CORRECTIVE TOOTH CUTTING METHOD FOR SADDLE TYPE WORM GEAR

PURPOSE:To improve contact of tooth and to machine front and rear tooth faces simultaneously by tooth cutting a worm through a conical tool with slightly large inter-shaft distance and reduction ratio with respect to relative motion when tooth cutting for worm wheel is formed. CONSTITUTION:Front and rear tooth faces of a worm 1 are tooth cut simultaneously through a conical tool 2 turnable around a center Q so as to form a hob for tooth cutting a worm wheel around the center (q) of the conical tool 2. Inter-shaft distance L and tooth cutting reduction ratio (j) when a worm 7 is tooth cut are set slightly larger than those (l) and (i) when the hob is formed. When a limit normal point on a common normal line 6 is employed as a design reference point P which is separated from the worm shaft 7 by a distance (r0) and gearing angle of the worm and the worm wheel is (delta), tandelta=(l-r0)/(r0.i), while if lead angle is delta' when tooth cutting is carried out, then tandelta=(L-r0)/(r0.j), and if delta=delta' then L=(l-r0).j/i+r0, and thereby the distance L can be obtained by making the tooth cut reduction ratio (j) equal to (i+n) and providing random integers 1, 2,... to (n).