A clamp is used for clamping a paper feed tractor to a support shaft at a predetermined distance from another paper feed tractor. The clamp comprises a semi-cylindrical elongated clamp guide member which is cantilevered from a frame of the paper feed tractor, and a cylindrical clamp member rotatably mounted about the clamp guide member. The clamp guide member has a clamping inner peripheral surface adapted to complementarily engage the support shaft, a first outer peripheral surface, a second outer peripheral surface having a radius of curvature larger than the first outer peripheral surface and a sloped outer peripheral portion joining the first and second outer peripheral surfaces. The clamp member has a clamping inner peripheral surface adapted to complementarily engage the support shaft, a first inner peripheral surface, a second inner peripheral surface having a radius of curvature larger than the first inner peripheral surface, and a sloped inner peripheral portion joining the first and second inner peripheral surfaces, such that the clamp member is rotatable between a clamping position and a release position.