Spindle Noise: Potential Causes & Troubleshooting

Before determining what might be wrong with your spindle, it helps to know exactly what to listen for.

You should be familiar with what your spindle sounds like during standard operation — a moderate amount of vibration is normal. However, listen for sounds that resemble whining, growling, screaming, chattering, skidding, or clunking; changes in pitch; or noises that sound like electrical sparking. Any of these are signs of some level of spindle wear or damage.

Noisy spindle vibration can be caused by any of the following:

• Bearing defects
• Bearing journal / housing bore out of tolerance
• Incorrect bearing lubrication
• Incorrect spindle mounting / drawbar
• Misaligned spindle components
• Out-of-balance assembly and interactions between rotating parts
• Out-of-tolerance tooling interfaces
• Resonant frequencies
• Low spindle bearing preload
• Spindle crashes
• And more

Besides noise, there are some physical signs a spindle may be in need of a repair, including:

• Issues with parts finish
• Wear at the spindle tooling
• Toolholders sticking
• Fretting in toolholders (created by the toolholder slipping inside the spindle)
• Excessive heat

On this last point, a spindle should remain relatively cool during operation, especially if the coolant system is working properly. Spindles equipped with chillers may have a temperature alarm that will sound if the temperature exceeds 140° F (60° C).

It’s unlikely that machine operators will be able to determine the root cause of unusual spindle noise on their own — the best thing you can do is call in the experts. Take the following steps at the first sign of trouble:

1. Isolate the spindle to confirm the noise is coming from the spindle itself, rather than another machine component.
2. Make sure the spindle is properly lubricated.
3. Verify whether the noise occurs at all RPM or just a particular RPM.
4. Check the workpiece for surface issues.
5. Test the spindle with and without a tool in the toolholder.
6.Check for increased/excessive runout.
7. Check whether the drive load is increased.
8. Check drawbar retention force.

If you have checked all of the above and still experience noise, pull the spindle and consult an expert repair technician. The sooner you address the issue, the better — don’t tempt fate by running your spindle past its limit. Delaying service could lead to extensive equipment damage and even costlier repairs.

At Northland Tool, we assess every spindle we receive with our comprehensive, multi-step evaluation. We will test the spindle in our facility to confirm the issue and identify any others, then rebuild the spindle to its required specifications. We explain the issue to the customer, determine whether it was a spindle or machine issue, and provide recommendations to avoid future issues.

If you have a spindle that’s sounding a little different than normal, don’t wait — call or message Northland Tool today for a comprehensive assessment and quote.