This invention concerns a set of surgical instruments for joining bone fragments (osteosynthesis) by screw fastening, especially in the case of cranial, facial, vertebral or hand fractures, comprising several plates of different shapes and curvatures and with holes and/or several screws and/or a screwdriver 8 and/or a bending instrument and/or a depth gauge and/or a drill and/or a cutting instrument. Special designs of said plates, screws and also said screwdriver 8 are given, whereby the latter comprises a blade 10, coaxially and movably a collet 11 with, at the lower end, radial, spring-supported jaws 15 and on said collet 11 an axially slidable retaining sleeve 12, which in its lowermost position presses said jaws 15 inwards.