The final stage in the spindle rebuilding process is run-in and testing.

During the run-in, the spindle is slowly accelerated to normal operating speeds. The spindle is then tested to ensure minimal heat rise and vibration levels. All electronic circuitry and critical run-outs are tested and verified. The spindle is then put through a series of tests and simulators specific to the customer's machine. All operating frameworks are closely monitored to guarantee that the spindle operates to its original specifications or better.

The final testing stages ensure the spindle is ready for operation.