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General information for design engineers

7. Bearings - general data

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7.1 Bearing design data

Besides the suitable type of bearing and the size of it, additional design characteristics that define the bearing in location design have to be defined. The location designed is the one usually responsible for the bearing design. This person has to consider the requirements for accuracy of run, service temperature and lubrication, as well as the assembly and disassembly method. In order to meet all different requirements for proper run of bearing, bearings are produced in many versions that are characterized with an additional identification of bearings. Thus, bearings with required tolerances, clearances, materials, cage design or sealing can be selected. Also, accordingly with the identification system, bearings can be specified for certain service conditions that may be characteristic with high revolutions or high temperature, or alternatives of bearings for certain locations can be selected by the knowledge of identification of other bearing manufacturers.

7.2 Main dimensions

Roller bearings are supplied as a final machine part, and the designer has at disposal fixed dimensions that ensure easy exchangeability. Standardisation applies to outer dimensions important in the assembly point of view. It is convenient for manufacturers and users of bearings for technological and thus also economic reasons. It however does not state inner dimensions, such as the quantity and dimensions of rolling bodies, or designs of cages. Despite that, due to the long-term development and various design and production technology optimisations even the inner design of bearings becomes united to a significant extent.
The ISO international organization came up with dimension plans for roller bearings of metric dimensions that are defined in the below listed documents:

ISO 15:1998 platí pro radiální valivá ložiska metrických rozměrů, s výjimkou kuželíkových ložisek
ISO 355:1997 platí pro radiální kuželíková ložiska metrických rozměrů
ISO 104:2002 platí pro axiální valivá ložiska metrických rozměrů
ISO 582:1995 uvádí maximální hodnoty sražení montážních hran ložisek

7.2.1 ISO dimension plans

ISO dimension plan allocates to each bearing hole diameter d multiple outer diameters D, and to those different widths B – or – more precisely - T for radial and H for axial bearings. Bearings with the same hole diameter and same outer diameter belong in one diameter row identified by ascending outer diameter with figures 7, 8, 9, 0, 1, 2, 3, 4. Every diameter row contains bearings of different width rows by ascending width: 8, 0, 1, 2, 3, 4, 5, 6 and 7 for radial bearings. Width rows of radial bearings correspond with height rows of axial bearings (height rows by ascending height 7, 9, 1 and 2).
Combining the diameter and width row creates dimension rows that are identified by double figure where the first figure identified the width row, and the second figure identifies the diameter row. This system is clearly indicated in Fig. 7.1.

Fig. 7.1

The ISO dimension plan also contains dimensions of bearing ring edge fillet, the so-called installation fillet (Fig. 7.2). The chart section of the catalogue indicates minimum installation fillet values for individual bearing types that you need to know when designing radiuses of transmission of components forming the bearing location.

Obr. 7.2

See Chart 7.1 for an overview of the installation fillet complying with the international standard ISO 582.

Limit dimensions of installation fillet
	Radial bearings except tapered				Tapered bearings				Axial bearings
r_{s min}	d or D		r_{s min}		d or D		r_{s min}		r_{s min}
	over	to	in radial direction	in axial direction	over	to	in radial direction	in axial direction	in radial and axial direction
mm

0,15	-	-	0,3	0,6	-	-	-	-	0,3
0,2	-	-	0,5	0,8	-	-	-	-	0,5
0,3	-	40	0,6	1	-	40	0,7	1,4	0,8
	40	-	0,8	1	40	-	0,9	1,6	0,8
0,6	-	40	1	2	-	40	1,1	1,7	1,5
	40	-	1,3	2	40	-	1,3	2	1,5
1	-	50	1,5	3	-	50	1,6	2,5	2,2
	50	-	1,9	3	50	-	1,9	3	2,2
1,1	-	120	2	3,5	-	-	-	-	2,7
	120	-	2,5	4	-	-	-	-	2,7
1,5	-	120	2,3	4	-	120	2,3	3	3,5
	120	-	3	5	120	250	2,8	3,5	3,5
	-	-	-	-	250	-	3,5	4	3,5
2	-	80	3	4,5	-	120	2,8	4	4
	80	220	3,5	5	120	250	3,5	4,5	4
	220	-	3,8	6	250	-	4	5	4
2,1	-	280	4	6,5	-	-	-	-	4,5
	280	-	4,5	7	-	-	-	-	4,5
2,5	-	100	3,8	6	-	120	3,5	5	-
	100	280	4,5	6	120	250	4	5,5	-
	280	-	5	7	250	-	4,5	6	-
3	-	280	5	8	-	120	4	5,5	5,5
	280	-	5,5	8	120	250	4,5	6,5	5,5
	-	-	-	-	250	400	5	7	5,5
	-	-	-	-	400	-	5,5	7,5	5,5
4	-	-	6,5	9	-	120	5	7	6,5
	-	-	-	-	120	250	5,5	7,5	6,5
	-	--	--	-	250	400	6	8	6,5
	-	-	-	-	400	-	6,5	8,5	6,5
5	-	-	8	10	-	180	6,5	8	8
	-	-	-	-	180	-	7,5	9	8
6	-	-	10	13	-	180	7,5	10	10
	-	-	-	-	180	-	9	11	10
7,5	-	-	12,5	17	-	-	-	-	12,5
9,5	-	-	15	19	-	-	-	-	15
12	-	-	18	24	-	-	-	-	18
15	-	-	21	30	-	-	-	-	21

7.2.2 Accuracy of bearings

Accuracy of bearings means accuracy of bearing dimensions and run. Bearings are made in the accuracy classes P0, P6, P5, P5A, P4, P4A, P2, SP and UP. The P0 accuracy is general, and is not stated in the bearing identification. Descending number in the identification indicates higher bearing accuracy.
Majority locations can utilise roller bearings of normal accuracy level. Bearings with higher accuracy level are used in locations that require higher running accuracy, such as location of machine tool spindles, and where bearings exceed their limit revolutions.
The limit dimension and run accuracy values are stated in charts 7.2 to 7.12. These values comply with international standards ISO 492 a ISO 199. The P5A and P4A designation is used for bearings made in relevant accuracy level P5 and P4 but selected parameters feature higher accuracy level than is P5 and P4.

Symbols of quantities and their meaning
d –nominal hole diameter
d1 –nominal diameter of bigger theoretical tapered hole diameter
d2 –nominal diameter of shaft ring of bidirectional axial bearings
Δds – deviation of individual hole diameter from nominal dimension
Δdmp – deviation of mean diameter of cylindrical hole in individual radial plane (for tapered hole applies Δdmp for theoretical hole diameter)
Δd1mp – deviation of mean theoretical tapered hole diameter
Δd2mp – deviation of mean shaft ring hole diameter of bidirectional axial bearings in individual radial plane
Vdp – dispersion of individual hole diameter in individual radial plane
Vdmp – dispersion of mean cylindrical hole diameter
Vd2p – dispersion of shaft ring hole diameter of bidirectional axial bearings in individual radial plane
D – nominal external diameter
ΔDs –deviation of individual outer diameter from nominal dimension
ΔDmp – deviation of mean outer cylindrical surface diameter in individual radial plane
VDp – dispersion of individual outer cylindrical surface diameter in individual radial plane
VDmp –dispersion of mean outer cylindrical hole diameter
B – nominal inner ring width
T – nominal total width of tapered bearings
T1 – nominal effective width of inner semi-unit
T2 – nominal effective width of outer semi-unit
ΔBs – deviation of individual inner ring width
ΔCs – deviation of individual outer ring width
ΔTs – deviation of (total) individual bearing width
ΔT1s – deviation of effective width of inner semi-unit
ΔT2s – deviation of effective width of outer semi-unit
C – nominal outer ring width
VBs – dispersion of individual inner ring width
VCs – dispersion of individual outer ring width
Kia – radial runout of assembled bearing inner ring
Kea – radial runout of assembled bearing outer ring
Si – axial runout of shaft ring orbit
Se – axial runout of body ring orbit
Sia – axial runout of basic front of assembled bearing inner ring
Sea – axial runout of basic front of assembled bearing outer ring
Sd – axial runout of basic front
SD –runout of outer surface against ring front
Ss – runout of inner ring support front against basic front for single row tapered bearings

Limit values of individual parameters for different accuracy levels are stated in the below charts.

