An expandable reaming tool including at least two reamer pads connected to a tool body. The reamer pads are adapted to be displaced between a retracted position and an expanded position. At least one spiral blade is formed on at least one reamer pad. A plurality of cutting elements are disposed on the at least one spiral blade. An expandable reaming tool including at least two reamer pads connected to a tool body. The reamer pads are adapted to be displaced between a retracted position and an expanded position. At least one blade is formed on the at least two reamer pads. A plurality of cutting elements are disposed on the at least one blade and at least one gage protection element is disposed on a gage surface of the at least one blade. The plurality of cutting elements are arranged so as to enable the expandable reaming tool to backream a formation in a wellbore.

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 adjacent to the guide member (10) with the eccentric portion (22) protruding to drill a hole larger than the casing tube (11). In an intermediate position 90° away from the drilling position, the follower (28) enters the cam groove (31) whereby the guide member (10) becomes axially movable the distance between the end grooves (30,32). In a rear axial position the guide member (10) by a continued 90° turn brings the follower (28) into the rear end groove (30) to axially define the retracted position of the drill bit (20), wherein it can be raised or lowered freely through the casing tube (11).

A drill (10) which is expansible and retractable for undercutting holes particularly in building materials comprises a drill body (11), at least one radially extending arm (16) attached at one end to the drill body, cutting means (18) formed at an end of said arm remote from the end attached to the drill body, and guide means (26, 27) for moving said arm radially outward, said guide means being movable axially relative to said drill body. That the arm is attached to the drill body by hinge means (19) such that the arm is pivotable radially outwards. The guide means comprise a shank portion (26) and a frustoconical wedge (27). Means (20) are provided for holding the arm in contact with the guide means and means for moving the guide means axially relative to the drill, wherein the arm is caused to pivot radially outwards forming an increasing cutting diameter as said arm moves along the divergent surface of the frustoconical wedge of the guide means.

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 adjacent to the guide member (10) with the eccentric portion (22) protruding to drill a hole larger than the casing tube (11). In an intermediate position 90° away from the drilling position, the follower (28) enters the cam groove (31) whereby the guide member (10) becomes axially movable the distance between the end grooves (30,32). In a rear axial position the guide member (10) by a continued 90° turn brings the follower (28) into the rear end groove (30) to axially define the retracted position of the drill bit (20), wherein it can be raised or lowered freely through the casing tube (11).

Es wird ein Fräswerkzeug, insbesondere für Handbohrmaschinen und Bohrhämmer, zum Ausfräsen zylindrischer Bohrlöcher unter Bildung konischer Erweiterungen bzw. Hinterschneidungen vor­geschlagen, bei dem der Fräskopf in axialer Richtung ver­schiebbar mit dem zur Aufnahme in ein Bohrfutter geeigneten Schaft des Werkzeugs verbunden ist und bei dem ein beweglich angeordnetes Schneidwerkzeug, das in der Normalstellung des Werkzeugs vollständig in einer Längsnut versenkt ist, in radialer Richtung, quer zur Längsachse des Fräswerkzeugs aus dessen Mantelfläche hervortritt, sobald die axial verschieb­baren Teile, nämlich der Schaft und der Fräskopf, aufeinan­der zubewegt werden. Hierdurch wird erreicht, daß die Bil­dung konischer Erweiterungen bzw. Hinterschneidungen von zu­vor in üblicher Weise gebildeten zylindrischen Bohrungen hinsichtlich ihres Ortes und ihrer geometrischen Form völlig unabhängig von Einflüssen des Benutzers des Werkzeugs er­folgt. Hierdurch wird ferner gewährleistet, daß konustragen­de Schwerlastanker paßgenau in die so hergestellten konisch erweiterten bzw. hinterschnittenen Bohrungen eingesetzt wer­den können. Das vorgeschlagene Verfahren ist durch die Ver­wendung des erfindungsgemäßen Fräswerkzeugs gekennzeichnet.

A borehole underreamer device comprises a downhole motor having a rotor part which carries by means of a pivot (2) an elongate clapper body (1) in which a series of abrasive teeth (8) are embedded. In use the device is pulled in upward direction through the borehole while the clapper body describes an orbital motion inside the borehole thereby forcing the teeth to penetrate into the surrounding side wall of the borehole so as to underream the hole.