JP2018187674A - Rolling die for self-drilling screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling die for a self-drilling screw which can smoothly perform screwing-in and can effectively prevent crack occurrence in a woody member.SOLUTION: A die 11 for rolling a self-drilling screw in which on a portion provided with a thread of a shank having a sharp tip at one end and a head at the other end, a cut groove having a depth reaching a valley part of the thread is so formed as to divide the thread. In this die, a groove molding part 14 for the cut groove is provided at a position on a rear end side of a thread processed face 12 in a stationery die 11a, and this groove molding part 14 is formed from: a groove processing part 15 which is located along a rolling direction of a screw material; and a relief groove 16 which is located at a position on a head 4 side of the screw material in parallel to the groove processing part 15, and is reentrant in a groove processed face 15a of the groove processing part 15.SELECTED DRAWING: Figure 2

Description

  The present invention has a sharp tip at one end of the shaft portion and a head at the other end, and a thread is provided on the outer peripheral surface of the shaft portion from the sharp tip to the head side. The present invention relates to a self-drilling screw rolling die in which a cutting groove having a depth reaching a trough portion of the thread is formed by dividing the thread in the middle of the provided portion.

  For example, in the screw used to fasten the wooden member, on the outer peripheral surface of the shaft portion with one end pointed, a thread is provided from the pointed tip toward the head side, and at the tip side or midway position of this shaft portion, Cutting grooves for cutting wood members and cutting grooves for cutting threads are formed, and the penetration of the sharp tip and the cutting action of the cutting blade grooves and cutting grooves enable smooth screwing and prevent cracking of the wooden members. Self-drilling screws that are capable are known.

  In addition, a self-drilling screw having a flat end on the shaft portion with respect to the self-drilling screw having the sharp tip as described above has also been proposed. There is an inconvenience that a hole must be drilled. On the other hand, a self-drilling screw having a pointed tip can be directly screwed into a wooden member and is frequently used because it is excellent in workability at the time of fastening.

  The manufacture of the self-drilling screw as described above is generally performed by rolling using a die from the viewpoint of mass productivity. However, a method for forming a cutting edge groove or a cutting groove in the self-drilling screw includes a screw. There is a cutting process that is performed after rolling the main body and a rolling process that is performed simultaneously during the rolling process of the screw body. The former cutting process requires additional cutting equipment, and additional processing time due to an increase in the number of processes. Therefore, the cost of the product is increased, and for this reason, the latter form of rolling, which can solve the problems of cutting, has become the mainstream (see, for example, Patent Documents 1 to 3).

  Patent Documents 1 and 2 are rolling dies for manufacturing a self-drilling screw having a plurality of cutting edge grooves around the tip portion of the shaft portion, and the die is a fixed die. It consists of a combination of moving dies, and has a structure in which a forming part of the cutting edge groove is provided at the position of the lower half part in the middle of the thread machining surface of one of the dies.

  When a self-drilling screw is rolled with the above-mentioned die, a screw thread is formed on the shaft portion of the screw material on the thread machining surface of both dies, and the formed portion divides the screw thread in the middle to reach the bottom of the shaft portion. Now, the cutting edge groove is machined, and in this molded part, the groove forming projection forming the groove machining surface has an inclination angle in the vertical direction, and the top of the groove forming projection protrudes from the thread machining surface of the die. As shown, it is fixed so that it fits into a notch provided in the die.

  Patent Document 3 is a rolling die for producing a self-drilling screw having a cutting groove that cuts a screw thread in the middle of the shaft portion, and the die is a fixed die and a moving die. The cutting groove forming portion is provided along the rolling direction of the screw material at a position on the rear end side of the thread machining surface of one of the dies.

When the self-drilling screw is rolled with the above dies, a thread is formed on the shaft part of the thread material at the thread machining surface of both dies, and the formed part cuts the thread that cuts the thread in the final process. The forming portion is provided integrally with the die body, or is fitted into and fixed to a notch formed in the die, and a cutting groove forming projection forming a cutting groove processing surface is perpendicular to the vertical direction. The top of the forming protrusion protrudes from the threaded surface of the die.

By the way, in rolling the self-drilling screw, when rolling a cutting edge groove or a cutting groove together with a thread on the screw body, a portion where the cutting edge groove or the cutting groove is to be formed is formed on the shaft portion of the screw body. Because the screw material is pushed in and crushed in the pushed part, the screw material in that part flows in the vertical axis direction of the shaft part. Part of the material to be formed.

