Abstract: Apparatus for monitoring the progress of operations on mechanical components, such as the fitting of railcar wheels to axles, includes a tachometer monitoring motion of the press ram and generating pulses indicative of increments of forward and rearward movement of a press ram, a chart recorder having a pen whose position indicates the pressure applied to the ram, and a stepper motor driving the chart of the recorder, the stepper motor being supplied with stepping pulses proportional to the net forward motion of the ram as calculated from the outputs of the tachometer. Provision is made for predetermined numbers of forward stepping pulses to be supplied to the motor during rearward movement of the ram so as to separate from the chart the traces generated during successive movements of the ram.