Product Catalogue

Single-row angular contact ball bearing will generate axial thrust force while supporting radial load, therefore, the two sets of bearings should be used in back-to-back or face-to-face configuration. The contact angle is between bearing ring and balls. The standard contact angle is 150, 250 and 400. The larger the contact angle is, the greater the axial load capacity will be, and the smaller the contact angle is, the more conductive the high speed will be.
The single-row bearing can take radial load and axial load in single direction.
Double-row angular contact ball bearing
The double-two angular contact ball bearing is divided into two constructions, including one outer ring and two inner rings as well as one outer ring and one inner ring. The axial clearance of two-inner ring structure is easy to control in processing. DB combination, DF combination and double-row bearings can support radial load and double-direction axial load. DF combination is suitable for areas where rated load of the single bearing under relative heavy single-direction axial load is insufficient. The two single-row angular contact ball bearings in back combination structure share the inner ring and outer ring together. They can take radial load and double-direction axial load.
Angular contact ball bearing is suitable for high speed and high precision rotation.
The bearing of this type is mainly applied in machine tool spindles, high frequency motors, combustion turbines, pumps, air compressors, printing machinery etc.
 
Four-point contact ball bearing
The bearings of this type are mainly used in aircraft jet engines and gas turbines. They can support radial load and double-direction radial load. The single bearing can replace the angular contact ball bearing with front combination or back combination. And the bearings are suitable for taking pure axial load or combined load with relative large axial load.
When under axial load in any direction, the bearings of this type will generate one of contact angles (a), thus, the bearing ring and ball always be two-point contact in the contact line.

The four-point contact ball bearing of QJF000(176000) type is of separable bearing. The QJF000（116000）type is also of separable bearing with a two-piece inner ring and contact angular of 350. The four-point contact ball bearing is mainly used for supporting double-direction axial load. It can take both axial load and radial load. The angular ball bearing mounted in pairs is classified into three types according to the end face combination of its outer ring:
Back-to-back configuration face-to-face configuration
The bearing in tandem configuration is able to support axial dominated combined load of axial and radial load as well as pure axial load.
The bearing combination is generally selected by the manufacturing factory or delivered to users in a whole set, and there is preload interference after installment. Since the bearing ring and steel ball is under axial preload, the load capacity and rigidity of the whole bearing is increased as single supporting.
The limit speed is high for angular contact ball bearings which can take radial load and axial load spontaneously as well as pure axial load. The axial load capacity is decided by contact angle, increasing with the contact angle. 
1. The main structural type
(1) The single-row angular contact ball bearing includes two types, separable type and inseparable type.
The basic type of separable angular contact ball bearing is S7 000 with separable inner ring. As the inner ring and outer ring can be mounted separately, thus the bearing is suitable for position in restricted installation conditions. The four-point contact ball bearing is also of separable bearing, of which the QJ 0000 type has a two-piece inner ring  and QJF 0000 type has a two-piece outer ring and they both have contact angle of 35°. The steel ball and bearing ring are four-point contact under no load or pure radial load and two-point contact in pure axial load, and it can take axial load in double directions. This type also can support torque load with function of both single and double row angular contact ball bearing. It can ensure normal work only in two-point contact.    
 
The structural type of separable angular ball bearing
The inner ring and outer ring of inseparable bearing, including a) S 70000 type, b)SN 70000 type, c)QJ 0000 type, d)QJF 0000 type, can not be mounted separately. They have the following basic structural types:   
Contact angle of α=15°, and lock on the outer ring is 70000 C type
Contact angle of α=25°, and lock on the outer ring is 70000 AC type
Contact angle of α=40°, and lock on the outer ring is 70000 B type
Single-row angular contact ball bearing can only support axial load in single direction (except four-point contact ball bearing). The bearings of this type are usually used in pairs since the corresponding reverse axial load must be applied for additional axial force caused by taking radial load. 
(2) The double-row angular contact ball bearing is able to support heavy double-direction combined load of radial and axial load based on radial load. With contact angle of 30°, it can restrict double-direction axial displacement of shaft or housing. 
