Single row angular contact ball bearings are particularly suitable where:
- bearing arrangements must support combined loads, – i.e. radial and axial loads acting simultaneously – ➤ Figure
- moderate to high loads are present on one side
- rigid axial guidance is required
- the bearing arrangement must be axially clearance-free or preloaded
- high speeds are required under higher radial and axial loads
- the bearing arrangement is to run quietly in addition to meeting the requirements stated above
Angular contact ball bearings:
speed comparison with tapered roller bearings
nG = limiting speed
The standard product range comprises bearings of series 718..-B, 70..‑B(‑2RS), 72..-B(-2RS), 73..-B(-2RS) and 74..-B. These bearings are also available for various applications as:
- bearings of basic design for bearing arrangements with single bearings ➤ Figure
- universal bearings for installation in sets in a tandem, O or X arrangement ➤ Figure, ➤ Figure, ➤ Figure
- X-life bearings ➤ link
Single row angular contact ball bearings are also available in other dimension series, designs and sizes. Information on these bearings is available from Schaeffler on request. Larger catalogue bearings GL 1.
Bearings of basic design for bearing arrangements with single bearings
The forces are transmitted oblique to the radial plane
Single row angular contact ball bearings are part of the group of radial ball bearings. The self-retaining units have solid outer and inner rings. The rolling elements are guided by cages made from polyamide, sheet steel, or brass. The bearing rings are designed with one high shoulder and one low shoulder ➤ Figure. As a result of the different shoulder heights, the mounting method differs from that of deep groove ball bearings. The possible number of balls for angular contact ball bearings with identical dimensions is higher than for deep groove ball bearings. In contrast to deep groove ball bearings, the raceways on the inner and outer rings are arranged obliquely to each other in the direction of the bearing axis. As a result, the forces are transmitted from one raceway to the other at a defined contact angle (oblique to the radial plane) ➤ Figure.
For bearing positions with only one bearing each
These angular contact ball bearings can be considered when only one bearing is used per bearing position. As the bearings have standard bearing ring tolerances (they are manufactured to tolerance class Normal), they are not suitable for mounting directly adjacent to each other. In such cases, universal bearings should be used.
Single row angular contact ball bearing
of basic design
Fr = radial load
Fa = axial load
α = nominal contact angle
Universal bearings for mounting in sets
Bearings can be mounted in pairs in any arrangement required
Single row angular contact ball bearings, which are intended for mounting in pairs (in sets) directly adjacent to each other, are manufactured in the so-called universal design ➤ Figure, ➤ Figure, ➤ Figure. These bearings can be used in pairs in any arrangement without shims. Depending on the design selected, the mounted bearing pair has the required axial clearance, freedom from clearance or preload. This gives easier design of the bearing arrangement and mounting of the bearings.
When ordering, please state the number of bearings, not the number of bearing pairs.
Suffixes: UA, UB, UO, UL, UM, UH
Bearings of a universal design are indicated by the suffix UA, UB, UO, UL, UM or UH ➤ Table. If bearings of the universal design are arranged in sets, this gives a defined axial clearance or an axial preload:
- UA = bearing set with small axial internal clearance
- UB = bearing set with smaller axial internal clearance than UA
- UO = bearing set clearance-free in O or X arrangement
- UL = bearing set with light preload
- UM = bearing set with moderate preload
- UH = bearing set with high preload
Reasons for mounting in sets
Single row angular contact ball bearings are mounted in sets if:
- the load carrying capacity of one bearing is not sufficient (bearing set in a tandem arrangement)
- combined or axial loads occur in both directions and the bearing arrangement must have a defined axial clearance (bearing set in O or X arrangement)
The following arrangements are possible for mounting in sets:
Bearing sets in tandem arrangement
In a tandem arrangement, the contact lines run parallel to each other ➤ Figure. Axial forces are distributed equally over both bearings, but can only be supported by the bearing set from one direction. In order to support axial forces from the opposing direction, as well as combined loads, the bearing set is always adjusted against a further bearing.
mounted in set in a tandem arrangement
Bearing set in tandem arrangement
Bearing sets in O arrangement
In an O arrangement, the apexes of the cones formed by the contact lines point outwards, i.e. they diverge relative to the bearing axis ➤ Figure. Bearing sets in an O arrangement support axial forces from both directions, but only ever with one bearing. Due to the large support spacing (i.e. the spacing between the contact cone apexes), these give relatively rigid bearing arrangements (small tilting clearance) and are also suitable for supporting tilting moments.
mounted in set in an O arrangement
Bearing set in O arrangement
S = contact cone apex
H = support spacing
Bearing sets in X arrangement
In an X arrangement, the apexes of the cones formed by the contact lines point inwards, i.e. they converge relative to the bearing axis ➤ Figure. Once again, bearing sets of this type support axial forces from both directions, but also only ever with one bearing. The support base is, however, smaller than in an O arrangement. As a result, the sets are not as rigid as in an O arrangement. Furthermore, they are less suitable for supporting tilting moments.
mounted in set in an X arrangement
Bearing set in X arrangement
H = support spacing
X-life premium quality
Many sizes in series 70..-B, 72..-B, 73..-B and 74..-B are available as X-life bearings ➤ link. These bearings exhibit considerably higher performance than standard single row angular contact ball bearings ➤ Figure. This is achieved, for example, through the modified internal construction, higher surface quality of the contact surfaces and optimised cage design, as well as through the improved quality of the steel and rolling elements.
