Abstract: A self drilling anchor for use in a friable material mounted on a member comprises an elongated body having an axis, an axial bore adapted to receive an elongated fastener, a flared end having torque transmitting surfaces therein, a proximal portion, an intermediate portion, a distal portion, and a drilling tip generally opposite the flared end, wherein the proximal portion has a threaded exterior having a root, a crest diameter, and a thread height, the intermediate portion has a threaded exterior having a root, a crest diameter substantially smaller than the crest diameter of the proximal portion, and a thread height substantially smaller than the thread height of the proximal portion, and the distal portion has a threaded exterior with a root that tapers toward the drilling tip, a crest diameter substantially smaller than the crest diameter of the proximal portion, and a thread height substantially smaller than the thread height of the proximal portion.

Abstract: There are disclosed various embodiments of surgical tacks for use in surgical procedures. The tacks generally include a head and a barrel portion extending distally from the head. Preferably the head and the barrel portion define a throughbore for receipt of a drive instrument. A thread on the head is provided to engage threads in the installation tool. A tissue thread is provided on the barrel portion to engage tissue. Distal and proximal surfaces of the tissue thread may be oriented at various angles relative to the barrel portion. There is also disclosed an insertion instrument to insert one or more tacks as well as a method of use. There is further disclosed a model device for use in explaining the operation of the instrument.

Abstract: A threaded engagement element comprising a body having a longitudinal axis and a thread adapted to be received by a corresponding thread of a second element. The threads are characterized by a thread parameter. The body has first and second portions that each has a different value for the thread parameter. The body may have more than one thread count or more than one geometry. This configuration creates a threaded engagement element with self-locking threads, which prevents unintentional loosening.

Abstract: A device and method for fastening two component members. The device includes a first component member including at least two protruded portions each having a predetermined lead angle, and a second component member which keeps predetermined positional relationship with the first component member and has at least two protruded portions which are engaged with the protruded portions of the first component member, among at least two of which protruded portions, at least one of the protruded portion has a different lead angle from the lead angle of the protruded portions of the first component member, and the first and second component members can be moved closer opposite each other, the protruded portions are engaged with each other after moving opposite each other by a certain distance, and the first and second component members are integrally fixed by frictional engagement of the protruded portions differing in the lead angle.

Abstract: A fastener for securing remnant-producing materials, a method of manufacturing the fastener, and a method of using the fastener are provided. The fastener is configured such that in use any remnants or slivers produced by rotation of the fastener are forcibly driven into the surface of the material. In one aspect, the fastener has two separate threaded portions, a first or lower threaded portion and a second or upper threaded portion. The threads on the lower threaded portion have a pitch that is different from the threads on the upper threaded portion. In one embodiment, the lower threaded portion threads have a larger pitch than the threads on the upper threaded portion. In use, after the lower threaded portion is completely inserted into the material, the upper threaded portion of the fastener enters the material.

Abstract: A fastener for securing remnant-producing materials, a method of manufacturing the fastener, and a method of using the fastener are provided. The fastener is configured such that in use any remnants or slivers produced by rotation of the fastener are forcibly driven into the surface of the material. In one aspect, the fastener has two separate threaded portions, a first or lower threaded portion and a second or upper threaded portion. The threads on the lower threaded portion have a pitch that is different from the threads on the upper threaded portion. In one embodiment, the lower threaded portion threads have a larger pitch than the threads on the upper threaded portion. In use, after the lower threaded portion is completely inserted into the material, the upper threaded portion of the fastener enters the material.

Abstract: An anti-cross threading screw (1) includes a first threaded portion (4) including a first thread (5) having a first outer diameter (6) and a first pitch (9) and a second threaded portion (12) having a second thread (13) having second outer diameter (18) and a second pitch (21). The second threaded portion (12) is designed as an anti-cross threading portion. The second thread (13) has enlarged an thread crest (15). The second outer diameter (18) of the second thread (13) is smaller than the first diameter (6) of the first thread (5). The first pitch (9) of the first thread (5) is different than the second pitch (21) of the second thread (13).

Abstract: A threaded element of plastic material for a joining assembly has a uniquely formed thread profile of a small profile angle between 30° and 50° and a rounded crest of a relatively large radius of curvature. The gap between the revolutions of the thread is of a volume which exceeds that of the thread. In order to provide for a specific cutting geometry of the thread profile the threaded element comprises a plurality of angular segments which are radially offset with respect to each other such that adjacent angular segments provide cutting edges. Furthermore, a tool and a method for making such a joining assembly are disclosed.

