The symmetrical and asymmetrical fillet are adopted to design the hob top.The formula of the asymmetric fillet radius is derived.Parametric finite element model of hob envelope cutting involute gear is founded by ANSYS APDL language.The results show that
tooth root bending stress is reduced by 8% by choosing the best symmetrical hob top fillet and the root bending stress is reduced by 11% by using the asymmetrical hob top fillet.