Screw with a countersunk recess in the head, a right-handed and a left-handed thread being located on the inner wall of said recess. Screwdriver with complementary threads on the outer border of the part which is screwed into the countersunk recess in order to screw in, and unscrew, the screw

摘要

The screw head or the shank end of the screw connection has a countersunk recess (2), two internal threads which run one above the other, a right-handed and a left-handed thread, being provided (3) on the inner border of said recess. On the outer border of the part which is screwed into the countersunk recess, the screwdriver likewise has right-handed and left-handed threads running one above the other (Figure 2). They are complementary to the internal threads of the countersunk recess. In order to screw in the screw or the screw connection, this part of the screwdriver is screwed into the countersunk recess corresponding to the direction of the external thread of the screw or of the screw connection. If the end of the countersunk recess is reached, the screw or the screw connection can be screwed into the workpiece. If the screwing procedure has been completed, the screwdriver can be unscrewed in the opposite direction. Unscrewing the screw or the screw connection takes place in a similar manner, but in opposite directions of rotation in each case. <IMAGE>