This paper will present a novel work for spiroid and worm gears that mathematically calculates the gear tooth profile in terms of the geometry of the machining tool (hob) and the machining setup. Because of similarity@ the work was also expanded to spiral bevel gear. We have developed software to plot the gear tooth when the parameters of the geometry of the tool and machining setup are entered. The gear tooth shape can then be altered and optimized by manipulating the input parameters until a desired tooth profile is produced. In effect@ the result will be designing the hob and machining setup for best gear tooth profile on the computer. Afterward@ the generated gear tooth data are entered into CAD software to generate a true 3D model of the gear. The tool path will also be generated from the data for CNC machining instead of hobbing.