Don't Miss This! Angular Contact Bearing Knowledge Overview

1. Angular Contact Bearing Product Overview

 

Rolling bearings are crucial components of rotating equipment. Both the axial and radial loads of the equipment are transmitted to the equipment support parts through the bearings. Generally, we select bearings according to different working conditions, such as load conditions, bearing arrangements, types of lubrication, etc. The correct selection and use of bearings have a significant impact on whether the bearings can reach their expected service life.

 

Angular contact bearings are rolling bearings that can withstand both radial and axial loads simultaneously. Their core feature is the single sided contact angle design. Compared with deep groove ball bearings, angular contact bearings have a single sided contact angle. Therefore, a single row angular contact bearing can only bear an axial load in one direction or a combined load. Due to the influence of the contact angle, an axial component force will also be generated after bearing the radial load. So, generally, two bearings are used in opposition or more than two are used in pairs. This type of bearing is suitable for scenarios with high rigidity, high precision, and combined loads, such as machine tool spindles, gearboxes, and motors.

 

2. Assembly Forms and Codes of Angular Contact Bearings (Refer to Standard GB/T 272)

 

a) Paired Assembly (Matching)

b) Triple Assembly

c) Quadruple Assembly

 

 

 

3. Understanding the Configuration of Matched Bearings (e.g., Paired assembled Bearings)

 

It is of great importance to understand the configuration of matched bearings during the selection and assembly process. Incorrect installation and lack of understanding of equipment applications may lead to problems such as slipping or overheating during equipment operation. The following analysis takes paired assembled bearings as an example:

 

1) Back - to - Back Arrangement (DB type)

 

Also known as the O - shaped arrangement (the bearing model generally contains the DB mark when selecting the bearing). This arrangement can provide maximum stability and rigidity. In this arrangement, the end faces of the inner rings are in contact with each other through pre - compression to achieve pre - load, and it can bear axial loads in both directions as well as radial loads.

For a back - to - back combination, the force on the inner ring of the bearing pushes the rolling elements towards the outer ring. The outer ring exerts a reaction force to the applied load, and this load is towards the centerline of the shaft. According to the contact angle, the reaction forces of the two bearings will diverge. The distance between the two reaction forces is L. Since L is greater than the width of the bearing, the back - to - back arrangement has a better rated resistance to the moment in the bearing system.

 

 

Advantages of DB Type Configuration:

 

• High rigidity
• Can bear moment loads.

 

2. Face - to - Face Arrangement (DF type)

 

Also known as the X arrangement (the bearing model generally contains the DF mark when selecting the bearing). This arrangement can tolerate a certain amount of misalignment error, but it cannot support moment loads as effectively as the back - to - back arrangement. If misalignment between bearing positions cannot be avoided, it is recommended to use a face - to - face bearing arrangement.

In this arrangement, compared with the back - to - back arrangement, the reaction load lines converge inward, the span L decreases, so the rigidity weakens, and the misalignment tolerance ability increases.

 

 

Advantages of DF Type Configuration:

 

• Can compensate for a certain amount of misalignment error, but the structural rigidity is not as good as that of the DB type.

 

Assembly Form	Code	Arrangement Characteristics	Advantages	Applicable Scenarios
Back - to - Back (DB type)	DB	Inner ring end faces are pre - tightened and in contact, with a large span L	High rigidity, strong moment - resistance ability	High - precision machine tools, spindles
Face - to - Face (DF type)	DF	Reaction force lines converge, with a small span L	Tolerates misalignment error	Occasions with installation deviations
Tandem (DT type)	DT	Axially stacked arrangement	Bears unidirectional heavy loads	Unidirectional thrust - load equipment

 

Note: Triple (TBT/TFT/ TT type) and quadruple assemblies (QBC/QFC/QT type) are suitable for higher loads or complex working conditions.

 

4. Key Parameters and Technical Requirements

 

Pre - load, Pre - clearance and Protrusion of Angular Contact Bearings

 

1. JB/T 2974 stipulates the representation methods of pre - load and pre - clearance of assembled bearings:

 

a) Pre - load

(G)A --- Light pre - load;

(G)B --- Medium pre - load;

(G)C --- Heavy pre - load.

Note: The symbol (G) in the code can be omitted.

For special pre - loads, the code representation method is GXXX. For example, for a special pre - load of 325N, the code is G325.

