TW201838739A - Rolling die for self-tapping screw capable of rolling mill a self-tapping screw which can be smoothly screwed in, and can effectively prevent cracking on a wooden component - Google Patents

Abstract

The invention provides a rolling die for a self-tapping screw, which can be smoothly screwed in, and can effectively prevent cracking of the wooden member. a die 11 for rolling a self-tapping screw having a sharp tip at one end and a screw portion at the other end having a shaft portion of the head, forming a broken thread and reaching the valley of the thread a groove having a depth of a portion, and a groove forming portion 14 of the cutting groove is formed at a position on the end side of the thread-finishing surface 12 of the fixed mold 11a, and the groove forming portion 14 is processed by a groove disposed along a rolling direction of the screw material. The portion 15 is formed in a relief groove 16 which is placed on the head portion 4 side of the screw material in parallel with the groove processing portion 15 and which is recessed with respect to the groove processing surface 15a of the groove processing portion 15.

Description

Self-tapping screw rolling die

The present invention relates to a rolling die of a self-tapping screw having a sharp tip at one end of the shaft portion and a head at the other end, and a peripheral surface of the shaft portion is provided from the sharp tip toward the head side In the thread, a cutting groove that breaks the thread and reaches the depth of the valley of the thread is formed in the middle of the thread portion of the shaft portion.

For example, a self-tapping screw is known which is provided with a thread on a peripheral surface of a shaft portion having a sharp end, and a thread on a shaft tip from the sharp tip toward the head side, in the thread for fastening the wooden member, on the shaft The cutting edge groove of the cutting wood member and the cutting groove of the cutting screw are formed at the tip side or the middle position of the portion, and the incision of the sharp tip and the cutting action of the cutting edge groove and the cutting groove can be smoothly performed Screw in and prevent cracks in the wooden components. Further, with respect to the self-tapping screw of the sharp tip as described above, although a self-tapping screw in which the tip end of the shaft portion is set as a flat surface is proposed, when the self-tapping screw is screwed in, the wooden member has to be preliminarily In contrast, the self-tapping screw having a sharp tip is commonly used because it can be directly screwed into the wooden member and has excellent operability at the time of fastening. From the point of mass production, the manufacture of the self-tapping screws as described above is common by rolling using a die, but in the method of forming the cutting edge groove and the cutting groove of the self-tapping screw, there is a roll on the screw body. The cutting process after rolling and the rolling process performed simultaneously with the rolling process of the screw body require the cutting process to be additionally required for the cutting process of the former, and the additional processing time is incurred due to the increase in the number of processes, resulting in the cost of the product. In the case of the problem of the cutting process, the rolling formation is gradually becoming mainstream (see, for example, Patent Documents 1 to 3). Patent Documents 1 and 2 are used for manufacturing a rolling die in which a tip end of a shaft portion is a flat surface and a plurality of cutting edges are provided around a tip end portion of the shaft portion, and the mold includes a combination of a fixed mold and a movable mold. The structure in which the formed portion of the cutting edge groove is provided at the position of the lower half in the middle of the thread processing surface of any of the molds. When the self-tapping screw is rolled by the above-mentioned die, the thread is formed on the shaft portion of the screw material by the threaded surface of the two molds, and in the middle, the formed portion is the thread that breaks the thread and reaches the bottom of the shaft portion. When the cutting edge groove is machined, the forming portion is fixed in such a manner that the groove forming protrusion forming the groove processing surface has an inclination angle in the up and down direction, and the top of the groove forming protrusion protrudes from the thread processing surface of the mold, and the The molding portion is incorporated in a slit provided in the mold. Patent Document 3 is a rolling die for manufacturing a self-tapping screw in which one end of a shaft portion is a sharp tip and has a cutting groove for breaking a screw in the middle of the shaft portion, and the mold includes a combination of a fixed mold and a movable mold. The position of the rear end side of the thread processing surface of one of the molds is such that the forming portion of the cutting groove is formed in the rolling direction of the screw material. When the self-tapping screw is rolled by the above-mentioned die, the thread is formed on the shaft portion of the screw material by the threaded surface of the two molds, and in the end step, the molded portion is a cutting groove for cutting the thread, the aforementioned The forming portion is integrally provided with the mold body, or is embedded and fixed to the slit formed in the mold, and the cutting groove forming protrusion forming the cutting groove working surface is perpendicular in the up and down direction, and the cutting groove forming the top of the protrusion protrudes from the screw processing surface of the mold . Further, in the rolling of the self-tapping screw, in the case where the cutting edge groove and the cutting groove are rolled together with the screw of the screw body, the groove forming projection and the cutting groove are formed with respect to the shaft portion of the screw body. The protrusion is formed by forming a portion of the cutting edge groove and the cutting groove, and is crushed by pressing the screw material into the pressed portion. Therefore, the screw material of the portion flows upward and downward in the axial direction of the shaft portion. Forming a portion of the material of the shaft portion. [PRIOR ART DOCUMENT] [Patent Document 1] Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei.