(3) Angular contact ball bearing with paired arrangement is composed of two single-row angular contact ball bearing with the same specification with arrangement method in the following picture. It can be divided into three forms in the following picture according to the different combinations of the end face 
The bearing is able to support radial and axial joint load based on radial load as well as withstand pure radial load. The tandem configuration can only withstand the axial load in the single direction, while the other two configurations can stand axial load in any one direction. The bearing of this type is submitted to users in pairs after being matched and combined by the manufacturer. Because of preload interference after installment and axial pre-load of bearing rings and balls, the support rigidity and rotational accuracy of entire set of bearings is increased as the single supporting.
2. Permissible tilt angle
The tilt of between bearing inner ring and outer ring of angular contact ball bearing is limited. The permissible tilt angle depends on inner clearance of the running bearing, bearing dimension, internal design and the force and torque on the bearing. And the maximum tilt angle should ensure the internal bearing not to generate excessive additional stress. If the tilt angle generates between bearing inner and outer rings, the service life of bearing will be affected, meanwhile, the bearing running accuracy will be declined and the running noise will be increased.
3. Tolerance and clearance
The angular contact ball bearing can be manufactured into a variety of tolerance classes according to the needs. The general type of angular contact ball bearing has tolerances of 0 class, 6 class, 5 class. The angular contact ball bearing mounted in pairs for machine tool spindles has tolerances of 4 class and 2 class. The tolerance value can be seen in “preface page 25” of sample aforementioned. The clearance of single row angular contact ball bearing depends on the requirement of contact angle and is ensured by manufacturing. Angular contact ball bearing is mainly used for machine tool and other high precision, high speed applications. It can take both radial and single-direction axial load at the same time with relative high speed limit. The axial component will be caused when supporting radial load. Therefore, angular contact ball bearing is always mounted with the matching bearing taking the axial load in the opposite direction. The contact angle of BEM angular contact ball bearing mainly includes two types of 15°(C) and 25°(E) , and the former is used under small axial load.
BEM angular contact ball bearing has four standard dimension series, including 718,719,70 and 72. Its structural design, contact state and dynamic characteristics are all optimized and the balls from different materials can be used through special design. The cage adopts high-quality phenolic cloth laminated tubes with small cross-sectional area, avoiding the interference of the flow of lubricant. In addition, the cage is in symmetrical structure and positioned and guided by outer ring to ensure its smooth running. Since the bearing ring is produced by high-quality bearing steel,  the bearing features with high precision, high speed, high rigidity, low vibration and low temperature rise through special heat treatment process, strict control of part geometry errors and organizational defects, and precious manufacturing. The bearing of this type can be replaced by other spindle bearings by adopting ISO standard dimension,.
The distinguishing features of BEM SH719, SH170 series of high-speed angular contact ball bearing include narrowed ball diameter, increased bearing number, greatly reduced inertial force and improved contact state. The bearing ring is thick, and in good stability and high rigidity. With slope on the inner ring and outer ring, it is more suitable to be used in oil-air lubrication. The inner and outer ring of HCSH719 and HCSH70 series of ultra-high speed angular contact ceramic ball bearings is matched with ceramic ball (silicon nitride Si3N4), which has density of 40% less than steel. The centrifugal force is greatly reduced, so that the dynamic characteristics of the bearing can be improved. The wear of hybrid bearing is less than general steel ball bearing and the service life is significantly prolonged.
The high speed sealed angular contact ball bearing BH719.2RZ BH70.2RZ, HCBH719.2RZ and HCBH70.2RZ is injected into high-speed durable grease and the two sides is set with non-contact seal ring, preventing the bearing from revolution and extending the application area of grease lubrication.
The assembly of bearing 
In order to improve the load capacity and rigidity of bearing, angular contact ball bearing is usually used with two or more bearings. The actual inner diameter and outer diameter deviation of the bearing in the same group should not exceed 1/3 of the corresponding inner and outer diameter tolerance value. The contact angle difference of the same bearing group should be as small as possible. Its preload can be divided into light (L), medium (M), heavy (H) and special preload. The arrangements of assembling angular contact ball bearing include back-to-back or face-to-face arrangement. The preload setting can be achieved without taking other adjustments, and the load could be evenly distributed in tandem arrangement. When the preload is set beforehand, the measuring of bearing projection amount and the manufacturing process of various widths of spacers can be diminished in installation.
