A tool assembly for forming a workpiece with an outer surface into a housing with a non-round design outer profile. The tool assembly includes a number of jaw segments, each jaw segment having an internal surface for engaging the outer surface. The jaw segments are movable between a first condition and a second condition, in which the internal surfaces of the jaw segments substantially define the design outer profile of the housing. Each internal surface has a preselected end point associated therewith defined by a radius centered on the preselected end point that is substantially coincident with the portion of the design outer profile defined by the internal surface. Each jaw segment is movable toward the preselected end point therefor when moved from the first condition to the second condition, and away from the preselected end point therefor when moved from the second condition to the first condition.