JP 59-126107 A JP-A-6-277778 Japanese Utility Model Publication No. 1-143646

  By the way, in a rolling die for manufacturing a self-drilling screw having a plurality of cutting edge grooves around the tip portion of the shaft portion, the tip portion of the shaft portion is formed in a flat surface as in Patent Documents 1 and 2. In order to ensure a flat surface at the tip of the part, the threaded surface of the pair of dies facing each other has a structure in which the lower part is widely opened and the amount of squeezing at the tip of the shaft part is reduced to prevent confinement.

For this reason, when the cutting edge groove is rolled with respect to the shaft portion, the screw material that is pushed into the portion that forms the cutting blade groove flows in the vertical axis direction of the shaft portion. In this case, since there is no confinement by the die, the flow of the screw material pushed in toward the tip end side of the shaft portion is smooth, and therefore, the diameter expansion force generated by the flow of the screw material on the tip end portion of the shaft portion is moved to the tip side. Can be escaped and does not put excessive load on the die when rolling the cutting groove, thus maintaining the durability of the die and preventing cracking, cutting groove deeper than the bottom of the thread valley A self-drilling screw having the following can be manufactured.

On the other hand, in a self-drilling screw rolling die in which one end of the shaft portion is a sharp tip, a pair of dies has a lower portion of the opposed thread processing surface to form a bullet-shaped sharp tip. It is formed in the structure of the approaching surfaces that are close to each other through a slight gap, and is substantially confined at the tip side of the shaft portion to prevent the thread material from flowing toward the tip and roll it. .

When a cutting groove deeper than the bottom of the screw thread is machined at a position near the sharp tip of the shaft with a die having such a structure, the screw material that is pushed into the part corresponding to the cutting groove is the upper part of the cutting groove. Although it flows to the lower part, as described above, the sharp tip end side of the shaft portion in the rolled screw body is confined with a die so as not to extend to the tip end side in the axial direction. The portion below the cutting groove is difficult to flow toward the tip of the shaft portion and loses a clearance, so that the screw material below the cutting groove tends to flow upward.

In addition, the screw material above the cutting groove flows to the head side of the shaft part, but the upper part from the cutting groove of the shaft part is sandwiched by dies, and the shaft part and the thread are processed and rolled. It is difficult to absorb the screw material that flows below the cutting groove to the upper side from the cutting groove. For this reason, in the part where the sharp tip is formed at the lower part of the die, the screw that tends to flow to the tip side. Depending on the material, the tip of the sharp tip tries to expand excessively, which causes an excessive spread force at the bottom of the die, which causes the die to crack, or even if it does not break, the molding near the sharp tip is poor. .

Furthermore, since the upper part of the threaded surface facing the die is in an open state, escape of the material from the cutting groove to the head side is allowed, and in particular, no excessive force is applied to the die. If the screw material that is about to flow to the tip side is added to the escape to the head side, there is a problem that the finished dimension of the entire length of the screw is greatly deviated. For this reason, a self-drilling screw having a sharp tip In the case of forming the cutting groove at the same time in the rolling using the die of this type, it is necessary to suppress the generation of the flow amount of the screw material to the shaft portion as much as possible. Only self-drilling screws with pointed tips with cutting grooves shallower than the valley bottom could be produced to divide the mountain.

Incidentally, as described above, the self-drilling screw provided with a cutting groove shallower than the bottom of the valley in the screw thread is merely a part of the thread, so it only has a cutting function that matches the cross-sectional shape of the screw thread. In addition, only the part of the screw thread trajectory is cut when screwing, and since there is no escape function of the generated cutting waste, the cutting waste bites between the wooden member and the shaft part and becomes a resistance element against screwing. The purpose of smoothing the screwing or preventing the wood member from cracking cannot be sufficiently achieved.

  Therefore, the object of the present invention is to have a cutting groove deeper than the trough in the shaft part, to improve the cutting efficiency at the time of screwing and to effectively handle the cutting waste, to facilitate the screwing and to prevent the cracking of the wooden member It is an object of the present invention to provide a rolling die that can be manufactured by rolling a self-drilling screw having a sharp tip that can sufficiently achieve the above.

