Abstract: Clamping device for simultaneously holding several workpieces between a fixed central jaw and two endjaws situated on either side of it and joined by a threaded, lengthwise moveable spindle. A helicoidal spring surrounding the spindle urges it towards its extremity which is actuated, so that when the spindle tightened the spring elastically presses the end jaw far from the operator against a workpiece placed between said far jaw and the central jaw. This workpiece is thus immobilized even without counterpressure from the near end jaw, and need not be held by the operator who can simultaneously insert a second workpiece between the near end jaw and the central jaw with one hand and tighten the spindle with the other.