Inner race

d		Δ_dmp		V_dp			V_dmp	K_ia	Δ_Bs		V_Bs	Δ_dmp		Δ_d1mp	-Δ_dmp	V¹⁾_dp
				diameter rows
				7,8,9	0,1	2,3,4
over	to	max	min	max	max	max	max	max	max	min	max	max	min	max	min	max

2,5	10	0	-8	10	8	6	6	10	0	-120	15	-	-	-	-	-
10	18	0	-8	10	8	6	6	10	0	-120	20	-	-	-	-	-
18	30	0	-10	13	10	8	8	13	0	-120	20	21	0	21	0	13
30	50	0	-12	15	12	9	9	15	0	-120	20	25	0	25	0	15
50	80	0	-15	19	19	11	11	20	0	-150	25	30	0	30	0	19
80	120	0	-20	25	25	15	15	25	0	200	25	35	0	35	0	25
120	180	0	-25	31	31	19	19	30	0	-250	30	40	0	40	0	31
180	250	0	-30	38	38	23	23	40	0	-300	30	46	0	46	0	38
250	315	0	-35	44	44	26	26	50	0	-350	35	52	0	52	0	44
315	400	0	-40	50	50	30	30	60	0	-400	40	57	0	57	0	50
400	500	0	-45	56	56	34	34	65	0	-450	50	63	0	63	0	56
500	630	0	-50	63	63	38	38	70	0	-500	60	-	-	-	-	-
630	800	0	-75	-	-	-	-	80	0	-750	70	-	-	-	-	-
800	1000	0	-100	-	-	-	-	90	0	-1000	80	-	-	-	-	-
1000	1250	0	-125	-	-	-	-	100	0	-1250	100	-	-	-	-	-

Outer race
D		Δ_Dmp		V_DP				V_Dmp	K_ea	Δ_Cs, Δ_Cs
				Diameter rows
				7,8,9	0,1	2,3,4	bearings ²⁾
							with covers
over	to	max	min	max	max	max	max	max	max
mm		µm								"Corresponds with Δ_Bs, V_Bs of inner race of the same bearing"
6	18	0	-8	10	8	6	10	6	15
18	30	0	-9	12	9	7	12	7	15
30	50	0	-11	14	11	8	16	8	20
50	80	0	-13	16	13	10	20	10	25
80	120	0	-15	19	19	11	26	11	35
120	150	0	-18	23	23	14	30	14	40
150	180	0	-25	31	31	19	38	19	45
180	250	0	-30	38	38	23	-	23	50
250	315	0	-35	44	44	26	-	26	60
315	400	0	-40	50	50	30	-	30	70
400	500	0	-45	56	56	34	-	34	80
500	630	0	-50	63	63	38	-	38	100
630	800	0	-75	94	94	55	-	55	120
800	1000	0	-100	125	125	75	-	75	140
1000	1250	0	-125	-	-	-	-	-	160
1250	1600	0	-160	-	-	-	-	-	190

Applies in optional radial hole plane
Applies only to bearings of diameter rows 2, 3 and 4

Accuracy of dimensions and run of radial bearings (except tapered)
Accuracy level P6

Inner race
d		Δ_dmp		V_dp			V_dmp	K_ia	Δ_Bs		V_Bs
				Diameter rows
				7,8,9	0,1	2,3,4,
over	to	max	min	max	max	max	max	max	max	min	max
mm		µm
2,5	10	0	-7	9	7	5	5	6	0	-120	15
10	18	0	-7	9	7	5	5	7	0	-120	20
18	30	0	-8	10	8	6	6	8	0	-120	20
30	50	0	-10	13	10	8	8	10	0	-120	20
50	80	0	-12	15	15	9	9	10	0	-150	25
80	120	0	-15	19	19	11	11	13	0	-200	25
120	180	0	-18	23	23	14	14	18	0	-250	30
180	250	0	-22	28	28	17	17	20	0	-300	30
250	315	0	-25	31	31	19	19	25	0	-350	35
315	400	0	-30	38	38	23	23	30	0	-400	40
400	500	0	-35	44	44	26	26	35	0	-450	45
500	630	0	-40	50	50	30	30	40	0	-500	50

Outer race
D		Δ_Dmp		V_Dp				V_Dmp	K_ea	Δ_Cs V_Cs
				Diameter rows
				7,8,9	0,1	2,3,4	bearings ¹⁾
							with covers
over	to	max	min	max	max	max	max	max	max
mm		µm								Corresponds with Δ_Bs, V_Bs of the inner race of the same bearing

6	18	0	-7	9	7	5	9	5	8
18	30	0	-8	10	8	6	10	6	9
30	50	0	-9	11	9	7	13	7	10
50	80	0	-11	14	11	8	16	8	13
80	120	0	-13	16	16	10	20	10	18
120	150	0	-15	19	19	11	25	11	20
150	180	0	-18	23	23	14	30	14	23
180	250	0	-20	25	25	15	-	15	25
250	315	0	-25	31	31	19	-	19	30
315	400	0	-28	35	35	21	-	21	35
400	500	0	-33	41	41	25	-	25	40
500	630	0	-38	48	48	29	-	29	50
630	800	0	-45	56	56	34	-	34	60
800	1000	0	-50	75	75	45	-	45	75

Applies only to bearings of diameter rows 0, 1, 2, 3 and 4

Accuracy of dimensions and run of radial bearings (except tapered)
Accuracy level P5

Inner race
d		Δ_dmp		V_dp		V_dmp	K_ia	S_d	S_ia¹⁾	Δ_Bs		V_Bs
				Diameter rows
				7,8,9	0,1,2,3,4
over	to	max	min	max	max	max	max	max	max	max	min	max
mm		µm

2,5	10	0	-5	5	4	3	4	7	7	0	-40	5
10	18	0	-5	5	4	3	4	7	7	0	-80	5
18	30	0	-6	6	5	3	4	8	8	0	-120	5
30	50	0	-8	8	6	4	5	8	8	0	-120	5
50	80	0	-9	9	7	5	5	8	8	0	-150	6
80	120	0	-10	10	8	5	6	9	9	0	-200	7
120	180	0	-13	13	10	7	8	10	10	0	-250	8
180	250	0	-15	15	12	8	10	11	13	0	-300	10
250	315	0	-18	18	14	9	13	13	15	0	-350	13
315	400	0	-23	23	18	12	15	15	20	0	-400	15

Outer race
D		Δ_Dmp		V_dp		V_Dmp	K_ea	S_D	S_ea1)	Δ_Cs	V_Cs
				Diameter rows
				7,8,9	0,1,2,3,4
over	to	max	min	max	max	max	max	max	max		max
mm		µm

6	18	0	-5	5	4	3	5	8	8	Corresponds with Δ_Bc of the inner race of the same bearing	5
18	30	0	-6	6	5	3	6	8	8		5
30	50	0	-7	7	5	4	7	8	8		5
50	80	0	-9	9	8	5	8	8	10		6
80	120	0	-10	10	8	5	10	9	11		8
120	150	0	-11	11	8	6	11	10	13		8
150	180	0	-13	13	10	7	13	10	14		8
180	250	0	-15	15	11	8	15	11	15		10
250	315	0	-18	18	14	9	18	13	18		11
315	400	0	-20	20	15	10	20	13	20		13
400	500	0	-23	23	17	12	23	15	23		15
500	630	0	-28	28	21	14	25	18	25		18
630	800	0	-35	35	26	18	30	20	30		20

Applies to ball bearings only
Does not apply to covered bearings

Accuracy of dimensions and run of radial bearings (except tapered)
Accuracy level P4

Inner race
d		Δ_dmp		Δ_ds¹⁾		V_dp		V_dmp	K_ia	S_d	S_ia²⁾	Δ_Bs		VBs
						Diameter rows
						7,8,9	0,1,2,3,4

over	to	max	min	max	min	max	max	max	max	max	max	max	min	max
mm		µm

2,5	10	0	-4	0	-4	4	3	2	2,5	3	3	0	-40	2,5
10	18	0	-4	0	-4	4	3	2	2,5	3	3	0	-80	2,5
18	30	0	-5	0	-5	5	4	2,5	3	4	4	0	-120	2,5
30	50	0	-6	0	-6	6	5	3	4	4	4	0	-120	3
50	80	0	-7	0	-7	7	5	3,5	4	5	5	0	-150	4
80	120	0	-8	0	-8	8	6	4	5	5	5	0	-200	4
120	180	0	-10	0	-10	10	8	5	6	6	7	0	-250	5
180	250	0	-12	0	-12	12	9	6	8	7	8	0	-300	6

Outer race
D		Δ_Dmp		V_Ds1)		V_Dp		V_Dmp	K_ea	S_D	S_e^a2)	Δ_Cs	V_Cs
						Diameter rows³⁾
						7,8,9	0,1,2,3,4
over	to	max	min	max	min	max	max	max	max	max	max		max
mm		µm
												"Corresponds with Δ_Bs of the inner race of the same bearing"
6	18	0	-4	0	-4	4	3	2	3	4	5		2,5
18	30	0	-5	0	-5	5	4	2,5	4	4	5		2,5
30	50	0	-6	0	-6	6	5	3	5	4	5		2,5
50	80	0	-7	0	-7	7	5	3,5	5	4	5		3
80	120	0	-8	0	-8	8	6	4	6	5	6		4
120	150	0	-9	0	-9	9	7	5	7	5	7		5
150	180	0	-10	0	-10	10	8	5	8	5	8		5
180	250	0	-11	0	-11	11	8	6	10	7	10		7
250	315	0	-13	0	-13	13	10	7	11	8	10		7
315	400	0	-15	0	-15	15	11	8	13	10	13		8

Applies only to bearings of diameter rows 0, 1, 2, 3 and 4
Applies to ball bearings only
Does not apply to covered bearings

Accuracy of dimensions and run of roller bearings with tapered hole
Accuracy level SP

