Abstract: A thrust screw assembly includes a thrust screw and two threading dies for working the thrust screw. The thrust screw includes a first shank, a second shank, an external thread, and a thrust member. Each of the threading dies is provided with an external thread forming section and a flat portion forming section. In a first molding process, the first shank is worked to form the thrust member with two wing-shaped stop pieces. In a second molding process, the second shank is processed by the external thread forming section of each of the two threading dies to form the external thread on the second shank, and the two wing-shaped stop pieces is processed by the flat portion forming section of each of the two threading dies to form two flat portions on the two wing-shaped stop pieces simultaneously.

Abstract: 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.

Abstract: A traction stud for endless tracks. The traction stud comprises a base and the base has a center point on a top surface and a center point on a bottom surface. There is an elongated shank rigidly surmounted on the top surface at the center point. The shank has a distal end. The distal end has at least one cutting flute located in it. The shank has a threaded surface. The base has, at the center point of the bottom, a means for torqueing the traction stud.

Abstract: A fastening clip for fastening coverings to body parts of a motor vehicle is provided. The fastening clip comprises a one-piece plastic part with a fastening foot for pressing into an opening provided in the respective body part, a supporting shaft adjoining the fastening foot and intended for receiving the covering by laterally pushing on a holding part provided on the covering, and a holding plate seated on the outer end of the supporting shaft. In order to improve and facilitate mounting, elastic ribs are provided on the periphery of the supporting shaft.

Abstract: A push clip assembly includes a clip tower and a retention clip carried on the clip tower. The retention clip includes a first set of retaining ribs projecting in a first direction and a second set of retaining ribs projecting in a second direction.

Abstract: A vehicle footrest assembly includes a bracket attached to a vehicle body structure and a foam footpad attached to the bracket. At least one fastener attaches a dead pedal to the footpad. The at least one fastener includes a head and a shank extending from the head. The shank includes a threaded portion screwed into the footpad. A collar extends radially outward from the shank and is spaced away from the head to define a clip receiving portion. One of the head and the collar are substantially frustoconical and define a lead-in surface in the clip receiving portion. The dead pedal includes at least one clip spaced apart from a pedal portion of the dead pedal. A portion of the clip is disposed within the clip receiving portion to attach the dead pedal to the footpad.

Abstract: An orthopedic fastener has a head and a shank. The shank has a leading end portion adjacent a distal tip and a trailing end portion adjacent a head. An intermediate transition is positioned between the leading and trailing end portions. At the intermediate transition, the shank increases in diameter. The leading end portion has a first thread which optionally may include one or more self-tapping cutting grooves extending adjacent the distal tip and through a plurality of the first threads. The trailing end portion has second threads extending toward the head from the intermediate transition. The second threads of the trailing end portion are larger in outer diameter than the first threads in the leading end portion. The intermediate transition has one or more cutting grooves traversing the increasing diameter.

Abstract: A self-drilling screw made of an austenitic or other stainless steel, is provided having a drilling tip. The shank is integrally formed of an austenitic or other stainless steel and has a galvanically applied thin coating at least in the tip region, with the coating being harder than a non-coated region. The thin coating has a pearl-like or columnar surface, a coating thickness of at least 2 ?m and a hardness in a range of from 500 to 1500 HV0.3. The self-drilling screw can be produced more simply than a typical self-drilling screw, in which the drilling tip consists of a harder material than the shank and is welded to the shank made of stainless steel. The coating ensures the drilling capacity and thread formation.

Abstract: A fastener is provided having a cylindrical shaft with a generally constant diameter located between a head and a tapered point. The fastener has a thread integrally extending from the shaft and extending along a portion of a length thereof that terminates at an end of the shaft proximate the head with a back-out discontinuity. At least one ring integrally extends from the shaft in an area of the shaft between the back-out discontinuity and the head. The at least one ring has an outside diameter that is less than an outside diameter of the thread.

Abstract: A fastener includes a shank having a first end and a second end. A first portion of a thread is formed with a first, symmetric thread angle and a second portion of the thread is formed with a second, asymmetric thread angle. The thread may be serrated or jagged over one or more portions of the fastener, including the area of the symmetric thread angle. A blunt end comprises the leading end of the fastener.

