JP2008183642A - Screw forming tool and metallic member with screw part formed by screw forming tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw forming tool capable of reducing burrs produced on a mouth of a screw part and a metallic member with the screw part on it capable of easily fastening and positioning a fastening member as the burrs at the mouth are reduced. <P>SOLUTION: This screw forming tool 10 has a prepared hole forming part 12 to drill a hole on a metallic plate W being a workpiece by rotation and pressurization and a screw forming part 16 to apply thread cutting in the hole 22 drilled by the prepared hole forming part 12. The prepared hole forming part 12 is furnished with a conical head end part 24 projected to a fore end and a burr-folding part 26 continuously provided on a base end side peripheral edge part of the conical fore end part 24 and curved and recessed toward the rear end side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a screw forming tool for forming a screw portion on a workpiece such as a metal plate and a metal member formed with a screw portion formed by the screw forming tool.

  Conventionally, in order to form a threaded portion (female threaded portion) in a workpiece such as a metal plate used in a vehicle or the like, a hole forming portion and a screw forming tool having a screw forming portion are used, and the metal plate is perforated. Methods of performing processing (burring processing) and screw processing (tapping processing) are known.

  In Patent Document 1, a punching part for punching a metal plate to make a hole, a tapered burring forming part for forming a burring part by enlarging the punched hole, and threading the inner peripheral surface of the burring part There is disclosed a screw forming tool including a relief screw portion and a forming blade portion for performing the above.

  In Patent Document 2, there is a screw forming tool for forming a thread part as described above, where a thin plate is plastically deformed by frictional heat generated by pressure and rotation at a tapered tip, and a hole is formed by burring. There is disclosed a technical idea that includes a perforated portion to be formed and a tapped portion for forming a female screw in a hole formed by the perforated portion, and forms a dull processed surface in the perforated portion.

Japanese Patent No. 2857943 JP-A-5-253747

  FIG. 12 is a front view of a thread forming tool 100 which is an example of such a conventional thread forming tool. FIGS. 13A to 14 are partially omitted side cross-sectional views for explaining a process of forming a screw portion on the metal plate W by the screw forming tool 100 shown in FIG.

  As shown in FIG. 12, the screw forming tool 100 includes a pilot hole forming portion 102 having a tapered portion 101 provided at the tip, a screw forming portion 104 provided on the rear end side of the pilot hole forming portion 102, It is composed of a shank (handle) 106 provided on the rear end side of the thread forming portion 104. On the rear end side of the shank 106, an engaging portion 108 having a polygonal cross section is formed which is held by a chuck of a screw forming apparatus (not shown).

  When a screw part is formed on the metal plate W as a workpiece by using such a screw forming tool 100, first, while rotating the screw forming tool 100 at a high speed, as shown in FIG. Insert the tip into the metal plate W. At this time, on the upper surface of the metal plate W on the insertion side (opposite to the traveling direction) of the screw forming tool 100, a burr 112 protruding outward is generated at the peripheral edge (mouth) of the hole 110.

  Next, as shown in FIG. 13B, when the pilot hole forming portion 102 gradually advances while breaking the metal plate W by frictional heat due to rotation and pressurization, burrs 112 are formed along the tapered portion 101 of the pilot hole forming portion 102. Grows greatly. As shown in FIG. 13C, when the taper portion 101 is completely inserted into the metal plate W and the burr 112 is removed from the taper portion 101, the greatly grown burr 112 has a slightly curved shape outward. Then, as shown in FIGS. 13D and 13E, when the tip of the prepared hole forming portion 102 penetrates the metal plate W, the drilling process is finished, and a hole 110 penetrating the metal plate W is formed.

  Subsequently, as shown in FIG. 14, the screw 110 is threaded into the hole 110 to complete the formation of the screw portion 114 on the metal plate W.

  In the thread forming tool 100, the threaded portion 114 is formed as described above. In this case, as shown in FIG. 14, the burr 112 protruding outward from the mouth of the threaded portion 114 after the forming is very It grows large and remains in a protruding state.

  For this reason, as shown in FIG. 15A, when a bolt (not shown) is fastened to the threaded portion 114 and the fastening member 116 is fastened to the metal plate W, the burr 112 interferes with the bolt insertion hole 118 of the fastening member 116. Alternatively, as shown in FIG. 15B, the burr 112 may jump out of the bolt insertion hole 118 after the fastening member 116 is positioned. If a large burr 112 remains on the metal plate W after the screw part 114 is formed, the burr 112 may damage the fastening member 116 during fastening. Further, when positioning the fastening member 116, it is necessary to position the bolt insertion hole 118 so as to avoid the burr 112, and the number of steps and time for fastening increase.

