Abstract: A clamping device having a first jaw, a second jaw and means for urging said first jaw toward said second jaw wherein a clamping plate is rigidly secured to the first jaw and a second clamping plate is pivotally secured to the second jaw so that the device can clampingly engage two workpieces having different diameters at the same time. In addition, one of the clamping plates includes a pair of swivelly mounted support members having a support surface so that regardless of the pivot position of the second clamping plate, the support surfaces flatly abut against the workpieces to urge them tightly against the flat surface of the other clamping plate in a coplanar alignment.