Abstract: A thermal break fastener includes a head that has a top side and an underside. The head has diameter. A shank depends from the underside of the head and has an end that has a longitudinal bore therein, opposite the head. The shank is formed from a thermally non-transmissive material. The shank has a diameter less than the diameter of the head. A seal is positioned on the shank. A driving/boring element has a driving point and a self-counter-bore cutter spaced from the driving point. The self-counter-bore cutter has a diameter about equal to the diameter of the shank. The driving/boring element is mounted to the shank with the self-counter-bore cutter disposed at about the end of the shank opposite the head. A two-piece configuration includes a driving/boring element including a self-counter-bore cutter and a separate a sealing head with a seal positioned on the sealing head.

Abstract: An ice screw comprises an elongated shaft with an external thread, and a bit with teeth. Each tooth has a cutting edge, and the bit is provided at a longitudinal end of the shaft. A notch is formed in bit at the base of each cutting edge in order to delimit a sharpening reserve of the associated tooth.

Abstract: A screw (10) and a connection produced therewith of a thin metal sheet forming a substructure (40) to a plastics component (30) having a through-bore (32) and having a seal (50) located between the substructure (40) and the component (30). The screw (10) has a shank (13) having a thread-cutting thread (16) and a tip (12) in the form of a boring part, and also a lower thread section (18) having a first thread outside diameter (D18) and an upper thread section (19) having a second, larger thread outside diameter (D19) and having a conically narrowing transition section (22) between the two thread sections (18, 19). The upper thread section (19) has a thread pitch (P2) which is smaller than the thread pitch (P1) of the lower thread section (18).

Abstract: A screw includes a shank and at least one end cutting groove. The shank includes a lower section disposed near an insertion end thereof and an upper section disposed near a head end thereof. The lower section has triangular transverse cross sections, and the upper section has circular transverse cross sections. A first thread is disposed on the lower section of the shank, and a second thread is disposed on the upper section of the shank. A non-threaded section is disposed between the lower section and the upper section of the shank. An outer diameter of the non-threaded section is larger than an outer diameter of the upper section. The end cutting groove is formed in the lower section of the shank, and an included angle between 3 and 9 degrees is formed between an extending direction of the end cutting groove and a longitudinal axis of the shank.

Abstract: A screw capable of drilling and cutting includes two inclined cutting planes with a cutting edge formed on a convergence of the cutting planes. A tapered positioning member extends from the convergence of the cutting planes, where the cutting edge is divided into dual sub cutting edges by means of the positioning member. Each sub cutting edge has an inclined angle. An included angle included by the sub cutting edges is smaller than 180 degrees. Threads spiral on a shank and extend to the sub cutting edges. Setting the positioning member against on an object permits a steady performance during the first stage of screwing. Subsequently, the sub cutting edges provides a scraping effect on the object during drilling. Torque is reduced and drilling speed is promoted.

Abstract: A fastener includes a shank having a point at a first end and a second, head end. A first portion of a thread is formed with a first thread angle and a second portion of the thread is formed with a second thread angle. One or more knurls are provided in the shaft in the threaded or unthreaded regions of the fastener. The thread may be serrated or jagged over one or more portions of the fastener, including the area of the first thread angle.

Abstract: A flat drill end of a screw mainly includes a cylinder with a drill end having a thread wrapped around the cylinder, and a flat drill portion formed to the cylinder along to the drill end of the cylinder with a predetermined length. The thickness of the flat drill portion is less than a half of the width of the flat drill portion for receiving more debris and ejecting the debris during the drilling so as to form a drill screw capable of drilling fast and preventing split on to the working piece.

Abstract: A screw includes a positioning member defined on inclined cutting planes of a drilling portion of the screw for stably allowing a cutting edge constructed at a convergence of the cutting planes to cut efficiently. A threaded section formed on a shank of the screw is extended toward the cutting edge and connected with one end of the cutting edge. The positioning member helps the screw fixedly stand on an object. The cutting edge and the cutting planes allow cutting debris to be swiftly and smoothly extruded therefrom into the threaded section for avoiding the piling of the considerable cutting debris. Thereby, the screwing torque is reduced and the drilling speed is promoted. Preferably, the fastened screw is sunken in the object, and the fastening operation is completed successfully.