[Problems to be Solved by the Invention] As described in Patent Documents 1 and 2, the tip end of the shaft portion is formed as a flat surface, and a self-tapping screw having a plurality of cutting edge grooves around the tip end portion of the shaft portion is rolled. In the mold, in order to secure a flat surface at the tip end of the shaft portion, the opposing threaded surface of the pair of molds has a structure in which the lower portion is liberated to be wide and the amount of gather of the shaft tip is reduced without being closed. Therefore, in the case where the cutting edge groove is rolled with respect to the shaft portion, the pressed screw material forming part of the cutting edge groove flows axially upward and downward on the shaft portion, since there is no mold closing at the tip end side of the shaft portion, Therefore, the flow toward the tip end side of the shaft portion of the screw material to be pressed is smooth, and therefore, the diameter expanding force due to the inflow of the screw material on the tip end side of the shaft portion can be dispersed toward the tip end side, and the cutting edge groove is formed. Since no excessive load is applied to the mold during rolling, the durability of the mold can be maintained and cracks can be prevented from occurring, so that a self-tapping screw having a cutting edge groove deeper than the bottom of the thread can be manufactured. On the other hand, in the rolling die of the self-tapping screw in which the one end of the shaft portion is a sharp tip, in order to form the sharp tip of the bullet shape, the pair of molds are configured such that the lower portions of the opposing threaded surface are formed as each other. The near-face configuration is approached with a slight gap, and the tip end side of the shaft portion is substantially closed and the flow of the screw material toward the tip is prevented from rolling. In the case of using a mold of such a configuration, in the case where a cutting groove deeper than the bottom of the screw is processed near the sharp tip of the shaft portion, the pressed screw material corresponding to the portion of the cutting groove flows to the upper portion of the cutting groove. And the lower part, but as described above, since the sharp tip end side of the shaft portion of the rolled screw body is closed by the mold so as not to extend toward the axial tip end side, the cutting groove of the screw material pressed is lower The flow toward the tip end of the shaft portion becomes difficult to lose the available inflow portion, and therefore, the screw material which is lower than the cutting groove flows toward the upper portion of the shaft portion. Further, the screw material that is located above the cutting groove flows toward the head side of the shaft portion, but the upper portion is sandwiched between the molds due to the cutting groove of the shaft portion, and the shaft portion and the screw are processed and rolled. Since it is pressed, it is difficult to absorb the screw material which is intended to flow toward the lower portion than the cutting groove on the upper side of the cutting groove. Therefore, in the portion where the sharp tip is formed by the lower portion of the die, the screw material intended to flow toward the tip side is required. The sharp tip is intended to be excessively expanded, thereby exerting excessive expansion force on the lower portion of the mold, thereby causing cracks in the mold, or forming defects in the vicinity of the sharp tip even if cracks are not generated. Further, since the upper portion of the threaded surface of the mold is opened, the inflow of the material from the cutting groove toward the head side is allowed, and in particular, the excessive force is not applied to the mold, but the intention is added to the tip. In the case where the laterally flowing screw material flows toward the head side, there is a problem that the final size of the entire length of the thread is greatly disturbed. Therefore, in the rolling using the mold of the self-tapping screw having a sharp tip, the cutting groove is simultaneously formed. In this case, it is necessary to suppress the generation of the flow amount toward the shaft portion of the screw material as much as possible. Therefore, as in Patent Document 3, it can be manufactured only on the screw, and the screw is provided to be shallower than the bottom. A self-tapping screw with a sharp tip at the cutting groove. Moreover, as described above, since the self-tapping screw having the cutting groove which is shallower than the bottom of the screw is only the middle of the broken screw, only the cutting function matching the sectional shape of the screw is screwed in. Only the part of the thread of the thread is cut, and since there is no function of discharging the generated chips, the chips are bitten between the wood member and the shaft portion and become a resistance element with respect to the screwing. The screwing is performed smoothly, or the purpose of preventing the crack of the wooden member is not sufficiently achieved. An object of the present invention is to provide a rolling die which can be manufactured by rolling a self-tapping screw which has a deeper cutting groove in the shaft portion than the valley portion, and can effectively perform cutting efficiency when screwing in. It is improved in the treatment of chips, and has a sharp tip that can sufficiently achieve the smoothing of the screwing and the generation of cracks in the wood member. [Technical means for solving the problem] In order to solve the above problems, the invention of claim 1 is a mold for rolling a self-tapping screw having a sharp tip at one end and a head at the other end The outer peripheral surface of the shaft portion is provided with a thread from the sharp tip toward the head side, and a depth is formed in the portion of the shaft portion where the thread is provided, and the thread is broken and reaches the valley of the thread. Cutting the groove, and the mold comprises a combination of a fixed mold and a movable mold, and a forming portion of the cutting groove is provided at a position on an end side of the thread processing surface of either of the molds, the forming portion being