  Therefore, it is conceivable to perform a deburring process for removing the burr 112 after the threaded portion 114 is formed. However, the number of processes increases after all.

  The present invention has been made to solve the above-described conventional problems, and in a screw forming tool for performing drilling and screwing on a workpiece, it is possible to reduce burrs generated at the mouth of the screw portion. The present invention provides a screw forming tool that can omit deburring after forming, and a metal member that can easily fasten and position a fastening member by reducing burrs at the mouth of the threaded portion. For the purpose.

  A screw forming tool according to the present invention has a pilot hole forming part that opens a hole in a workpiece by rotation and pressurization, and a screw forming part that performs screw processing on a hole formed in the pilot hole forming part, The pilot hole forming portion includes a conical tip portion projecting from the tip, and a burr return portion that is provided continuously to the base end side peripheral portion of the cone tip portion and is curved and recessed toward the rear end side. It is characterized by providing.

  According to such a structure, the burr | flash which generate | occur | produces by the taper surface of a cone-shaped front-end | tip part at the time of insertion to a workpiece can be returned in a base material by a burr | flash return part, and the generation amount is reduced. be able to.

  In addition, when a tapered portion having a diameter increased toward the rear end side is formed in a portion continuous from the outer peripheral side edge portion of the burr turning portion of the prepared hole forming portion, the burr is formed in a small curl shape. Therefore, the burr can be used as a positioning portion when positioning the fastening member.

  Furthermore, when a spiral groove is formed on at least a part of the outer surface of the prepared hole forming portion, it is possible to expand the diameter while pushing the workpiece downward, and the thickness and shape of the hole after forming And the generation of burrs can be effectively reduced by the spiral groove.

  The metal member according to the present invention is a metal member in which a threaded portion that has been threaded after forming a pilot hole is formed, and the threaded portion has a burr tip projecting outward from a peripheral portion on the burr. It is curled so as to be included.

  According to such a configuration, it is possible to use the curled burr formed on the screw portion as a positioning portion when positioning the fastening member. In addition, the fastening member can be effectively prevented from being damaged when the fastening member is fastened or positioned.

  According to the screw forming tool of the present invention, the burr generated by the tapered surface of the conical tip portion can be returned into the base material by the burr returning portion when inserted into the work piece. The amount can be reduced.

  Further, according to the metal member of the present invention, it is possible to use the burr formed in a curl shape from the peripheral edge of the screw portion as a positioning portion when positioning the fastening member, Damage to the fastening member during positioning can be prevented.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thread forming tool according to the present invention will be described in detail with reference to the accompanying drawings by giving preferred embodiments in relation to a metal member formed with a thread portion formed by the thread forming tool. .

  FIG. 1 is a front view of a thread forming tool (thread forming tool) 10 according to an embodiment of the present invention. The screw forming tool 10 is held by a chuck such as a screw forming device or a drilling machine mounted on an industrial robot (not shown), thereby drilling and screwing a metal plate (metal member) as a workpiece. Used when performing.

  As shown in FIG. 1, the screw forming tool 10 includes a pilot hole forming part (perforated part) 12 provided at the tip, and a cylindrical part 14 provided continuously on the rear end side of the pilot hole forming part 12. And a thread forming portion (tap portion) 16 provided continuously on the rear end side of the cylindrical portion 14 and a shank (handle) 18 provided continuously on the rear end side of the screw forming portion 16. Has been. On the rear end side of the shank 18, an engagement portion 20 having a polygonal cross section that is held by a chuck of a screw forming apparatus (not shown) is formed.

  The pilot hole forming portion 12 is a pilot hole before screw processing by plastically deforming a metal plate (metal member) W that is a workpiece by frictional heat generated by rotation and pressurization applied by the screw forming device or the like. It is a part which opens the hole 22 (refer FIG. 6). The pilot hole forming portion 12 is formed continuously in a radial direction from a conical distal end portion 24 having a small diameter protruding from the center of the distal end surface and a proximal end side peripheral portion of the conical distal end portion 24. And a burr turning portion 26 that is curved toward the rear end side and is shallowly recessed. Further, the pilot hole forming portion 12 is formed with a taper portion 28 whose diameter is increased from the outer peripheral side peripheral portion of the burr return portion 26 toward the rear end side, and a screw forming tool is provided from the taper portion 28 to the rear end side. 10 straight portions 30 parallel to the axial direction are formed.

