explore these advantages:
As mentioned earlier, self-aligning ball bearings are capable of compensating for angular misalignment. This makes them ideal for applications where shafts are not perfectly aligned, such as in conveyor systems, electric motors, or pumps. Misalignment can occur due to mounting errors, deflection under load, or manufacturing tolerances, and self-aligning ball bearings help mitigate the risk of bearing damage due to these factors.
The self-aligning feature of these bearings helps to reduce friction between the balls and races. The spherical outer race allows for smoother operation, which not only extends the lifespan of the bearing but also reduces wear and tear on other components. Lower friction also leads to reduced heat generation, improving overall system efficiency.
Self-aligning ball bearings are capable of handling both radial and axial loads, which means they can support a combination of forces in various directions. This makes them suitable for high-load applications, such as industrial machinery, automotive systems, and heavy equipment.
Due to their ability to compensate for misalignment and their low wear rates, self-aligning ball bearings generally require less maintenance compared to other types of bearings. This translates to reduced downtime and increased productivity in manufacturing and industrial applications.
While self-aligning ball bearings may have a slightly higher initial cost than conventional bearings, their durability, ability to handle misalignment, and reduced maintenance costs make them a cost-effective choice in the long run.
Installing self-aligning ball bearings correctly is crucial to ensuring optimal performance and longevity. Here’s a step-by-step guide to installing these bearings:
Before installing the bearing, make sure to clean the bearing housing and shaft thoroughly. Any dirt or debris can cause premature wear. Additionally, ensure the shaft and housing are aligned properly to avoid unnecessary stress on the bearing.
Lubricate the bearing with the appropriate lubricant (grease or oil) based on the manufacturer’s recommendations. Some self-aligning ball bearings come pre-lubricated, but additional lubrication may be required for certain applications.
Place the bearing onto the shaft or housing, making sure the orientation is correct. The spherical outer race allows for easy alignment, but it’s important to ensure the bearing is properly seated.
Use the appropriate tools to secure the bearing in place. This may involve tightening retaining rings, set screws, or other fastening mechanisms.
Once installed, manually rotate the bearing to ensure smooth operation. Check for any unusual noises or resistance. If necessary, make adjustments to the alignment.
Identifying a self-aligning ball bearing can be done by examining a few key features. These are some distinguishing characteristics of self-aligning ball bearings:
The most obvious feature of a self-aligning ball bearing is its spherical outer race. This spherical shape allows the bearing to accommodate slight misalignments without causing undue wear.
Self-aligning ball bearings typically feature two rows of balls, which help distribute the load more evenly across the bearing.
If the bearing allows for angular misalignment between the shaft and the housing, it's likely a self-aligning ball bearing. This can be tested by rotating the bearing in its housing and observing its ability to compensate for slight misalignments.
Self-aligning ball bearings are used in various industries where misalignment is common or where long-lasting, reliable performance is needed. Some key applications include:
In the automotive industry, self-aligning ball bearings are used in alternators, motors, and wheels, where shafts may not always remain perfectly aligned due to vibrations and operational stresses.
Conveyor systems, fans, and pumps often use self-aligning ball bearings. These applications involve continuous motion, and slight misalignments are common due to the long operational hours and vibrations.
Electric motors require bearings that can handle both radial and axial loads. Self-aligning ball bearings ensure smooth performance even when the shaft is slightly misaligned.
Farm machinery like harvesters and tractors can benefit from self-aligning ball bearings, which handle the rough, misaligned conditions often encountered in agricultural environments.
In textile production, machinery is often subject to vibrations and alignment challenges. Self-aligning ball bearings help reduce the risk of failure in these machines.
Self-aligning ball bearings play a crucial role in modern machinery and industrial applications by providing reliable performance even in the face of misalignment. Their ability to handle both radial and axial loads, reduce friction, and extend bearing life make them an excellent choice for various industries, including automotive, manufacturing, and agriculture.
By understanding the different types, advantages, and applications of self-aligning ball bearings, you can make informed decisions about their usage in your equipment. Whether you’re looking to install these bearings in new machinery or replace worn-out bearings, BYWB Bearings offers high-quality, reliable self-aligning ball bearings tailored to your specific needs.
To ensure you choose the right bearing for your needs, be sure to consult with BYWB Bearing for the best quality products designed to meet your operational requirements.