An improved oscillator assembly that can be used on a chopper for chopping strands of fiber and other long or continuous it items into segments. The improved oscillating assembly moves the items back and forth across the surface of a working layer of the chopper while also rotating a guide roll for the item(s). The improved oscillating assembly uses separate motors to rotate the guide roll and to provide the oscillation and has reduced maintenance than prior art devices. The motor for moving the guide roll is a servo motor and is controlled with a programmable controller. Th3 invention reduces maintenance and increases the uniformity of wear on the chopping blades or cutting roll blade. The controller of the servo motor is programmed to provide dwell time at the reversing points.