key or 6 key square serration axle is the traditional structure of starter armature shaft for auto and tractor and has been replaced by cold rolling multi key involuting serration axle.

• 铣削加工的四键或六键矩形花键是汽车、拖拉机用起动机电枢轴上的传统结构,已逐渐被用冷滚轧加工的多键渐开线螺旋花键所代替。