What is the Most Common Reason for Bearing Failure?

The bearing is the heart of a machine tool spindle. Optimal operating conditions result in a smooth functioning machine with little noise and vibration. However, when a bearing fails, it can result in lengthy and expensive downtime. There are many reasons for bearing failure, but only one type contributes to most machine tool spindle failures—bearing contamination.

Bearings rely on a clean operating environment to function efficiently and quietly. Therefore, introducing contaminants can and will result in premature bearing failure. Some common contaminants are:

• Airborne dust – dust is generated from virtually any source, such as a cutoff wheel, spray paint can, or even an air hose. This dust enters the bearing from outside the spindle and contaminates the bearing lubrication causing excess heat.
• Coolant – in heavy duty operations, an external cutting fluid or coolant may be needed to cool the tool or workpiece. This coolant can enter a bearing and contaminate the bearing lubrication causing excess heat and even rust if conditions are right.
• Contaminated air – a shop air hose isn’t always the cleanest and installing a dirty air line onto a spindle can cause dirt and grime to enter the bearings and contaminate the bearing lubrication. As mentioned before, this causes excess heat, which results in premature bearing failure.
• Chips – raw material chips freshly removed from a part can also enter a bearing and cause catastrophic bearing failure.

The best way to ensure that contaminants do not enter the spindle bearings is to operate the machine in the cleanest environment possible. Keep dust prone operations and tools away from machine tool machines. Verify that the spindle seals are working correctly and are in good condition to keep coolant and chips from entering the bearings. And always clean and purge air lines before installing onto a machine or directly on a spindle.