# Angular Contact Ball Bearing

Single row angular contact ball bearings can not only withstand radial load and axial load in one direction, but also accommodate only axial load in single direction, radial loads produce axial forces in these bearings that need to be balanced by counter forces.Therefore, the single row angular contact ball bearings often need to be installed with other bearings which withstand axial load in the opposite direction. In other words, the angular contact ball bearings are commonly used in pair, or in groups with three, four and even five bearings. Angular contact ball bearings have higher limiting speed.

The bearings codes designation:

The bearings matched ways as below :

 DBThe load lines in a pair of bearings by back to back assembly are enlarging from the bearing axis. It can bear axial load in two directions and relative larger moment because of larger angular rigidity. DFThe load lines in a pair of bearings by face to face assembly are convergence toward the bearing axis. It can bear axial load in two directions and smaller moment because of smaller angular rigidity. DTA pair of bearings by series a ssembly only bear axial load in one direction, but it is able to bear larger axial load related to DB and DF. TBTThe tri-bearing matching TBT or TFT isobtained by increasing the same type of the bearing based on DB or DF There are higher axial and radial rigidity for TBT and TFT, so larger load can be supported. QBCThe four bearing matching QBC (or QFC) is obtained by matching double set of DB (or DF) bearings. QBT (or QFT) is formed when three bearings are installed in a same direction and another one back (or face) to them. PBCDivide the five bearings into two groups of three and two bearings respectively, in which the bearings are all installed in the same direction, PBC is formed when the groups match each other by back to back and PFC by face to face. If four bearings are installed in the same direction and another one back (or face) to them, then PBT (or PFT) is formed.

1.MONTON Angular contact ball bearings performance and Characteristics.

The MONTON precision angular contact ball bearings for spindle, have four size series, 718,719,70 and 72. With the same inner diameter, but the outer diameter and the width of 718,719,70 and 72 series increase in turn.

Fig.1  Angular contact ball bearing dimension series

MONTON precision angular contact ball bearings with 15° (C) and 25° (AC) contact angles. As for the angular contact ball bearings, the bigger the contact angle is, the greater the axial load capacity is, but the lower the limiting speed of bearings becomes. Therefore, the spindle, with high speed and small axial load, should adopt the 15° angular contact ball bearings, whereas the 25° angular contact ball bearings should be adopted.

MONTON precision angular contact ball bearings with high-speed angular contact bearings (standard series), super high-speed angular contact ball bearings, high-speed sealed angular contact ball bearings and high-speed spindle bearings.

The inner ring, outer ring and rolling element of rolling bearing under normal operating conditions are made of high carbon chromium bearing steel, but the steel bearings cannot meet the requirements of such special conditions as high speed, wear-resisting, low temperature rising, long life and high reliability etc., then Si3N4 ceramics are believed to be present optimum rolling bearing materials to replace bearing steel.

Table 1. Main performance comparison between Si3N4 and bearing steel

 Performance Code and unit Si3N4 Bearing steel Density γ[g/mm3] 3.2 7.8 Coefficient of thermal expansion α[1/℃] 20～1000℃ 3.2×10-6 - 20～300℃ - 11.8×10-6 Modulus of elasticity E[N/mm2] 3.15×105 2.08×105 Poisson's ratio μ 0.26 0.3 Rigidity HV10 1700 700 Stress  intensity σB[N/mm2] 20℃ 700 2400 1000℃ 700 0 Fracture toughness Kie[MN/m1.5] 7 25 Coefficient of heat conductivity λ[W/m℃] 30～40 40～50 Electrical resistivity [Ωmm2/m] 1017～1018 0.1～1

MONTON also offers widely used hybrid angular contact ball bearings for spindles in high-speed precision machine tools and other high-speed precision machines, that is, the inner and outer rings are made of high-quality bearing steel materials, while the rolling element is made of Si3N4 ceramics.

Compared to the angular contact ball bearings made of steel, hybrid angular contact ball bearings with the same structure and size have high speed, high stiffness, low friction heat, and long life etc.

MONTON precision hybrid bearings with ceramic ball (HQ1) can significantly improve the speed, rigidity, reliability, and productivity of machine tools, and greatly reduce the friction heat, then extend the service life of host machine etc.

