Rotatory condition at initial stage of external spline rolling

In spline rolling process, the billet is mainly driven by frictional moment at initial forming stage that from starting rolling to billet/workpiece rotated half circle. If the rotation of billet is not normally driven by rolling die, then the motion between billet and rolling die is not coordinated, and then dividing precision of external spline will be reduced. Thus, the rotatory condition of rolled billet was established in this work. The rotatory condition for the rolling process of spline with even number of teeth is different from that with an odd number of teeth. However, the changing trends for both rotatory conditions are the same. The results indicated that (i) the rotatory condition can be improved when the friction between die and billet increases or the outside diameter of rolling die increases, (ii) the rotatory condition for odd number of teeth is better than that for even number of teeth, and (iii) the outside diameter of rolling die should be five times greater than the diameter of billet before rolling according to the rotatory condition. The reasonable decrement can be selected by comprehensive considering of rotatory condition and geometry of rolling die.