Back-to-back arrangement: Since action line is divergent in this arrangement, the distance of the effective pivot between bearings is enlarged in this arrangement. It can support axial load and radial load in either direction with good axial rigidity, radial rigidity and the capacity of taking overturning movement. The contact angles of two sets of bearings may different when applying various preloads according to the application conditions.

The limiting speed of angular contact ball bearings are usually reduced in back-to-back and face-to-face arrangements. The details are in “The limiting speed of bearing” 
Grease lubrication
The angular contact ball bearing should be pay special attention to the grease filling of cavity between the cage and the bearing outer ring rib. It is recommended to fill in grease cautiously with a syringe to make it be distributed evenly in the cavity of its guiding clearance. The grease filling amount is seen in table data of “The grease filling amount of BEM bearing” for reference. The grease supplement and replacement should be adopted regularly. When supplying grease, it should be paid attention that the different types of grease can not be mixed used, or the performance of grease will be reduced. When replacing grease, the old grease should be cleaned with special gasoline when is also be adopted when soiling bearing accidentally during installation.
The preload and rigidity of bearing
Angular contact ball bearing: The preload of the bearing is generally divided into the three grades of light (L), medium (M) and heavy (H). If the users have special requirement, BEM also can provide precision bearing with special load. The limiting speed of bearing
1. Angular contact ball bearing
Under the same condition, the limiting speed of angular contact ball bearing is highest in all precision rolling bearings. The model catalog provides the bearing limiting speed under grease lubrication and oil lubrication (oil-air or oil mist lubrication) just for reference. The speed value is suitable for the following cases:
(1) Bearing accuracy of ISO4 standard
(2)Single set of bearing under fixed pressure and light preload (such as spring)
(3) Normal installation, suitable fit of bearing with shaft and housing, rotating parts dynamic balance
(4) Grease adopt suitable high quality grease, moderate amount of grease
(5) The performance of lubricants is good under oil lubrication. Suitable viscosity, adequate amount of oil
(6) Bearing can not be overloaded, and it rotates in the normal operating temperature 
The limiting speed value given in the model catalog indicates the highest speed in the ideal state. The actual use of the rotational speed may be higher or lower due to the limitation of the variety of conditions depending on the bearing number, configuration, preload, external load, and lubrication and heat dissipation etc. The limiting speed given in bearing dimension table is the single set of precision bearing produced in accordance with ISO4 standard. As for ultra-precision IS02 and IS05 stand bearing, the limiting speed should be the sample value multiplied by 1.1 and 0.9 respectively. The limiting speed of assembled bearing should be determined based on assembling method and preload etc.
The working temperature of angular contact ball bearing is related to bearing material, preload, working cooling form, and ambient temperature etc. Under normal circumstances, the greater the load is, the higher the speed will be, and the working temperature will be higher. Moreover, the working temperature of grease lubricated bearing is higher than oil lubricated bearing.
The bearing ring of BEM precision angular contact ball bearing can withstand the high temperature of 150 ℃. While adopting the high quality cage manufactured inhigh quality phenolic laminated fabric tube, the highest temperature is up to 120℃. 
Under normal circumstances, if the bearing does not take artificial cooling and are not influenced by the external heat source, the temperature of the inner ring is always higher than the temperature of the outer ring, and the temperature of rolling elements is higher than inner ring.
The over high temperature will change the internal state of the bearing. For precision angular contact ball bearing, the difference in temperature between the inner and outer rings will cause bearing working preload force is greater than assembly preload force and even result in bad situation such as the bearing premature wear, sticking etc in high temperature. Therefore, it is necessary to control the working temperature of the bearing.
When the bearing is applied with high-quality anti-aging grease lubrication, the measured temperature of the outer ring should not exceed 55℃, Otherwise, the grease will be in a sharp deterioration, which will directly impact on work status and life of the bearing. When using oil mist or oil-air lubrication, the permissible working temperature of the bearing is much higher than grease lubrication according to lubrication and cooling condition. If the high-temperature bearing is needed, please place special order after consulting BEM technical department.