Table 2. The type and performance of MONTON angular contact ball bearing

 MONTON angular contact ball bearing series Structures Dimension series Bore size range Performance High precision angular contact ball bearing 718 C718 AC719 C719 AC70 C70 AC72 C72 AC 718：10～360mm719：8～460mm70： 8～380mm72： 8～220mm High speedLarge loading capacitySuit for grease or oil-mist lubrication High speed angular contact ball bearing(hybrid ball bearing) H719 CH719 ACH70 CH70 ACH719 C/HQ1H719 AC/HQH70 C/HQ1H70 AC/HQ1 H719：8～220mmH70：8～220mmH719/HQ1：8～220mmH70/HQ1：8～220mm Super speedHigh rigiditySuit for air-oil or oil injection lubrication Super speed angular contact ball bearing(incl.hybrid ball bearing) HS719 CHS719 ACHS70 CHS70 ACHS719 C/HQ1HS719 AC/HQHS70 C/HQ1HS70 AC/HQ1 HS719：8～220mmHS70：8～220mmHS719/HQ1:8～220mmHS70/HQ1:8～220mm Super speed(higher than H series)High rigiditySuit for air-oil or oil injection lubrication Super speed angular contact ball bearing with direct lubrication(incl. hybrid ball bearing) H719 C-DLH719 AC-DLH70 C-DLH70 AC-DLH719 C/HQ1-DLH719 AC/HQ-DLH70 C/HQ1-DLH70 AC/HQ1-DL H719-DL：20～220mmH70-DL：30～220mmH719/HQ1-DL：20～220mmH70/HQ1-DL：30～220mm Super speed (higher than H and HS series)High rigidity.Suit for direct lubrication High speed sealed angular contact ball bearing(incl. hybrid ball bearing) B719 C-2RZB719 AC-2RZB70 C-2RZB70 AC-2RZB70 C-2RZ/HQ1B719 AC-2RZ/HQ1B70 C-2RZ/HQ1B70 AC-2RZ/HQ1 B719-2RZ：10～220mmB70-2RZ：10～220mmB719-2RZ/HQ1:1～220mmB70-2RZ/HQ1：10～220mm High speedHigh rigidityGrease lubrication

2.The principles of selecting precision bearings

MONTON has developed and produced various kinds and structures of high-speed precision bearings, each of which has special working conditions. Selecting different types and structures should depend on specific working conditions. When choosing bearings, the following properties should be taken into consideration.

2.1 Dimension series

Among MONTON precision bearings, angular contact ball bearings have four diameter series 18,19, (1) 0, (0) 2; the ball screw support bearings have two diameter series, (0) 2, (0) 3. With the bore diameters in the same size, the outer diameters and width dimensions of 18,19, (1) 0, (0) 2, (0) 3 series increase in turn.

Fig. 13 The comparison of each dimension series between angular contact ball bearings and ball screw support bearings

The (1) 0 diameter series bearings are most usually used among angular contact ball bearings, cylindrical roller bearings, double direction angular contact thrust ball bearings and tapered roller bearings for high-speed precision machine spindle.

As for the angular contact ball bearings, if the radial space in mounting position is limited or the required speed of spindle is higher, (1) 0 or 19 diameter series are recommended, and even 18 diameter series; if spindle supports large load, speed is not quite high and mounting space is not limited, the (0) 2 diameter series are preferred.

the greater the axis diameter of spindle is, the higher the rigidity becomes. To improve the bearing rigidity is to increase the number of balls, which is more favorable than increasing the ball diameter.

3. Bearing precision

MONTON can supply the P5,P4,P2 accuracy angular contact ball bearings.

