Abstract: A gripper for fitting to a robot and adapted to grip circular work pieces or work pieces comprising a circular bore, comprising a support, articulated parallelograms which are disposed in planes converging towards an axis X--X and a first arm of which is mobile with respect to said support, parallel to said axis X--X, the opposite arm being mobile in a direction perpendicular to said axis but fixed in the direction of this latter, and having a clamping finger, and means carried by said support for moving the first arms of said parallelograms having said clamping fingers are provided with at least two rollers disposed on each side of said support, in contact with tracks provided thereon.