Abstract: A bone fragment wire connects a bone fragment to an anchor bone for a healing duration. The bone fragment wire has a distal bone penetration section which is advanced into the bone and a proximal bone exterior section. The proximal bone exterior section is longer than the bone penetration section, and thus extends substantially out of the bone during healing of the bone. The bone penetration section includes a distal bone anchor section which threadingly engages the anchor bone, and a proximal fragment section of small diameter. The fragment section fits within the overbore created by advancing the bone anchor section through the bone fragment, and thus extends through but does not positively engage the bone fragment. A compression engagement on a distal end of the bone exterior section provides a compression shoulder. In one embodiment the compression engagement is provided by a threaded compression nut, while in another embodiment the compression engagement is permanently affixed to the bone wire.

Abstract: A fastener for composite or plastic material having a dense composition employs a head which has a socket and a recessed underside and a lower rim. In one embodiment, the shank has an upper portion with an enlarged diameter and a left hand thread while the lower portion has a tri-lobed configuration and is traversed by a right hand thread. The right hand thread may have a plurality of notches which, in one embodiment, are arranged in a spiral array. One embodiment of a fastener has longitudinally spaced rings which project from an enlarged diameter portion of the shank. The lower portion of the shank has a thread with a plurality of notches. The rings have a major diameter and spacing greater than the major diameter and spacing of the thread.

Abstract: A thread structure for an optical lens comprises a plastic lens barrel, and the thread structure is formed on an outer surface of the lens barrel. In each single circle of the thread structure there is a normal thread and a partial withdraw thread. The partial withdraw thread is located on a longitudinal parting line of the thread structure, a top diameter and a pitch circle diameter of the partial withdraw thread are smaller than those of the normal thread, the thread structure is provided with ribs that are located at the root of a first normal thread close to the front end of the lens barrel. The withdraw thread produces an interval between the thread structure and the base, thus preventing the burrs on the parting surface from contacting the inner threads of the base and causing powder.

Abstract: The present invention pertains to a bimate screw providing with a first section alternating with a second threaded section; wherein, the second threaded section has a smaller outer diameter than the first threaded section, and further a plurality of concavities are disposed on each thread of the second threaded section for defining two flanks therein. In this manner, both the first and the second threaded sections facilitate to sever and shatter cuttings so as to reduce the screwing resistance and prevent the object from being damaged under the accumulation of cuttings; simultaneously, the bimate screw effectively attains to a good resistance of extraction from the object by the concavities receiving the remaining cuttings which are not guided out of the object.

Abstract: A screw anchor for fastening wooden construction parts on concrete or masonry comprises a shaft having a first threaded portion with a wood screw thread to be screwed into wood and a second threaded portion with a concrete thread to be screwed into concrete, the wood screw thread having the same or a somewhat smaller pitch than the pitch of the concrete thread.

Abstract: The present invention pertains to a screw for use in nonmetal objects comprising a plurality of cut-aiding portions formed by the longer and shorter cutting surfaces inclined toward opposite directions. Further, a cutting edge formed by the junction of any two adjacent cutting surfaces presents in a fastening direction of the screw. Thus, the cutting edge assists the threads to thoroughly severe and to shatter the fibers and debris of the objects, which can also be accommodated into the cut-aiding portions. Also, the ridge of the longer cutting surface aids in cutting fibers and further guides the debris out. In this manner, the present invention facilitates to enhance cutting capability for obtaining less screwing resistance, to prevent the destruction of the object and to increase the screwing speed.

Abstract: A pin with threads that extend along a portion of a stem of the pin interact with framing members as the pin pierces and is axially driven through the framing members. The interaction of the threads with the framing members cause the pin to rotate as the threads pass through the framing members and fastens the framing members together.

Abstract: The present invention pertains to a screw including a head, a shank having a first clockwise-threaded section and a counterclockwise-threaded section, and a drilling portion with a bottom end. Particularly, the counterclockwise-threaded section spiraling downward from the head connects to the first clockwise-threaded section by concurrently engaging their respective thread ends together. Therefore, the present invention applies the convergence of the two thread ends to efficiently guide the debris cutting by the first clockwise-threaded section and the counter force of the counterclockwise-threaded section to squeeze the debris back and share it among the threaded sections during the gradual travel of the shank through the articles, thereby reducing the drilling resistance and saving the labor imparting to the screw. Furthermore, the clockwise and the counterclockwise sections also counterbalance to steadily keep the screw buried in the articles without loosening.

