| 摘要 |
A drilling tool including a central, laterally flattened primary drill adapted to produce a cylindrical main drillhole and a secondary drill, pivotally displaceable relative to the primary drill, in a laterally outward direction to produce an undercut, a sleeve which concentrically surrounds the primary drill and is axially slidable on the shaft of the primary drill against the action of a spring and a slotted link system adapted to effect pivoting of the secondary drill relative to the primary drill. The sleeve is constructed as a cage having a rear portion adapted to guide it for axial movement along the shaft, webs extend from the rear portion in the general direction of the shaft axis and leave large passages in the axial and circumferential direction, and an end ring joins the webs at their outer ends. |
