A drill comprising a drill shank having a taper portion adjacent to a threaded portion provided on the rear or basal portion of the shank. When the drill is screwed into an axial hole in a drill holder of a drilling machine, the opening edge or inner tapered wall of the axial hole of the drill holder bites into the taper portion of the drill shank, consequently to bring the drill into firm connection with the drill holder of the drilling machine.

A drill produced from a substantially rod-like blank containing high speed steel has at one end thereof a pointed tip which is intended to penetrate the material to be drilled. The drill is preferably a helical drill having edge parts which extend essentially from the outer part of the drill tip to the periphery of the drill cross-section, and further includes a radially open groove which extends helically along the drill, for the purpose of removing chippings from the drill. The drill is partic...

A drill, which is excellent in sharpness and strength, capable of preventing burrs at an exit of a machined bore and of suppressing an excessive enlargement of the machined bore size, and is low in manufacturing costs, and easy te re-grind. A rake face (30) is provided to improve sharpness of a single chisel edge (3) formed between the tip of the drill and a first main cutting edge (1), and a non-chisel-edge-forming portion (B.sub.1 OB.sub.2) is provided between the drill tip end and a second ma...

A drill in which a drilling apparatus is releasably mounted on the bottom of a drill string and on release can be withdrawn upwardly through the drill string by wire-line. The main cutting bit is disposed on the bottom end of the removable apparatus and the apparatus includes expandable cutters disposed above the main cutting bit to ream the hole cut by the main bit to permit the drill string to follow down the hole. The cutters are retracted for withdrawal of the apparatus.

A drill for drilling holes in masonry and comprising a depth stop mounted on the drill shank and formed as a resilient anti-vibration element.

A drill has a solid material shank (10), which is provided in its front region with a cold-forged drill point (11) with two cutting edges (12) approximately parallel to one another in projection and two flutes (13) running approximately in the longitudinal direction of the shank (10).

A drill having a shank formed with helical or straight flutes for discharging chips therethrough and a pair of cutting edges formed at one end of the shank and extending continuously from the center of rotation of the drill to the periphery thereof. Each of the flutes is defined by a wall which is positioned rearward with respect to the direction of rotation of the drill and against which a flat plate portion of the chip formed by the portion of the cutting edge on the peripheral side is to be p...

A drill comprising a drill body (11) and a drill tip (22). The drill tip is detachably secured in a slot in the drill body. The drill tip (22) consists of a tip body and cutting portions. The drill body (11) and the tip body comprise cooperating surfaces in order to receive the radial and axial forces acting on the cutting portions.

A drill comprises a holder (1) and a cutting member in the form of a pair of discs (2,3). Each disc (2,3) has at least five facets (11,12) arranged along its periphery and symmetrically with respect to its center line (13, 14), the discs (2, 3) being mounted in such a manner that angles (.phi.) of inclination of their facets (11, 12) with respect to an axis (4) of the holder (1) are equal to one another.

An earth drilling apparatus including centralizer means for stabilizing a drive rod during drilling operations.