Abstract: An adjusting device for repositioning a movable component relative to a stationary component includes a shank having a head at one end thereof and a distal tip at an opposite end thereof. The adjusting device also includes a first thread formed on the shank, the first thread disposed in a helical pattern along the shank, and a reversing thread formed on the shank, the reversing thread disposed in a helical pattern along the axial surface of the shank, the reversing thread helical pattern is formed in a direction that is opposite to the helical pattern of the first thread. Also described herein is a linear adjustment assembly that includes an adjusting device and a retaining device. The retaining device includes a thread disposed in a helical pattern along an interior surface of the retaining device having a helical pattern that is substantially similar to the first thread helical pattern.

Abstract: A thread-forming screw includes a screw end, a shank, and a thread-free head, wherein the shank is provided at least partly with a thread and has a pre-forming region, an intermediate region, which is arranged to follow the pre-forming region, and an anchoring region, which is arranged so as to adjoin the intermediate region and below the head, wherein the pre-forming region is arranged so as to directly adjoin the screw end.

Abstract: A screw fastener includes a head portion, a shaft portion extending from the head portion, and at least one locking serration. The shaft portion has a helical thread structure defining a thread part and a root part. The locking serration protrudes from the root part of the helical thread structure. The locking serration is configured and arranged to allow rotation of the shaft portion in a fastening direction and to restrict rotation of the shaft portion in a non-fastening direction upon engaging with a workpiece.

Abstract: A variably threaded screw has a first end and a second end, the first end of the shaft terminating in a tip and the second end having a widened head thereon. A first helical thread portion is located on the shaft adjacent the widened head. A second helical thread portion is located on the shaft adjacent the tip of the shaft. A third helical thread portion is located on the shaft between the first helical thread portion and the second helical thread portion. The first helical thread portion and the second helical thread portion have right hand thread pitches. The third helical thread portion has a left hand thread pitch. A helical ridge having a right hand thread pitch intersects the third helical thread portion.

Abstract: The system contains a rod body having a first end and a second end. A conical section is integral with the rod body at the first end of the rod body. The conical section tapers off at a triangular tip section. The triangular tip section has a proximate end integral with the conical section and a substantially pointed distal end. A higher helical rib is formed on the rod body and the conical section. A lower helical rib is integral with the higher helical rib at a first rib end. The lower helical rib extends onto the conical section and tapers toward the substantially pointed distal end. A partial groove is formed in the conical section along a proximate side of the lower helical rib. The groove does not extend entirely between adjacent lower helical rib elements. A gripping portion is proximate to the second end of the rod body.

Abstract: A deck screw and an installation method is intended for use with composite lumber, although it can be used with other products. The deck screw may be provided with a head and a shaft that has two regions of varying diameter. The upper region has threads that exceed the number of threads of the lower shaft, on a unit length basis. The threads of the upper shaft may be configured in an inverted buttress design. The lower region of the shaft terminates at a tapered distal end having a pointed tip that leads the screw through the wood material. The head of the screw is provided with an upper surface, a lower surface, and a crown that extends around the perimeter of the head. The crown extends beyond the lower surface of the head, forming a recessed region between the lower edge of the crown and the shaft of the screw. During installation the geometry of the deck screw functions to direct and capture displaced composite material to prevent volcanoing.

Abstract: A threaded fastener, such as a screw, includes a head, a tapered tip portion including a pair of opposing lands disposed between a pair of flutes, and a shank that extends between the head and the tapered tip portion. The shank includes a first threaded portion and a second threaded portion. The first threaded portion of the shank extends along a portion of the shank and at least a portion of the tip portion. The second threaded portion of the shank extends along a portion of the shank between the head and the first threaded portion.

Abstract: A threaded fastener includes a curved-line path thread provided in a helical pattern along a shank of the fastener. The curved-line path can be provided on either side of the standard straight-line path or on opposite sides of the straight-line path. The curved-line path and can be provided on all or a portion of the thread from near the tip end thereof to near the head end thereof.