Abstract: An extension fastener for portable tool is described. The housing of the tool or the useful part of it encompasses a self-taping screw. The termination of the fastening screw is a perpendicular base plate for a firm support. The tool is fasten to the surrounding vegetation of any diameter or machined extensions in order to increase the tool reach of the light compact tool.

Abstract: A method for integrally forming a drilling tip on a wire nail, in particular in order to produce a screw with the aid of a pair of pinching jaws, provides for the bulge formed by the displaced material during the integral forming of the drilling tip to be sheared off the drilling tip along the entire length of the cutting edges of the drilling tip produced and to be left connected to the drilling tip only along the longitudinal side edges of the latter by a predetermined breaking point.

Abstract: A thread-forming screw comprising, at least in part, a shaft (1.1) provided with a screw thread (2) and further comprising a screw tip (1.2) at one end of the shaft (1.1), wherein the shaft (1.1) comprises a thread-forming screw-threaded portion (4) that extends away from the screw tip (1.2) and an adjoining load-bearing screw-threaded portion (3), wherein the load-bearing screw-threaded portion (3) has a round cross-section, characterized in that the load-bearing screw-threaded portion (3) displays, in the direction away from the screw tip (1.2), an increase d in a flank diameter DF and/or an outside diameter DA of the screw thread at a gradient of from 1:50 to 1:500 based on a length LG of the load-bearing screw-threaded portion (3), preferably at a gradient DA or DF to LG of from 1:100 to 1:400, wherein the increase d in the flank diameter DF and/or the outside diameter DA remains constant over the length LG of the load-bearing portion.

Abstract: A threaded fastener including a shank extending along an axis away from an enlarged head to a tip. A thread extends in a helix around the shank from the tip of the shank towards the enlarged head. A driving recess on a top surface of the enlarged head receives a tool for driving the fastener in a rotational manner around the axis of the shank. Cutter teeth are formed on a lower surface of the enlarged head. The fastener may be assembled with a hard composite non-wood material decking and a supporting metal I-beam.

Abstract: A building structure including a first building member and a second building member may be connected by fasteners, each fastener having a head, a tapered lead portion having an angle from 30 to 60° of at least HRC 50 hardness adapted to start into a pilot hole, a thread-forming portion of at least HRC 50 hardness adapted to thread the fastener into at least the second steel building member, and a threaded portion having a through hardness from about HRB 70 to HRC 40, such that the fastener is capable of providing a ratio of failure torque to thread-forming torque of at least 3.0 and a ratio of failure torque to drive torque greater than 10 when the second steel building member has a thickness of about 0.25 inch and the pilot hole has at least one diameter within nominal diameter from 80 to 98% of major diameter.

Abstract: A self-tapping screw includes a head, a shank provided on the head and threads provided on the shank, wherein the threads include a first contact surface and a second contact surface forming a thread angle of 40 degrees therebetween. A vertical line from a vertex of the thread angle is drawn perpendicular to the shank, and the first contact surface forms a first inclination angle with the vertical line, and the second contact surface forms a second inclination angle with the vertical line, wherein the first inclination angle is different from the second inclination angle. The present invention can be used to replace mechanical screws as it has a smaller assembly torque suitable for fastening onto lighter objects.

Abstract: A building structure including a first building member and a second building member may be connected by a plurality of fasteners, each fastener having a head, a threaded portion having a through hardness of between HRB 70 and HRC 40, a thread-forming portion of at least HRC 50 hardness enabling the fastener to form threads in at least the second steel building member, and a fluted lead portion of at least HRC 50 hardness with a nominal diameter between 70 and 95% of major diameter, such that the fastener is capable of providing a ratio of strip torque to thread-forming torque of at least 3.0 and a ratio of strip torque to drive torque greater than 6.0 when the second steel building member having a thickness of 0.25 inch and the fluted lead portion having at least one diameter within nominal diameter between 80 and 98% of major diameter.

