Abstract: An arrangement for driving a rotary tool is provided in which the tool shank is engaged and frictionally driven by the engagement of three or more drive rollers. Axial movement of the tool is accomplished by tilting the axes of the rollers as permitted by flexible portions of the shafts which drive the rollers. The tool is released by moving one roller away from the other two. A pressure foot is provided at the bottom of the assembly reciprocated by a cam arrangement to engage the workpiece when the tool is in operation. A position pick-off senses the axial position of the tool so that the tilt angle of the rollers can be controlled by a dual feedback path servo loop having an improved preconditioning circuit for its feedback position counter.