formed by the rolling direction of the screw material The groove processing portion is formed so as to be placed at a position on the head side of the screw material with respect to the groove processing portion, and a relief groove recessed with respect to the groove processing surface of the groove processing portion. According to a second aspect of the invention, the molding unit is configured such that the groove processing portion is disposed at a position of an upper portion and a lower portion of the mold, and the lower groove machining portion and the upper groove machining portion are vertically spaced apart from each other by a relief groove provided therebetween. Break. According to a third aspect of the invention, the groove processing portion of the forming portion has a height at which a groove forming a groove forming surface forms a protrusion protruding from a surface of the threaded surface of the mold. According to a fourth aspect of the invention, the groove processing surface of the groove processing portion is formed as an upward inclined portion, an intermediate flat portion, and a downward inclined portion from an upstream side to a downstream side with respect to a rolling direction of the screw material, and the upward inclined portion is set at 1 In the range of ～2.5°, the downward slope is set in the range of 2 to 4°. According to a fifth aspect of the invention, the length of the groove processing surface of the groove processing portion in the rolling direction of the screw material is set to be 1.5 to 2 times the length of the downward inclined portion when the length of the downward inclined portion is set to 1, The intermediate flat portion is set to a length of 2.4 to 3 times. According to the invention of claim 6, the width of the screw material along the axial direction of the undercut is set to be more than one pitch of the thread of the self-tapping screw of the rolling and not more than three pitches. According to a seventh aspect of the invention, the groove processing portion and the undercut groove are disposed relative to the die in a rolling direction from the screw material until the end of the final process, and the thread is processed at the rear end of the undercut groove. A finishing machine for threading is provided between the rear ends of the faces. Here, the fixed mold and the movable mold are disposed so as to face each other at a distance between the shaft portions of the machineable self-tapping screws, and the screw material of the two thread-finishing surfaces corresponds to the lower end portion of the tip end side. The shape of the sharp-pointed end can be formed in a state close to each other, and the thread-finishing surface is disposed in a state in which the portion for forming the thread into a specific diameter and the protrusion of the thread is alternately juxtaposed with the trough, And the protrusion and the trough are at a specific inclination angle in the rolling direction of the screw material. The groove processing surface of the groove processing portion is formed by juxtaposing the groove forming protrusions inclined at an angle steeper than the convex portion of the mold and the groove grooves alternately in the rolling direction of the screw material, the groove processing portion and the undercut groove having The shaft portion is rotated by a length of several weeks in the rolling direction of the screw material, and the groove machining portion is integrally formed with the undercut groove to form an angular block shape, and is disposed on the thread processing surface of the mold. The concave portion or the corner hole on the end side after the rolling direction is fixedly arranged, and the groove processing portion forms a breaking screw and reaches the screw material between the half after the thread is formed and until the final process is reached. A cutting groove that is recessed to the valley of the thread. [Effect of the Invention] According to the invention, in a mold for rolling a self-tapping screw having a sharp tip, a forming portion of the cutting groove is provided at a position on the end side after the threaded surface of the mold, and the forming portion is formed The groove machining portion is formed by the undercut groove provided at the position of the head portion of the screw which is rolled with respect to the groove machining portion, so that the groove portion is processed at the position of the sharp tip end by the shaft portion of the screw material. In the case of the cutting groove reaching the depth of the valley of the thread, the position of the head side of the cutting groove becomes the undercut groove with respect to the shaft portion, so that the groove can be ensured by the undercut when the groove is formed The portion where the pressing force is applied, and the pressed screw material can flow to the portion, thereby suppressing the flow of the material toward the sharp tip side without applying excessive pressure to the portion forming the sharp tip of the two molds, and Preventing the occurrence of cracks in the mold and the formation of sharp tips, and thus having a self-tapping screw that cuts the screw near the sharp tip and reaches the depth of the groove of the thread Rolling possible. Further, even if the machining groove reaches the depth which is recessed to the valley of the thread, the undercut of the shaft portion can efficiently prevent the flow of the crushed material in the portion where the rolling is not applied, thereby It is possible to suppress the occurrence of dimensional confusion with respect to the entire length of the shaft portion of the screw, and it is possible to roll a self-tapping screw having a sharp tip having excellent length accuracy. Further, by providing a finishing surface for the finishing thread between the rear end of the undercut and the rear end of the threaded surface of the die, even if the undercut causes the screw material to flow into the portion where the rolling is not applied, the The machined surface finally corrects the thread and the valley diameter corresponding to the portion of the undercut, and can roll a self-tapping screw having a sharp tip having improved dimensional accuracy of each portion and excellent quality.

