A clamp to retain a block of material on a machining table including a body having a first face, a first front face oriented toward the machining table and the block of material when in use, a nose projecting relative to the first front face having a second front face parallel to the first front face, first and second edges connecting the first and second front faces, and at least one internally threaded hole opening at least partly at the level of the second front face with an axis forming a non-zero angle with the first face and the second front face, at least one grub screw screwed into the internally threaded hole having a pointed free end configured to penetrate into the block of material when in use when screwing in the grub screw, and a connecting system to demountably connect the clamp to the machining table.