  2 is a partially omitted side sectional view in the axial direction of the pilot hole forming portion 12 of the screw forming tool 10 shown in FIG. 1, and FIG. 3 is a pilot hole forming portion 12 of the screw forming tool 10 shown in FIG. FIG.

As shown in FIGS. 2 and 3, in the case of the present embodiment, the conical tip 24 is formed in a truncated cone shape having a flat tip. The tip shape of the conical tip 24 may be a curved surface or a sharp tip other than the flat surface. The burr return portion 26 is a substantially hemisphere that is provided around the base end side of the cone tip 24. Burr 32 (see FIG. 4A and the like) generated along the outer peripheral tapered surface of the conical tip 24 by the perforation of the conical tip 24 is returned to the metal plate W as a base material. Play the function to put.

  As shown in FIG. 1, the angle θ at which the tapered portion 28 is inclined with respect to the axial direction of the thread forming tool 10 is set to 15 ° in the present embodiment. Further, the length L of the taper portion 28 in the axial direction is configured to be sufficiently shorter than the length of the straight portion 30, and the length L is set equal to or less than the plate thickness of the metal plate W. .

  The screw forming portion 16 is a portion for threading the hole 22 formed by the pilot hole forming portion 12 to form a screw portion (female screw portion) 34 (see FIG. 8). A threading spiral groove 36 that is a large-diameter thread cutting blade is formed. For example, when the metal plate W is a thin plate, it is necessary to effectively use the material of the metal plate W as the screw portion 34. Therefore, the thread forming by the screw forming portion 16 is not a cutting process but a rolling process. Is preferably performed. Since rolling scraps do not generate cutting waste as compared with cutting processing, there is an advantage that a process and an apparatus for removing scraps can be omitted.

  In addition, in this embodiment, although the pilot hole shaping | molding part 12 and the screw shaping | molding part 16 are comprised integrally, you may comprise these detachably. In this case, either one can be individually replaced depending on the degree of wear, a desired screw diameter, or the like.

  Next, with reference to FIG. 4A to FIG. 8, a screw part forming process for forming the screw part 34 at a predetermined position of the metal plate W that is a workpiece by using the screw forming tool 10 configured as described above. explain.

  4A to 4E are side cross-sectional views with partial omission for explaining a process related to drilling for forming the hole 22 by the pilot hole forming portion 12 of the screw forming tool 10.

  First, while the screw forming tool 10 is held by a chuck of a screw forming apparatus (not shown), the conical tip 24 at the tip is moved to the metal plate W while being rotated at high speed by the screw forming apparatus as shown in FIG. 4A. Insert into. That is, the metal plate W is melted by the frictional heat generated by the rotation and pressurization of the screw forming tool 10 to cause plastic deformation, and insertion (perforation) of the conical tip 24 into the metal plate W is started. At this time, on the upper surface of the metal plate W on the insertion side (opposite to the traveling direction) of the screw forming tool 10, a burr 32 protruding outward is generated at the peripheral edge (mouth) of the hole 22.

  Here, FIG. 5A and FIG. 5B are partially omitted enlarged side sectional views for explaining a state in which the hole 22 is formed in the metal plate W by the conical tip portion 24. As shown in FIG. 5A, when the conical tip 24 is inserted into the metal plate W, the burr 32 tends to protrude along the tapered surface of the conical tip 24. However, as shown in FIG. 5B, most of such burrs 32 are reduced while being returned into the metal plate W as a base material by the burr return portion 26 provided at the peripheral edge portion of the conical tip portion 24. The remaining portion is curved outward.

  As the screw forming tool 10 gradually advances, the conical tip 24 is completely inserted into the metal plate W, and the tapered portion 28 and the straight portion 30 begin to be inserted. As shown in FIG. 4B, the burrs 32 generated along the tapered portion 28 have a shape that is curved outward by coming off the tapered portion 28 when reaching the straight portion 30.