Abstract: A power tap structure comprises a screw head, a bolt being a rod body extended underneath the screw head, and at least two screw thread units having different cutting surfaces respectively called a cutting thread and a retaining thread. Each of the crew thread units further includes a plurality of thread sections connected by a transition screw thread. The cutting thread has a plurality of indentations distributed along a cutting thread surface thereon, whereby the indentations on the cutting thread will effectively cut fibers of a material the bolt is being inserted. Therefore, the screw will penetrate the material quickly and easily. Further, an additional thread unit with narrower pitch can be formed right below the screw head for enhancing the locking effect of the screw when it is embedded into the material.

Abstract: A threaded fastener has opposite hand threads provided thereon for securing two components together, such as a companion flange and a flange yoke assembly that is used in a vehicular drive train system. The companion flange includes a hollow cylindrical sleeve portion and a disc-shaped flange portion having an aperture formed therethrough. The flange yoke includes a disc-shaped flange portion and a yoke portion having an aperture formed therethrough. The flange yoke aperture is aligned with the companion flange aperture. A threaded fastener extends through the companion flange aperture and the flange yoke aperture. The threaded fastener includes a first threaded portion having a first hand that is disposed within the companion flange aperture. The threaded fastener further includes a second threaded portion having a second hand that is disposed within the flange yoke aperture.

Abstract: A deck screw is intended for use with composite lumber, although it can be used with other wood products, such as pressure treated lumber. The deck screw has a head and a shaft that has two regions of different diameter. The upper region has threads that exceed the number of threads of the lower shaft, on a unit length basis. The threads of the upper shaft may be configured in an inverted buttress design. The lower region of the shaft terminates at a tapered distal end having a pointed tip that leads the screw through the wood material. Threads are provided on the lower region of the shaft. A crown extends around the perimeter of the head.

Abstract: A thread-cutting screwed dowel has an essentially cylindrical, sleevelike dowel body with an axial bore and with a load engagement device disposed in the interior of the dowel body, for example with a female thread. On its outer face, the dowel body is equipped with at least one cutting edge, which extends helically along a majority of the outer face of the dowel body and protrudes radially past it. The helical cutting edge is embodied as a primary cutting edge and wraps around the dowel body over its length in at least three windings. Besides the load engagement device, an additional engagement is provided for transmitting a torque in the interior of the dowel body.

Abstract: The screw with a plurality of helix angles comprises a first section having a first thread with a first helix angle, at least one third section having a third thread with a third helix angle; and a fifth section having a fifth thread with a fifth helix angle wherein the fifth thread is identical to the first thread. The third helix angle is equal or not equal to the first helix angle. Moreover, the screw further comprises a second section connected between the first section and the third section; the second section having a second thread with a second helix angle; a fourth section connected between the third section and the fifth section; and the fourth section having a fourth thread with a fourth helix angle. A mold device for forming the screw is also included. The mold device further comprises a second mold line-symmetrical to the first mold.

Abstract: A metal fastener for frangible material has a threaded shank, a head proximate one end of the shank and a tip at the opposite end. The fastener has a coarse pitch and relatively large ratio of major to minor diameters suited for securing the fastener into frangible material such as drywall or masonry.

Abstract: In accordance with an embodiment of the invention the threads of the two thread sections have an opposite pitch. Further, chips are reduced in that the tip of the screw near the thread section has been configured as a multiple screw-thread, in particular a double screw-thread, where the pitch of the threads of the multiple screw-thread is greater than the pitch of the single screw-thread of the thread section near the head of the screw.

Abstract: A plurality of screws (21) are aligned in parallel with each other, and head side portions (21b) of shaft portions (21A) of the screws are fixed, by a band (30) fixed to a strip sheet (31), to be band-shaped connected screws (20). Further, in the band-shaped connected screws (20), the head side portion (21b) of the shaft portion (21A) of each screw (21) is formed with an inverse screw thread (23) formed inverse direction to a screw thread (22) formed at the shaft portions (21A).

Abstract: The present invention is directed to a deck screw intended for use with composite lumber, although it can be used with other wood products, such as pressure treated lumber. The deck screw of the present invention may be provided with a head and a shaft that has two regions of varying diameter. The upper region has threads that exceed the number of threads of the lower shaft, on a unit length basis. The threads of the upper shaft may be configured in an inverted buttress design. The lower region of the shaft terminates at a tapered distal end having a pointed tip that leads the screw through the wood material. Threads are provided on the lower region of the shaft. The head of the screw is provided with an upper surface, a lower surface, and a crown that extends around the perimeter of the head, The crown extends beyond the lower surface of the head, forming a recessed region between the lower edge of the crown and the shaft of the screw. The head may also be provided with an undercut.

