IMPROVEMENT OF GEAR ACCURACY IN GEAR HOBBING (3RD REPORT, RELATION BETWEEN THE GEOMETRICAL AND SETTING ERRORS OF HOB AND THE TOOTH PROFILE ERRORS OF GEAR).

Recently, smooth tooth surfaces have been obtained by hobbing with accurate finish hobs, resulting in the production of as-hobbed gears for practical use. However, further improvement of the gear accuracy in gear hobbing is needed in order to obtain high load-carrying capacity. In this study, the relation between the hob accuracy and the hobbed gear accuracy is investigated by calculating the tooth profile errors of gears caused by the various hob errors. From the analytical comparison of both hob and gear accuracy, the following are summarized. (1) The tooth profile of hobbed gears are not always highly accurate, even if they are hobbed with a highly accurate hob. (2) For the improvement of the gear accuracy, it is necessary not only to reduce the tooth profile error of hob, the lead variation of hob and the eccentricity in hob setting, but also to consider the hob error patterns.