A joining method is a method of joining a plate set composed by a plurality of stacked plate members including a first plate member and a second plate member by using a tapping screw. When the tapping screw is advanced into the plate set while the tapping screw is rotated in a state of applying a pressure onto the plate set so as to form through-holes in the first plate member and the second plate member, a first pressure applied onto the tapping screw is reduced down to a second pressure at the time when the tapping screw penetrates the first plate member.

A method produces a composite component from a first joining element and a second joining element by use of an adhesive and a flow drill screw. Before attaching the second joining element to the first joining element, a recess is made around the at least one screw position in which the respective flow drill screw penetrates the second joining element, in a joining surface of the second joining element.

A wood screw that includes a head and a shank is revealed. The shank is formed by a main shank portion and a tapered portion whose diameter is smaller than that of the main shank portion, both provided with a locking thread. A plurality of drilling units, whose outside diameter of the drilling unit is smaller than that of the locking thread, is disposed on the tapered portion. The drilling units first destroy workpiece material corresponding to the main shank portion so that the workpiece material becomes loose and the resistance of the locking thread of the main shank portion is reduced. Thereby the wood screw is screwed into the workpiece more smoothly. Moreover, an internal thread segment whose thread depth matches that of the locking thread of the main shank portion is formed so that the wood screw and the workpiece are fastened more firmly.

A screw anchor for a trussed foundation system to support single-axis trackers and other structures and related methods of driving such a screw anchor into underlying ground. A hollowed tube of uniform diameter is open at both ends with a thread form beginning at one end and circumscribing a portion the tube, the thread form having a tapered lead-in. The open-ended geometry allows a mandrel or rock drill to be inserted and operated through the anchor during driving to expedite the driving process. The tapered thread form provides a lead-in for driving the anchor into a rock bore.

Electrically assisted flow drill screwdriving processes (EAFDS) and devices are described. The methods can augment traditional FDS and allow for softening of metals of a stack-up, which can enable FDS joining of thicker and stronger materials such as boron steel. EAFDS methods can reduce cycle time and can be used to join thicker cross-sections with reduced installation torque. Also disclosed are fixtures for attachment to existing devices that can provide for the electrical augmentation of existing FDS processes.

A composite screw includes a tapping end portion that includes a circular bottom surface, a peripheral surface and a main thread. The peripheral surface extends from the circular bottom surface. The main thread is formed around the peripheral surface. A reception recess is recessed from the circular bottom surface and the peripheral surface. The main thread has a discontinuation where the reception recess opens at the peripheral surface. A rigid body and a weld material fill the reception recess. The rigid body has an outer surface and an auxiliary thread. The outer surface is exposed from the reception recess. The auxiliary thread is formed on the outer surface and connected to the main thread to fill the discontinuation.

A screw anchor for a trussed foundation system to support single-axis trackers and other structures and related methods of driving such a screw anchor into underlying ground. A hollowed tube of uniform diameter is open at both ends with a thread form beginning at one end and circumscribing a portion the tube, the thread form having a tapered lead-in. The open-ended geometry allows a mandrel or rock drill to be inserted and operated through the anchor during driving to expedite the driving process. The tapered thread form provides a lead-in for driving the anchor into a rock bore.

A method for producing a composite screw includes: providing a screw body a circular bottom surface, a peripheral surface and a main thread; processing the screw body to format least one reception recess indented upwardly from the circular bottom surface and inwardly from the peripheral surface; providing at least one composite unit including a weld material and a rigid body of high stiffness material; disposing the weld material in the at least one reception recess and subsequently inserting and moving the rigid body into the at least one reception recess; and melting the weld material to secure the rigid body to the screw body.

A self-drilling, self-countersinking fastener is provided that includes a shaft, a countersunk head located at a first end of the shaft, and a tapered point located at an opposite end of the shaft. A thread integrally extends from the shaft and extends along at least a portion of a length thereof. The countersunk head includes a frustoconical region having a first, smaller diameter in a shaft connection region and a second, larger diameter at a second end defining an edge area of the head. A plurality of radially extending ribs are located on the frustoconical region and extend from an area of the first, smaller diameter to a respective radially outer rib end spaced radially inwardly by a distance X from the edge area of the head. A respective cutting edge is located on each of the ribs.

In a joining method for joining a first plate material and a second plate material by screwing a self-tapping screw from one direction in a state where the first plate material and the second plate material are put on top of each other, a recessed portion is formed in at least one of the first plate material and the second plate material, and in a state where the first plate material and the second plate material are put on top of each other such that the recessed portion is opened in a contacting face between the first plate material and the second plate material, the self-tapping screw is screwed from the one direction. When the self-tapping screw penetrates through the first plate material due to the screwing of the self-tapping screw, an excess part generated from the first plate material flows into the recessed portion.