The invention discloses a method for controlling the symmetry of a
machining keyway and the center of a tooth or a
tooth space, through which the cost is reduced, the product quality is improved, and the work efficiency is improved. The method includes following steps: 1) selecting a cross section of a single
helical gear, marking the center O1 of the
tooth space or the tooth on the cross section, and establishing a rectangular coordinate
system XOY on a
base plane by regarding a connecting line of the O1 and the center O of the cross section as a Y axis, wherein the height from the cross section to the
base plane is h; 2) calculating L, wherein L=h*tan[beta], and beta is an inclination angle of the
tooth space or the tooth of the single
helical gear; 3) calculating a rotation angle theta, wherein theta=2*(theta / 2)=2*arcsin((L / 2) / R); 4) rotating the XOY rectangular coordinate
system for the theta angle, and re-establishing an X'OY' rectangular coordinate
system; and 5) milling the keyway by regarding the X'OY' rectangular coordinate system as the datum. By employing the method for controlling the symmetry of the
machining keyway and the center of the tooth or the tooth space, the operation is simple, the labor intensity of workers is reduced, the work efficiency is improved by multiple times, and the quality and the precision can be guaranteed.