The adjustment of bearing
Angular contact ball bearings: The angular contact ball bearing is mostly used for two and more assemblies. Bearing group or general bearing assembly group is produced according to the prescribed three preloads of light, medium and heavy or the preload required by the user. The pre-load is determined before installation. The preload will be greatly increased by the fitted adaptability of the shaft and the housing, the manufacturing error with other adjacent parts and improper installation, and then cause the bad result. In order to achieve the best performance and consistent accuracy during the installation process, the following aspects are proposed to paid attention to besides the principles offered.
The spindle axis journal and bearing saddle bore should be better matched with the actual bearing inner and outer diameter according to the fitting requirement to ensure that the fitting gap or interference will meet the design requirements.
Spacer is often used to separate bearings from each other in many bearing applications.
See diagram of "Back-to-back, spacer separation". The internal and external spacer should be manufactured with very high accuracy. The width should be the same and plane parallel, and the shaft mated shoulder can run without run-out. The spacer manufacturing is shown in “The internal and external spacer tolerance of bearing mating parts” table of “Bearing mating parts manufacturing tolerances”.
The internal and external spacer is advised to grind and polish spontaneously to make it affect the preload value as small as possible. If the preload is needed to be changed, it can be achieved through changing the width of the spacer in back-to-back or face-to-face configuration.
To increase the preload of back-to-back configuration, the internal spacer must be narrower than the external spacer; and to reduce the preload, the external spacer should be narrower than the internal spacer. For face-to-face configuration, the opposite method should be applied.
The bearing dimension table provides the axial rigidity of single bearing in different standards of preloads.

Bearing installation should take directional assembly, which means the highest point of outer ring run-out of several bearings in bearing assembly should be in line and placed in 180° position of bearing block eccentric amount. For spindle, the highest point of inner ring run-out of several bearings should be in line and placed in 180° position of maximum eccentric amount of spindle. The impact of eccentricity should be reduced at the minimum during installation.
When the spindle bearing is fixing bearing inner ring, the bad influence caused by non-perpendicularity between locking nut and axis should be avoided, therefore, the locking nut must also be precision manufacturing, and the axial run-out deviation of the thread with respect to the end face is 2μm. The tightening torque of nut should be determined through experience and testing based on actual conditions corresponding to different preloads.
Most of the bearing outer rings apply axial positioning through flange plate with the round-headed bolt. Especially for the bearing series with small cross-sectional area, the outer ring deformation will appear when the bolt preload is too large, and preload of the bolt on one side. Therefore, the several bolts should be used for flange plate with not-so-small uniform controlled top spin force to obtain the ideal effect. The preload clearance between the bearing cover and the bearing block can be controlled in the range of 0.01-0.04mm.
The introduction of precious angular contact ball bearing
The BEM precision angular contact ball bearing specially produced for machine tools and other applications has very high requirements for the bearing accuracy and the speed. BEM precision angular contact ball bearing is inseparable and there must be a contact angle. In these bearings, the load is in the axial direction, delivering a bearing ring to the other bearing ring through angular contact. Thus, the bearings can also take axial load in single direction besides taking radial load. Since axial load derived from radial load must be counteracted with an external axial force, the bearing should be mounted oppositely with the second bearing. 
The internal design of BEM precision angular contact ball bearing differs significantly from the ordinary single row ball bearings, reflecting the style of modern machine tool spindle bearings. One of the two bearing ring only has one rib, reducing the weight of the bearing. The structural features include small contact angle, light cage and many steel balls etc.
In order to meet the needs of modern machine tools as far as possible, BEM manufactures precision angular contact ball bearings in multiple series and structures. They can be supplied in two ways of single and in pairs.
The BEM precision angular contact ball bearings have three dimensions series, including 719,70 and 72, which are set with the 15-degree contact angle (code suffix C) or the 25-degree contact angle (code suffix E). For area requiring high axial rigidity and axial carrying capacity, the bearing with large contact angle should be recommended to use.
As a part of the BEM sustainable development plan, the bearings of C and E contact angle series are redesigned, therefore the performance has been improved fundamentally. After the improvement, the contact between the ball and raceway is better, the cage is guided by outer ring, the rolling elements are more and larger, which makes greatly enhance of the rigidity of the bearing and carrying capacity and allows the bearing run at higher speeds.