  In this case, since the tapered portion 28 is set to a desired length L equal to or less than the thickness of the metal plate W as described above, the burr 32 is curved almost simultaneously with the insertion of the tapered portion 28. In particular, in the screw forming tool 10, most of the burr 32 generated by the conical tip 24 at the tip is returned to the base material by the burr return portion 26. As a result, the amount of the burr 32 projecting outward from the mouth of the hole 22 is further reduced and the taper portion 28 is formed short, so that the curl so that the tip end side is enclosed by the burr 32 itself. A small burr 32 is formed.

  Subsequently, as shown in FIGS. 4C and 4D, when the formation of the hole 22 proceeds while the pilot hole forming portion 12 further proceeds and the metal plate W is stretched in the traveling direction (downward) along the straight portion 30. 4E, the pilot hole forming portion 12 penetrates the metal plate W. As shown in FIG. Therefore, a hole 22 having a desired shape, that is, a uniform and sufficient thickness and depth is formed (see FIG. 6).

  Then, the screw portion 34 is formed at a desired position of the metal plate W by performing screw processing on the hole 22 by the screw processing spiral groove 36 constituting the screw forming portion 16 (see FIGS. 7A and 7B). Formed (see FIG. 8).

  As described above, according to the screw forming tool 10, the burr 32 generated by the tapered surface of the conical tip 24 immediately after being inserted into the metal plate W is brought into the metal plate W as a base material by the burr return portion 26. Reduced while being put back.

  Furthermore, since the length L of the taper portion 28 is set to a sufficiently short length as a desired ratio (in this embodiment, equal to or less than the plate thickness) with respect to the plate thickness of the metal plate W, the burr 32 is curved. Caused early. Therefore, the amount of the burr 32 protruding outward from the mouth of the hole 22 or the screw part 34 is further reduced and reduced in relation to the retraction action by the burr return part 26 so that the tip side is included in the burr 32 itself. A small burr 32 curled is formed.

  FIG. 9 is a partially omitted side cross-sectional view showing a state in which a fastening member 38 fastened by a bolt or the like (not shown) is positioned on the screw portion 34 formed on the metal plate W.

  As described above, the burr 32 remaining in the threaded portion 34 has a small shape curled so that the tip protruding outward from the mouth is included in the burr 32 itself (see FIGS. 8 and 9). .

  Therefore, as shown in FIG. 9, it is possible to effectively prevent the burr 32 from interfering with the bolt insertion hole 40 of the fastening member 38, and the burr 32 does not protrude from the bolt insertion hole 40 after positioning. Further, since the burr 32 has a curled shape as described above, the fastening member 38 can be prevented from being damaged at the time of fastening or positioning, the burr 32 need not be removed, and the deburring process can be reduced. it can.

  Moreover, since the burr 32 has a small curl shape, the burr 32 can also be used as a positioning part (preliminary and simple positioning part) when positioning the fastening member 38. Such time can be shortened.

  In addition, as shown in FIG. 10, the screw forming tool 10 according to the present embodiment may be a screw forming tool 10a in which the prepared hole forming part 12 is changed to the prepared hole forming part 12a. In FIG. 10, the same reference numerals as those shown in FIG. 1 indicate the same or similar configurations, and therefore the detailed description thereof will be omitted as they exhibit the same or similar functions and effects.

  As shown in FIG. 10, in the screw forming tool (screw forming tool) 10a, a spiral groove 42 is provided around the outer surface of the prepared hole forming portion (perforated portion) 12a. In the present embodiment, the spiral groove 42 has the same pitch as the screw processing spiral groove 36 constituting the screw forming portion 16. Such a spiral groove 42 is not necessarily provided in the entire pilot hole forming portion 12a, and may be provided only in a part of the pilot hole forming portion 12a, for example, only in the tapered portion 28 or only in the straight portion 30. Good.

  FIG. 11A is an explanatory view schematically showing the pressing direction of the pilot hole forming portion 12a during drilling with the screw forming tool 10a, and FIG. 11B shows a hole in the screw forming tool 10 having no spiral groove 42. It is explanatory drawing which shows typically the pressing direction of the pilot hole shaping | molding part 12 at the time of an opening process.

  As shown in FIG. 11A, the pilot hole forming portion 12a has the spiral groove 42, so that when the hole 22 is formed, the direction of the pressing force from the tapered portion 28 or the straight portion 30 to the metal plate W is as shown in FIG. 11A. In the direction indicated by the arrows (downward and diagonally downward). Thereby, it becomes possible to expand the diameter while pushing the metal plate W downward, and after forming, the thickness and shape of the hole 22 depending from the lower surface of the metal plate W are made uniform, and the strength of the screw portion 34 is also improved. . In addition, the spiral groove 42 can effectively reduce the backflow of the metal plate W through the surfaces of the tapered portion 28 and the straight portion 30 during the drilling process, that is, the generation of burrs 32.