 

b) Pre - clearance

CA --- Smaller axial clearance

CB --- Medium axial clearance

CC --- Larger axial clearance

 

Code	Axial Clearance	Applicable Scenarios
CA	Smaller	High - precision positioning
CB	Medium	General working conditions
CC	Larger	High - temperature or expansion compensation

 

2. Protrusion

The protrusions b and f of a single - set bearing in an assembled bearing and the protrusion after configuration (taking DB and DF types as examples) are shown in the figure:

 

Protrusion of single bearing

 

The protrusion of an assembled bearing

 

The sum of the protrusion deviations of two adjacent bearings in an assembled bearing, △b1 + △b2 or △f1 + △f2 (for back - to - back and face - to - face configurations), and the difference of the protrusion deviations, △b1 - △f2 or △f1 - △b2 (for tandem configuration) shall comply with the following regulations (unit: μm):

 

d mm		The sum (or difference) of the protrusion deviations of two adjacent sets of bearings
		Bearing tolerance grade
		6		5		4		2
>		min	max	min	max	min	max	min	max
10°	18	-1.5	+1.5	-1	+1	-1	+1	-1	+1
18	30	-1.5	+1.5	-1	+1	-1	+1	-1	+1
30	50	-2	+2	-1.5	+1.5	-1	+1	-1	+1
50	80	-2	+2	-1.5	+1.5	-1.5	+1.5	-1.5	+1.5
80	120	-3	+3	-2	+2	-1.5	+1,5	-1.5	+1.5
120	150	-3	+3	-2	+2	-1.5	+1.5	-1.5	+1.5
150	180	-4	+4	-3	+3	-2	+2	-2	+2
180	250	-4	+4	-3	+3	-2	+2	-2	+2
*Including 10mm.

 

For universal - assembled bearings, the protrusions of the two end faces of a single - set bearing should be equal, that is, b = f.

 

3. Spacer Ring

Inner and outer spacer rings can be used between the two bearings in an assembled bearing, as shown in the figure:

 

 

The width tolerance △H of the inner and outer spacer rings shall comply with the regulations in the following table. The parallelism error of the two end faces should not exceed 1/2 of the width tolerance.

 

d/mm		Width tolerance △n/pm
>	≤	min	max
10*	55	-1	+1
55	150	-1.5	+1.5
150	220	-2	+2
*Including 10mm.

The spacer ring is made of high carbon chromium bearing steel GCr15 or materials with equivalent performance. The heat - treatment hardness is 45HRC - 60HRC, or the same as the hardness range requirements of the bearing rings.

 

5. Measurement Method of the Protrusion of Assembled Bearings

 

The measurement method of the protrusion of assembled bearings is shown in the figure (taking the measurement of the protrusion b of the back end face as an example).

Install the inner ring of the bearing onto the mandrel to ensure the correct horizontal positioning of the inner ring end face. Rotate the inner ring to make the raceway of the ring and the rolling elements in a normal contact state. Measure the height difference between the back end face of the outer ring and the end face of the inner ring, which is the protrusion at a certain point. Measure the protrusions at multiple points and calculate the average value, which is the average protrusion of the measured bearing. When the measurement load applied on the end face of the outer ring reaches the specified pre - load, the protrusion is 0. The measurement standards for other items shall comply with the provisions of GB/T 307.2.

 

Schematic diagram of the protrusion measurement method

 

6. Marking and Labeling

 

In addition to the markings specified in GB/T 24605, assembled bearings are also marked as follows for correct use:

 

a) On the outer diameter surface of assembled bearings (except universal - assembled bearings), angular lines (V - shaped lines) with an included angle of 30° are marked. The direction of the included angle of the angular lines points to the direction of the axial load acting on the inner ring of the bearing (when bearing bidirectional axial loads, the included angle points to the direction of the larger axial load), as shown in the figure:

 

Marking of the assembled angular lines

 

b) On the outer diameter surface of a single set bearing of a universal assembled bearing, angular lines with an included angle of 30° are marked. The vertex of the included angle of the angular lines points in the same direction as the contact angle of the bearing (i.e., the direction of the axial load acting on the inner ring of the bearing), as shown in the figure.

 

 

Marking of the contact angle angular lines

 

c) For individual bearings in assembled bearings with a tolerance grade of 4 or above, the maximum points of the thickness variation Ki between the inner ring raceway and the inner hole and the thickness variation Ke between the outer ring raceway and the outer surface shall be marked at the corresponding positions on the end faces of the inner and outer rings respectively. The marking symbol is “*”.

