Extending the service life of your machine tool spindle

Spindles, the heart of your machine, are commonly overlooked as they are generally hidden in your machine. An overlooked spindle may result in a machine crash, stopped production, wasted labor, and missed delivery dates. Machine operators make all the difference when it comes to the life of a spindle. They can help you avoid these issues by following the steps below to keep your machine tool spindle in good working order and aid in maintaining spindle longevity in the process.

Tool Holder

For example, a tool holder should be balanced properly. As a tool holder assembly spins during operation, imbalance of the spinning components creates centrifugal force, which increases exponentially with speed. As this force increases, excessive and potentially troublesome vibration may follow and result in poor machining and difficulty holding close tolerances. The imbalance of the tool holder may be in its design, it possibly was not appropriately balanced from the beginning, or the tool holder may have been damaged or modified by the end-user. The use of high-quality, balanced tool holders is your best bet for optimum performance.

Balance Tolerance

Calculating a balance tolerance provides an acceptable range for operation. Once the intended operating speed is designated, a maximum allowable imbalance is set within the speed parameter. Balancing within the “tolerance” range can help boost spindle performance and accuracy while avoiding problems. Typically balancing to a specification of G.04 or better is acceptable.


Vibration should stay within normal parameters. Excessive or abnormal machine vibration will generally indicate a potential spindle problem. When this happens, the spindle should undergo a checkup.


Machine operators should consciously make every effort to protect spindles from coolant. Contamination from tool coolant spray or flood coolant may wash the grease or oil out of the spindle’s bearings and attack the spindle’s shaft, motor, and electronics. When using coolant, it should be directed at the tool and away from the spindle.


Monitoring the operating temperature of the spindle for fluctuations can offer an early warning sign of potential failures to come. Once you determine the normal operating temperature, it’s helpful to record baseline temperatures of the front and rear spindle bearings for comparison (and possible corrective action).

Additional tips to help extend the life of your spindle include:

  • Listen for unusual or noticeable audible noise as a potential warning of impending trouble.
  • Supply clean and dry compressed air.
  • Keep clean and ensure proper oil flow.
  • Watch your feeds and speeds to arrive at the perfect combination for the application.
  • If your spindle is liquid-cooled, make sure your flow rate is per OEM specifications.
    • TIP: Be sure the fluid is circulating as these ports do clog up at times.
  • Do not use a compressed air gun to blow off the spindle. Doing so may force contaminants directly into the spindle.

Have questions regarding your spindle? We are happy to discuss them with you. Contact MZI Precision at (714) 379-6505.