The form of implementation of the present invention will be described below based on the drawings. Figure 1 shows an example of a self-tapping screw 1 having a sharp tip made by using the rolling die of the present invention, the shaft portion 2 having a specific length and diameter having a conical or bullet-shaped sharp tip 3 at one end, at the other end The head portion 4 is provided with a thread 5 in the outer peripheral surface of the shaft portion 2 from the sharp tip end 3 to the side of the head portion 4, and the thread 5 and the head portion 4 become the largest outer diameter of the thread 5 The threadless portion 7 having a slightly smaller diameter is in the middle of the portion of the shaft portion 2 where the thread 5 is provided, and the position close to the sharp tip 3 and the number of threads from the position toward the head portion 4 At two places away from the pitch, a cutting groove 6 is formed which is formed in the middle of the breaking screw 5 and reaches the valley portion 5a and recessed. In the case of the illustration, the screw 5 of the tapping screw 1 is set to be a double thread of a large-diameter screw and a small-diameter screw, and is disposed in a range from the sharp tip 3 toward the head 4 side, and In the portion of the sharp tip 3, the height is gradually decreasing toward the tip, but it is also possible to set the thread 5 to a single thread. The length of the cutting groove 6 in the axial direction of the shaft portion 2 is set to be 1 pitch or more and 3 pitches or less of the thread, and the longitudinal direction is opposite to the axial direction of the shaft portion 2, and the end portion on the head 4 side is opposed to each other. The screwing direction of the screw 5 is inclined at an angle of 1 to 25° after the screwing rotation, and further, the recessed depth with respect to the valley portion 5a is set to about 0.2 to 0.3 mm. 6 is arranged at equal intervals at three or four positions with respect to the circumferential direction of the shaft portion 2. When the length of the cutting groove 6 and the arrangement of the inclination angle, the depth, and the circumferential direction are set to be fastened by the self-tapping screw 1 for the fastening of the wooden member, the cutting efficiency and the cutting can be effectively obtained by screwing in. A preferred example derived from the conditions of the processing of the chips. Fig. 2 shows a die 11 for rolling the above-mentioned tapping screw 1, which is composed of a combination of a fixed die 11a and a movable die 11b which are formed in a rectangular shape in which the screw material is rolled, and a shaft portion of a rolling screw is provided. The thread-finishing surface 12 of the two oppositely opposed to each other is provided in a state in which the projections 12a and the troughs 12b of the troughs 5 and the troughs 5a are alternately arranged in parallel, and the projections 12a have a shape for forming The top of the valley portion 5a has a flat trapezoidal cross-sectional shape, and the adjacent groove portion 12a is a V-shaped groove 12b of the forming screw 5, and the projection portion 12a and the valley groove 12b are lowered in the rolling direction of the screw material. The specific tilt angle. Further, in the fixed mold 11a and the movable mold 11b, the position of the lower portion of the thread processing surface 12 is as shown in Fig. 2(b), and the full length of the taper screw 1 is formed to face the sharp end of the tapping screw 1 The side is raised to form an approaching portion 13 for bringing the fixed mold 11a into close contact with the threaded surface 12 of the movable mold 11b, and the lower end portion of the threaded surface 12a and the lower end of the groove 12b is curved. The thread is moved to the approaching portion 13, and the thread 5 can be machined at the tip end of the shaft portion 2 at the sharp tip 3 and its outer peripheral surface. Another mold, shown in the fixed mold 11a, is provided with a groove forming portion 14 of the cutting groove 6 at the end side of the thread processing surface 12, half after the formation of the thread with respect to the screw material until now Between the front and the end of the process, a cutting groove 6 is formed which breaks the thread 5 and reaches the valley portion 5a and is recessed. The groove forming portion 14 is formed by a groove processing portion 15 disposed at a position close to the sharp tip 3 of the shaft portion 2 along a rolling direction of the screw material of the thread processing surface 12; The processing portion 15 is disposed side by side on the head portion 4 side of the screw material, and is recessed into the undercut groove 16 with respect to the groove processing surface 15a of the groove processing portion 15; and is disposed at the head of the screw material with respect to the undercut groove 16 The groove processing portion 17 at the upper portion on the side of the portion 4; and the groove processing portion 15 formed at the lower portion and the groove processing