Abstract: A percussion bores for forming borer in a stone material and including a chisel stem (2) having a prismatic cross-section and provided with a chiseling head (3) and at least one radial opening (4), a twist drill (6) extending through the cylindrical through-bore (3) of the chisel stem and projecting beyond the chiseling head (7), a drilling head (10) with cutting elements (9) provided at the projecting end of the twist drill and a shank (12) provided at another end of the twist drill, and a stop (13) provided between the shank (12) and the chisel stem (2), with a drill stem being offset radially inwardly with respect to an outer diameter of the shank in the region of the stop.

Abstract: A rock drill having a hydraulic pressure reservoir formed by the drill housing, and an anvil rotation mechanism enclosed in the housing. A piston of substantial length and a mechanical hydro-operated valve means, provide favorable pulse duration and low impact velocity. The piston has only two sliding seal diameters which permits simplified valve and cylinder configuration. The friction surfaces of the fronthead drill assembly are lubricated and cooled by integration with the circulating hydraulic system. A floating seal cartridge between the piston and anvil, tends to rotate the piston with the anvil to minimize rotative scrubbing at impact.

Abstract: An impact drilling power tool has a housing, a spindle element mounted in the housing for rotation about an axis and for displacement in axial direction, and an impact element mounted in the housing for displacement axially toward and away from the spindle element. The impact element has an axially arranged extension coaxially received within a blind bore of the spindle element. The impact element has a plurality of cam surfaces provided on helical radial projections of the impact element, and rolling bodies of a cam follower element contact the respective cam surfaces and displace the impact element against the force of coaxial helical springs until encountering interruptions of the projections, upon which the springs rapidly displace the impact element toward the spindle element and an end face of the axial extension impacts the bottom of the blind bore. An output shaft of a driving motor drives a countershaft and via the same and meshing gears also the impact element and the spindle element.