A method of forming a flapper assembly (200) for a throttle valve (100) is provided. The method includes steps of forming a flapper (110) comprised of hub (112) having an opening (114) and at least one vane (116a,b) coupled to the hub (112), disposing a shaft (210) in the opening (114), and pressing a punch (P) into an outer surface (112a) of the hub (112) such that a torque dimple (118) extends from the hub (112) into the shaft (210) to fasten the flapper (110) to the shaft (210).