Fixed-torque torque screwdrivers(without scale) with a slip mechanism that eliminates the possibility of exceeding the preset value; when the preset torque is reached, the handle turns to zero. These torque tools must be pre-set with a suitable calibration device and locked to the desired value (within the range provided for the chosen tool), alternatively for an additional cost it is possible to order them already pre-set by specifying the desired torque.