Here below is the list for the different accuracy:

Table 4. Tolerances for the inner ring of angular contact ball bearing in P5 (μm)

 dmm △dmp Vdp(1) Vdmp Kia Sd Sia △Bs VBS Diameter series 9 0、2 All Normal Revise From to Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 2.51018305080120180 1018305080120180250 00000000 -5-5-6-8-9-10-13-15 55689101315 4456781012 33345578 444556810 7788891011 7788891013 00000000 -40-80-120-120-150-200-250-300 -250-250-250-250-250-380-380-500 555567810

Table 5. Tolerances for the outer ring of angular contact ball bearing in P5(μm)

 Dmm △Dmp VDp(1)(2) VDmp Kea SD Sea △Cs VCS Diameter series 9 0、2 From to Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 618305080120150180250315 18305080120150180250315400 0000000000 -5-6-7-9-10-11-13-15-18-20 5679101113151820 45578810111415 33455678910 5678101113151820 888891010111313 88810111314151820 Width   deviation △Cs is identical with △Bs of the corresponding inner ring. 5556888101113

Table 6. Tolerances for the inner ring of angular contact ball bearing in P4(μm)

 dmm △dmp △ds(1) Vdp(2) Vdmp Kia Sd Sia △Bs VBS Diameter series 9 0、2 All Normal Revise From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 2.51018305080120180 1018305080120180250 00000000 -4-4-5-6-7-8-10-12 00000000 -4-4-5-6-7-8-10-12 4456781012 33455689 222.533.5456 2.52.5344568 33445567 33445578 00000000 -40-80-120-120-150-200-250-300 -250-250-250-250-250-380-380-500 2.52.52.534456

Table 7. Tolerances for the outer ring of angular contact ball bearing in P4(μm)

 Dmm △Dmp △Ds(1)(2)(3) VDp(2)(3) VDmp Kea SD Sea △Cs VCS Diameter series 9 0、2 From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 618305080120150180250315 18305080120150180250315400 0000000000 -4-5-6-7-8-9-10-11-13-15 0000000000 -4-5-6-7-8-9-10-11-13-15 45678910111315 345567881011 22.533.5455678 3455678101113 44445557810 5555678101013 Width   deviation △Cs is identical with △Bs of the corresponding inner ring. 2.52.52.53455778

Table 8. Tolerances for the inner ring of angular contact ball bearing in P4A(μm)

 dmm △dmp △ds(1) Vdp(2) Vdmp Kia Sd Sia △Bs VBS All Normal Revise From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 2.51018305080120150180 1018305080120150180250 000000000 -4-4-5-6-7-8-10-10-12 000000000 -4-4-5-6-7-8-10-10-12 2.52.52.52.545778 1.51.51.51.522.53.53.54 1.51.52.52.52.52.52.555 1.51.51.51.51.52.52.545 1.51.52.52.52.52.52.555 000000000 -40-80-120-120-150-200-250-250-300 -250-250-250-250-250-380-380-380-500 1.51.51.51.51.52.52.545

Table 9. Tolerances for the outer ring of angular contact ball bearing in P4A(μm)

 Dmm △Dmp △Ds(1)(2)(3) VDp VDmp Kea SD Sea △Cs VCS From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 618305080120150180250315 18305080120150180250315400 0000000000 -4-5-6-7-8-9-10-11-13-15 0000000000 -4-5-6-7-8-9-10-11-13-15 2.54445578810 1.52222.52.53.5445 1.52.52.54555778 1.51.51.51.52.52.52.5457 1.52.52.54555778 Width   deviation △Cs is identical with △Bs of the corresponding inner ring. 1.51.51.51.52.52.52.5457

Table 10. Tolerances for the inner ring of angular contact ball bearing in P2(μm)

 dmm △dmp △ds Vdp(1) Vdmp Kia Sd Sia △Bs VBS All Normal Revise From 到 to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 2.51018305080120150180 1018305080120150180250 000000000 -2.5-2.5-2.5-2.5-4-5-7-7-8 000000000 -2.5-2.5-2.5-2.5-4-5-7-7-8 2.52.52.52.545778 1.51.51.51.522.53.53.54 1.51.52.52.52.52.52.555 1.51.51.51.51.52.52.545 1.51.52.52.52.52.52.555 000000000 -40-80-120-120-150-200-250-250-300 -250-250-250-250-250-380-380-380-500 1.51.51.51.51.52.52.545

Table 11. Tolerances for the outer ring of angular contact ball bearing in P2(μm)

