a screwdriver of the present invention is designed for use with power tools . the screwdriver provides an automatic disengagement mechanism to prevent excess penetration of the screw into a work surface . the screwdriver has a housing enclosing the motor and a bracing member inserted into the housing , in which the bracing member is shaped to slide inside the housing . a sleeve member adjustably secured to the bracing member so that when the sleeve member is in a fully extended position in relation to the bracing member the spindle containing a driver bit is engaged to the motor through a transmission assembly , such as clutches or ball bearings . alternatively , if the sleeve member is in a retracted position , then the spindle is disengaged from the motor thus stopping the rotation of the screw even if the motor is still rotating .