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Load Formulas for Rotary Bearings

This section contains the bearing data that is needed for calculating the load and life of rotary bearings, including

    1. Deep Grove Ball Bearings

    2. Cylindrical Roller Bearings

    3. Needle Bearings

    4. Tapered Roller Bearings

    5. 40º Angular Contact Ball Bearings

    6. Self-Aligning Ball Bearings

    7. Self-Aligning Spherical Roller Bearings

    8. Thrust Ball Bearings

Deep Groove Ball Bearings

1. Equivalent Static Load:

If Fsax/Fsrad > 0.8, Fstatic = 0.6 Fsrad + 0.5 Fsax
If Fsax/Fsrad < 0.8, Fstatic = Fsrad

2. Equivalent Dynamic Load:

Fdyn = Xdrad · Fsrad + Xdax · Fsax

where X and Y are dependent upon the ratio Co/Fsax, as listed in the following table:

Co / Fsax e Fsax / Fsrad < e Fsax / Fsrad > e
Xdrad Xdax Xdrad Xdax
5      0.35 1 0 0.56 1.26
10      0.29 1 0 0.56 1.49
15      0.27 1 0 0.56 1.64
20      0.25 1 0 0.56 1.76
25      0.24 1 0 0.56 1.85
30      0.23 1 0 0.56 1.92
50      0.20 1 0 0.56 2.13
70      0.19 1 0 0.56 2.28

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Cylindrical Roller Bearings

Cylindrical roller bearings do not typically experience significant axial loads, so we can assume the following:

1. Equivalent Bearing Static Load:

Fstatic = Fsrad

2. Dynamic Load:

Fdyn = Fsrad

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Needle Bearings

Needle bearings are designed to only withstand radial, not axial loads so that:

1. Equivalent Bearing Static Load:

Fstatic = Fsrad

2. Dynamic Load:

Fdyn = Fsrad

3. Safety Factor:

So >= 3

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Tapered Roller Bearings

A load component is produced in the axial direction when radial loads are experienced by angular contact and tapered roller bearings. Because of this asymmetry, these types of bearings are often used in pairs, either face to face or back to back. The axial loads can be calculated using the following equation:

Component load in the axial direction = Fai = 0.6 Fsrad / Xdax Let us assume that radial loads R1 and R2 are applied to bearings 1 and 2 respectively, and an external axial load Fae is applied as illustrated. If the axial load factors Xdax1 and Xdax2 and the radial load factor Xdrad apply, then the equivalent loads P1 and P2 can be calculated as follows:

1. Combined, equivalent static load:

2. Combined, equivalent dynamic load:

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Angular Contact Ball Bearings (40º Angle of Contact)

A load component is produced in the axial direction when radial loads are experienced by angular contact and tapered roller bearings. Because of this asymmetry, these types of bearings are often used in pairs, either face to face or back to back. The axial loads can be calculated using the following equation:

Component load in the axial direction = Fai = 0.6Fsrad / Xdax

Let us assume that radial loads R1 and R2 are applied to bearings 1 and 2 respectively, and an external axial load Fae is applied as illustrated. If the axial load factors Xdax1 and Xdax2 and the radial load factor Xdrad apply, then the equivalent loads P1 and P2 can be calculated as follows:

A. Single or in tandem 40º angular contact ball bearings

  1. Combined, equivalent static load:

  2. Combined, equivalent dynamic load:

B. Back to back or face to face 40º angular contact ball bearings

  1. Combined, equivalent static load:

  2. Combined, equivalent dynamic load:

where Fsrad and Fsax are the loads acting upon the bearing pair.

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Self-Aligning Ball Bearings

1. Combined, equivalent static load:

where Xsax is given in NSK-RHP bearing tables (phone: 734-761-9500) for each type of bearing.

2. Combined, equivalent dynamic load:

The numerical values for e, Xsax, Xdax2, Xdax3 are given in NSK-RHP Bearing Tables (phone: 734-761-9500).

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Self-Aligning Spherical Roller Bearings

1. Combined, equivalent static load:

2. Combined, equivalent dynamic load:

The numerical values for e, Xsax, Xdax2, Xdax3 are given in NSK-RHP Bearing Tables (phone: 734-761-9500).

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Thrust Ball Bearings

Combined, equivalent static load:

Combined, equivalent dynamic load:

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Glossary