Various embodiments provide a fastener including a head, a shank connected to the head and having a tip, one or more helical thread formations extending outwardly from the shank, and wherein a bottom portion of the head includes a plurality of ribs that extend towards the tip of the shank and that are shaped to abruptly frictionally engage a surface of a first object being attached to a second object to create an immediate frictional torsional resistance of a desired force level to the tightening of the fastener. This frictional resistance is provided back to the tightening tool to inform the operator of the tightening tool that the head of the fastener has sufficiently engaged the first object and that further tightening or clockwise rotation of the fastener is unnecessary.

A method for temporarily releasing a screw anchorage includes unscrewing and removing a primary screw having a thread that is tappingly engaged in a mating thread in an ungrouted hole in a mineral substrate from the ungrouted hole. Subsequently to the unscrewing and removing, a retrofitting screw is screwed into the hole to form an annular gap between the retrofitting screw and the mineral substrate. A hardenable grout is placed in the annular gap and the hardenable grout is hardened in the annular gap.

The invention relates to a system for securing an anchor in a borehole in a mineral substrate, in particular concrete, mortar, or brickwork, comprising an anchor with a core section and a threaded section and comprising a furrowing tool for furrowing an internal thread in the borehole, said furrowing tool comprising the following: a main part with a leading end and a trailing end, wherein a force is applied via which a torque can be transmitted to the main part in order to rotate the furrowing tool (10) into the borehole and furrow the thread, and the main part has an outer surface equipped with a furrowing thread which is suitable for furrowing the internal thread into the wall of the borehole. The furrowing tool has a drive element on the leading end of the furrowing tool, said drive element being suitable for interacting with an application of force to the anchor or a part thereof which is to be screwed into the borehole machined by the furrowing tool.

Disclosed herein is a system for fastening an anchor in a borehole in a mineral substrate, in particular concrete, mortar or masonry, comprising an anchor having a core section and a thread section, and a grooving tool for grooving an internal thread in the borehole, the grooving tool comprising the following: a base body having a leading and a trailing end, a force application device being provided, via which a torque for screwing the grooving tool into the borehole and for grooving the thread is transmitted to the base body, the base body having an outer surface on which a grooving thread is formed, which is suitable for grooving the internal thread into the wall of the borehole, the following applying to the ratio of the length h.sub.eff of the thread section of the anchor and the nominal diameter d.sub.b of the borehole: h.sub.eff/d.sub.b≥10.0, preferably ≥12.0, particularly preferably ≥15.0, and in particular ≥30.0.

The invention relates to a system for securing an anchor in a borehole in a mineral substrate, in particular concrete, mortar, or brickwork, comprising an anchor with a core section and a threaded section and comprising a furrowing tool for furrowing an internal thread in the borehole, wherein the furrowing tool comprises the following: a main part with a leading end and a trailing end, said main part having an outer surface on which a furrowing thread is formed that is suitable for furrowing the internal thread into the wall of the borehole. The outer surface of the main part is equipped with a plurality of elevations, each of which has a cutting edge, and all of the cutting edges lie at least partly on an imaginary cylinder with a diameter (do). The cutting edges are suitable for at least partially removing the inner wall of the borehole when the furrowing tool is rotated into the borehole in order to adapt the internal wall of the borehole to the imaginary cylinder.

A self-tapping screw made of synthetic material has a threaded shank defining a screw center line. The screw has proximal and distal insertion ends, the shank including first and second portions, the second proximal to the first. The pitch is the same in the first and second portions, and has a complete thread cross-section in the second portion. In the first portion, in the direction of the thread, the thread is divided into segments having an incomplete thread cross-section, the thread segments having leading end and trailing ends. The leading end of one thread segment extends further radially than the leading end of the thread segment preceding it and forms a cutting edge. In most of the thread segments the thread top in question, for substantially its full length, starting with the leading end, considered in thread direction, is situated at a constant radial distance from the center line.

A concrete screw is adapted to be driven into a hole predrilled in a concrete structure and includes a head, a shank extending from the head, a thread formed on the shank, and a plurality of bump units. The shank includes front and rear segments spaced along a longitudinal axis. The bump units are distributed on at least the front segment of the shank and staggered along the longitudinal axis. Each bump unit includes a plurality of bumps constitute an inclined pattern relative to the longitudinal axis. Each bump protrudes from the periphery of the shank. In the course of the screw being driven into the hole, the bumps pulverize concrete debris in the hole, and waste debris accumulates at a segment of the shank on which the bump units are distributed for development of a pressing segment and promotion of anti-pullout strength of the screw.

A self-driving masonry anchor that includes ahead configured to receive a driving bit, a threaded section extending from the bottom of the head, a drilling section following the threaded section, and a drill tip at the end of the drilling section. The threaded section includes alternating high and low threads. The high threads include notches or serrations. The low threads are double low threads such that there are two low threads between each high thread. The drilling section includes at least two flutes for the removal of debris. The drill tip includes an abrasive material which is different than the material of the drilling section such that the drill tip and drill section predrill a hole in a masonry material for the threaded section, the threaded section fastening to the masonry material.

A fastener includes a shank having a first end and a second end defining a length. The fastener includes a thread provided on the shank, the thread including a first region adjacent to the first end and a second region between the first region and a head at the second end, the thread includes a leading edge and a trailing edge, each edge forming an angle with a surface of the shank, the leading edge forming a non-normal angle with the surface of the shank and the trailing edge forming an angle about normal to the surface of the shank. The fastener may include an arcuate detent region in the shank between respective turns of the thread, the detent region having a length, the length decreasing from the first end toward the second end between the respective turns. The fastener may include a plurality of flutes positioned along a length of the shank.

A fastener includes a shank having a first end and a second end defining a length. The fastener includes a thread provided on the shank, the thread including a first region adjacent to the first end and a second region between the first region and a head at the second end, and a pilot thread. The pilot thread may have first second and third revolutions with different heights and widths which are designed to remove various portions of material from a pre-drilled hole into which the fastener is to be inserted.