Principle and Practice of the Measurement for Hourglass Worms and Hobs

Compared with cylindrical worm gears, hourglass worm gears have better transmission performance. The measurement of the hourglass worms and the hobs is a critical issue to restrict the application of the hourglass worm gear transmission. To solve this problem, an hourglass worm and hob measuring principle and a measuring machine which achieves the inspection of each deviation are proposed. In this paper, the measuring principle is explained. The models of the deviations based on the cylindrical-coordinate system are determined. The machine controls the movement of the probe in accordance with the path created by the models. By checking the geometric deviations, including the helix deviation and the axial tooth profile deviation of the worm, and the cutting edge helix deviation and the cutting edge tooth profile deviation of the hob, the principle is proved to be feasible.