  On the other hand, as shown in FIG. 11B, in the pilot hole forming part 12 having no spiral groove 42, most of the pressing force from the taper part 28 and the straight part 30 to the metal plate W during drilling is shown in FIG. 11B. Acts in the direction indicated by the arrow (diagonally below). For this reason, the thickness in the part suspended from the metal plate W which comprises the hole 22 and the thread part 34 tends to decrease a little. However, in the case of such a screw forming tool 10, since the processing of the spiral groove 42 is unnecessary, it can be manufactured at a lower cost than the screw forming tool 10a, and the use of the threaded portion 34 after forming, etc. Some can be used effectively.

  As described above, the amount of burrs generated on the metal plate W can be effectively reduced by using the screw forming tools 10 and 10a according to the embodiment of the present invention. Can be effectively used for various metal plates W such as aluminum, iron, and copper.

  Examples of the aluminum plate used for the metal plate W include JIS (AA) 5000 series and JIS (AA) 6000 series aluminum alloys, and of course, JIS (AA) 1000-4000 series and JIS (AA) 7000 series. It may be. Carbide WC (tungsten carbide), high-speed steel or the like can be used particularly effectively as the material of the screw forming tools 10 and 10a suitable for processing such an aluminum plate.

  When the aluminum plate (metal plate W) is processed by the screw forming tool 10 (10a), first, the aluminum plate is 200 to 300 by frictional heat generated by rotation and pressurization of the screw forming tool 10 (10a). At the same time as heating to about ° C., plastic working of the hole 22 which is a pilot hole is performed by the pilot hole forming part 12 (12a). At this time, the aluminum plate is heated to about 220 ° C. when the holes 22 are formed in a single shot, and the aluminum plate is heated to about 290 ° C. when a plurality of the holes 22 are formed close to each other. Next, screw processing by the screw forming portion 16 is performed on the hole 22. The temperature of the aluminum plate at this time is not particularly a problem, but it is usually about 120 ° C. during single processing, and about 220 ° C. when processing near continuously. That is, since the melting point of aluminum is about 660 ° C., the pilot hole processing by the pilot hole forming portion 12 (12a) is performed in a semi-molten state, so that the pilot hole processing can be performed more easily and reliably.

  Moreover, as an iron plate used for the metal plate W, the steel plate for motor vehicles (270kg class-980kg class, the presence or absence of galvanization is not ask | required) is mentioned, for example, Of course, another steel plate may be sufficient. Carbide WC (tungsten carbide) can be used particularly effectively as the material of the screw forming tools 10 and 10a suitable for processing such a steel plate (steel plate) for automobiles.

  When the automotive steel plate (metal plate W) is processed by the screw forming tool 10 (10a), first, the automotive steel plate is made 600 by friction heat generated by rotation and pressurization of the screw forming tool 10 (10a). At the same time as heating to about ° C., plastic working of the hole 22 which is a pilot hole is performed by the pilot hole forming part 12 (12a). Next, screw processing by the screw forming portion 16 is performed on the hole 22.

  Thus, the screw forming tools 10 and 10a according to the embodiment of the present invention can be effectively used for the metal plate W made of various materials, and the material of the screw forming tools 10 and 10a and the material of the metal plate W By effectively combining the above and making the processing temperature at the time of prepared hole processing appropriate temperature according to the material of the metal plate W, it is possible to perform prepared hole processing and screw processing more suitably.

  As described above, the present invention has been described with the embodiments. However, the present invention is not limited to this, and it is naturally possible to adopt various configurations without departing from the gist of the present invention.

