A lancing device comprising a movable parallelogram-shaped rack. The rack rotates a linearly fixed pinion which drives a slider-crank system. The slider-crank system in turn drives a lance holder. The parallelogram-shaped rack defines one or more predetermined paths along which the pinion moves. The lance holder is prevented from being extended beyond a predetermined depth when the pinion reaches a predetermined position along the one or more predetermined paths. The pinion is mechanically stopped from further progress by intersecting two legs of the parallelogram-shaped rack. Teeth of the rack may be modified to reduce the change the pinion may jam in the rack.