A surgical instrument includes an end effector, a handle assembly, and a knife drive assembly. The end effector includes a first jaw, a second jaw, a knife, and an electrode assembly. The second jaw is pivotably coupled with the first jaw and is operable to move between an open position and a closed position. The knife is configured to actuate between a pre-fired position and a fired position. The electrode assembly is configured to apply RF energy to tissue. The handle assembly includes a housing associated with the first jaw and an arm associated with the second jaw. The arm is configured to pivot the second jaw between the open position and the closed position. The knife drive assembly includes an input assembly, an output assembly, and a threaded member rotatably disposed within the housing. The threaded member includes a first threaded portion and a second threaded portion. The first threaded portion is associated with the input assembly and includes a first pitch extending in a first pitch orientation. The second threaded portion is associated with the output assembly and includes a second pitch extending in a second pitch orientation. The second pitch orientation is opposite the first pitch orientation. The input assembly is capable to travel a first proximal distance in order to rotate the threaded member. The threaded member is capable to rotate to drive the output assembly a first distal distance to actuate the knife from the pre-fired position to the fired position.
