An obturator adapted for use in penetrating a body wall of a patient includes an elongate shaft having an axis extending between a proximal end and a distal end. A handle is disposed at the proximal end and an arcuate cutting edge is formed at the distal end of the shaft. The shaft may include a plurality of inner walls and passages, with a shield mechanism movable within the passages from a retracted cutting position to an advanced position. A system of flanges and walls can be used to maintain the shield elements in close proximity to and sliding engagement with the associated inner walls. In an associated method of manufacture, the shaft of the obturator can be extruded.