Abstract: A fluid actuator for mechanical components in general comprises at least one piston (1, 3, 31, 32) which slides inside a cylindrical chamber (100) and which, during manual operation, moves integrally with a threaded rod (9) moved between two end-of-travel positions, by means of rotation of a screw nut (10). Indicator means indicate the displacement of the threaded rod (9) between the two end-of-travel positions.