A form feature based modeller implemented on a personal computer is developed to design turned parts. The interactive environment provides the designer with a means of conveying the design intent and functionality without manipulating low-level graphics. Geometric defaults, tolerances, and warnings are embedded in the system and may be expanded for effective design for manufacture. The implementation of the modeller and usefulness of feature based design is discussed. This modeller is implemented in AutoLisp to run within AutoCAD.