Inner race
d		Δ_dmp		Δ_d1mp	-Δ_dmp	V_dp	Kia	Sd	ΔBs		VBs
over	to	max	min	max	min	max	max	max	max	min	max
mm		µm

18	30	10	0	4	0	3	3	8	0	-100	5
30	50	12	0	4	0	4	4	8	0	-120	5
50	80	15	0	5	0	5	4	8	0	-150	6
80	120	20	0	6	0	5	5	9	0	-200	7
120	180	25	0	8	0	7	6	10	0	-250	8
180	250	30	0	10	0	8	8	11	0	-300	10
250	315	35	0	12	0	9	10	13	0	-350	13
315	400	40	0	13	0	12	12	15	0	-400	15
400	500	45	0	15	0	14	12	18	0	-450	25

Outer race
D		Δ_Dmp		V_Dp	K_ea	S_D	Δ_Cs, V_Cs
over	to	max	min	max	max	max
mm		µm

50	80	0	-9	5	5	8	"Corresponds with Δ_Bs and V_Bs of inner race of the same bearing"
80	120	0	-10	5	6	9
120	150	0	-11	6	7	10
150	180	0	-13	7	8	10
180	250	0	-15	8	10	11
250	315	0	-18	9	11	13
315	400	0	-20	10	13	13
400	500	0	-23	12	15	15
500	630	0	-28	14	17	18
630	800	0	-35	18	20	20

Accuracy of dimensions and run of roller bearings with tapered hole
Accuracy level UP
Inner race
d		Δ_dmp		Δ_d1mp	-Δ_dmp	V_dp	K_ia	S_d	Δ_Bs		V_Bs
over	to	max	min	max	min	max	max	max	max	min	max
mm		µm

18	30	6	0	2	0	3	1,5	3	0	-25	1,5
30	50	7	0	3	0	3	2	3	0	-30	2
50	80	8	0	3	0	4	2	4	0	-40	3
80	120	10	0	4	0	4	3	4	0	-50	3
120	180	12	0	5	0	5	3	5	0	-60	4
180	250	14	0	6	0	6	4	6	0	-75	5
250	315	17	0	8	0	8	5	6	0	-90	6

Outer race
D		Δ_Dmp		V_Dp	K_ea	S_D	Δ_Cs, V_Cs
over	to	max	min	max	max	max
mm		µm
50	80	0	-6	3	3	2	"Corresponds with Δ_Bs and V_Bs of inner race of the same bearing"
80	120	0	-7	4	3	3
120	150	0	-8	4	4	3
150	180	0	-9	5	4	3
180	250	0	-10	5	5	4
250	315	0	-12	6	6	4
315	400	0	-14	7	7	5

Accuracy of dimensions and run of tapered bearings
Accuracy level P0
Inner race and total bearing width
d		Δ_dmp		V_dp	V_dmp	K_ia	Δ_Bs		Δ_Ts		Δ_T1s		Δ_T2s
over	to	max	min	max	max	max	max	min	max	min	max	min	max	min
mm		µm
10	18	0	-12	12	9	15	0	-120	200	0	100	0	100	0
18	30	0	-12	12	9	18	0	-120	200	0	100	0	100	0
30	50	0	-12	12	9	20	0	-120	200	0	100	0	100	0
50	80	0	-15	15	11	25	0	-150	200	0	100	0	100	0
80	120	0	-20	20	15	30	0	-200	200	-200	100	-100	100	-100
120	180	0	-25	25	19	35	0	-250	350	-250	150	-150	200	-100
180	250	0	-30	30	23	50	0	-300	350	-250	150	-150	200	-100

Outer race
D		Δ_Dmp		V_Dp	V_Dmp	K_ea	Δ_Cs
over	to	max	min	max	max	max	max	min
mm		µm
18	30	0	-12	12	9	18	0	-120
30	50	0	-14	14	11	20	0	-120
50	80	0	-16	16	12	25	0	-150
80	120	0	-18	18	14	35	0	-200
120	150	0	-20	20	15	40	0	-250
150	180	0	-25	25	19	45	0	-250
180	250	0	-30	30	23	50	0	-300
250	315	0	-35	35	26	60	0	-350
315	400	0	-40	40	30	70	0	-400

Accuracy of dimensions and run of tapered bearings
Accuracy level P6X
Inner race and total bearing width
d		Δ_dmp		V_dp	V_dmp	K_ia	Δ_Bs		Δ_Ts		Δ_T1s		Δ_T2s
over	to	max	min	max	max	max	max	min	max	min	max	min	max	min
mm		µm
10	18	0	-12	12	9	15	0	-50	100	0	50	0	50	0
18	30	0	-12	12	9	18	0	-50	100	0	50	0	50	0
30	50	0	-12	12	9	20	0	-50	100	0	50	0	50	0
50	80	0	-15	15	11	25	0	-50	100	0	50	0	50	0
80	120	0	-20	20	15	30	0	-50	100	0	50	0	50	0
120	180	0	-25	25	19	35	0	-50	150	0	50	0	100	0

Outer race
D		Δ_Dmp		V_Dp	V_Dmp	K_ea	Δ_Cs
over	to	max	min	max	max	max	max	min
mm		µm
18	30	0	-12	12	9	18	0	-100
30	50	0	-14	14	11	20	0	-100
50	80	0	-16	16	12	25	0	-100
80	120	0	-18	18	14	35	0	-100
120	150	0	-20	20	15	40	0	-100
150	180	0	-25	25	19	45	0	-100
180	250	0	-30	30	23	50	0	-100
250	315	0	-35	35	26	60	0	-100

Accuracy of dimensions and run of tapered bearings
Accuracy level P6
Inner race and total bearing width
d		Δ_dmp		K_ia	Δ_Bs		Δ_Ts
over	to	max	min	max	max	min	max	min
mm		µm
10	18	0	-7	7	0	-200	200	0
18	30	0	-8	8	0	-200	200	0
30	50	0	-10	10	0	-240	200	0
50	80	0	-12	10	0	-300	200	0
80	120	0	-15	13	0	-400	200	-200
120	180	0	-18	18	0	-500	350	-250

Outer race
D		Δ_Dmp		K_ea	Δ_Cs
over	to	max	min	max
mm		µm

18	30	0	-8	9	"Corresponds with Δ_Bs of inner race of the same bearing"
30	50	0	-9	10
50	80	0	-11	13
80	120	0	-13	18
120	150	0	-15	20
150	180	0	-18	23
180	250	0	-20	25
250	315	0	-25	30

Accuracy of dimensions and run of tapered bearings
Accuracy level P5
Inner race and total bearing width
d		Δ_dmp		V_dp	V_dmp	K_ia	S_d	Δ_Bs		Δ_Ts
over	to	max	min	max	max	max	max	max	min	max	min
mm		µm
10	18	0	-7	5	5	5	7	0	-200	200	-200
18	30	0	-8	6	5	5	8	0	-200	200	-200
30	50	0	-10	8	5	5	8	0	-240	200	-200
50	80	0	-12	9	6	7	8	0	-300	200	-200
80	120	0	-15	11	8	8	9	0	-400	200	-200
120	180	0	-18	14	9	11	10	0	-500	350	-250

Outer race
D		Δ_Dmp		V_Dp	V_D	K_ea	S_D	Δ_Cs
over	to	max	min	max	max	max	max
mm		µm

18	30	0	-8	6	5	6	8	Corresponds with Δ_Bs of the inner race of the same bearing
30	50	0	-9	7	5	7	8
50	80	0	-11	8	6	8	8
80	120	0	-13	10	7	10	9
120	150	0	-15	11	8	11	10
150	180	0	-18	14	9	13	10
180	250	0	-20	15	10	15	11
250	315	0	-25	19	13	18	13

Accuracy of dimensions and run of axial bearings
Accuracy level P0, P6 and P5
Shaft ring
d		Δ_dmp		V_dp	S_i		1)
d₂		Δ_d2mp		V_d2p	P0	P6	P5
over	to	max	min	max	max	max	max
mm		µm
-	18	0	-8	6	10	5	3
18	30	0	-10	8	10	5	3
30	50	0	-12	9	10	6	3
50	80	0	-15	11	10	7	4
80	120	0	-20	15	15	8	4
120	180	0	-25	19	15	9	5
180	250	0	-30	23	20	10	5
250	315	0	-35	26	25	13	7
315	400	0	-40	30	30	15	7
400	500	0	-45	34	30	18	9
500	630	0	-50	38	35	21	11
630	800	0	-75	-	40	25	13

Casing ring
D		Δ_Dmp		V_Dp	S_e	1)
over	to	max	min	max
mm		µm

18	30	0	-13	10	"Corresponds with Si of shaft ring of the same bearing"
30	50	0	-16	12
50	80	0	-19	14
80	120	0	-22	17
120	180	0	-25	19
180	250	0	-30	23
250	315	0	-35	26
315	400	0	-40	30
400	500	0	-45	34
500	630	0	-50	38
630	800	0	-75	55
800	1000	0	-100	75
1000	1250	0	-125	-
1250	1600	0	-160	-

Does not apply to axial spherical-roller bearings

7.2.3 Inner clearances of bearings

Clearance in bearing is the value of length of displacement of one assembled bearing ring towards the second ring from one marginal position to another (see Fig. 7.3). The displacement can be in radial direction (radial clearance), or in axial direction (axial clearance).

