Spindle Bearing Break-in Procedure: Steps & Explanation

Just like a new pair of shoes, the bearings on new or recently repaired spindles need to be “broken in” to ensure proper lubrication and performance.

Spindle break-in is essential for units with grease lubricated bearings, since the procedure will settle the grease into the spaces between the bearings and the raceway. Bearing break-in should be standard for all new and recently repaired spindles, as well as grease lubricated units that have been in storage for an extended period of time.

During break-in, the initial grease placement may result in excessive friction and resistance, which will cause a mild temperature increase. Operators should continuously monitor their spindles for changes in heat, vibration, and acceleration, as bearings will continue to break in over time.

Properly breaking in spindle bearings will help:

• Extend spindle maintenance cycles
• Improve and ensure the consistency of the spindle bearing system
• Ensure that the lubrication system is working correctly
• Avoid “grease fling” through proper grease placement

All spindle repair facilities should include spindle break-in as a standard step in every repair. Experienced repair technicians can guide owners and operators through the process for all new spindle assemblies.

Here at Northland Tool & Electronics, virtually every rebuilt spindle is test-run and broken in before it is returned to the customer. Below, you can see an outline of how the procedure is utilized. Break-in can and should also be implemented after the spindle is reinstalled in the machine, but in most cases will not surface any issues, since it was already completed at the repair facility.

Break-in prep

Before performing a spindle break-in procedure, make sure all oil feed tubes are long enough and properly aligned to provide sufficient lubrication. Inspect the entire delivery system to confirm oil is passing through, verify the jet pressure, and inject a small amount of oil into the bearing housing to prep the bearings before commencing any rotation.

Performing the break-in procedure

Once the bearings are sufficiently lubricated, the actual break-in can begin. Below is a standard step-by-step procedure, which may vary based on the application.

1. Start the spindle at 10% of its maximum speed.
2. Run at constant speed for about 30 minutes.
3. Monitor the temperature closely, making sure it does not exceed 140°F (60°C) at the bearing housing.

a. Account for the position of the temperature sensor. A sensor on the spindle housing will read much cooler than the actual bearing temperature. The machine manual should provide temperature adjustments and acceptable limits.

4. If the temperature is within acceptable range at 30 minutes, increase the RPM by 10%.
5. Repeat steps 2–4 until maximum RPM is reached and the temperature at the bearing housing remains consistently acceptable.
6. If at any point the temperature exceeds 140°F, stop the spindle immediately and let it cool to room temperature. Begin the procedure again at a speed 10% below where you left off.
7. Likewise, if excessive noise or vibration occurs at any time, stop the spindle and follow the same procedure to re-start.

Storing your spindle

Whether you keep spare spindles in-house or at a dedicated facility, they should be stored in a clean, dry, temperature-controlled environment away from ambient vibration. If stored for long periods of time, spindle shafts should be rotated every 3–4 weeks to ensure grease stays between the bearing balls and the raceways, which will prevent damage from prolonged metal-to-metal contact.

If you have a spindle in need of evaluation or repairs, send it to Northland Tool & Electronics for our team’s expert assessment. Call us or send us a message today.