It is a front view of the screw forming tool concerning one embodiment of the present invention. FIG. 2 is a partially omitted side cross-sectional view in the axial direction of a pilot hole forming portion of the screw forming tool shown in FIG. It is a partially-omission perspective view which expanded the pilot hole forming part of the screw forming tool shown in FIG. 4A is a partially omitted side cross-sectional view showing a state in which drilling by the pilot hole forming part of the screw forming tool shown in FIG. 1 is started, and FIG. 4B shows the pilot hole forming part from the state shown in FIG. 4A. FIG. 4C is a partially omitted side sectional view showing a state where the pilot hole forming portion is further advanced from the state shown in FIG. 4B, and FIG. 4C is a partially omitted side cross-sectional view showing a state in which the pilot hole forming portion is further advanced from the state shown in FIG. 4C, and FIG. 4E is a state in which the pilot hole forming portion is further advanced from the state shown in FIG. It is a partially-omission side surface sectional view which shows the state made to do. 5A is a partially omitted enlarged side cross-sectional view showing a state in which a hole is started to be formed in the metal plate W by the conical tip of the screw forming tool shown in FIG. 1, and FIG. 5B is a conical view from the state shown in FIG. 5A. It is a partially omitted side cross-sectional view showing a state in which the shape tip portion is further advanced. FIG. 2 is a partially omitted enlarged side cross-sectional view showing a hole formed by the screw forming tool shown in FIG. 1. FIG. 7A is a partially omitted side cross-sectional view showing a state in which screwing of the hole formed by the drilling shown in FIGS. 4 to 4E is started by the screw forming portion of the screw forming tool shown in FIG. 7B is a partially omitted side cross-sectional view showing a state in which the screw forming portion is advanced from the state shown in FIG. 7A and the screw portion is formed on the metal plate. It is a partially-omission perspective view which shows the thread part shape | molded by the screw forming tool shown in FIG. It is a partially omitted side sectional view showing a state in which a fastening member is positioned on a threaded portion formed on a metal plate. It is a front view which shows the modification of the screw forming tool shown in FIG. FIG. 11A is an explanatory view schematically showing the pressing direction of the pilot hole forming portion at the time of drilling with the screw forming tool shown in FIG. 10, and FIG. 11B is a hole with a screw forming tool having no spiral groove. It is explanatory drawing which shows typically the pressing direction of the pilot hole shaping | molding part at the time of a drilling process. It is a front view which shows an example of the conventional screw forming tool. 13A is a partially omitted side sectional view showing a state in which drilling is started by the pilot hole forming portion of the conventional screw forming tool shown in FIG. 12, and FIG. 13B is a pilot hole forming from the state shown in FIG. 13A. FIG. 13C is a partially omitted side sectional view showing a state in which the pilot hole forming portion is further advanced from the state shown in FIG. 13B. FIG. 13C is a partially omitted side cross-sectional view showing a state in which the pilot hole forming portion is further advanced from the state shown in FIG. 13C, and FIG. 13E is a diagram showing a state where the pilot hole forming portion is further advanced from the state shown in FIG. It is a partially-omitted side sectional view showing a state in which is penetrated. FIG. 13 is a partially omitted side sectional view showing a state in which a thread portion is formed on a metal plate by a thread forming portion of the conventional thread forming tool shown in FIG. 12. FIG. 15A is a partially omitted side cross-sectional view showing a state before positioning a fastening member on a screw portion formed on a metal plate by the conventional screw forming tool shown in FIG. 12, and FIG. 15B is shown in FIG. 15A. It is a partially omitted side sectional view showing a state in which the fastening member is positioned from the state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10a, 100 ... Screw forming tool 12, 12a, 102 ... Pilot hole forming part 16, 104 ... Screw forming part 22, 110 ... Hole 24 ... Conical tip part 26 ... Burr return part 28, 101 ... Tapered part 30 ... Straight part 32, 112 ... Burr 34, 114 ... Screw part 36 ... Spiral groove for screw machining 42 ... Spiral groove W ... Metal plate

Claims (4)

A pilot hole forming part that opens a hole in the workpiece by rotation and pressurization;
A screw forming part that performs threading on the hole formed in the pilot hole forming part; and
Have
The prepared pilot hole is a conical tip projecting from the tip;
A screw forming tool, comprising: a burr turning portion which is provided continuously to a base end side peripheral portion of the conical tip portion and is curved and recessed toward a rear end side. The thread forming tool according to claim 1,
A thread forming tool, wherein a taper portion having a diameter increased toward a rear end side is formed in a portion continuous from an outer peripheral side edge portion of the burr turning portion of the prepared hole forming portion. The thread forming tool according to claim 1 or 2,
A screw forming tool, wherein a spiral groove is formed on at least a part of the outer surface of the prepared hole forming portion. A threaded metal part that is threaded after forming the pilot hole,
The screw member is curled so that a tip of a burr protruding outward from a peripheral portion is included in the burr.

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