A rotary clamp having a linkage assembly that provides an over-center condition for providing high actuation and clamping forces without excessively wearing the components of the linkage assembly. The linkage assembly is connected to a linear actuator for converting linear actuator motion into rotary clamp motion between a clamped position and an unclamped position. The linkage assembly provides a first link having an aperture for receiving a pin and a roller wherein the roller is coaxially connected o the pin. The second link is pivotally connected to the first link, and the third link is pivotally connected to the second link. The roller of the first link rollably engages a surface on the third link when moving in and out of the clamped position. A beam-like structure connected to the housing provides a wear surface wherein the pin engages the wear surface in response to the roller engaging the third link to prohibit the first link from reaching an over-center position. A spring detent is provided in the third link to engage the roller in the clamped position and resist movement of the roller from moving toward the end clamped position when power is lost to the rotary clamp.