 

Marking of Ki, Ke, △dmp, and △Dmp

 

d) The average inner diameter deviation △dmp and the average outer diameter deviation △Dmp (unit: μm) of individual bearings in an assembled bearing are marked on the end faces of the inner and outer rings. For universal - assembled bearings in individual packaging, the corresponding markings are on the bearing model on the packaging box.

 

7. Reference Values of Pre - load for Matched Bearings

 

The light, medium, and heavy pre - load values of back - to - back (DB type) or face - to - face (DF type) matched bearings are shown in the following table:

Table A Pre - load of matched bearings (DB and DF types) with a nominal contact angle a = 15°
Unit: N

 

Inner diameter Code	(B)71800 C			(B)71900 C			(B)7000 C			(B)7200 C
	A	B	C	A	B	C	A	B	C	A	B	C
6	-	-	-	-	-	-	7	13	25	-	-	-
	-	-	-	-	-	-	h	18	35	12	24	48
8	-	-	-	-	-	-	10	20	40	14	28	56
9	-	-	-	-	-	-	10	20	40	15	30	60
00	10	30	60	10	20	40	15	30	60	20	40	80
01	11	33	66	10	20	40	15	30	60	20	40	80
02	12	36	72	15	30	60	20	40	80	30	60	120
03	12	37	75	15	30	60	25	50	100	35	70	140
04	20	60	120	25	50	100	35	70	140	45	90	180
05	22	66	132	25	50	100	35	70	140	50	100	200
06	23	70	140	25	50	100	50	100	200	90	180	360
07	25	75	150	35	70	140	60	120	240	120	240	480
08	26	78	155	45	90	180	60	120	240	150	300	600
09	27	80	160	50	100	200	110	220	440	160	320	640
10	40	120	240	50	100	200	110	220	440	170	340	680
11	55	165	330	70	140	280	150	300	600	210	420	840
12	70	210	420	70	140	280	150	300	600	250	500	1000
13	71	215	430	80	160	320	160	320	640	290	580	1160
14	73	220	440	130	260	520	200	400	800	300	600	1200
15	76	225	450	130	260	520	200	400	800	310	620	1 240
16	78	235	470	140	280	560	240	480	960	370	740	1 480
17	115	345	690	170	340	680	250	500	1000	370	740	1 480
18	116	350	700	180	360	720	300	600	1 200	480	960	1 920
19	117	355	710	190	380	760	310	620	1 240	520	1 040	2 080
20	120	360	720	230	460	920	310	620	1 240	590	1180	2 360
21	130	390	780	230	460	920	360	720	1 440	650	1 300	2 600
22	160	500	1 000	230	460	920	420	840	1 680	670	1340	2 680
24	180	550	1 100	290	580	1160	430	860	1 720	750	1500	3 000
26	210	620	1 230	350	700	1 400	560	1120	2 240	800	1 600	3 200
28	240	720	1 440	360	720	1 440	570	1140	2 280	一	-	-
30	270	820	1 630	470	940	1 880	650	1 300	2 600	-	-	-
32	280	850	1 700	490	980	1 960	730	1 460	2 920	-	-	-
34	一	-	-	500	1.000	2 000	800	1 600	3 200	-	-	-
36	-	-	-	630	1 260	2 520	900	1 800	3 600	-	-	-
38	-	-	-	640	1280	2 560	950	1 900	3 800	-	-	-
40	-	-	-	800	1600	3 200	1100	2 200	4 400	-	-	-
44	-	-	-	850	1700	3 400	1 250	2 500	5 000	-	-	-
48	-	-	-	860	1720	3 440	1 300	2 600	5 200	-	-	-
52	-	-	-	1050	2110	4 220	1 550	3 100	6 200	-	-	-
56	-	-	-	1 090	2 180	4360	-	-	-	-	-	-
60	-	-	-	1 400	2 800	5 600	-	-	-	-	-	-
64	-	-	-	1 400	2 800	5 600	-	-		-	-	-

 

 