 Dmm △Dmp △Ds VDp VDmp Kea SD Sea △Cs VCS From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 618305080120150180250315 18305080120150180250315400 0000000000 -2.5-4-4-4-5-5-7-8-8-10 0000000000 -2.5-4-4-4-5-5-7-8-8-10 2.54445578810 1.52222.52.53.5445 1.52.52.54555778 1.51.51.51.52.52.52.5457 1.52.52.54555778 Width   deviation △Cs is identical with △Bs 1.51.51.51.52.52.52.5457

Table 28. Tolerances for inner ring of ball screw support bearings in P4(μm)

 dmm △dmp △ds Vdp Vdmp Kia Sd Sia △Bs VBS All Normal Revise From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 1018305080120 18305080120150 000000 -4-5-6-7-8-10 000000 -4-5-6-7-8-10 345568 22.533.545 2.534456 344556 222334 000000 -80-120-120-150-200-250 -250-250-250-250-380-380 2.52.53445

Table 29. Tolerances for outer ring of ball screw support bearings in P4(μm)

 Dmm △Dmp △Ds VDp VDmp Kea SD Sea △Cs VCS From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 18305080120150180250 305080120150180250315 00000000 -5-6-7-8-9-10-11-13 00000000 -5-6-7-8-9-10-11-13 455678810 2.533.545567 4556781011 44455578 22334445 Width   deviation △Cs is identical with △Bs of the corresponding inner ring. 2.52.5345577

Table 30. Tolerances for inner ring of ball screw support bearings in P2(μm)

 dmm △dmp △ds Vdp Vdmp Kia Sd Sia △Bs VBS All Normal Revise From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 1018305080120 18305080120150 000000 -2.5-2.5-2.5457 000000 -2.5-2.5-2.5457 2.52.52.5457 1.51.51.522.53.5 1.52.52.52.52.52.5 1.51.51.51.52.52.5 222334 000000 -80-120-120-150-200-250 -250-250-250-250-380-380 1.51.51.51.52.52.5

Table 31. Tolerances for outer ring of ball screw support bearings in P2(μm)

 Dmm △Dmp △Ds VDp VDmp Kea SD Sea △Cs VCS From to Upper deviation Lower deviation Upper deviation Lower deviation max max max max max Upper deviation Lower deviation max 18305080120150180250 305080120150180250315 00000000 -4-4-4-5-5-7-8-8 00000000 -4-4-4-5-5-7-8-8 44455788 2222.52.53.544 2.52.5455577 1.51.51.52.52.52.545 22334445 Width   deviation △Cs is identical with △Bs of the corresponding inner ring. 1.51.51.52.52.52.545

4.The limiting speed

The limiting speed of angular contact ball bearing is the highest in all rolling bearings under the same condition.

The limiting speed of rolling bearing depends on the structural types, dimensional series, dimensional sizes, cage materials and structures, bearing precision, internal clearance, preload, external load, lubrication methods and conditions, allowable working temperature, cooling measures, the precisions of fitting shaft and housing, etc. The limiting speeds in the condition of grease lubrication and oil (oil gas or oil mist) lubrication, listed in the sample, are only for reference. The speed values are appropriate for the following conditions:

(1)Bearing precision: The precision of angular contact ball bearings and ball screw support bearings is in P4 level, the precision of cylindrical roller bearings and double direction angular contact thrust ball bearings is in SP level, the precision of tapered roller bearings is in P5 level.

(2)It's used for single bearing with light preload.

(3)The bearing should be assembled regularly with shaft and housing with appropriate fitting, running the bearing parts is to keep a dynamic balance.

(4)The lubricating grease, with high quality and suitable for precision bearing, is adopted to grease lubrication with appropriate amount of grease.

(5)The lubricating oil keeps excellent performance, suitable viscosity and sufficient amount of oil.

(6)The preload of bearings can not be excessive with bearing running at the normal working temperature.

The limiting speeds value given in the catalogue are the maximum speeds under ideal conditions, while the actual speeds are generally lower than the given value according to the variety of conditions.

The limiting speeds of matched bearing are determined by matching methods, preload level, and bearing precision level. The limiting speeds will be reduced with the reduction coefficient in the Table 32.