portion 17 at the upper portion are disposed apart from each other in the axial direction of the screw material with the undercut groove 16 interposed therebetween. The groove processing portions 15 and 17 and the undercut groove 16 therebetween are integrally formed of the same material and have an angular shape as a whole, and are housed in the concave portion or the corner hole provided at the rear portion with respect to the fixed mold 11a. The state in the 18 is fixed, and the recessed portion or the corner hole 18 suppresses the occurrence of the strength reduction of the fixed mold 11a by retaining a portion of the fixed mold 11a on the rear end side. The groove forming projections 19 of the groove-finished portions 15 and 17 of the groove forming portion 14 have a trapezoidal shape having the same trapezoidal shape or a circular arc at the top as the projection portion 12a, and are inclined with respect to the upper and lower directions of the fixed mold 11a. The top of the 19 has a height protruding from the thread processing surface 12 of the fixed mold 11a, and the protruding height determines the depth with respect to the valley portion 5a of the cutting groove 6. As shown in FIG. 2(c), the groove-finished surfaces 15a and 17a are formed as an upward inclined portion a, an intermediate flat portion b, and a downward inclined portion c from the upstream side to the downstream side with respect to the rolling direction of the screw material, and The upstream inclined portion a is set in the range of 1 to 2.5 degrees, the intermediate flat portion b is parallel to the rolling direction of the screw material, and the downward inclined portion c is in the range of 2 to 4 degrees, and the beginning and the downward direction of the upward inclined portion a are set. The rear end of the inclined portion c coincides with the thread processing surface 12 of the fixed mold 11a. Further, when the length of the grooved surface 15a, 17a in the rolling direction of the screw material is set to 1 in the length of the downward inclined portion c, the upward inclined portion a is set to have a length of 1.5 to 2 times, and the intermediate flat portion is formed. b is set to be 2.4 to 3 times the length. By setting such a condition from the upstream side to the downstream side, the impact of the press-in screw material at the time of formation of the cutting groove 6 caused by the groove forming projection 19 can be alleviated, and the groove forming portion 14 and the fixed mold can be made. The generation of the load of 11a has been alleviated. Further, the width of the screw material along the axial direction of the undercut groove 16 is set to be more than one pitch of the thread 5 of the self-tapping screw 1 of the rolling and is less than 3 pitches, and the surface height of the undercut groove 16 is set. In order to be the same as or lower than the groove 12b of the thread processing surface 12 of the fixed mold 11a, when the shaft portion of the screw material passes through the groove forming portion 14, the thread formed on the threaded surface 12 of the mold 11 is made 5 Without deformation or damage, and the rolling pressure of the die 11 is not applied to the portion facing the undercut groove 16 of the shaft portion 2, when the groove forming projection 19 bites into the shaft portion 2, it faces the shaft portion 2 The flow of the screw material of the portion of the sipe 16 is facilitated, reducing the amount of flow of the screw material toward the sharp tip 3, thereby not applying excessive pressure to portions of the sharp tips 3 forming the two dies 11a and 11b, thereby improving the dies 11a. The durability of 11b and the prevention of cracks and the formation of the sharp tip 3 are poor. In the case of the illustration, the tapping screw 1 is shown as being formed at the position of the sharp tip 3 side and the head 4 side at a position away from the pitch of 1 to 3 of the thread, and the self-tapping screw 1 is rolled. The die 11 shows an example in which the groove forming portion 14 is disposed such that the groove processing portions 15 and 17 are separated in the axial direction of the screw material with the undercut groove 16 interposed therebetween, but the tapping screw 1 may be only sharply close. The position of one of the tips 3 forms the cutting groove 6. When the self-tapping screw 1 is rolled, the groove forming portion 14 provided in the mold omits the groove processing portion 17 of the upper portion of Fig. 2(a) as long as it includes the lower portion. The groove processing portion 15 and the undercut groove 16 may be configured. With respect to the groove processing portion 15 of the lower portion, the undercut groove 16 is located on the side of the head portion 4 of the portion where the cutting groove 6 is machined with respect to the shaft portion 2 of the screw material, due to the intention Since the rolling pressure of the die 11 is not applied to the portion of the shaft portion 2, the tapping screw 1 having the cutting edge 6 having the sharp tip 3 and