Abstract: With respect to a device on diamond hollow drills, the actual component (4, 8) of the drill (1) that forms the coupling to the clamping device of a drilling machine or an additional component that has a clamping device for the drill and a holder for coupling to the clamping device is developed as an adapter that can be adjusted and fixed in position with respect to its length.

Abstract: In the case of a diamond hollow drill (1) whose hollow drill head (3) comprises a diamond coating the drill head (3) is arranged in the region of the diamond coating in a cutting crown (4) with outer, e.g. groove-like recesses and segments (5) at least between said recesses, with the segments outwardly projecting beyond the adjacent drill head part in its diameter. A counterboring ring (6) which can optionally be attachable to the drill head (3) comprises an insertion opening with recesses for the segments (5) of the cutting crown (1), which opening is substantially adjusted with respect to its shape to the outer contour of the cutting crown (4). The formation of burrs at the transition point between bore and counterbore is prevented through the cooperation of the segments (5) which determine the outside diameter of the bore and the counterboring regions projecting into a smaller dimensional region.