  In order to solve the above problems, the invention of claim 1 is provided with a thread on the outer peripheral surface of the shaft portion having a sharp tip at one end and a head at the other end from the sharp tip toward the head side, A die for rolling a self-drilling screw in which a cutting groove having a depth reaching the valley of the thread is formed by dividing the thread in the middle of the part where the thread is provided in the shaft part, The die is a combination of a fixed die and a moving die, and a forming portion of the cutting groove is provided at a position on the rear end side of the thread machining surface of one of the dies, and this forming portion is arranged in the rolling direction of the screw material. A grooved portion disposed along the grooved portion and a relief groove that is arranged in parallel at a position on the head side of the screw material with respect to the grooved portion and is recessed with respect to the grooved surface of the grooved portion. It is what I did.

According to a second aspect of the present invention, the forming portion is divided into upper and lower portions with the grooved portion provided at the upper and lower positions of the die, and the lower grooved portion and the upper grooved portion sandwiching the relief groove provided therebetween. It is something that has been arranged.

According to a third aspect of the present invention, the groove processing portion of the molding portion has a height at which the top of the groove forming projection forming the groove processing surface protrudes from the thread processing surface of the die. .

According to a fourth aspect of the present invention, the groove processing surface of the groove processing portion is formed in an upward inclined portion, an intermediate flat portion, and a downward inclined portion from the upstream side to the downstream side with respect to the rolling direction of the screw material, The ascending slope is set in the range of 1 to 2.5 °, and the descending slope is set in the range of 2 to 4 °.

The invention according to claim 5 is that the length along the rolling direction of the screw material on the grooved surface of the grooved portion is 1.5 to 2 times the upward inclined portion when the length of the downward inclined portion is 1. The length of the intermediate flat part is set to 2.4 to 3 times the length.

In the invention of claim 6, the width along the axial direction of the screw material of the escape groove is set to be 1 pitch or more and less than 3 pitches of the thread in the self-drilling screw to be rolled.

According to a seventh aspect of the present invention, the grooved portion and the relief groove are arranged between the latter half of the rolling direction of the screw material with respect to the die and immediately before the final process, and the rear end of the relief groove and the screw thread of the die. A finishing thread machining surface is provided between the rear end of the machining surface.

  Here, the fixed die and the moving die are arranged so that the respective thread machining surfaces face each other at an interval at which the shaft portion of the self-drilling screw can be machined, and the tip side of the screw material on both screw machining surfaces The lower part corresponding to is shaped so as to be close to each other so that the pointed tip can be formed, and this threaded surface is formed with a protrusion and a trough for finishing the valley to a predetermined diameter to form the thread Are provided in a state of being alternately arranged in parallel, and the protrusion and the trough have a predetermined inclination angle in the rolling direction of the screw material.

  The groove machining surface of the groove machining part is formed by alternately arranging groove forming protrusions and valley grooves inclined at a steeper angle than the protrusion part of the die along the rolling direction of the screw material. The escape groove has a length such that the shaft portion rotates several times along the rolling direction of the screw material, and the groove processing portion and the escape groove are formed integrally to form a square block, while the thread machining surface in the die In the rolling direction, it is fixedly placed so that it fits in the recess or square hole provided on the rear end side of the rolling direction, and the groove processing part passes through the second half of the thread formation with respect to the screw material and immediately before the final process. Then, the thread is divided to form a cutting groove having a depth that reaches the valley of the thread and is recessed.

  According to the present invention, in a die for rolling a self-drilling screw having a sharp tip, a cutting groove forming portion is provided at a position on the rear end side of the thread machining surface of the die, and this forming portion is defined as a groove processing portion. Since it is formed by the escape groove provided at the position on the head side of the screw to be rolled with respect to the groove processed portion, the shaft portion of the screw material is sharpened at the position on the tip end side and at the groove root portion at the groove processed portion. When machining a cutting groove with a depth that reaches, the position on the head side of the cutting groove with respect to the shaft portion is an escape groove, so that when the groove is formed, the portion where the pressing pressure is not applied to the shaft portion by the escape groove Since the screw material that is pushed in can flow into this part, the flow of material to the sharp tip side is suppressed, and excessive pressure is not applied to the part forming the sharp tip of both dies. Cracking and sharpness It is possible to prevent the occurrence of defective molding at the end, and to roll a self-drilling screw with a cutting groove that has a depth that reaches the trough of this thread and is recessed by cutting the thread near the sharp tip. become.

