The curvature radius of tooth root fillet curve affects the diameter of involutes initial circle and the bending strength of tooth root.The design and calculation of maximum fillet was quantitatively analyzed

and using the relationship of Eulor-Savary conjugate tooth surface curvature

the corresponding relationship between tool tip fillet of rack cutter and the tooth fillet of the being cutter gear was set up in theory.It provides the basic theory for the design and manufacture of gear.From the mechanics aspect

the design and selection principles of tool tip fillet of rough hob was studied

the interrelationship between tool tip fillet of grinding rack and involutes initial circle was also researched.The results of study are of practical application value in reasonable design of the tooth fillet

reasonable design and selection of gear rack

precision gear wheel dressing

and guaranteeing the diameter of involutes initial circle.