CORE PRINCIPLES
What to establish first
- Equivalent dynamic load combines the relevant radial and axial loading.
- Basic rating life varies strongly with the C/P ratio.
- Lubrication, contamination and misalignment can dominate real bearing life.
Bearings
Bearing selection, life, lubrication and load analysis.
MODULE OVERVIEW
Bearings in practical engineering work.
Bearing selection balances load, speed, life, stiffness, mounting, lubrication and contamination. Rating life is a statistical reference quantity, not a service-life guarantee.
DESIGN CONCEPTS
Terms worth checking
- Dynamic rating
- Equivalent load
- L₁₀ life
Common applications: Electric motors · Gearboxes · Pumps and rotating fixtures
KEY RELATIONSHIP
Basic rating life for a ball bearing
L₁₀ = (C/P)³ × 10⁶ revolutions
- C — dynamic load rating, N
- P — equivalent dynamic load, N
- L₁₀ — basic rating life
L₁₀ is a 90% reliability rating-life basis under the standard's stated conditions.
WORKED EXAMPLE
Known values → substitution → interpretation
- Known values
- C = 19,500 N; P = 6,500 N; n = 1450 rpm
- Method
- (19,500/6,500)³ = 27 million revolutions
- Interpretation
- That corresponds to roughly 310 operating hours before adjustment factors; it is a screening calculation, not selection approval.
KEY DESIGN CHECKS
Confirm the conditions behind the number
- Define the governing load case, duty cycle and required design life before using a simplified relation.
- Use compatible units and material data for the actual condition, temperature and manufacturing state.
- Compare the result with strength, stiffness, fatigue, safety, serviceability and applicable-code requirements.
COMMON ENGINEERING MISTAKES
Keep the model within its scope
- Applying basic rating life for a ball bearing outside the assumptions shown on this page.
- Using a nominal condition while a peak, alternating, transient or environmental case governs the design.
- Treating a calculated value as a final component selection without checking interfaces, tolerances and the current governing standard.
AVAILABLE CALCULATORS
Select a calculator
RELATED RESOURCE
Open Bearing Life Calculator
Calculate preliminary basic life with stated load and speed assumptions.
Open related resource →REFERENCES & LIMITATIONS
Use this content as a transparent starting point
ReferenceISO 281:2007, Rolling bearings — Dynamic load ratings and rating life; use the current licensed edition and manufacturer data.ScopeRelationships are presented for the assumptions stated on this page and linked tool.Design reviewCheck material condition, loads, environment and the applicable current code.SafetyResults are educational/preliminary and do not certify safety or compliance.
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