Inner diameter Code	(B)71900 AC			(B)7000 AC			(B)7200 AC			7200 B,7300 B
	A	B	C	A	B	C	A	B	C	A	B	C
8	-	-	-	20	40	80	-	-	-	-	-	-
9	-	-	-	20	40	80	-	-	-	-	-	-
00	15	30	60	25	50	100	35	70	140	80	330	550
01	15	30	60	25	50	100	35	70	140	80	330	560
02	25	50	100	30	60	120	45	90	180	80	330	660
03	25	50	100	40	80	160	60	120	240	80	330	660
04	35	70	140	50	100	200	70	140	280	120	480	970
05	40	80	160	60	120	240	80	150	320	120	480	970
06	40	80	160	90	180	360	150	300	600	120	480	970
07	60	120	240	90	180	360	190	380	760	160	630	1 280
08	70	140	280	100	200	400	240	480	960	160	630	1280
09	80	160	320	170	340	680	260	520	1 040	160	630	1280
10	80	160	320	180	360	720	260	520	1 040	160	630	1280
11	120	240	480	230	460	920	330	660	1 320	380	1 500	3 050
12	120	240	480	240	480	960	400	800	1600	380	1 500	3 050
13	120	240	480	240	480	960	450	900	1800	380	1500	3 050
14	200	400	800	300	600	1 200	480	960	1920	380	1500	3 050
15	210	420	840	310	620	1 240	500	1 000	2 000	380	1 500	3 050
16	220	440	880	390	780	1 560	580	1160	2.320	380	1 500	3 050
17	270	540	1 080	400	800	1 600	600	1 200	2 400	410	1600	3 250
18	280	560	1 120	460	920	1 840	750	1 500	3 000	410	1 600	3 250
19	290	580	1-160	480	960	1 920	850	1 700	3.400	410	1 600	3 250
20	360	720	1 440	500	1 000	2 000	950	1 900	3 800	410	1 600	3 250
21	360	720	1 440	560	1120	2 240	1 000	2 000	4 000	410	1600	3 250
22	370	740	1 480	650	1 300	2 600	1 050	2100	4 200	410	1 600	3 250
24	450	900	1 800	690	1 380	2 760	1 200	2 400	4 800	410	1600	3.250
26	540	1 080	2 160	900	1 800	3 600	1 250	2 500	5 000	540	2 150	4 300
28	560	1 120	2 240	900	1 800	3 600	-	-	-	540	2 150	4 300
30	740	1 480	2 960	1 000	2 000	4 000	-	-	-	540	2 150	4 300
32	800	1 500	3 200	1 150	2 300	4 600	-	-	-	540	2 150	4 300
34	800	1 500	3 200	1 250	2 500	5 000	-	-	-	540	2 150	4 300
36	1 000	2.000	4 000	1 450	2 900	5 800	-	-	-	540	2 150	4 300
38	1 000	2 000	4 000	1 450	2 900	5 800	-	一	-	940	3 700	7 500
40	1 250	2 500	5 000	1 750	3 500	7.000	-	-	-	940	3 700	7 500
44	1 300	2 600	5 200	2 000	4.000	8 000	一	-	-	940	3 700	7 500
48	1 430	2 860	5 720	2 050	4 100	8.200	-	-	-	940	3 700	7 500
52	1 730	3 510	7 020	-	-	-	-	-	-	-	-	-
56	1820	3 640	7 280	-	-	-	-	-	-	-	-	-
60	2.200	4.400	8 800	-	-	-	-	-	-	-	-	-
64	2 200	4 400	8 800	-	-	-	-	-	-	-	-	-

Table B Pre - load of matched bearings (DB and DF types) with nominal contact angles a = 25° and a = 40°   

Unit: N

Data from JB/T10186 - 2000

 

8. Key Points of Installation and Maintenance

 

• Paired Use: Install strictly according to the DB/DF/DT type configurations and avoid single - row use.
• Pre - load Control: Select the pre - load level according to the working conditions. Overload easily leads to temperature rise, and insufficient pre - load results in a decrease in rigidity.
• Alignment Calibration: The DF type can tolerate slight deviations, but the alignment should be checked regularly.
• Lubrication Management: Use high - speed grease or oil mist lubrication, replenish regularly, and monitor the pollution degree.

 

9. Standards and Resources

 

Main Standards: GB/T 272, JB/T 2974, GB/T 307.2, JB/T 10186 - 2000.

This document is compiled based on JB/T standards and practical engineering experience. Engineers need to verify the parameters according to specific working conditions to ensure the reliability and service life of the system.