Abstract: A self-drilling screw (10) has a first cutting edge (21) provided exclusively in a radially inner region of the drilling tip (12), extending at a first acute angle (?1) to the longitudinal axis (L), and a second cutting edge (22) provided in radially outer region of the drilling tip (12) and extending at a second acute angle (?2) to the longitudinal axis (L), with a first enveloping conical circumferential surface (A1) which is defined by the first cutting edge (21) corresponding, with a maximum deviation of +/?10%, to a second enveloping conical circumferential surface (A2) defined by the second cutting edge (22), and with the first acute angle (?1) corresponding, with a maximum deviation of +/?5°, to the second acute angle (?2).

Abstract: A thread forming fastener for use in concrete, masonry, brick, and the like, having a first thread, second thread, and third thread about a shank, the second thread having a major diameter greater than the major diameter of at least one of the first and third threads with grooves on either side of the second thread adapted to accommodate chips of material during fastening, and the second thread having notches in the major diameter of at least one turn adapted to engage at least one of concrete, masonry, and brick, a helical land axially extending between the third thread and adjacent first thread having an outside diameter greater than the minor diameter and less than the major diameter of the first thread and third thread, the axial land width between the third thread and adjacent first thread being at least 25% of the thread pitch.

Abstract: A hybrid fastener is provided in combination with a structural insert. The insert is disposed about a shank of the fastener at an unthreaded section. In another aspect, a sleeve surrounds the shank of the fastener and has apertures for receiving the insert therethrough. Methods of using the above-described hybrid fastener for securing workpieces are also disclosed.

Abstract: A threaded fastener includes a top head portion, a shank, a thread and first and second flutes. The shank includes a threaded portion that extends axially along a central axis and a connecting portion that extends upwardly and axially along the central axis from the threaded portion to the top head portion. The thread extends upwardly and helically around an outer periphery of the threaded portion and along the central axis. The first flute is indentedly formed on the threaded portion and extends upwardly along the central axis. The second flute is indentedly formed on the threaded portion and above the first flute, and extends upwardly and axially along the central axis and opposite to the first flute.

Abstract: A fastener includes a shank having a point at a first end and a second, head end. A first helical thread region is formed at the first end adjacent to the point and has having a first helical thread having a first effective diameter. A sub-region of a second helical thread formed within the first helical thread region adjacent to the first end. A head at the second end includes a cutting structure, the cutting structure positioned to intersect a bottom surface of the disk and the shank, the cutting structure has a square cross-section formed by four walls intersecting the disk. A third helical thread region may be provided between the first region and the head. The shank diameter in the sub-region and the first region is smaller than the other regions.

Abstract: A thermal break fastener includes a head that has a top side and an underside. The head has diameter. A shank depends from the underside of the head and has an end that has a longitudinal bore therein, opposite the head. The shank is formed from a thermally non-transmissive material. The shank has a diameter less than the diameter of the head. A seal is positioned on the shank. A driving/boring element has a driving point and a self-counter-bore cutter spaced from the driving point. The self-counter-bore cutter has a diameter about equal to the diameter of the shank. The driving/boring element is mounted to the shank with the self-counter-bore cutter disposed at about the end of the shank opposite the head. A two-piece configuration includes a driving/boring element including a self-counter-bore cutter and a separate a sealing head with a seal positioned on the sealing head.

Abstract: A screw capable of drilling and cutting includes two inclined cutting planes with a cutting edge formed on a convergence of the cutting planes. A tapered positioning member extends from the convergence of the cutting planes, where the cutting edge is divided into dual sub cutting edges by means of the positioning member. Each sub cutting edge has an inclined angle. An included angle included by the sub cutting edges is smaller than 180 degrees. Threads spiral on a shank and extend to the sub cutting edges. Setting the positioning member against on an object permits a steady performance during the first stage of screwing. Subsequently, the sub cutting edges provides a scraping effect on the object during drilling. Torque is reduced and drilling speed is promoted.

Abstract: An extraction tool lifting apparatus having a load bearing coupling capable of being removably connected to an extraction tool; an hydraulic cylinder assembly being operatively connected at a first end to the load bearing coupling; a mounting bracket being operatively connected to the second end of the hydraulic cylinder assembly; three legs, each operatively connected at a first end to the mounting bracket; the load bearing coupling being adapted to be removably connected to an extraction tool having, an elongated base member having first and second ends, and a drill bit being removably attachable to a socket in the first end, the base member having a threaded portion being disposed approximate the first end, the second end being adapted to be removably connected to the load bearing coupling.