Obr. 7.3

In an in-built bearing we usually detect lower radial clearance than has the same bearing in unassembled state. Reduction of radial clearance is caused by the overlap sizes of bearing rings on the journal and in the body hole, and is therefore dependant on the selected tolerances of location surface diameters for the bearing. Further change of radial clearance, particularly its reduction, takes place during the operation due to temperature induced by the bearing operation itself, and by external sources, and also due to flexible deformations caused by load. Decisive is for bearing in stabilised service effects. Small prestress between the balls and orbits usually does not have negative effect.

Roller, tapered spherical-roller bearings feature higher rigidity, and therefore they are supposed to have smaller service clearance that is necessary to ensure safe and reliable run, mainly in heavy service conditions. If extremely high rigidity of location is required, e.g. for machine tools, prestressed bearings are mounted.

For normal design bearings the clearance is adjusted so that one of the bearing rings could be located firmly which is sufficient for majority of service ratios in location. Special cases of location with other requirements for radial clearance require bearings with radial clearance designated C1 to C5.

Values of different inner clearance levels according to ISO 5753 standard are for individual design bearing groups stated in charts 7.17 to 7.23 whilst these values apply to non-mounted bearings in zero load during measuring.

Radial clearance of single row ball bearings
Hole diameter		Radial clearance										Single row ball bearings separable of E and BO type	Radial clearance

d		C2		Normal		C3		C4		C5
over	to	min	max	min	max	min	max	min	max	min	max		min	max
mm		µm											µm
2,5	10	0	7	2	13	8	23	14	29	20	37	E10, E12	15	30
10	18	0	9	3	18	11	25	18	33	25	45	E15	15	30
18	24	0	10	5	20	13	28	20	36	28	48	BO17, E17	25	45
24	30	1	11	5	20	13	28	23	41	30	53	E20	20	40
30	40	1	11	6	20	15	33	28	46	40	64
40	50	1	11	6	23	18	36	30	51	45	73
50	65	1	15	8	28	23	43	38	61	55	90
65	80	1	15	10	30	25	51	46	71	65	105
80	100	1	18	12	36	30	58	53	84	75	120
100	120	2	20	15	41	36	66	61	97	90	140
120	140	2	23	18	48	41	81	71	114	105	160
140	160	2	23	18	53	46	91	81	130	120	180
160	180	2	25	20	61	53	102	91	147	135	200
180	200	2	30	25	71	63	117	107	163	150	215
200	225	2	35	25	85	75	140	125	195	175	265
225	250	2	40	30	95	85	160	145	225	205	300
250	280	2	45	35	105	90	170	155	245	225	340
280	315	2	55	40	115	100	190	175	270	245	370
315	355	3	60	45	125	110	210	195	300	275	410
355	400	3	70	55	145	130	240	225	340	315	460
400	450	3	80	60	170	150	270	250	380	350	520
450	500	3	90	70	190	170	300	280	420	390	570
500	560	10	100	80	210	190	330	310	470	440	630
560	630	10	110	90	230	210	360	340	520	490	700
630	710	20	130	110	260	240	400	380	570	540	780
710	800	20	140	120	290	270	450	430	630	600	860
800	900	20	160	140	320	300	500	480	700	670	960
900	1000	20	170	150	350	330	550	530	770	740	1040
1000	1120	20	180	160	380	360	600	580	850	820	1150

Axial clearance of double row angular-contact ball bearings
Hole diameter		Axial clearance
d		C2		normal		C3		C4
over	to	min	max	min	max	min	max	min	max
mm		µm
6	10	1	11	5	21	12	28	25	45
10	18	1	12	6	23	13	31	27	47
18	24	2	14	7	25	16	34	28	48
24	30	2	15	8	27	18	37	30	50
30	40	2	16	9	29	21	40	33	54
40	50	2	19	11	33	23	44	36	58
50	65	3	22	13	36	26	48	40	63
65	80	3	24	15	40	30	54	46	71
80	100	3	26	18	46	35	63	-	-
100	110	4	30	22	53	42	73	-	-

Radial clearance of double row tilting ball bearings
Hole diameter		Cylindrical hole										Tapered
		Radial clearance										Radial	clearance
d		C2		normal		C3		C4		C5		C2		normal		C3		C4		C5
over	to	min	max	min	max	min	max	min	max	min	max	min	max	min	max	min	max	min	max	min	max
mm		μm										μm
2,5	6	1	8	5	15	10	20	15	25	21	33	-	-	-	-	-	-	-	-	-	-
6	10	2	9	6	17	12	25	19	33	27	42	-	-	-	-	-	-	-	-	-	-
10	14	2	10	6	19	13	26	21	35	30	48	-	-	-	-	-	-	-	-	-	-
14	18	3	12	8	21	15	28	23	37	32	50	-	-	-	-	-	-	-	-	-	-
18	24	4	14	10	23	18	30	25	39	34	52	7	17	13	26	20	33	28	42	37	55
24	30	5	16	11	24	19	35	29	46	40	58	9	20	15	28	23	39	33	50	44	62
30	40	6	18	13	29	23	40	34	53	46	66	12	24	19	35	29	46	40	59	52	72
40	50	6	19	14	31	25	44	37	57	50	71	14	27	22	39	33	52	45	65	58	79
50	65	7	21	16	36	30	50	45	69	62	88	18	32	27	47	41	61	56	80	73	99
65	80	8	24	18	40	35	60	54	83	76	108	23	39	35	57	50	75	69	98	91	123
80	100	9	27	22	48	42	70	64	96	89	124	29	47	42	68	62	90	84	116	109	144
100	120	10	31	25	56	50	83	75	114	105	145	35	56	50	81	75	108	100	139	130	170
120	140	10	38	30	68	60	100	90	135	125	175	-	-	-	-	-	-	-	-	-	-
140	160	15	44	35	80	70	120	110	161	150	210	-	-	-	-	-	-	-	-	-	-

Radial clearance of single row roller bearings
Hole diameter		Radial clearance
d		C2		normal		C3		C4		C5
over	to	min	max	min	max	min	max	min	max	min	max
mm		µm

10	24	0	25	20	45	35	60	50	75	65	90
24	30	0	25	20	45	35	60	50	75	70	95
30	40	5	30	25	50	45	70	60	85	80	105
40	50	5	35	30	60	50	80	70	100	95	125
50	65	10	40	40	70	60	90	80	110	110	140
65	80	10	45	40	75	65	100	90	125	130	165
80	100	15	50	50	85	75	110	105	140	155	190
100	120	15	55	50	90	85	125	125	165	180	220
120	140	15	60	60	105	100	145	145	190	200	245
140	160	20	70	70	120	115	165	165	215	225	275
160	180	25	75	75	125	120	170	170	220	250	300
180	200	35	90	90	145	140	195	195	250	275	330
200	225	45	105	105	165	160	220	220	280	305	365
225	250	45	110	110	175	170	235	235	300	330	395
250	280	55	125	125	195	190	260	260	330	370	440
280	315	55	130	130	205	200	275	275	350	410	485
315	355	65	145	145	225	225	305	305	385	455	535
355	400	100	190	190	280	280	370	370	460	510	600
400	450	110	210	210	310	310	410	410	510	565	665
450	500	110	220	220	330	330	440	440	550	625	735
500	560	120	240	240	360	360	480	480	600	695	815
560	630	140	260	260	380	380	500	500	620	780	900
630	710	145	285	285	425	425	565	565	705	870	1010
710	800	150	310	310	470	470	630	630	790	980	1140
800	900	180	350	350	520	520	690	690	860	1100	1270
900	1000	200	390	390	580	580	770	770	960	1220	1410
1000	1120	220	430	430	640	640	850	850	1060	1360	1570
1120	1250	230	470	470	710	710	950	950	1190	1520	1760

Radial clearance of double row roller bearings with tapered hole
Bearings with incommutable races designed for work spindles of machine tools
Hole diameter		Radial clearance
d		C1NA		C2NA
over	to	min	max	min	max
mm		µm
24	30	15	25	25	35
30	40	15	25	25	40
40	50	17	30	30	45
50	65	20	35	35	50
65	80	25	40	40	60
80	100	35	55	45	70
100	120	40	60	50	80
120	140	45	70	60	90
140	160	50	75	65	100
160	180	55	85	75	110
180	200	60	90	80	120
200	225	60	95	90	135
225	250	65	100	100	150
250	280	75	110	110	165
280	315	80	120	120	180
315	355	90	135	135	200
355	400	100	150	150	225
400	450	110	170	170	255
450	500	120	190	190	285
500	560	130	210	210	315
560	630	140	230	230	345
630	710	160	260	260	390
710	800	180	290	290	435
800	900	200	320	320	480
900	1000	-	-	355	540