Increased customer benefits due to X-life
The technical enhancements offer a range of advantages, such as:
- a more favourable load distribution in the bearing and thus a higher dynamic load carrying capacity of the bearings ➤ Figure
- quieter running
- running with reduced friction and greater energy efficiency
- lower heat generation in the bearing
- higher possible speeds
- lower lubricant consumption and, consequently, longer maintenance intervals
- a measurably longer operating life of the bearings
- high operational security
- compact, environmentally-friendly bearing arrangements
Lower operating costs, higher machine availability
In conclusion, these advantages improve the overall cost-efficiency of the bearing position significantly and thus bring about a sustainable increase in the efficiency of the machine and equipment.
Single row X-life angular contact ball bearings include the suffix XL in the designation ➤ Figure, ➤ Figure and ➤ link.
Comparison of basic dynamic load rating
Cr – bearing series 73..‑B‑XL, bore code 05 to 26 with a bearing which is not of X-life quality (73..-B)
Cr = basic dynamic load rating
Areas of application
Wide application range
Due to their special technical features, single row X-life angular contact ball bearings are highly suitable for bearing arrangements in:
- fluid and hydraulic pumps
- automotive chassis and gearboxes
- industrial gearboxes
- electric motors
- industrial ventilators
- machine tools
- textile machinery
X-life indicates a high product performance density and thus a particularly significant benefit to the customer.
Single row angular contact ball bearings can support high radial forces. Pure radial loads are also possible, if the bearings are adjusted.
Axial loading is only possible on one side
Due to the geometry and position of the raceway shoulders, axial loads are only transmitted from one direction ➤ Figure. If these angular contact ball bearings are required to support axial forces from both directions, they are adjusted against a second bearing in a mirror image arrangement ➤ Figure and ➤ Figure.
The axial load carrying capacity of the bearings increases with the contact angle
The contact angle α is the angle encompassed by the contact line and the radial plane, under which the load is transmitted from one raceway to the other ➤ Figure. The axial load carrying capacity of the bearing increases with the value of α, i.e. the greater the angle, the higher the axial load to which the bearing can be subjected. As a result, angular contact ball bearings are more suitable than deep groove ball bearings for supporting higher axial forces. Due to the nominal contact angle of α = 40°, single row angular contact ball bearings can support high axial loads on one side.
For information on angular contact ball bearings available with contact angles other than α = 40°, please consult Schaeffler.
Contact angle and force flow
Load carrying capacity of bearing sets
The basic dynamic and static load ratings Cr and C0r in the product tables always refer to the single bearing. If two bearings of the same size and design are arranged immediately adjacent to each other in an O or X arrangement, the following will apply to the bearing pairs:
- Cr = 1,625 · Cr single bearing
- C0r = 2 · C0r single bearing
The angular adjustment facility of the bearings is very limited
Single row angular contact ball bearings are not suitable for the compensation of angular misalignments. In addition, misalignments induce internal forces in the bearing, which not only lead to higher temperatures, but also to a reduction in the bearing rating life.
Angular contact ball bearings arranged in sets
Misalignments in angular contact ball bearings mounted in sets lead – particularly with a small internal clearance and an O arrangement – to increased loads on the balls and cage, as the angular misalignments are supported under constraint between the balls and raceways. This can, in turn, have a negative effect on the operating life of the bearings. In addition, it should be noted that running noise is increased by a misalignment of the bearing rings.
Greased bearings are maintenance-free
Angular contact ball bearings sealed on both sides are greased with a high quality grease and do not require relubrication.
Ungreased bearings must be lubricated
Open bearings and bearings with seals on one side are not greased. These bearings must be lubricated with 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.
Sealing with contact seals 2RS
Bearings with the suffix 2RS have lip seals on both sides ➤ Table. Due to their good sealing action, they are suitable for use in dusty, contaminated or damp environments.
In the case of unsealed bearings, sealing of the bearing position must be carried out by the adjacent construction. The sealing system should reliably prevent:
- moisture and contaminants from entering the bearing
- the egress of lubricant from the bearing
Limiting speeds and reference speeds in the product tables
Two speeds are generally indicated in the product tables:
- the kinematic limiting speed nG
- the thermal speed rating nϑr
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 or shields and for grease lubrication where bearings are supplied greased and with seals or shields.
Values for grease lubrication
For grease lubrication, 75% 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 15312:2004. As a result, only the limiting speed nG is given in the product tables for these bearings.
Bearing sets of universal design
Bearing pairs usually operate at lower speeds than single bearings
Angular contact ball bearings of universal design can be used in an X, O or tandem arrangement ➤ Figure to ➤ Figure. The thermally safe operating speed of the bearing pair is then approximately 20% below the calculated permissible operating speed of the single bearing.
The Schaeffler Noise Index (SGI) has been developed as a new feature for comparing the noise level of different bearing types and series. As a result, a noise evaluation of rolling bearings can now be carried out for the first time.
Schaeffler Noise Index
The SGI value is based on the maximum permissible noise level of a bearing in accordance with internal standards, which is calculated on the basis of ISO 15242. In order that different bearing types and series can be compared, the SGI value is plotted against the basic static load rating C0.
This permits direct comparisons between bearings with the same load carrying capacity. The upper limit value is given in each of the diagrams. This means that the average noise level of the bearings is lower than illustrated in the diagram.
The Schaeffler Noise Index is an additional performance characteristic in the selection of bearings for noise-sensitive applications. The specific suitability of a bearing for an application in terms of installation space, load carrying capacity or speed limit for example, must be checked independently of this.
Schaeffler Noise Index
for single row angular contact ball bearings
SGI = Schaeffler Noise Index
C0 = basic static load rating
The operating temperature of the bearings is limited by:
- the dimensional stability of the bearing rings and rolling elements
- the cage
- the lubricant
- the seals
Possible operating temperatures of single row angular contact ball bearings ➤ Table.
Permissible temperature ranges