| 主权项 |
1. A screw tap comprising a shaft, having two cutting portions spaced apart from each other by a polygonal drive portion, the drive portion having a contour having a cross section complementary to fittable tools and adapted to act on the drive portion for purposes of torque transmission, wherein there is provided a supplementary drive portion for manually applying a torque to said screw tap to produce on one of the two cutting portions a cutting force, a recess of non-circular cross section is disposed in the front end and in the back end of said shaft, and extends with a negative cross section in an axial direction, and is provided to receive a manually driveable positive-locking drive having a positive cross section corresponding to said cross section of said recess. |