Table 32. The reduction coefficient of limiting speed

 Matched methods Preload level Tolerance class 2 4 5 DT A 0.99 0.9 0.81 B 0.88 0.8 0.72 C 0.7 0.65 0.58 DB A 0.88 0.8 0.72 B 0.77 0.7 0.63 C 0.6 0.55 0.5 TBT A 0.77 0.7 0.63 TFT B 0.6 0.55 0.5 TT C 0.38 0.35 0.31 QBT、QBC A 0.71 0.65 0.58 QFC、QFT B 0.5 0.45 0.4 QT C 0.27 0.25 0.22

High-speed spindle bearing and ball screw support bearings , in normal working condition, should be preloaded with axial load, aiming at improving bearing running accuracy, reducing rolling elements' sliding in high speed, increasing bearing rigidity, decreasing the axial and radial movement of support, increasing bearing damping, reducing noise, increasing bearing service life, etc.

1)The preload and stiffness of angular contact ball bearing

The usual offered preloads of angular contact ball bearing are Light (A), Medium (B) and High (C). Moreover, we can preload bearings with special value on customers' request.

As the position preloaded bearing running, the relative position of parts in supporting is fixed. While the angular contact ball bearing running in high speed, the balls tend to be throwed out due to the centrifugal force, which makes the inner ring and outer ring tend to move relatively in axial direction. However, since the position has been relatively constant, the bearing preload will be enlarged and the friction heat willt be intensified. Moreover, with the change of working temperature, the housing dimension and the positioning components dimension will also change, and then bearing preload will be affected. Therefore, pay attention to the effect that the change of preload plays on bearing working performance, while adopting the position preload.

The constant pressure preload is to make use of coil spring, belleville spring and other elastic components to make the bearing preloaded properly in the supporting position. Since the rigidity of spring preload is usually much smaller than that of bearing, the constant pressure preload is decided by the preload devices with the constant value. Moreover, the preload level of bearing supporting will not affected by the working temperature.

Summary:The fixed position preload is good for improving bearing rigidity, while the fixed pressure preload is used to high-speed running occasions.

Table. 48 The Axial Rigidity Ra of B70 C/HQ1Series Bearings Matched in DB or DF N/μm

 dmm B70 C B70 C/HQ1 Preload level A B C A B C 10121517202530354045505560 14151718232933374145485557 20222526334147536065697982 2528313342535966768187100103 16171920263237414650546264 22252829374653596773778892 2831353747596674859197112115

Why choose the high precision angular contact ball bearings?

 REASONS BENEFIT REDUCED RUN OUT (P4,P2) HIGH WORKPIECE ACCURACY HIGH SPEED SHORTER WORKING TIMEBETTER SURFACE FINISHING LOW FRICTION LOW WORKING TEMPERATURE PRELOAD HIGH STIFFNESS

How to choose the bearings series during the real application?

 MACHINE BEARING TYPE BEARING SERIES TURNING HIGH LOAD 70/719/72 MILLING HIGH LOAD 70/719/72 MACHINING CENTER HIGH SPEED H70/H719 HIGH SPEED MILLING HIGH SPEED +CERAMIC BALL H70+CERAMIC BALL GRINDING HIGH SPEED +CERAMIC BALL H719+CERAMIC BALL H718+CERAMIC BALL

How to choose the lubrication ways?

 BEARING TYPE SPEED FACTOR LUBRICATION HIGH LOAD <1.0 Mndm Grease >1.0 Mndm Oil Bath or circulation HIGH SPEED <1.5 Mndm Grease >1.5 Mndm Oil injection or mist or air-oil HIGH SPEED+CERAMIC BALL <1.8 Mndm Grease >1.8 Mndm Air-oil or minimal oil lubrication

How to calculate the speed factor

Speed factor ndm is calculated to compare working conditions of different bearings, regardless their dimensions.

D  = outer diameter (mm)

d  = bore diameter (mm)

n  = shaft speed (rpm)

dm = pitch diameter (mm)

dm = 0.5x(D+d)

ndm = dm x n

How to calculate the grease qty?

Q0 = 33% free space

Q = Q0 x K   [cm3]