Inputs
Example Data Table
| Example Bearing | Type | Dynamic C (kN) | Static C0 (kN) | Typical RPM | Notes |
|---|---|---|---|---|---|
| 6205 | Ball | 14.0 | 7.8 | 3,000 | General purpose; good for moderate radial loads. |
| 6308 | Ball | 49.0 | 30.0 | 2,200 | Higher capacity; confirm axial ratings from catalog. |
| 30206 | Roller | 43.0 | 48.0 | 1,500 | Handles higher combined loads; setup and preload matter. |
| 22210 | Roller | 74.0 | 68.0 | 1,200 | Good misalignment tolerance; check lubrication requirements. |
Formula Used
This calculator uses the basic rating life approach:
X, Y depend on bearing type and Fa/Fr compared with a threshold e.
p = 3 for ball bearings, and p = 10/3 for roller bearings.
where n is speed in RPM.
a1 accounts for reliability; aISO is a user life modifier.
Tip: For final design, use catalog X/Y/e values for your exact bearing series.
How to Use This Calculator
- Select Calculation Mode: compute life or size the bearing.
- Pick Bearing Type to set the exponent and load factors.
- Enter C and C0 from a bearing catalog.
- Input Fr, Fa, and RPM from your duty cycle.
- Set Service Factor and life modifiers to match conditions.
- Press Calculate; results appear above the form.
- Use Download CSV or Download PDF for documentation.
Load Inputs and Equivalent Dynamic Load
Accurate bearing life starts with realistic radial and axial loads. This calculator applies a service factor to represent shock, vibration, and duty cycle. Select consistent units; the form converts N, kN, and lbf automatically for accuracy. It then estimates an equivalent dynamic load, P = X·Fr + Y·Fa, using typical X, Y, and e thresholds. When Fa/Fr is small, radial load dominates; when it rises, axial effects quickly increase P and reduce life.
Interpreting L10 Life and Adjusted Life
The basic rating life is computed as L10 = (C/P)p in million revolutions. The exponent p is 3 for ball bearings and 10/3 for roller bearings, so load changes have a strong impact. For example, reducing P by 10% increases L10 by about 37% for ball bearings. The calculator converts revolutions to hours using speed, giving a clear operating-life estimate. At higher RPM, the same revolutions translate into fewer hours.
Reliability and Lubrication Modifiers in Practice
L10 corresponds to 90% reliability. If you need higher reliability, the a1 factor reduces life to reflect stricter expectations; common values include 0.62 at 95% and 0.21 at 99%. The aISO factor allows a practical adjustment for lubrication quality and cleanliness. Use 1.0 when data is limited, then refine with inspection history, oil analysis, and supplier guidance. Choose a1 and aISO conservatively when uncertainty is high.
Using Results for Maintenance Planning
Use the adjusted life as a planning baseline, not a guarantee. Compare life across operating points, record the equivalent load and speed, and standardize reporting with the CSV and PDF exports. Combine the output with temperature, contamination, and alignment checks to set inspection intervals. If the static safety factor s0 is low, consider handling practices, start‑stop loads, and risk of permanent indentations.
Sizing Bearings with Target Life Mode
When you select the target-life mode, the calculator reverses the equation to estimate the dynamic rating required to meet your desired adjusted hours at the given loads and RPM. This is useful for early selection before detailed catalog checks. After choosing candidates, verify exact X/Y/e factors, internal clearance, mounting fits, and lubrication limits from the manufacturer for final approval.
FAQs
1) What is L10 life?
L10 is the basic rating life at which 90% of identical bearings are expected to survive under stated conditions. It is expressed in million revolutions or converted to hours using the operating speed.
2) Which load should I enter if loads vary?
Use an equivalent load representative of your duty cycle, such as a time‑weighted average or a load spectrum from measurements. For severe peaks, increase the service factor or analyze multiple cases to find the limiting condition.
3) How do I choose aISO?
Start with 1.0 when lubrication and cleanliness are unknown. Increase slightly for clean systems with good film formation, and decrease for contamination, thin oil, or poor lubrication regimes. Confirm with supplier recommendations and field data.
4) Why are X, Y, and e typical values?
Exact X/Y/e values depend on bearing series, contact angle, and internal design. This calculator uses common estimates to support early sizing. For procurement or final verification, replace them with the catalog values for your exact bearing designation.
5) What does static safety factor s0 indicate?
s0 compares static rating C0 to an estimated static equivalent load. Values near or below 1 suggest higher risk of permanent indentation during shocks or standstill loads. Use it to flag handling, mounting, and peak-load concerns.
6) Can I export results for reports?
Yes. After calculating, use the CSV button for spreadsheets and the PDF button for a formatted summary. Both exports capture inputs, factors, equivalent load, life values, and any warnings for easy documentation.