Radial clearance of single row cageless needle bearings with interchangeable races
Hole diameter		Radial clearance
d		normal		C3
over	to	min	max	min	max
mm		µm
10	14	10	50	25	70
14	18	15	55	35	75
18	24	25	65	40	80
24	30	30	65	50	80
30	40	40	75	60	95
40	50	40	85	65	100
50	65	45	90	70	120
65	80	50	110	75	135
80	100	60	115	95	150
100	120	70	125	115	70
120	140	80	155	130	205
140	160	80	160	140	210

Radial clearance of double row spherical-roller bearings
Hole diameter		Cylindrical hole
		Radial clearance
d		C2		normal		C3		C4		C5
over	to	min	max	min	max	min	max	min	max	min	max
mm		µm
30	40	15	30	30	45	45	60	60	80	80	100
40	50	20	35	35	55	55	75	75	100	100	125
50	65	20	40	40	65	65	90	90	120	120	150
65	80	30	50	50	80	80	110	110	145	145	180
80	100	35	60	60	100	100	135	135	180	180	225
100	120	40	75	75	120	120	160	160	210	210	260
120	140	50	95	95	145	145	190	190	240	240	300
140	160	60	110	110	170	170	220	220	280	280	350
160	180	65	120	120	180	180	240	240	310	310	390
180	200	70	130	130	200	200	260	260	340	340	430
200	225	80	140	140	220	220	290	290	380	380	470
225	250	90	150	150	240	240	320	320	420	420	520
250	280	100	170	170	260	260	350	350	460	460	570
280	315	110	190	190	280	280	370	370	500	500	630
315	355	120	200	200	310	310	410	410	550	550	690
355	400	130	220	220	340	340	450	450	600	600	760
400	450	140	240	240	370	370	500	500	660	660	820
450	500	140	260	260	410	410	550	550	720	720	900
500	560	150	280	280	440	440	600	600	780	780	1000
560	630	170	310	310	480	480	650	650	850	850	1100
630	710	190	350	350	530	530	700	700	920	920	1190
710	800	210	390	390	580	580	770	770	1010	1010	1300
800	900	230	430	430	650	650	860	860	1120	1120	1440
900	1000	260	480	480	710	710	930	930	1220	1220	1570
1000	1120	290	530	530	780	780	1020	1020	1330	1330	1720

Radial clearance of double row spherical-roller bearings
Hole diameter		Tapered hole
		Radial clearance
d		C2		normal		C3		C4		C5
over	to	min	max	min	max	min	max	min	max	min	max
mm		µm
30	40	25	35	35	50	50	65	65	85	85	105
40	50	30	45	45	60	60	80	80	100	100	130
50	65	40	55	55	75	75	95	95	120	120	160
65	80	50	70	70	95	95	120	120	150	150	200
80	100	55	80	80	110	110	140	140	180	180	230
100	120	65	100	100	135	135	170	170	220	220	280
120	140	80	120	120	160	160	200	200	260	260	330
140	160	90	130	130	180	180	230	230	300	300	380
160	180	100	140	140	200	200	260	260	340	340	430
180	200	110	160	160	220	220	290	290	370	370	470
200	225	120	180	180	250	250	320	320	410	410	520
225	250	140	200	200	270	270	350	350	450	450	570
250	280	150	220	220	300	300	390	390	490	490	620
280	315	170	240	240	330	330	430	430	540	540	680
315	355	190	270	270	360	360	470	470	590	590	740
355	400	210	300	300	400	400	520	520	650	650	820
400	450	230	330	330	440	440	570	570	720	720	910
450	500	260	370	370	490	490	630	630	790	790	1000
500	560	290	410	410	540	540	680	680	870	870	1100
560	630	320	460	460	600	600	760	760	980	980	1230
630	710	350	510	510	670	670	850	850	1090	1090	1360
710	800	390	570	570	750	750	960	960	1220	1220	1500
800	900	440	640	640	840	840	1070	1070	1370	1370	1690
900	1000	490	710	710	930	930	1190	1190	1520	1520	1860
1000	1120	530	770	770	1030	1030	1300	1300	1670	1670	2050

For double row ball bearings with angular contact, axial clearance measured at axial load of 100 N is stated instead of radial clearance.

If different clearance is selected than normal, one needs to process carefully and consider the effect if operating conditions at stabilised state. Radial clearance smaller than normal is selected quite rarely, e.g. in roller bearings for machine tool spindles. More often bearings with radial clearance bigger than normal are needed. This happens mostly in case the limit revolutions are exceeded, or in case of higher temperature gradient between the inner an outer ring and, finally, to increase axial load capacity of single row ball bearings. Axial load capacity of these bearings is increased at the clearance of C3 by approx. 10%, and at clearance C4 by approx. 20% in normal conditions.

It is understandable that not only too small but also too big radial clearance has negative effect on the operation and life service of roller bearing. As we know from experience, roller bearing is more negatively affected by small radial clearance than by big. If the thermal service conditions in the bearing are unclear, it is safer to select quite bigger radial clearance that might in an extreme case reduce the service life of the bearing which is insignificant.

Single row ball bearings with angular contact and single row tapered bearings are usually mounted in pairs in which radial or axial clearance or prestress are adjusted during the assembly. With advantage the property of the so-called combined bearings can be utilised in which the final axial clearance is set by the bearing manufacturer.

Dependence of radial and axial clearance in some bearing types is clear from chart 7.24.

Dependence of radial clearance V_r and axial clearance V_a
Bearing type	V_a/V_r
Single Row Ball Bearings	-
Double Row Angular Contact Ball Bearings, type 32, 33	1,4
Self-Aligning Ball Bearings	1,5/e
Tapered Roller Bearings
Spherical Roller Bearings

Figure 7.4 shows an informative graph of dependence of radial an axial clearance in bearing, applicable to single row roller bearings.

Fig. 7.4

7.3 Roller bearings materials

7.3.1 Materials of bearing rings and rolling bodies

In terms of materials used for production of roller bearings, durability and reliability of roller bearings is specifically increased by using more accurate metallurgical technologies based on recent surveys. Previous studies already demonstrated a direct connection between micropurity of the bearing steel used, and the occurrence of subsurface fatigue damage in the rolling contact. With regard to high pressures in the area of the rolling contact, strict requirements for micropurity and uniformity of distribution of carbidic phases are reasonable. The requirement of continuous durability increase can be satisfied by highly accurate and quality production combined with using materials with low content of oxygen and non-metal intrusions, and technologically correct thermal processing of rings and bearing rolling bodies when specified hardness, microstructure and dimensional stability is achieved. This provides resistance to wear and necessary load capacity of rolling contact. Chemical composition and maximum contents of undesired elements are defined in the international standard for bearing steels ISO 683-17.
For locations with a risk of damage in the area of rolling contact due to passage of electric current, bearings with ceramic insulation coating of the outer ring can be supplied.
If there are special requirements for material, design or use of bearings, information is available at the ZKL's technical an consultancy centre.

Semiproducts

Besides economic criteria, a semiproduct for production of roller bearings and rolling bodies has to comply with technological requirements in terms of proper course of fibres and proper distribution of carbidic phases. For the economic reason and also due to convenient passage of fibres, the most convenient is using a tube semiproduct that is cold rolled to final shape prior to thermal processing. In this way, the majority of the bearing assortment with increased basic durability is produced with the identification “NEW FORCE“.

Through-hardening steels

Majority of standard produced ZKL roller bearings are made of through-hardening steels designed for production of roller bearings. Those are carbon – chromium steels with an approximate content of 1% carbon and 1.5% chromium, complying with the international standard ISO 683-17 “Heat-treated steels, alloy steels and free-cutting steels, Part17: Steels for rolling bearings”. After thermal treatment, material has the same structure and hardness throughout the component section. After performed martensitic or bainite hardening and subsequent yielding, the hardness of final surfaces is 58 to 65 HRC.
Depending on the type, the highest service temperature of 120°C to 200°C is recommended for standard ZKL roller bearings. The maximum temperature for using the bearings depends on heat treatment of bearing components. For operation at temperatures to 250°C, bearing components can stabilize in a special heat treatment process. In case of thermal stabilization for operation at higher temperatures, the hardness of components reduces significantly, and thus also the dynamic load capacity of the bearings. If long-term operation above 250°C is required, we recommend bearings from high alloy steels designed for high temperatures.

Case hardening steels

After saturation with carbon and hardening, bearing components feature hard surface and simultaneously also tough core. They are used for production of bearings that are loadable with big strokes, locations with big overlap or alternatively for locations with a possibility of contaminated lubrication.

Corrosion-proof steels

These steels are used for bearings intended for operation in oxidizing environment, for instance for aviation technology or food processing industry.

Steels for high temperatures

These materials are used for bearings operating permanently at temperatures over 250°C whilst maintaining hardness and standard service properties, e.g. in aircraft engines.

Steels for surface hardening

These steels offer convenient combination of hardened tough orbit with tough section core. They are used mainly in large bearings, or bearings with clamp flanges which are contained in bearing rings.