If only a small radial space is available or high-speed running is required, the 719 or 70 bearings series should be selected. For heavy loads, the medium speed is more applicable for 72 bearing series. If rigid requirements are primary, the 719 bearing series with large spindle diameter has its great advantages.
They are equipped with many steel balls. The two factors of the increase of shaft diameter and the increase of ball number are beneficial for improving the rigidity of spindle system. In fact, the increase of ball number is able to increase the rigidity more than the increase of shaft diameter, so the bearing of light series has better rigidity than the bearing of heavy series.
The main structural features and related parameters:
Pre-tightening
For single set of bearings, the preload is obtained immediately after installed and its size depends on the adjustment degree for the second set of bearing. The second set of bearing can adjust axial load acting on the first set of bearing in the opposite direction.
In order to meet the requirements related to the speed and rigidity, the sets of bearings in the back-to-back, face-to-face paired installments can be divided into three classes of preloads.
Class L: light preload
Class M: Medium preload
Class H: heavy preload
The size of the actual pre-load depends on the bearing series, contact angle and bearing size. The preload values listed is taken as the standard value before the back-to-back and face-to-face installments. When the three, four or even five sets of bearings are applied in back-to-back or face-to-face installment, the preload is greater than the paired combinations. After the installment, the preload value of combined bearings in pairs is always increased. The increase depends on the fitting between bearing and shaft or saddle bore and the rigidity of shaft or saddle bore.
Cage
All BEM precision angular contact ball bearings are used with outer ring guided enforced phenolic rubberized fabric cage. This type of cage has light weight and small centrifugal force, allowing lubricating media entering into the contact surface of steel ball and raceway freely.
The code of precision angular contact ball bearing 
The code of a complete single bearing will mark the bearing series, bore diameter, contact angle and structure, and the suffix shows the precision grade of the bearing, such as the suffix of 71906C/P4A. bearing combination mated in pairs also indicates the bearing set number, row, and  the preload of combination,
Limiting speed
The limiting speed in drip lubrication chooses the maximum value, while this value will be reduced when adopting other lubrications. The limiting speed of grease lubrication takes the maximum value, the maximum limiting speed will be obtained from high-quality flexible viscosity.
If taking two sets, three sets, four set and even five sets of combined bearings in pairs, the limiting speed is lower than the value given in the table. The proper limiting speed should be of multiplying these coefficients by the index value given in the table.
If the limiting speed obtained above is improper, such as a single structural change, adding intermediate ring between bearings, the properly increase of the limiting speed value is allowed. For example, the limiting speed run of bearings with three combinations can be calculated according to bearing combination in pairs. It is very favorable to take preload for bearings with spring. This preload form is usually used in high-speed running to get the even preload in the whole process of machine tool.
combined bearings in pairs
BEM can supply two, three, four or even five sets of combined bearings in pairs assemblies according to requirement.
These combined bearings in pairs are adjusted during manufacturing. When bearing is installed adjacently, the predetermined pre-load value can be obtained and the load is evenly taken by each set of bearing. The tolerance of inner bore and outer diameter of combined bearings in pairs are slightly higher than the half of tolerance of single set of bearing.
The pressure line of bearing in back-to-back installation diverges along the axis, which can withstand the axial load in double directions. The bearing in back-to-back installation has pretty good rigidity and can support the overturning torque.
The pressure line of bearing in face-to-face installation restrains diverges along the axis, which can also withstand the axial load in double directions. The rigidity of bearing in face-to-face installment is not as good as the bearing in back-to-back installation and not suitable to support the overturning torque.
With bearing pressure line installed parallel in series, the radial load and axial load are evenly distributed in the bearing while the bearing can only take axial load in single direction, therefore, the other set of bearing undertaking the axial load in the opposite direction should be set for this tandem installment. When the other set of bearing undertaking the axial load in the opposite direction is not allowed, only tandem installment in back-to-back or face-to-face paired combination are generally applied.
Oil lubrication
The oil lubrication is applied when grease lubrication can not meet the speed requirement of high-speed precision angular contact ball bearing. The oil lubrication methods include mist lubrication, oil-air lubrication and oil jet lubrication etc.