A surgical instrument is disclosed. The surgical instrument includes a handle assembly, a body, a tool assembly and an articulation assembly. The articulation mechanism includes a receptacle, and a main shaft. A lower clutch is fixedly positioned within the receptacle and has a serrated portion including a plurality of serrations. An upper clutch includes at least one projection positioned to engage the serrations of the lower clutch to releasably retain the main shaft at a rotatably fixed position. An angle between a first pair of adjacent serrations is defined as a first angle, an angle between a second pair of adjacent serrations is defined as a second angle, and an angle between a third pair of adjacent serrations is defined as a third angle. The first angle, the second angle, and the third angle are each different from one another.