A screw includes a head and a shank extending from the head, and a hole-enlarging portion formed on the shank. The hole-enlarging portion features no thread and a substantially triangular transverse section. The hole-enlarging portion includes three inclined edges spaced from one another in the circumferential direction of the shank, and a guiding slope is formed between two adjacent inclined edges. The shank defines a longitudinal axis and is provided with a thread. Each inclined edge extends toward the head in an inclined direction relative to a horizontal axis perpendicular to the longitudinal axis. The inclined direction of each inclined edge is identical to a direction in which the thread extends toward the head.

A machine for rotary driving screw anchors into underlying ground and related. The machine has a mast with a rotary driver and a mandrel driver oriented on a common axis. The mandrel driver passes a mandrel through the rotary driver and the screw anchor to allow the mandrel to be actuated ahead of the screw anchor while the rotary driver drives the screw anchor into the ground. Alternatively, the mandrel driver may also drive a hammering drill through the screw anchor to clear a path ahead of it through subsurface rocks.

A screw includes: a head end, a shank and a tapered end, the head end including a tool engaging part, the head end located at one end of the shank and the tapered end located at an opposite end of the shank, wherein a thread is formed along the shank, the thread begins on the tapered end, extends onto the shank and terminates at a set location short of the head end, the thread being a right-hand thread and having a peripheral edge, at least a first helical portion of the peripheral edge includes a plurality of notches and a second helical portion of the thread lacks any notches, wherein the first helical portion is closer to the tapered end than the second helical portion, wherein the head includes an underside formed by a frustoconical part with a plurality of nibs. The head may also include an outer ledge.

A screw includes a shank with an outer periphery, a head connected to the shank, and thread convolutions spiraling around the shank in a right-hand direction. The outer periphery defines opposite first and second peripheral envelope surfaces. A cutting slot unit is formed on the shank and arranged on the first peripheral envelope surface. The cutting slot unit includes a first cutting slot with two first edges and a second cutting slot with two second edges. The first edge extends in an extension direction opposite to the right-hand direction. One first edge of the first cutting slot is parallel to one second edge of the second cutting slot . The opposite extension of the cutting slot unit assists the screw in screwing quickly, attains quick removal of chips, and increases the fastening effect by pressing chips downwards.

A thrust screw includes a head, a first shank, a second shank, and a drilling member. The first shank and the second shank are arranged between the head and the drilling member. The second shank is provided with an external thread. The first shank is provided with a thrust member corresponding to the external thread. The thrust member includes two wing-shaped stop pieces and two flat portions. The two flat portions are formed on the two wing-shaped stop pieces respectively and correspond to the external thread. The two flat portions have an outer diameter greater than that of the external thread. The two flat portions of the thrust member stop a further screwing motion of the external thread.

A machine for rotary driving screw anchors into underlying ground and related. The machine has a mast with a rotary driver and a mandrel driver oriented on a common axis. The mandrel driver passes a mandrel through the rotary driver and the screw anchor to allow the mandrel to be actuated ahead of the screw anchor while the rotary driver drives the screw anchor into the ground. Alternatively, the mandrel driver may also drive a hammering drill through the screw anchor to clear a path ahead of it through subsurface rocks.

The present invention relates to a screw element (1) comprising a threaded shaft (2), a screw tip (4) formed on one shaft end and a screw head (5), formed on an opposite shaft end and with force application means (7), and comprising a screw thread (12) extending on the threaded shaft (2) and on the screw tip (4), wherein the screw tip (4) has a front tip section (4a) tapering toward the screw element end, when viewed in the screwing-in direction (Z), and a section (4b) formed on the threaded shaft with a polygonal cross section, when viewed in cross section, whose enveloping circle diameter (d.sub.h) is greater than a core diameter (d.sub.k) of the screw tip (4), and the polygonal cross section has a corner point (15) lying on the enveloping circle of the section (4b), and a front edge surface (9), radially oriented with respect to a longitudinal center axis (X-X), ends in said corner point in the sense of an increased diameter. The screw tip (4) has a first tapering tip section (4a) with a circular cross section and a second, cylindrical tip section (4c) with a circular cross section formed between the first tip section (4a) and the polygonal section (4b), wherein the screw thread (12) is continuously formed without interruption across the first and second tip sections (4a, 4c) of the screw tip (4).

A self-drilling, self-tapping bone screw is described in which the bone screw has a drill tip free of threads and having a length at least as great as about the thickness of a proximal cortical bone layer, with the drill tip having opposed lands and a helical flute between each of the lands with each of the lands having a cutting edge configured to cut bone as the drill tip is rotated into the bone with the flutes conveying the bone debris away from the drill tip, where a lead thread begins to self-tap internal threads in the proximal cortical bone layer after the drill tip has drilled through the proximal cortical bone layer so as to avoid stripping the threads formed in the bone layer. A method of installation is also disclosed.

The present invention relates to a screw, in particular a plug screw, having a screw shank (1), a screw head (2) and a tapering screw tip (4), and having a screw thread (6) that extends at least over a portion of the screw shank (1) and over the screw tip (4), the flight (6a) of said screw thread (6) having a triangular cross section as seen in longitudinal section, with two thread flanks (8, 9) that intersect at a flank tip (7). The flank tip (7) is rounded, wherein a radius of the rounding of the rounded flank tip (7) is selected to be from 1% to 10% of the nominal diameter of the screw. The thread flanks (8, 9) are each formed from two flank portions which enclose an obtuse angle with one another.

A screw with a flat drilling end comprises a cylinder (1) with a thread (11) wrapped around and a flat drill portion (2) longitudinally extended from a distal end of the cylinder (1); a maximum thickness (T) of a transversal cross section of the flat drill portion (2) being less than a half of the maximum width (D) of the transversal cross section of the flat drill portion (2); the maximum width (D) of the transversal cross section of the flat drill portion (2) being smaller than an outer diameter of the thread (11) of the cylinder (1); the width and thickness of the transversal cross section of the flat dill portion (2) being reduced to a point tip end of the flat drill portion (2). Two opposite lateral sides form as sharp knife blades.