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Bearing Grease Speed Factor Guide - Suitability & Regreasing Interval

Check grease compatibility with bearing speed and temperature, get regreasing interval estimates

Free bearing lubrication guide that checks whether your grease is suitable for the bearing speed and operating temperature, then estimates the regreasing interval. Grease lubrication is the simplest and most common method for bearings, but it has limits. Run a grease too fast and the base oil separates from the thickener, starving the contact zone. Run it too hot and the base oil oxidizes and the thickener breaks down. This calculator evaluates your grease against the ndm speed factor, base oil viscosity, NLGI consistency grade, and operating temperature to determine suitability. It then estimates the regreasing interval in operating hours using standard guidelines adjusted for temperature, speed, contamination level, and bearing orientation. The result includes a clear recommendation: OK, marginal, or not suitable for the operating conditions.

Pro Tip: Temperature is the grease killer. Every 15°C (27°F) above 70°C (158°F) cuts grease life roughly in half. A bearing running at 90°C needs regreasing twice as often as the same bearing at 70°C. If your regreasing intervals are too short to be practical, look at reducing the bearing temperature first before switching to a more expensive grease.

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Start Using This Tool See How It Works

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Bearing Grease Speed Factor Guide
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How It Works

  1. Enter Bearing Information

    Input the bearing bore and pitch diameter in millimeters, bearing type, and operating speed in RPM. The calculator computes the ndm speed factor to evaluate against the grease speed limit.

  2. Select Grease Properties

    Choose the NLGI grade (1, 2, or 3) and base oil viscosity class. NLGI 2 is the most common general-purpose grade. Higher-viscosity base oils are better for slow, heavy-load applications. Lower-viscosity oils are needed for high-speed bearings.

  3. Enter Operating Temperature

    Input the bearing operating temperature. The calculator checks against the grease dropping point and base oil oxidation limits. Temperature above 70°C starts reducing grease life significantly.

  4. Select Environment Factors

    Indicate the contamination level (clean, moderate, or severe) and bearing orientation (horizontal or vertical). Vertical shafts require more frequent regreasing because grease migrates away from the contact zone under gravity.

  5. Review Recommendations

    Get a grease suitability rating, estimated regreasing interval in hours, and recommendations for grease type changes if the current selection is marginal.

Built For

  • Maintenance teams setting up lubrication schedules for plant equipment
  • Reliability engineers evaluating grease selection for high-speed or high-temperature bearings
  • Millwrights determining regreasing intervals after bearing replacements
  • Plant managers standardizing lubrication practices across multiple machines
  • Lubrication technicians verifying that specified grease is appropriate for operating conditions

Frequently Asked Questions

NLGI 2 is the default for most industrial bearing applications. It stays in the bearing without leaking in horizontal applications and provides adequate lubrication across a wide speed and temperature range. NLGI 1 (softer) is better for cold environments, low-speed applications, and centralized lubrication systems. NLGI 3 (firmer) is better for vertical shafts and high-temperature applications where softer grease would run out.
The conservative approach is to calculate the regreasing interval using bearing size, speed, and temperature, then regrease at 50% of that interval. In practice, many plants use ultrasonic grease monitors that listen for the frequency signature of inadequate lubrication and trigger regreasing based on actual condition rather than calendar time.
Generally no. Mixing greases with different thickener types (lithium with polyurea, for example) can cause the mixture to soften, harden, or separate, leading to lubrication failure. If you must change grease types, purge the old grease completely by running the bearing with the new grease and flushing through until only new grease exits.
Excess grease in the bearing cavity gets churned by the rolling elements, generating friction heat. This heat breaks down the grease, raises the bearing temperature, and can cause seal failure. The correct fill level is one-third to one-half of the bearing free space. More is not better.
Disclaimer: Regreasing intervals are estimates based on general industry guidelines. Actual intervals depend on specific grease formulation, bearing precision class, seal type, and operating environment. Follow the bearing and grease manufacturer recommendations for your specific application. Critical applications should use condition-based monitoring to optimize regreasing timing.

Learn More

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Bearing Speed Limits: What ndm Means and Why It Matters

How to check if your bearing is running too fast for the lubrication method, what ndm represents, and what to do when grease cannot keep up with the speed.

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Bearing Grease: Choosing the Right One and Knowing When to Apply It

Base oil viscosity, NLGI grade, thickener type, regreasing intervals, and why over-greasing causes as many failures as under-greasing.

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Bearing Failure Modes: Reading the Evidence

How to tell what killed a bearing by looking at the damage pattern. Fatigue spalling, lubrication failure, contamination, electrical fluting, and corrective actions.

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Bearing Lubrication Intervals: SKF Method & Grease Selection

Calculating regreasing intervals using the SKF method. Speed factor, temperature correction, contamination adjustment, grease quantity, and common relubrication mistakes.

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