Abstract: A second material is fastened to a first material by a tapping screw having a male thread. The first material includes a hole and a concave portion around the hole. The hole has a surface in which a female thread is formed as the tapping screw is screwed in.

Abstract: A fastener for securing remnant-producing materials, a method of manufacturing the fastener, and a method of using the fastener are provided. The fastener is configured such that in use any remnants or slivers produced by rotation of the fastener are forcibly driven into the surface of the material. In one aspect, the fastener has two separate threaded portions, a first or lower threaded portion and a second or upper threaded portion. The threads on the lower threaded portion have a pitch that is different from the threads on the upper threaded portion. In one embodiment, the lower threaded portion threads have a larger pitch than the threads on the upper threaded portion. In use, after the lower threaded portion is completely inserted into the material, the upper threaded portion of the fastener enters the material.

Abstract: A screw includes a rod-shaped portion, and a spiral-shaped thread winding around the rod-shaped portion. The rod-shaped portion has a straight portion, and a front end portion tapering towards a pointed front end. Several cutting trenches are formed on the rod-shaped portion for cutting bits off a workpiece with which when the screw is being screwed into the same. The tapering front end portion is provided with a notch, and cutting teeth are provided on that portion of the thread corresponding to the tapering front end portion. Cut-off bits of a workpiece can be received in the trenches as well as the cutting teeth so that the same can't have excessive resistance against the screw.

Abstract: A fastener for securing remnant-producing materials, a method of manufacturing the fastener, and a method of using the fastener are provided. The fastener is configured such that in use any remnants or slivers produced by rotation of the fastener are forcibly driven into the surface of the material. In one aspect, the fastener has two separate threaded portions, a first or lower threaded portion and a second or upper threaded portion. The threads on the lower threaded portion have a pitch that is different from the threads on the upper threaded portion. In one embodiment, the lower threaded portion threads have a larger pitch than the threads on the upper threaded portion. In use, after the lower threaded portion is completely inserted into the material, the upper threaded portion of the fastener enters the material.

Abstract: In accordance with an embodiment of the invention the threads of the two thread sections have an opposite pitch. Further, chips are reduced in that the tip of the screw near the thread section has been configured as a multiple screw-thread, in particular a double screw-thread, where the pitch of the threads of the multiple screw-thread is greater than the pitch of the single screw-thread of the thread section near the head of the screw.

Abstract: A fastener for securing remnant-producing materials, a method of manufacturing the fastener, and a method of using the fastener are provided. The fastener is configured such that in use any remnants or slivers produced by rotation of the fastener are forcibly driven into the surface of the material. In one aspect, the fastener has two separate threaded portions, a first or lower threaded portion and a second or upper threaded portion. The threads on the lower threaded portion have a pitch that is different from the threads on the upper threaded portion. In one embodiment, the lower threaded portion threads have a larger pitch than the threads on the upper threaded portion. In use, after the lower threaded portion is completely inserted into the material, the upper threaded portion of the fastener enters the material.

Abstract: A fastener having an aligning lead thread that does not follow the helical pattern of the fill threads around the shank of the fastener. The aligning lead thread is located on the shank distant from the first full thread to enable the engage the threads of a receiving member to pull the fastener elements into alignment rather than a standard lead thread which becomes trapped behind the threads of a receiving member.

Abstract: A double pitch screw having a head at one and a drive point at the other end thereof, with a clear unthreaded shank between a set of low pitch threads adjacent to the drive point and a set of high pitch threads adjacent to the head and the break point.

Abstract: A fastener for securing remnant-producing materials, a method of manufacturing the fastener, and a method of using the fastener are provided. The fastener is configured such that in use any remnants or slivers produced by rotation of the fastener are forcibly driven into the surface of the material. In one aspect, the fastener has two separate threaded portions, a first or lower threaded portion and a second or upper threaded portion. The threads on the lower threaded portion have a pitch that is different from the threads on the upper threaded portion. In one embodiment, the lower threaded portion threads have a larger pitch than the threads on the upper threaded portion. In use, after the lower threaded portion is completely inserted into the material, the upper threaded portion of the fastener enters the material.

