An ultrasonic surgical instrument, comprising: (a) a shaft assembly having an acoustic waveguide configured to acoustically couple with an ultrasonic transducer; and (b) an end effector projecting from the shaft assembly, the end effector including: (i) an ultrasonic blade in acoustic communication with the acoustic waveguide, (ii) a clamp arm coupled with the shaft assembly and configured to selectively move relative to the ultrasonic blade from an open position toward a closed position, the clamp arm and the ultrasonic blade being configured to receive the tissue therebetween in the open position and selectively move from the open position and toward the ultrasonic blade until reaching the closed position for compressing the tissue against the ultrasonic blade, and (iii) a first clamp pad coupled with the clamp arm and positioned between the clamp arm and the ultrasonic blade, wherein the clamp arm is configured to prevent direct contact between the first clamp pad and the ultrasonic blade when the clamp arm is in the closed position, characterised in that the clamp arm includes an abutment configured to engage the acoustic waveguide when the clamp arm is in the closed position thereby inhibiting further movement of the clamp arm toward the ultrasonic blade, wherein the acoustic waveguide is configured to resonate and thereby define a nodal position, wherein the abutment is configured to engage the acoustic waveguide at the nodal position, and wherein the clamp arm is configured to maintain a gap between the first clamp pad and the ultrasonic blade in response to engagement between the abutment and the corresponding portion of the ultrasonic waveguide. (a) a shaft assembly having an acoustic waveguide configured to acoustically couple with an ultrasonic transducer; and (b) an end effector projecting from the shaft assembly, the end effector including: (i) an ultrasonic blade in acoustic communication with the acoustic waveguide, (ii) a clamp arm coupled with the shaft assembly and configured to selectively move relative to the ultrasonic blade from an open position toward a closed position, the clamp arm and the ultrasonic blade being configured to receive the tissue therebetween in the open position and selectively move from the open position and toward the ultrasonic blade until reaching the closed position for compressing the tissue against the ultrasonic blade, and (iii) a first clamp pad coupled with the clamp arm and positioned between the clamp arm and the ultrasonic blade, wherein the clamp arm is configured to prevent direct contact between the first clamp pad and the ultrasonic blade when the clamp arm is in the closed position, characterised in that the clamp arm includes an abutment configured to engage the acoustic waveguide when the clamp arm is in the closed position thereby inhibiting further movement of the clamp arm toward the ultrasonic blade, wherein the acoustic waveguide is configured to resonate and thereby define a nodal position, wherein the abutment is configured to engage the acoustic waveguide at the nodal position, and wherein the clamp arm is configured to maintain a gap between the first clamp pad and the ultrasonic blade in response to engagement between the abutment and the corresponding portion of the ultrasonic waveguide. (i) an ultrasonic blade in acoustic communication with the acoustic waveguide, (ii) a clamp arm coupled with the shaft assembly and configured to selectively move relative to the ultrasonic blade from an open position toward a closed position, the clamp arm and the ultrasonic blade being configured to receive the tissue therebetween in the open position and selectively move from the open position and toward the ultrasonic blade until reaching the closed position for compressing the tissue against the ultrasonic blade, and (iii) a first clamp pad coupled with the clamp arm and positioned between the clamp arm and the ultrasonic blade, characterised in that the clamp arm includes an abutment configured to engage the acoustic waveguide when the clamp arm is in the closed position thereby inhibiting further movement of the clamp arm toward the ultrasonic blade, wherein the acoustic waveguide is configured to resonate and thereby define a nodal position, wherein the abutment is configured to engage the acoustic waveguide at the nodal position, and wherein the clamp arm is configured to maintain a gap between the first clamp pad and the ultrasonic blade in response to engagement between the abutment and the corresponding portion of the ultrasonic waveguide.