Abstract: A screw with double notches includes a head portion, a shank portion extended outward from the head portion, a threaded section spirally surrounded on the shank portion. Wherein, a raw section on the shank portion is provided with a cambered surface formed integral with the shank portion in cross-section, and a notched section relative to the raw section has two cutting notches separately depressed into the shank portion and disposed near an end of the shank portion, thereby forming a protrudent part between the two cutting notches. By means of the cooperation of the cutting notches and the raw section, the cutting capability and the removal of debris are increased so that a fastened object is prevented from split. Thereby, the drilling speed is promoted, and the effort to rotate the screw is lessened. While the supporting strength of the screw is improved, the screw does not break easily while screwing.

Abstract: A method of fastening a plurality of parts together with a flow drill screw. An indentation is formed on one side of a first part and a second part is assembled into engagement with the side of the first part with the indentation facing the second part. The flow drill screw is inserted through the indentation and material is displaced from the part into a void defined by the indentation. Two or more panels or parts may be joined by aligning a flow drill screw with voids formed by indentations that are formed by embossing one or more panels.

Abstract: A device for fastening equipment parts such as photovoltaic panels on a sandwich or single-shell building envelope using a plurality of fastening elements (20, 20?) in the form of bolts, which can be supported at least by a connection part (30, 30?) and on a load-bearing part (12) of the building or the building envelope. If an outer shell (14) is present, the fastening elements (20, 20?) can be guided through the outer shell (14) and supported on the load-bearing part (12) and/or the outer shell (14). Each fastening element (20, 20?) can be positively engaged with the connection part (30, 30?) and/or, if present, with the outer shell (14) so as in each case to support the connection part (30, 30?) on the load-bearing part (12) and, if present, on the outer shell (14).

Abstract: An ice screw comprises an elongated shaft with an external thread, and a bit with teeth. Each tooth has a cutting edge, and the bit is provided at a longitudinal end of the shaft. A notch is formed in bit at the base of each cutting edge in order to delimit a sharpening reserve of the associated tooth.

Abstract: A fastener mountable to a rigid substrate such as a fiber cement panel and also mountable to the panel and an underlying support, such as a metal or wooden stud. The fastener may include a drilling portion having a reaming portion for reaming out the material within the panel, a fastening portion for engaging the panel and, if encountered, the underlying support, and a tapered portion between the drilling and fastening portions. The drilling portion may have a length generally equal to, or slightly longer than, a length of the panel so that reaming out of the panel may be completed before engagement of the fastener threads with the interior of the panel begins.

Abstract: A screw, in particular a self-tapping screw, has a screw thread which covers up to the front end of the screw formed as a drilling tip or cutting tip. In the front area, starting with a distance from the front end of the screw, there is an opposite thread showing the same pitch as the screw thread, however, its thread height is lower than the thread height of the screw thread. This second, opposite single-thread, double-thread or triple-thread/multi-thread forms a cutting edge with its thread edge which is used to cut fibers in order to reduce wedge effect during screwing in the screw. The screw is particularly suitable for wood or wood-like materials in the edge areas of structural elements.

Abstract: A screw having a polygonal cross section exhibits a threaded section and a forming section adjoining the threaded section and extending as far as a front rounded end of the screw and, if necessary, being free of threads. The lateral line of the forming section, if necessary free of threads, runs smoothly and without interruption from the threaded section as far as the tip at a constant curvature. The screw serves for the attachment of an element to a sheet metal component, whereby said screw engages in an existing hole in the sheet metal component and forms the thread itself. Said screw is thereby also capable of enlarging the hole and forming a raised rim hole.

Abstract: An extraction tool having an elongated base member having first and second ends, and a drill bit being removably attachable to a socket in the first end; the base member having a first threaded portion being disposed approximate the first end; the second end being adapted to be removably connected to a load bearing coupling.

Abstract: A fastener includes an elongated body having a first end and a second end, a helical thread having a crest, a root, and flank portions formed on at least a portion of the elongated body, and at least one protrusion extending from the crest and flank portion. The at least one protrusion is an axially extending V-shape of the crest, flank portions, and root of the helical thread with a peak of the at least one protrusion having a ridge that extends radially outward from the root of the thread.