7.3.2 Materials for production of cages

Materials used for production of cages are selected with regard to the service temperature of the bearing, whether the bearing will operate in standard or vibrating environment, alternatively upon the requirements for chemical or corrosion resistance.
The basic quality of materials used for production of cages is good abrasion resistance and slip properties along with sufficient ductility.

Pressed steel cages

They are pressed from low carbon steels that ensure accuracy of final cage shape, as well as sufficient ductility. To improve slip properties and abrasion resistance, the surface of pressed cages is chemically and thermally treated. They suit typical temperature regimen of bearing operation up to 300°C.
In smaller bearings sizes, pressed cages are even made of brass sheet.

Massive brass cages

They are made in routing from roughened or spun semiproducts. Service temperature should not exceed 250°C.

Massive steel cages

In justified cases they are an alternative to brass massive cages. Service temperature may range up to 300°C. The surface of the cage can be chemically and thermally treated.

7.3.3 Other materials

Polymers

Polymers, usually of polyamide 66 reinforced with glass fibres, are used mainly for production of cages and cage guide rings of double row spherical roller bearings of CJ design. Service operation of these components should not exceed 120°C in the long term with the use of common lubricants, 150°C in the short term (within 10 hours), and 170°C in peaks (within 20 minutes). Usefulness of bearings with polyamide components at lower temperatures is, with regard to polyamide elasticity loss, up to the temperatures of -40°C.

Ceramic materials

Are used mostly to prevent bearings from damage by passage of electric current, either in form of thermally layered coats on the surface of the outer or inner ring, alternatively by using rolling ceramic bodies. Use of rolling bodies from ceramic material is justified even in special high-revolution bearings.

Other

Materials of contact seals are selected so as their thermal and degradation resistance suited the selected use.

7.4 Cages

Cage has the below functions in a roller bearing: Distributes rolling bodies uniformly around the circumference and prevents their mutual contact which reduced friction in the bearing. It prevents slippage of rolling bodies in the bearing and falling rolling bodies out of separable bearings during their assembly.

In terms of design and materials, cages are divided in pressed (Fig. 7.5) and massive (Fig. 7.6).
Pressed cages are made mostly by pressing from steel or brass sheet, and usually are used in dimensionally smaller up to medium bearings. Comparing to massive cages, their advantage is lower weight.

Massive cages are made of steel, brass, bronze, light metals or plastics in various designs. Metal cage materials are used whenever increased requirements are imposed on the rigidity of the cage, and the bearing is designed for higher service temperatures. Cages in bearing run radially on rolling bodies which is the most common way, or on collar of one of the bearing rings (Fig. 7.7).

Fig. 7.5

Fig. 7.6

Fig. 7.7

Massive polymer cages are made in injection moulding. The injection moulding technology allows to production such cage shapes that enable designing bearings with high load capacity. Elasticity and low polyamide weight applies positively in shock stress of bearings, high acceleration and deceleration. Polyamide cages feature good slip properties. During lubrication of bearings with oil, the additives contained in the oil may affect negatively the service life of the cage.

Cages made of phenological resin are light but not suitable to high temperatures. They however feature good resistance to centrifugal forces. They are typically use in accurate ball bearings with angular contact.

Journal cages are made of steel; the condition is use of holy rolling bodies (Fig. 7.8). Journal cages are used mainly in large bearings

Fig. 7.8

Cageless bearings, i.e. with full number of rolling bodies, are used rarely - only in some types of bearings, e.g. single row roller bearings.

In texts to individual design bearing groups the section dedicated to cages always states an overview of cages made in the general design, and delivery option of bearings with cages in different designs.

7.5 Covers and seals

Bearings with covers on one or both sides are made with cover sheets (Z, 2Z, ZR, 2ZR – Fig. 7.9), or with contact seal ((RS, 2RS, RSR, 2RSR – Fig. 7.10). Cover sheets create contact-free sealing. In Z or 2Z version, the fitting for cover sheet is on the inner ring; ZR or 2ZR variants have cover sheet adhered to the smooth collar of the inner bearing ring.

Fig. 7.9

Fig. 7.10

The seal consists of sealing rings of nitrile rubber vulcanized on metal reinforcements that form an efficient contact seal in a design with rounded fitting on the inner ring (RS, 2RS), or in a design with contact on the smooth collar of the inner ring (RSR, 2RSR).

Covers and sealing rings are fastened in the outer ring recess, and are not detachable.
Bearings in basic design are filled with a quality plastic lubricant with temperature range between -30°C and + 100°C, in the short term even up to + 120°C. Filler of plastic lubricant usually ensures greasing throughout the service life in normal service conditions. Bearings in this design cannot be additionally greased.

7.6 Identification of roller bearings

Bearing is designated by basic identification and extension expressing the difference between this bearing and the standard version bearing. Identification of bearings contains numerical and literal characters that determine the type, size and design of the bearing. Overview of symbols and their order is based on the scheme shown in figure 7.11.

Fig. 7.11

7.6.1 General bearing version

In standard version, bearings are identified with basic designation consisting of the identification of the type and size of the bearing. The designation usually consists of a symbol expressing the design of the bearing (position 3 of the scheme), and a symbol for the dimensional group or diameter row (positions 4 and 5), e.g. type 223, 302, NJ22, 511, 62, 12 and so on. Designation of the bearing size contains characters for nominal bearing hole diameter d (position 6).

Bearings with hole diameter d < 10 mm:

Figures separate with fraction line or the last digit states directly the nominal hole dimension in mm, e.g. 619/2, 624.

Bearings with hole diameter d = 10 up to 17 mm:

double issue 00 identifies the hole d = 10 mm, e.g.: 6200
       01        d = 12 mm, e.g. 51101
       02        d = 15 mm, e.g. 3202
       03        d = 17 mm, e.g. 6303
Exception in designation are single row ball bearings of separable type E and BO where the double issue states directly the hole diameter in mm, e.g.: E17.

Bearings with hole diameter d = 20 mm up to 480 mm

Hole diameter is quintuple of the last double issue, e.g. bearing 1320 features hole diameter d = 20 x 5 = 100 mm.
Exceptions are bearings with hole diameter d = 22, 28 a 32 mm where the double issue separated with fraction line stated directly the diameter of hole in mm, e.g. a320/32AX, and some bearing types, such as e.g. separable single row ball bearings of E type, and single row ball bearings of NG type where the double or triple issue states directly the hole diameter in mm, e.g.: E20, NG160.

Bearings with hole diameter d > 500 mm:
The last double issue or triple digit separated with fraction line states directly the hole dimension in mm, e.g. 230/530M, NU29/1060.

7.6.2 Full identification of bearings

Bearing produced in designs different from the standard are identified by the so-called designation, as is shown in the scheme in Fig. 7.11. It consists of the basic identification and supplementary characters that express the difference from the basic version.

Meaning of supplementary characters

The following part states, in accordance with full designation, an overview and meaning of supplementary characters used. The digit in the bracket stated with individual groups corresponds with the position number in the scheme. The scheme also states positions in full naming of the bearing that us separated with a gap. Other characters are written together without a gap. Characters for extension of designation that mean a digit are separated with a dash from the basic designation, e.g. 6305-2Z.
The meaning of supplementary characters for design variances of different bearing types is described in relevant chapters of the chart section of the catalogue.

Supplementary characters before basic designation

Other material than common steel for roller bearings (1)

C   –   rolling bodies from ceramics – e.g. C B7006CTA
HAA – high speed steel, e.g.: HSS 6215
X   –   corrosion resistant steel, e.g.: X 623
T   –   case hardening steel, e.g.: T 32240

Bearing incompleteness (2)

L    –    separate detachable ring of separable bearing, e.g. L NU206, in axial ball bearings without a shaft ring, e.g. L 51215
R    –    Separable bearing without detachable ring, e.g. R NU206 nebo R N310
E    –    separate shaft ring or axial ball bearing, e.g. E 51314
W    – separate body ring of axial ball bearing, e.g. W 51414
K    –    cage with rolling bodies e.g.: K NU320

Supplementary characters behind the basic designation

Difference in inner design (7)

A   –   single row angular-contact ball bearings with contact angle α = 25°, e.g. B7205ATB P5
   –   single row tapered bearings with higher load capacity and higher limit revolution frequency, e.g. 30206A
   –   axial ball bearings with higher limit revolution frequency, e.g. 51,105A
AA   - single row angular-contact ball bearings with contact angle α = 26°, e.g. B7210AATB P5
B   –   single row angular-contact ball bearings with contact angle α = 40°, e.g. 7304B
   –    single row tapered bearings with contact angle α = 17°, e.g. 32315B
BE   - single row angular-contact ball bearings with contact angle α = 40°, in new design, e.g. 7310BETNG
C   –   single row angular-contact ball bearings with contact angle α = 15°, e.g. 7220CTB P4
   –   double row spherical roller bearings in new design, e.g. 22216C
CA   –   single row angular-contact ball bearings with contact angle α = 12°, e.g. B7202CATB P5
CB   –   single row angular-contact ball bearings with contact angle α = 10°, e.g. B7206CBTB P4
D   –   single row ball bearing of type 160 with higher load capacity, e.g. 16004D
E   –   single row ball bearings with higher load capacity, e.g. NU209E
   –    double row spherical roller bearings with higher load capacity, e.g. 22215E
   –    Axial spherical roller bearings with higher load capacity, e.g. 29416E

