Because it is difficult to manufacture the multi head worm gear hob, and it is not easy to manufacture accurately, the single head worm gear hob can be used to process the worm gear meshing with the multi head worm. When the tooth profile cut by this method is meshed with the working worm, only the middle part can contact each other. But it does not affect the correct meshing transmission. It only has certain influence on service life and load. However, because the small module worm gear is generally used for transmission and its stress is small, it is feasible to use this method for machining. With this method, the single head worm gear hob and multi head worm must meet the following conditions:
- The normal modulus of the two should be equal;
- The normal pressure angle of the two should be equal;
- The pitch diameter of single head worm hob is 0.5-1mm larger than that of multi head worm.
The other parts of the hob are exactly the same as the ordinary single head worm gear hob. The above condition is to ensure that the base joints of the multi head worm gear pair are equal when meshing transmission, otherwise, it will cause “interference” and destroy the correct meshing transmission.