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[Technical Calculation] [Technical Calculation]
Calculation method and the concept of basic rating life of the ball bearing Excerpted from GB/T 6391—2010 Dimension of Normal Parallel Key Type Excerpted from GB/T 1096—1979

1. ■ Life Dimension of Normal Parallel Key Type (Excerpted from GB/T 1096—1979)
Life (of a single set of rolling bearings) refers to the number of revolutions that one collar or washer of a bearing rotates relative to an-
other collar or washer before the first sign of fatigue expansion appears on one collar or washer or rolling element material of the
bearing. Type A Type B Type C
Note: Life can also be expressed in hours of operation at a given constant speed.
h c or r
2. ■ Basic rating life
For bearings with currently used common high-quality materials, good processing quality and operating under normal operating condi- R＝b/2 R＝b/2
tions, it refers to the rated life related to 90% reliability. b
3. ■ Modified rating life L L L
The rating life obtained by modifying the basic rating life considering 90% or other reliability levels, bearing fatigue loads and/or spe-
cial bearing performance and/or contaminated lubricants and/or other unconventional operating conditions.
Mark Example:
4. ■ Basic dynamic radial load rating Round end normal parallel key (Shape A) b＝16mm, h＝10mm, L＝100mm Mark: Key 16×100 GB/T 1096—1979
It refers to the constant radial load that a set of rolling bearings can bear theoretically. The basic rated life of the bearing under this Mark with the same dimension (Shape B), (Shape C): Key B16×100 GB/T 1096—1979, Mark: Key C16×100 GB/T 1096—1979
load is one million revolutions.
Note: For a single row angular contact bearing, the load refers to the radial component of the load that causes the bearing rings to Table 1 Correspondence of b and h with Nominal Size and Limit Deviation
produce pure radial displacement between each other. Nominal Dimension 2 3 4 5 6 8 10 12 14 16 18 20 22
b Limit Deviation 0 0 0 0 0
5. ■ Dynamic equivalent radial load (h9) －0.025 －0.030 －0.036 －0.043 －0.052
It refers to a constant radial load, under which the rolling bearing has the same life as that under the actual load condition. Nominal Dimension 2 3 4 5 6 7 8 8 9 10 11 12 14
h Limit Deviation 0 ( 0 ) ① 0 ( 0 ) ① 0 0
6. ■Dynamic equivalent radial load (h11) －0.06 －0.025 －0.075 －0.030 －0.090 －0.110
6.1 Dynamic equivalent radial load of single set of bearing C or r 0.16～0.25 0.25～0.40 0.40～0.60 0.60～0.80
The dynamic equivalent radial load of radial contact and angular contact ball bearings under constant radial and axial loads is: Nominal Dimension 25 28 32 36 40 45 50 56 63 70 80 90 100
Pr ＝XFr + YFa EEEEEEEEEEEEEEEEEEEEEEEEEEEEE （3） b Limit Deviation 0 0 0 0
See Table 1 on P.649 for X and Y values. These coefficients are applicable to bearings with raceway groove curvature radius comply- (h9) －0.052 －0.062 －0.074 －0.087
ing with requirements listed on P.649. For the curvature radius of the other raceway grooves, the X and Y values can be calculated by
4.2 in ISO/TR 8646:1985. Nominal Dimension 14 16 18 20 22 25 28 32 32 36 40 45 50
h Limit Deviation 0 0 0
6.2. Dynamic equivalent radial load of bearing group (h11) －0.110 －0.130 －0.160
6.2.1 Single row angular contact ball bearing "back-to-back" or "face-to-face" configuration C or r 0.60～0.80 1.0～1.2 1.6～2.0 2.5～3.0
Two sets of identical single row angular contact ball bearings are installed side by side on the same shaft in "back-to-back" or "face- ① The values in parentheses (corresponding to h9) apply to Shape B keys.
to-face" configuration, and rotate as a whole (installed in pairs). When calculating their dynamic equivalent radial load, it should be
considered as a set of double row angular contact bearings. Table 2 Correspondence of L with Nominal Size and Limit Deviation
Note: If two sets of identical single row radial contact ball bearings operate in a "back-to-back" or "face-to-face" configuration, users Nominal Dimension 6 8 10 12 14 16 18 20 22 25 28 32 36 40 45 50 56 63 70 80 90 100 110
should consult the bearing manufacturer for the calculation method of their dynamic equivalent radial load. L Limit Deviation 0 0 0 0 0 0
(h14) －0.36 －0.43 －0.52 －0.62 －0.74 －0.87
7. ■Basic rating life
7.1 Life formula Note: Key Length L
Row: 6,8,10,12,14,16,18,20,22,25,28,32,36,40,45,50,56,63,70,80,90,100,110,125,140,160,180,200,220,250,280,320,360,400,500 Tolerance is h14
The basic rating life formula for radial ball bearings is:
3 1. Parallel key, Keyway profile size should comply with regulations of GB/T 1095—2003 “Keyway profile sizes for parallel keys”.
C r
L 10＝( ) EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE （4） 2. Technical conditions for normal parallel keys should comply with regulations of GB/T 1568—2008 "Technical specifications for keys".
P r
3. When the key length is longer than 500mm, its length should be selected according to R20 series of GB/T 321—2005 "Preferred numbers -Series of preferred numbers".
The life formula is also applicable to the life estimation of a bearing group consisting of two or more sets of single row bearing group.
At this time, the rated load C r is calculated according to the whole bearing group, the equivalent load P r is calculated according to the
total load acting on the bearing group, and the X and Y values used are based on the requirements listed in 6.2.
7.2 Load limiting conditions of life formula
The life formula can give a satisfactory result in a wide range of bearing loads. However, excessive loads can produce harmful plastic
deformation at the point of contact between the ball and the groove. Therefore, when P r is greater than the smaller of C 0r or 0.5C r, the
user should consult the bearing manufacturer to determine the applicability of the life formula.
Too small load can cause other failure modes, which are not included in this standard.

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