Abstract: A clamp assembly for fastening and holding workpieces has a mandrel with flexible retaining fingers that are normally extended at a reference position for ease of insertion and removal from the workpiece, which assembly is secured to the workpiece by withdrawal of a spindle shaft coupled to the extending fingers to radially expand the fingers over a spreader bar. The spindle shaft and flexible fingers are maintained in the retracted and workpiece-securing position until rotation of an end cap disengages the secured retaining tabs from the spindle shaft and aligns them with planar surfaces for clamp recovery to the reference position by a biasing means.