Difference in main dimensions (8)

X – Change in main dimensions, established by new international standards, e.g. 32028AX

Covers (9)

RS   –   seal on one side, e.g. 6304RS
-2RS   –   seal on both sides, e.g. 6204-2RS
RSN   –   seal on one side and snap ring groove on the outer ring on the opposite side than the seal, e.g. 6306RSN
RSNB   - seal on one side and snap ring groove on the outer ring on the same side as the seal, e.g. 6210RSNB
-2RSN   - seal on both sides and snap ring groove on the outer ring, e.g. 6310-2RSN
RSR   –   seal on one side, adhering to the smooth inner ring collar, e.g. 624RSR
-2RSR   –těsnění na obou stranách přiléhající na hladký nákružek vnitřního kroužku,
např. 608-2RSR
Z   –   Cover sheet on one side, e.g. 6206Z
-2Z   –   Cover sheet on both sides, e.g. 6304-2Z
ZN   –   seal on one side and snap ring groove on the outer ring on the opposite side than the cover sheet, e.g. 6208ZN
ZNB   –   cover sheet on one side and snap ring groove on the outer ring on the same side as the cover sheet, e.g. 6306ZNB
-2ZN   –   cover sheets on both sides and snap ring groove on the outer ring, e.g. 6208-2ZN
ZR   –   cover sheet on one side, adhering to the smooth inner ring collar, e.g. 608ZR
-2ZR   –   cover sheets on both sides, adhering to the smooth inner ring collars, e.g. 608-2ZR

Design change of bearing rings (10)

K   –   Tapered hole, taper ratio 1:12, e.g. 1207K
K30   –   Tapered hole, taper ratio 01:30:00, e.g. 24064K30M
N   –   snap ring groove on the outer ring, e.g. 6308N
NR   –   snap ring groove on the outer ring, and inserted snap ring, e.g. 6310NR
NX   –   snap ring groove on the outer ring, dimensions of which do not comply with ČSN 02 4605, e.g. 6210NX
D   –   split inner ring, e.g. 3309D
W33   –   groove and lubrication holes on the outer ring circumference, e.g. 23148W33M
O   –   lubrication slots on outer ring fillet of the bearing , e.g. NU1014O

Cage (11)

Material of cages for standard design bearings is usually not specified.
J   –   cage pressed from steel plate, guided on rolling bodies e.g.: 6034J
J2   –   cage pressed from steel plate, guided on rolling bodies. New design of single row tapered bearings, e.g. 30206AJ2
Y   –   cage pressed from brass sheet, guided on rolling bodies e.g.: 6001Y
F   –   massive steel cage, guided on rolling bodies e.g.: 6418F
L   –   massive light metal cage, guided on rolling bodies e.g.: NG180L C3S0
M   –   massive brass or bronze cage, guided on rolling bodies e.g.: NU330M
T   –   massive textite cage, guided on rolling bodies e.g.: 6005T
TN   –   massive cage of polyamide or similar plastic, guided on rolling bodies e.g.: 6207TN
TNG   - massive cage of polyamide or similar plastic, stiffened by glass fibres, guided on rolling bodies e.g.: 2305TNG

Cage design (stated characters are always used in combination with cage material characters).
A   –    cage guided on outer ring, e.g. NU226MA
B    –    cage guided on inner ring, e.g. B7204CATB P5
P    –    massive window cage, e.g.: NU1060MAP
H    –    open single-piece cage, e.g.: 629TNH
S    –    cage with lubrication slots, e.g.: NJ418MAS
R    –    silver-plated cage, e.g.: 6210MAR
V    –    bearing without cage with full number of rolling bodies, e.g. NU209V

Accuracy level (12)

P0   –   normal accuracy level (is not designated), e.g. 6204
P6   –   higher accuracy level than normal, e.g. 6322 P6
P5   –   higher accuracy level than P6, e.g. 6201 P5
P5A   –   higher accuracy level than P5 in some parameters, e.g. 6006TB P5A
P4   –   higher accuracy level than P5, e.g. B7204CBTB P4
P4A   –   higher accuracy level than P4 in some parameters, e.g. B7205CATB P4A
P2   –   higher accuracy level than P4, e.g. B7200CBTB P2
P6E   –   higher accuracy level for rotary electrical machines, e.g. 6204 P6E
P6X   –   higher accuracy level for single row tapered bearings, e.g. 30210A P6X
SP   –   higher accuracy level for roller bearings with tapered hole, e.g. NN3022K SPC2NA
UP   –   higher accuracy level such as SP for roller bearings with tapered hole, e.g. N1016K UPC1NA

Clearance (13)

C2   –   smaller clearance than normal, e.g. 608 C2
   –   normal clearance (is not designated), e.g. 6204
C3   –   bigger clearance than normal, e.g. 6310 C3
C4   –   bigger clearance than C3, e.g. NU320M C4
C5   –   bigger clearance than C4, e.g. 22330M C5
NA   –   radial clearance in bearings with incommutable rings (is indicated always behind the radial clearance group), e.g. NU215 P63NA
R...   –   radial clearance in non-standardised range (range in µm) , e.g. 6210 R10-20
A...   –   axial clearance in non-standardised range (range in µm) , e.g. 3210 A20-30

Noise level (14)

C6   –    reduced noise level lower than normal (is not designated), e.g. 6304 C6
C06   - reduced noise level lower than C6, e.g. 6205 C06
C66   - reduced noise level lower than C06, e.g. 6205 C66
Specific values for C06 and C66 are determined based on an agreement between customer and supplier.
Note: Bearings in accuracy level P5 and higher feature noise level within C6.

Increased operational safety (15)

C7, C8, C9 – bearings with increased operational safety designed mainly for use in aviation industry, e.g. 6008MB P68

Combining characters (12-15)

Characters/symbols of accuracy level, clearance in bearing, noise levels and increased operational safety are combined with simultaneous omission of C character and following special property of bearings, e.g.
P6 + C3 = P63    e.g. 6211 P63
P6 + C8 = P68    e.g. 16002 P68
C3 + C6 = C36    e.g. 6303-2RS C36
P5 + C3 + C9 = P539    e.g. 6205MA P539
P6 + C2NA + C6 = P626NA    e.g. NU1038 P626NA

Bearing association (16)

Designation of associated pair, triplet or quaternion of bearings consists of characters expressing arrangement of bearings and of characters defining the inner clearance or prestress of associated bearings.

Fig. 7.12

Apart from characters stated in the chart the U character is used to identify that relevant bearings can be associate universally, example of designation B7003CTA P4UL.

Inner clearance or prestress

Stated characters are always used in combination with association characters.
A   –   Association of bearings with clearances, e.g. 7305OA
O   –   Association of bearings without clearances, e.g. 7305 P6XO
L   –   Association of bearings with small prestress, e.g. B7205CATB P4UL
M   –   Association of bearings with medium prestress, e.g. B7204CATB P5XM
S   –   Association of bearings with big prestress, e.g. B7304AATB P4OS

Stabilisation for operation at higher temperature (17)

Both rings have stabilised dimensions for operation at higher temperature.
S0 – for service temperature    up to 150 °C
S1    up to 200 °C
S2    up to 250 °C
S3    up to 300 °C
S4    up to 350 °C
S5    up to 400 °C
Example of designation NG160LB C4S3

Friction torque (18)

JU   –   reduced friction torque, e.g. 619/2 JU
JUA   –   bearings with defined friction torque at start-up 632 JUA
JUB   –   bearings with defined friction torque at after-running, e.g. 623 JUB

Plastic lubricant (19)

For bearings with cover or seal on both sides, the plastic lubrication other than common is designated by means additional characters. The first two characters define the range of service temperature, and the third character (letter) defines the name or type of lubricant according to the manufacturer's specification, or another character (digit) defines the amount of plastic lubricant that fills the covered space of the bearing.
TL   –   lubricant for low service temperatures from -60 °C to +100 °C
       example of designation 6302 2RSTL
TM   –   lubricant for medium service temperatures from -35 °C to +140 °C
       example of designation 6204 2ZRTM
TH   –   lubricant for high service temperatures from -30 °C to +200 °C
       example of designation 6202 2ZTH
TW   –   lubricant for both low and high service temperatures from -40 °C to +150 °C
       example of designation 6310 2ZC4TW
Note: The TM marking need not be stated on bearings and containers.

Bearings by special technical conditions

Single purpose bearings dimensions of which comply with the dimensional plan but the list of all characters of extension expressing their technical characteristics would cause confusion of marking, can be upon agreement between manufacturer and customer replaced with basic designation, attaching the TPF or TPFK marking and a two- or three-digit number behind the basic designation of the bearing, which defines the number of the agreed technical specification determining all technical parameters of bearings.
TPF – bearings made by special technical conditions agreed with customer, e.g. bearing 6205MA P66 by technical terms TPF 11142-71 is designated as follows: 6205MA P66 TPF 142.
TPFK - bearings by special technical terms agreed with customer which have high number of characters stating changes against the basic version. In this case, basic characters are replaced with designation TPFK containing relevant number of technical terms, e.g. bearing NU1015 made by technical terms. TPFK 11137-70 is designated as NU1015 TPFK137.