recessed to the depth of the valley portion 5a can be rolled by the die 11 in the same manner as described above. The groove processing portions 15, 17 and the undercut groove 16 are disposed relative to the threaded surface 12 of the die 11 between the second half of the rolling direction of the screw material and immediately before the final process, at the rear end of the undercut 16 A finishing surface 20 for finishing is provided between the rear end of the thread processing surface 12 of the mold 11, and the threading surface 20 for finishing is extended by the projection 12a and the groove 12b of the thread processing surface 12. The arrangement is retained, and the portion 5 passing through the portion of the undercut groove 16 and the thread 5 are corrected by the shaft portion 2 of the screw material. The mold 11 of the present invention is configured as described above, and a screw material for which the head portion 4 is previously processed is supplied between the fixed mold 11a and the movable mold 11b in a state where the movable mold 11b is at the retracted position. When the movable mold 11b is moved to the advanced position, the shaft portion 2 of the screw material sandwiched between the two molds 11a and 11b is rolled while being rolled on the thread-machined surface 12 of the two molds 11a and 11b, and is gathered by the valley portion 5a. A part of the material flows into the trough 12b to form the thread 5, and together with this, the tip end side of the shaft portion 2 gathers at the lower portion of the thread processing surface 12, gradually forming the sharp tip 3. In addition, the same reference numerals as those of the completed tapping screw 1 are described in the shaft portion, the screw, the cutting groove, and the like which are gradually formed in the middle of the rolling process. When the processing of the screw 5 of the screw material is close to the second half, the shaft portion 2 of the screw material enters the groove forming portion 14 while rolling, and the groove processing portion 15 and the upper portion are formed during the movement toward the rear end of the fixed mold 11a. The groove forming projections 19 of the groove processing faces 15a and 17a of the groove processing portion 17 bite into the shaft portion 2 and are crushed to form a cutting groove 6 which is deeper than the valley portion 5a in the middle of the breaking screw 5. The groove processing portions 15 and 17 form a groove forming surface 15a, 17a. The top of the groove forming projection 19 has a height protruding from the thread processing surface 12 of the fixed mold 11a, since the groove processing surface 15a, 17a is along the screw material. Since the rolling direction is formed from the upstream side to the downstream side as the upward inclined portion a, the intermediate flat portion b, and the downward inclined portion c, the upward inclined portion a can be used to start the biting of the thread 5 of the groove processing surfaces 15a and 17a. The impact is moderated and the thread 5 is broken. Secondly, the intermediate flat portion b forms a deeper cutting groove 6 than the valley portion 5a at the portion where the thread 5 is broken. Finally, the groove is formed by the downward inclined portion c. 19 is away from the cutting groove 6, so that the cutting groove 6 is gradually formed smoothly and with high precision. As described above, when the cutting groove 6 of the groove forming portion 14 is formed toward the cutting groove 6 of the shaft portion 2, the shaft portion 2 is formed by the groove forming portion 14 being pressed by the two molds 11a, 11b to continue the sharp tip 3 and the thread 5 In such a state, as described above, when the groove forming portion 19 of the groove processing portion 15 and the upper groove processing portion 17 bites into the shaft portion 2, the press-fitting portion of the screw material flows in the axial direction. At this time, since the groove forming portion 14 is provided with the undercut groove 16 between the groove processing portions 15 and 17, it is adjacent to the shaft portion 2 at a position where the cutting groove 6 is formed and is not rolled by the two molds 11a, 11b. Because of the pressure, the flow of the pressing screw material toward the portion of the shaft portion 2 facing the undercut groove 16 is facilitated, whereby the formation of the cutting groove 6 by the groove forming portion 14 can be reduced. The amount of flow on the sharp tip end 3 side of the shaft portion 2 of the screw material, whereby excessive pressure is not applied to the two molds 11a, 11b in the forming process of the sharp tip 3, so that cracks of the two molds 11a, 11b can be prevented. Produces and produces a poor forming of the sharp tip 3. Further, in the formation of the cutting groove 6 in the middle of the shaft portion 2 by the upper groove processing portion 17, the head portion 4 is rolled by the two molds 11a and 11b by the cutting groove 6, so that the shaft portion 2 is moved toward the shaft portion 2 The flow of the screw