Abstract: A unit is provided for grasping and clamping generally circular shaped parts such as lenses, comprising a central body on which three grasping and clamping elements are mounted adapted to bear tangentially on said part at three points or regions of tangential contact forming, pairwise, angles greater than 90.degree., one of the grasping and clamping elements being arranged to lie on the axis of said central body at one end of a movable central push rod, the other two said elements being arranged symmetrically with respect to said axis at the distal end of two levers, the push rod being urged by at least one clamping spring in the axial clamping direction, and the other two elements being urged to rotate in the direction of clamping by at least one lever-action producing spring, release of clamping being obtained by application of fluid pressure to a piston adapted to operate in opposition to said clamping spring.