Abstract: A balance monitoring system utilizes existing Z-axis servo motor and control features of a machine tool to sense disturbances directly related to rotary table imbalance. It has been found that a Z-axis following error signal is the most noise free and most asily correlated axis control indictor. Since the Z-axis following error signal is already available using existing hardware and software, there is no need for additional transducers or devices. The balance monitoring of system can be used for three different purposes; for monitoring table balance at startup of the rotary table, for diagnosing table balance, and for in-process monitoring during a turning operation.