material facing the portion of the undercut 16 is facilitated, and the amount of inflow of the screw material toward the head portion 4 side of the shaft portion 2 can be reduced. Therefore, variation in the length dimension of the shaft portion 2 can be suppressed. Further, in the second half of the rolling process of the forming of the thread 5 of the mold 11, the groove forming portion 14 provided in the fixed mold 11a is snail with respect to the portion facing the undercut groove 16 between the cutting groove 6 and the same The tooth 5 is formed only by the movable mold 11b. However, since the material is inflowed in the portion of the shaft portion 2 facing the undercut groove 16, the thread 5 facing the undercut portion 16 can be formed to be substantially the same as the other portion. The same height. Further, in the formation of the cutting groove 6 of the groove forming portion 14, in the case where the groove processing portions 15 and 17 are processed to the depth of the concave valley portion 5a, the groove processing is performed for the thread processing surface 12 of the fixed mold 11a. Since the groove processing surfaces 15a and 17a of the portions 15 and 17 become high, there is a fear that a large load is applied to the groove forming portion 14 when the thread 5 enters the groove processing portions 15 and 17. On the other hand, in the present invention, the groove processing faces 15a, 17a of the groove processing portions 15 and 17 are from the upstream side to the downstream side with respect to the rolling direction of the screw material, by the upward inclined portion a and the intermediate flat portion b and down The inclined portion c is formed in a trapezoidal shape, whereby the occurrence of an impact when the shaft portion 2 is entered due to the upward inclined portion a can be alleviated, and the occurrence of cracks or the like of the groove forming portion 14 can be reduced, and the threaded portion 5 is formed from the groove forming portion. When the 14 is far away, the downward inclined portion c is formed, so that the thread 5 can be prevented from biting into the mold 11. Further, the finishing machined surface 20 provided between the rear end of the undercut groove 16 and the rear end of the threaded surface 12 of the die 11a can be used even if the undercut 16 causes the screw material to flow into the portion where the rolling is not applied. The diameter of the thread 5 and the valley portion 5a corresponding to the portion of the undercut 16 is finally corrected by the processing surface 20. As shown in FIG. 1, the self-tapping screw 1 which has been discharged from the end side of the above-described fixed mold 11a has a sharp tip 3 at one end of the shaft portion 2 and a head portion 4 at the other end, on the outer peripheral surface of the shaft portion 2, At a position close to the sharp tip 3 of the portion provided with the thread 5 and at a position away from the position at the head 4 side by the number of threads of the thread, there is formed a broken thread 5 and arrives halfway. The configuration of the cutting groove 6 to the depth of the valley portion 5a. In the self-tapping screw 1 as described above, the precision of the screwing position and the screwing property at the initial stage of screwing are improved by the sharp tip 3, and the cutting groove 6 provided in the middle of the thread 5 is the breaking screw 5 and is recessed into the valley portion 5a. The depth is such that the portion of the split screw 5 is turned into a blade edge after the screwing rotation, and the screwing portion of the thread 5 is cut when screwing into the wood member, and the screwing of the portion of the recessed valley portion 5a is rotated. After that, the square edge becomes the cutting edge and the cutting portion of the cutting shaft portion 2 is cut. Therefore, the cutting amount can be increased, and the cutting groove 6 can accommodate the cutting chips, thereby suppressing the biting of the cutting chips between the wooden member and the tapping screw 1. The resulting screwing resistance increases. Further, the longitudinal direction of the cutting groove 6 is inclined with respect to the axial direction of the shaft portion 2, and the length thereof is set to be one pitch or more and three pitches or less of the thread 5, and if the length is one pitch or less, a sufficient amount cannot be accommodated. Further, if the length is 3 pitch or more, the amount of inflow of the material facing the portion of the shaft portion 2 facing the undercut 16 is reduced, and the height of the screw 5 near the center of the portion can be prevented from being lowered. . As described above, the self-tapping screw 1 manufactured by the mold 11 of the invention is formed by the sharp tip 3 and the cutting groove 6 which is formed to cut the thread 5 at the shaft portion 2 and reach the valley portion 5a and is recessed to the depth. By multiplying the effect, the screwing can be smoothly entered and the cracking of the wooden member can be effectively prevented.

