The invention provides an improved method and apparatus for indicating an apparent error in the operation of a fluid-powered attachment (A) mounted on a machine tool for controlled movement toward and away from a workpiece (W) upon which an operation (e.g., thread rolling, knurling, burnishing, etc.) is to be performed during a cycle. The improved apparatus (60) broadly includes: a fluid-powered actuator (64) for selectively moving the attachment (A) relative to workpiece (W) during the cycle; a sensor (73) operatively arranged to monitor the value of at least one of the pressure within the actuator, and the time of operation, during at least a portion of the cycle, and arranged to provide an output signal; and a programmable logic unit (75) provided with the sensor output signal, arranged to store minimum and maximum permissible values of the selected pressure and/or time of operation, and operatively arranged to indicate an apparent error in the performance of the operation on the workpiece if the sensed value is not between the stored minimum and maximum stored values.