Tooth profile design for the manufacture of helical gear sets with small numbers of teeth

Based on gear theory and generating mechanism, this investigation presents a complete mathematical model of a helical gear set with small number of teeth. The unavoidable tooth-profile undercutting of the gears with small number of teeth is examined by using the developed mathematical model and the conventional method of tooth-profile shifting. Furthermore, an alternative method for lessening the tooth-profile undercutting is also presented by considering a modification of the basic fillet geometry using a modified rack cutter. A third method, combining the aforementioned two methods for the design of helical gears with small number of teeth is also proposed to yield a gear set without tooth undercutting. The mating gear with profile shifting is generated using the pinion as a shaper. The tip fillet and root fillet are modified and a clearance between the pinion and the mating gear is also included in the design. Analysis results indicate that the change of distance between the centers of gear set depends only on gear shifting. Moreover, computer graphs are demonstrated the profile-shifted and the proposed modified gear tooth profiles.