Screw tapping spindle or bush - has spindle carried tap chuck permitting decoupling after tapping and recoupling on opposite rotation

摘要

The screw thread tapping unit comprises a downwards open bush (1) with an upward shank (3) for fixing in a drill head and containing a relatively rotatable and axially movable spindle (5), which carries a chuck (7) for a tap and can be coupled to the bush. The bush wall has two axially spaced axial slots (23,37) containing coupling elements (25,39) engageable by a radially projecting pin (13) on the spindle. As the spindle moves down during tapping, it is driven via the upper coupling element (25) until the pin disengages to permit relative rotation of the spindle in the bush. When the bush is withdrawn and driven in opposite direction, the pin is engaged by the lower coupling element (39) and the spindle unscrews the tap from the work.