Bearings by special drawing documentation PLC

Bearings which by some of their dimension do not comply with the dimensional plan or are in line with the next development are marked with PLC by their manufacturer, as well as with other numerical characters. Usually they are single purpose bearings for one customer or a certain application method.

PLC ABC-DE.F (designation structure until 2012)

PLC   –   identification of special roller bearing
A   –   design assembly
0   –    single row ball bearings
1   –   double row ball bearings:
2   –   axial ball bearings
3   –   Not completed.
4   –   single row roller, spherical-roller and needle bearings
5   –   double and multirow roller, spherical-roller and needle bearings
6   –   single row, double row and four row tapered bearings
7   –   special double row bearings
8   –   assembly units and separate parts
9   –   axial roller, spherical-roller, tapered and needle bearings
BC   –   dimensional assembly – two digit characters
DE   –   ordinal number within dimensional assembly – two digit characters
F   –   difference in design - one digit or combination of numerical character and letter

Due to extending the assortment of special bearings, it was decided in 2013 to change the structure of designating special bearings: Upon the establishing of a new system, the designation on already produced bearings will not be changed.

PLC AB-CD-EF.G (designation structure since 2013)

PLC   –   identification of special roller bearing
A   –   design assembly
1   –   ball bearings
2   –   axial ball bearings
3   –   roller bearings
4   –   axial roller bearings
5   –   needle bearings
6   –   spherical-roller bearings
7   –   axial spherical-roller bearings
8   –   tapered bearings
9   –   axial tapered bearings
0 – other bearings and mounting assemblies
B   –   number of rolling units or bearings in mounting assemblies
CD   –   dimensional assembly – two digit characters
EF – ordinal number within dimensional assembly – two digit characters
G   –   difference in design - one digit or combination of numerical character and letter

7.7 NEW FORCE bearings

In order to satisfy the needs of technically advanced customers, ZKL pays particular attention to technical development of products and investments in new technologies. The outcome of one of the recent key innovations is initiation of successive start up of production of ZKL bearings with higher quality standard with designation NEW FORCE.

The NEW FORCE bearings represent a new generation of ZKL bearings. Launching of bearings brings customers higher durability of bearings, enhanced operational safety, prolonged maintenance intervals and thus substantial reduction of operating costs. NEW FORCE bearings are designed for extreme locations of transmissions, railway vehicles, presses, rolling mills, paper machines, pumps, machine tools, power engineering plants, polygraphic machines, etc.
As the first integrated new generation bearings, the radial spherical-roller bearings were launched on the market, double row tilting ball bearings, double row angular-contact ball bearings and axial ball bearings. The next phase of launching bearings of this standard was the production assortment of bearings with outer diameter over 400 mm.

The achieved parameters of NEW FORCE bearings are the result of ZKL development in the following areas:

Material of roller bearing components
Technology of bearing ring flaring
Optimisation of inner construction
Surface treatments of bearing components

The achieved results allowed ZKL to offer NEW FORCE roller bearings with high utility properties to their customers:

high dynamic load capacity
low friction
reliability in the extreme operating conditions

High durability of bearings

Increase of dynamic load capacity by 8% to 25% brings increase of durability of bearings by 30% up to 110%, comparing to the up-to-now designs.

Fig. 7.13

Increase of dynamic load capacity allows customer to design construction with smaller dimensions to transfer the same load. Thus ZKL brings to their customer an opportunity to reduce total price of the equipment, and achieve power savings during operation.

Use of quality bearing material

Steels for production of bearings meet the parameters of international standards defined by ISO 683- 17. Production of bearing rings and rolling bodies utilised high quality material of selected smelting houses. Long-term cooperation with suppliers ensures continuous process of improving parameters of input material.

Key quality parameters of steel and its processing affect the service properties of bearing, i.e. resistance to fatigue damage, abrasion resistance and dimensional stability. These are:

chemical composition and heat treatment
Selection of the type of bearing steel and optimisation of heat treatment conditions is conducted by the dimension of the component. The heat treatment processing technology of NEW FORCE bearings ensures stabile hardness values of bearing components in the entire section. Spherical-roller bearing components are heat treated to ideal material structure and hardness that enable using of the bearings at service temperatures to 200 °C. The final material structure ensures dimensional stability of bearing components throughout their service life.
Content of non-metal intrusions - micropurity
Reduction of content of non-metal intrusions is the key quality parameter in the bearing steel metallurgy development. In production of bearings, ZKL utilises bearing steel with minimum oxygen content.
Type of semiproduct
The quality of bearing and production economics are affected also by selection of the semiproduct type. The level of forming and positive angle of forming fibre contact towards the orbit are the parameters that positively increase resistance of the NEW FORCE bearings against fatigue damage.

Technology of bearing ring flaring

Základní výzkum prokázal vliv směru vláken materiálu vzhledem ke kontaktní ploše na trvanlivost ložiska. Nejvýhodnější je takové uspořádání vláken, kdy jejich směr je rovnoběžný s kontaktní plochou. Se zvětšujícím se úhlem směru vláken ke kontaktní ploše se trvanlivost snižuje. Technologie rozválcování za studena nebo poloohřevu přinesla ložiskům NEW FORCE optimální strukturu materiálu pro dosahování vyšší trvanlivosti ložisek.

Fig. 7.15

Optimised design and inner geometry

Advanced design and calculation programs, together with new bearing production technologies, enabled optimisation of inner construction of bearings and improved accuracy of functional areas. Thus the NEW FORCE version bearings achieved better quality of functional surfaces and improved course of discharge voltages in bearing component sections, comparing to the standard bearing designs.

This brings reduced noise level and higher accuracy of bearing run, as well as extended durability of bearings.

Special surface treatment

Within innovation programs, a new design of sheet cages for radial and axial spherical-roller bearings was launched in the production. Cages are made of steel plate with surface treatment in order to improve slip properties and reduce wear of cages. The design of cages allows achieving better lubrication and extended service life of bearings. Surface treatments of bearing components represent a well tested way of improving bearing properties for certain locations. The benefit of surface layers lies in better keeping the lubricant in the rolling contact, reduced friction and enhanced resistance to wear and corrosion. We recommend that suitability of surface treatment for special operating condition is discussed with the technical and consultancy services of ZKL.

Bearings NEW FORCE +

ZKL bearings with NEW FORCE+ marking represent a brand new generation of ZKL bearings which is characterised by an innovated modification of the bearing inner structure geometry towards optimum voltage course in the area of rolling contact. This ZKL bearings' innovation is associated with further enhancement of accuracy, comparing to the standardly produced bearing assortment, including the NEW FORCE bearings.
Optimisation of the shape of rolling surfaces brings improved dynamic load capacity of bearings and thus also significant extension of bearings' durability. Development of the NEW FORCE+ generation is associated with the introduction of new calculation methods in the structure of bearings based on MKP and production upgrade by introducing numerically controlled machines that enable achieving final shapes of functional surfaces with modified geometry.
With regard to the fact that the entire design optimisation and production process of modified parts is unique for every bearing application, the NEW FORCE+ bearing generation is not designed to be launched in the standard production program of ZKL. The bearings will be manufactured upon request for extreme locations for selected OEM customers.

7.8 Technical support

ZKL operates as bearing manufacturer and supplier already since 1947. Since the beginning, the company has been cooperating with their customers worldwide. This allows continuous expansion of the ZKL roller bearing production assortment offered in maximum quality at reasonable price. Experience in operation of bearings obtained in cooperation with customers, along with continuous education of their employees allows ongoing development of technical support to ZKL customers and extension of services for ZKL bearing users.

Proposal verification

The ZKL bearings' structure and their basic parameters are designed by the ZKL's own well tested methodologies that adhere to the international ISO standards. Designing new bearings utilises most sophisticated design and calculation CAD systems. Designs of new bearings are optimised and their rigidity checked by means of MKP based numerical calculations. When creating designs, information obtained in achieved test results and experiences from production and operation of ZKL bearings are utilised.

Verification of quality parameters of ZKL bearings

Parameters of ZKL roller bearings are verified in tests within development, as well as in periodical quality assessment during series production. Tests are conducted according to the company's own methods in the test stations of the bearing test room. Bearing and input material tests results are analysed and serve as the basis for new design, technological and investment solutions.

Technical support for ZKL bearing users

Customer needs are solved by fully available workers of ZKL technical and consultancy services. Expert workers are ready to solve operatively requests and questions of ZKL bearing users in the area of selection of bearings, design of rolling location and assembly procedures. ZKL technical support provides users with information in the area of roller bearings, accessories and tribology. Upon user's request it also provides professional supervision over assembly and disassembly of bearings directly at customer, and organizes professional training course of user employees. It cooperates with manufacturers in development of rolling location. It draws up expert opinions on broken bearings. It determines causes of accidents and proposes measures to prevent them.

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