Abstract: The invention relates to a floor anchor (10) made of steel pipe. The floor anchor comprises a hollow shaft segment (14) having an external thread (16) at least in segments, and a head segment adjacent to the shaft segment (14) and facing downward in the anchored state in the floor. The head segment (12) is designed as a drill head and comprises elements for removing earth.

Abstract: A hole-forming and thread-forming screw for screwing into a sheet piece, including a slotted screw head for accommodating a tool, a threaded shank and a tapering hole-forming part having outer sides with a continuous convex-shaped curve along an entire length thereof, ribs running like threads along the hole-forming part being provided. The hole-forming part ends in a rounded, blunt end piece, and the rounded ribs, which chiplessly displace the material of the sheet part, are situated symmetrically opposite one another and have a pitch that is a multiple of the thread pitch.

Abstract: A screw has a screw head and a shank. The screw head has a square cavity, a hexagonal cavity or a hexagonal boss to be wedged by a screw driver for wrenching. The shank has a first asymmetrical thread at the taper to facilitate drilling holes, asymmetrical saw-type threads behind the first asymmetrical thread, and a second asymmetrical thread behind the asymmetrical saw-type threads. The shank further has a carved V-shaped tail between the first asymmetrical thread and the asymmetrical saw-type threads to facilitate cutting and debris dispelling. The screw thus formed can rapidly perform thread tapping and debris dispelling, and reduce friction and expand drilling holes and achieve fast fastening.

Abstract: A versatile fastener including at least two flat areas formed on a cutting part, and an accommodating area disposed between any two of the flat areas. At least two cutting faces are convergent to form the accommodating area, and first and second cutting edges are respectively formed at a connection between each cutting face and flat area. In operation, the flat areas facilitate the first and the second cutting edges to promote a stable balance with the object, thereby allowing the debris to be swiftly guided out of the accommodating areas. Consequently, it is difficult to crack the object while imparting forces thereon, so as to lower the screwing resistance and the fastening torque as well as increase the combining efficiency.

Abstract: A fabricating method for the self-drilling screw has acts of forming a main section and a secondary section by punching, forming a flat drilling blade with a tapered end at a bottom end of the small diameter portion by punching, and forming a thread portion on an outer surface of the main section and a chip removal thread portion with a spiral chip removal groove on an outer surface of the secondary section by rolling. The self-drilling screw utilizes the flat drilling blade with the tapered end and the chip removal section having chip removal function to reduce the size of the drilling blade. Therefore, the self-drilling screw reduces the size of the punching die, lowers the punching force, lowers both the load of the punching die and the load of the punching machine, and lowers both the die cost and the manufacturing cost.

Abstract: A tubule assembly for thermally isolating a surface-mounted wall anchor and an anchoring system employing the same are disclosed. The thermally-isolated tubule assembly is adaptable to varied anchor structures and for use with interlocking veneer ties and reinforcement wires to provide a high-strength surface mounted anchoring system for cavity walls. The stepped cylinders sheath the mounting hardware to limit insulation tearing and resultant loss of insulation integrity. The tubule assembly is thermally-isolated through the use of a series of strategically placed compressible nonconductive fittings and set within the perimeter of the anchor base. Seals are formed which preclude penetration of air, moisture, and water vapor into the wall structure.

Abstract: A fastener configured to couple a first substrate to a second substrate may include a head, a shank, and a tip. The shank may have a generally constant diameter between the head and tip, and the shank may include an unthreaded portion proximate the head, a threaded portion proximate the tip, and a reverse threaded portion therebetween. The threaded portion may include a plurality of right handed threads that continue onto the tip, and the reverse threaded portion includes a plurality of left handed threads. The unthreaded portion may have an axial length greater than an axial length of the reverse threaded portion. In addition, the fastener may include one or both of a cut extending radially inward toward the fastener axis proximate the tip and serrations on at least one of the plurality of right handed threads.

Abstract: A fastener for locking two or more sheet sections together comprises a shaft tapered at one end and having a driving head at the other end with a relatively coarse thread running from the tapered end towards the head and a relatively fine thread between the coarse thread and the head. The fine thread has a pitch which is approximately equal to the thickness of the sheet sections and extends from the head for from two to six threads.