an ironworker is provided with a powered set of opposed workpiece clamps for accurately locating a workpiece beneath a punch or the like . the preferred form employs a rotary powered , numerically controlled means for moving the clamps . a unique timing - belt drive is provided for moving long workpieces , such as elongated channels or the like , from a rotary powered input . a workpiece clamp is provided with a stationary first workpiece - engaging member and a movable second workpiece - engaging member which is slidable along its longitudinal axis from an extended position where it is closely spaced and aligned above the first workpiece - engaging member to a retracted position where it is moved upwardly away from the first workpiece - engaging member and slid longitudinally rearwardly of the first workpiece - engaging member for lifting or placing a workpiece in position for clamping .