Abstract: An eccentric drilling tool comprises a guide member (10) rotatably centered by the mouth of a casing tube (11) that follows the tool downhole during drilling. A pilot bit (23) on the guide member (10) is provided with axially oriented hard metal pilot button inserts (57, 57.sup.I -57.sup.III) peripherally thereon directed to define the diameter of the pilot hole to be cut during drilling. A laterally extending eccentric bit (22) behind said pilot bit (23) has axially oriented hard metal reaming button inserts (48-51) at the eccentric top portion thereof directed to ream up the pilot hole to a maximum diameter. The eccentric bit (22) is movably supported relative to said guide member (10) between a drilling position, in which the eccentric bit (22) projects laterally beyond said casing tube (11) so as to drill jointly with said pilot bit (23) a hole larger than said casing tube (11), and a retracted position, in which the drill bit can be retracted or lowered through the casing tube (11).

Abstract: A flushing device for drilling tools comprises a guide member (10) carrying a drill bit (20) and being rotatably centered by the mouth of a casing tube (11) which is adapted to follow the drilling tool downhole during drilling. The drill bit (20) has a bit portion (22) that projects laterally beyond and is spaced axially in front of the casing tube (11) so as to drill a hole larger than the casing tube (11). There are external flushing grooves (70,71) on the guide member (10) adapted to lead the outflow of flushing medium and debris from the hole during drilling into the casing tube (11). At least one of these grooves (70) extends from front to rear of the guide member (10). One or more further grooves (71) are open towards said rear while ending blindly into the periphery of the guide member (10) spaced from its front. By retraction of the guide member (10) its front enters the casing tube (11).

Abstract: A drilling tool is followed by a casing tube (11) down the drilled hole. The mouth of the casing tube (11) centers rotatably a guide member (10) which receives rotation and impact energy via the interior of the casing tube (11). A drill bit (20) consists integrally of an axially protruding pilot portion (23), a sidewise projecting eccentric portion (22) and a rear shaft (21). The shaft (21) extends pivotally and axially movably into an eccentrically disposed bore (24) in the guide member (10). Axially spaced peripheral end grooves (30,32) extend in opposite direction from an axial cam groove (31) on the shaft (21) and are engaged by a follower (28) in the guide member (10) defining positively the axial and angular movability and positions thereof relative to the drill bit (20). In the forward end groove (32) the follower (28) maintains the drill bit (20) axially in drilling position (FIG.

Abstract: Boring apparatus comprising a tubular casing containing a cylindrical body adapted for being driven by a boring rod and a filter body adjacent the cylindrical body. A boring tool is mounted outside the tubular casing at the end of the filter body. The filter body has a cross-section of polygon shape with axially extending edges in contact with the inner surface of the tubular casing to define clearance spaces between the inner surface of the tubular casing and the outer surface of the filter body. The cylindrical body has axial grooves extending to the clearance spaces for passage of boring particles. The cylindrical body can also be provided with annular grooves. Preferably, the cylindrical body and filter body are constituted as a single unit.