Abstract: A fastening system for fixing a first assembly unit to a second component for use especially in the motor vehicle industry is presented, which has at least one fastening screw, a corresponding first preassembly thread on the first assembly unit, in which the fastening screw is fixed after the preassembly, and a fastening thread on the first assembly unit or on the second component for fixing the first assembly unit to the second component by means of the fastening screw. The fastening screw has at least two threaded areas for preassembly and for fastening with different thread pitches, wherein the preassembly thread and the fastening thread as well as the threaded areas are provided with different pitches and the second threaded area, which is used for fastening and is facing away from the screw head, has a smaller diameter than the threaded area that is used for the preassembly and is adjacent to the screw head.

Abstract: An elongate threaded fastener (50) for attaching the roofing panels (8) has a first part (20) and a second part (30), both made of a steel, and the first part (20) is composed of an elongate non-threaded shank (22) and a fastening rod portion (23) continuing from the shank and of a reduced diameter. The second part (30) is composed of an increased-diameter rod portion (35) and a head (36) formed at the proximal end of this portion. The first and second parts (20,30) are resistance welded together, before a boring means (24) such as a drill tip is formed on the distal end of the fastening rod portion (23). Then, both the fastening and increased-diameter rod portions (23,35) are rolled to form screw threads (23a,35a) respectively on them such that a method is provided to manufacture more efficiently at an improved productivity the threaded fastener (50) having the proximal threaded rod portion (35) whose diameter can be designed large enough.

Abstract: A screw has a shank portion (20) provided with a thread (21) and passing over via a transition into a conical tip (22). One or more parallel fins (24) are provided at least in the area of the tip. They are formed with cutting edges (23) and preferably disposed at an angle of inclination (13) of no less than 5° with respect to the longitudinal axis of the screw. The fins (24) project beyond the core diameter (1) of the shank portion (20). The conical tip (22) includes a finless end portion (26). The thread (21), however, extends across the full length of the tip (22).

Abstract: In a screw (1) for fastening wooden laths (10) to a roof substructure provided with wooden beams (9) among other alternatives, one threaded portion (2, 3) each adjoining the head (5) of the screw and adjoining a penetrating or boring point (6) is provided, these two threaded portions (2, 3) having the same major diameter. A thread-free shank portion (4) is provided between the two threaded portions (2, 3).

Abstract: The present invention provides a fastening method for fastening a first member to a second member by a bolt, comprising the steps of: inserting the bolt through a hole in the first member into a hole in the second member to start threadably engaging the bolt in a threaded hole provided in the second member; then, in a subsequent threadably engaging process, shaping, for example by plastically deforming or cutting, the holes of both the first and second members by a large-diameter portion provided around a bolt shank and having a diameter larger than that of the holes. The invention also provides a fastening system and a bolt used for the above-described method. With this method, it is possible to accurately connect the first and second members by the bolt, and to miniaturize the parts without increasing costs or lowering productivity.

Abstract: A fastener has a screw with an anchor located thereon, the anchor being spaced apart from the head. The anchor has a cut-away portion with a leading edge and a trailing edge of the cut-away portion angling downward. The leading edge angles downward a further distance than the trailing edge. The anchor is spaced apart from the head by a distance corresponding to a thickness of a layer of material to be affixed to a support by an adjustable distance. The layer of material has a small opening therein to accommodate the screw. When the screw is inserted through the opening and into the support, the anchor turns through the opening, even though the opening is smaller than the anchor so that the material is located between the anchor and the head. The screw can then be turned further into the support or further out of the support to adjust the distance between the material and the support in order to align the material as desired.

Abstract: A screw having a root and threads formed on the root. The screw is configured to generate and/or maintain axial compression between threads formed in leading and trailing sections of the screw either by virtue of pitch differential in the threads or the way in which the screw is installed.

Abstract: A wood screw is proposed for use with a material made mainly of plastic waste and wood chips. The wood screw includes a shank which has leading threads extending from the tip of the tapered portion to an intermediate point of the straight portion and have a first lead angle and a first thread angle. Trailing threads extend from the intermediate point toward a head and have a second lead angle and a second thread angle. The first lead angle is greater than the second lead angle, and the first thread angle is smaller than the second thread angle.