Abstract: A method to make the hourglass worm gearing with the property of mismatched point contact is proposed. The worm and the hob of the worm gearing is generated by a cone and a straight line located on the cone respectively. The basic principle of the worm gearing is analysed. The formulas for calculating the machining parameters is obtained. And the tooth contact of the worm gearing is investigated. The result shows that this worm gearing could get point contact well.

Key words: Hourglass worm gearing, Point contact Tooth contact analysis