1‧‧‧ Self-tapping screws

2‧‧‧Axis

3‧‧‧ sharp tip

4‧‧‧ head

5‧‧‧ threaded teeth

5a‧‧‧谷部

6‧‧‧Cutting trough

7‧‧‧No thread

11‧‧

11a‧‧‧Fixed mode

11b‧‧‧Moving mode

12‧‧‧ threaded surface

12a‧‧‧Protruding

12b‧‧‧谷槽

13‧‧‧Access Department

14‧‧‧Slot forming department

15‧‧‧Slot processing section

15a‧‧‧Slot processing surface

16‧‧‧Unslot

17‧‧‧Slot processing section

17a‧‧‧Slot processing surface

18‧‧‧ corner hole

19‧‧‧ grooves forming protrusions

20‧‧‧Machining surface for finishing

A‧‧‧ arrow

B‧‧‧ arrow

C‧‧‧arrow

Figure 1 (a) is a front view of a self-tapping screw having a sharp tip made using the mold of the present invention, and Figure 1 (b) is an enlarged cross-sectional view of the arrow b-b of Figure 1 (a). Figure 2 (a) is a front view showing a mold of the mold of the present invention, Figure 2 (b) is an enlarged longitudinal sectional side view of the arrow b-b of Figure 2 (a), Figure 2 (c) is Figure 2 (a) An enlarged cross-sectional view of the arrow c-c.

Claims (7)

A rolling die for a self-tapping screw for rolling a self-tapping screw having a sharp tip at one end and a peripheral portion having a shaft portion at the other end, from a sharp tip toward the head side a thread is provided, and a cutting groove is formed in the middle of the portion of the shaft portion where the thread is provided, and the cutting thread is formed to reach a depth of the valley of the thread, and the mold includes a combination of a fixed mold and a moving mold. a forming portion of the cutting groove provided at a position on an end side of the thread processing surface of either of the molds, the forming portion being juxtaposed with the groove processing portion by a groove processing portion disposed along a rolling direction of the screw material It is formed at the position of the head side of the screw material, and is formed in the undercut groove which is recessed with respect to the groove processing surface of the groove processing part. The rolling die of the self-tapping screw of claim 1, wherein the forming portion has a configuration in which the groove processing portion is disposed at an upper portion and a lower portion of the mold, and the lower groove processing portion and the upper groove processing portion are disposed therebetween. The squeezing groove is separated between the upper and lower sides. The rolling die of the self-tapping screw of claim 1 or 2, wherein the groove-finishing portion of the forming portion has a height at which the groove forming the groove-forming surface forms a protrusion protruding from the die-machined surface of the mold. The rolling die of the tapping screw according to any one of claims 1 to 3, wherein the groove processing surface of the groove processing portion is formed as an upward inclined portion and an intermediate portion from the upstream side to the downstream side in a rolling direction with respect to the screw material. In the flat portion and the downward inclined portion, the upward inclined portion is set in a range of 1 to 2.5 degrees, and the downward inclined portion is set in a range of 2 to 4 degrees. The rolling die of the tapping screw of claim 3, wherein the length of the groove processing surface of the groove processing portion along the rolling direction of the screw material is set to 1 in the case where the length of the downward inclined portion is set to 1, the upward inclined portion is set The length of the intermediate flat portion is set to be 2.4 to 3 times the length of 1.5 to 2 times. The rolling die of the tapping screw according to any one of claims 1 to 5, wherein a width of an axial direction of the screw material along the undercut is set to be more than one pitch of the thread of the self-tapping screw of the rolling and Less than 3 pitches. The rolling die of the tapping screw according to any one of claims 1 to 6, wherein the groove processing portion and the undercut are disposed relative to the die half after the rolling direction of the screw material until the final process is reached. A finishing machined surface is provided between the rear end of the undercut and the rear end of the threaded surface of the die.