An improved design of inserted tooth finishing hob for involute gears

Gear hobs are widely used to machine involute gears. However, using Archimedes worm as a base worm of the gear hob, which is common used in industry, leads to the generating of theoretical error of the gears. Even though this error can be eliminated by using the accurate involute base worm or be greatly reduced by complicated modification of the shape of cutting edges, the manufacturing cost is very high. Reported in this paper is an improved design of inserted tooth finishing hob for involute gears on a conventional hobbing machine aiming to eliminate this error in an economical way. For that purpose, both descriptive-geometry-based method and mathematical analyzing are employed to illustrate the major parameters of the base worm and the formation and parameters of the inserted tooth finishing hob. In addition, an approximating formation of the flank for the convenience of grinding the inserted tooth finishing hob is proposed and the errors that this substitution arc surface is discussed. Ultimately, the other advantages of this inserted finishing hob are demonstrated.