  In addition, even if a cutting groove having a depth that reaches the valley of the thread and is recessed is processed, the flow of the crushed material can be efficiently stopped at the portion where no rolling pressure is applied by the relief groove of the shaft part. Thus, it is possible to roll a self-drilling screw having a sharp tip with excellent length accuracy while suppressing the occurrence of dimensional deviation with respect to the entire length of the shaft portion of the screw.

  Furthermore, by providing a finishing threaded surface between the rear end of the relief groove and the rear end of the screw threading surface of the die, even if the screw material flows to the part where no rolling pressure is applied by the relief groove. The thread and valley diameter of the part corresponding to the relief groove can be finally corrected on the machining surface, and the self-drilling screw having a sharp tip with improved quality is improved by improving the dimensional accuracy of each part. be able to.

(A) is a front view of the self-drilling screw which has the sharp tip manufactured with the die | dye which concerns on this invention, (b) is an expanded cross-sectional view in the arrow bb of (a). (A) is a front view showing one die of the die according to the present invention, (b) is an enlarged vertical side view taken along arrow bb in (a), and (c) is taken along arrow cc in (a). Enlarged cross section

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an example of a self-drilling screw 1 having a pointed tip which is manufactured by the rolling die of the present invention, and a shaft part 2 having a predetermined length and diameter has a conical or bullet-shaped pointed tip 3 at one end. And a head 4 at the other end, and a screw thread 5 is provided in the middle of the head 4 side from the sharp tip 3 on the outer peripheral surface of the shaft portion 2, and a screw thread 5 is connected between the screw head 5 and the head 4. The unthreaded portion 7 has a slightly smaller diameter than the maximum outer diameter of the ridge 5, and in the middle of the portion of the shaft portion 2 where the ridge 5 is provided, a position close to the sharp tip 3 and from this position toward the head 4 side. Cutting grooves 6 having a depth that divides in the middle of the screw thread 5 to reach the trough 5a and is recessed are formed at two positions that are separated by several pitches of the screw thread.

In the case of illustration, the thread 5 of the self-drilling screw 1 is a double thread of a large-diameter thread and a small-diameter thread, and is provided in the middle of the sharp tip 3 on the head 4 side. However, the thread 5 may be a single thread.

The length of the cutting groove 6 along the axial direction of the shaft portion 2 is set to be 1 pitch or more and 3 pitch or less of the thread, and the length direction is the head 4 with respect to the axial direction of the shaft portion 2. The side end portion is inclined at an angle in the range of 1 to 25 ° so as to be located behind the screwing rotation direction with respect to the screwing rotation direction of the screw thread 5, and the recess depth with respect to the valley portion 5 a is 0.2. The cutting grooves 6 are arranged at equal intervals at three or four positions with respect to the circumferential direction of the shaft portion 2.

Such setting of the length, inclination angle, depth, and circumferential arrangement number of the cutting grooves 6 can be achieved by improving the cutting efficiency when screwing the wood member with the self-drilling screw 1 and processing the cutting waste. Is a preferred example derived from the conditions that can be effectively obtained.

FIG. 2 shows a die 11 for rolling the self-drilling screw 1. The die 11 is composed of a combination of a fixed die 11a and a moving die 11b that are long rectangles in the rolling direction of the screw material. Both thread processing surfaces 12 that are opposed to each other with an interval for rolling the shaft portion 2 are provided in a state in which the protrusions 12a and the valley grooves 12b forming the thread 5 and the valley 5a are alternately arranged in parallel, The protrusion 12a has a trapezoidal cross-sectional shape with a flat top for forming the valley 5a, and a gap between the adjacent protrusions 12a becomes a V-shaped valley groove 12b for forming the screw thread 5. The part 12a and the trough groove 12b have a predetermined inclination angle that falls along the rolling direction of the screw material.

Further, in the fixed die 11a and the moving die 11b, the lower position of the thread machining surface 12 forms the sharp tip 3 of the self-drilling screw 1 as shown in FIG. Is raised to the mating die side and becomes an approaching portion 13 for bringing the threading surface 12 of the fixed die 11a and the moving die 11b close to each other, and the lower portion of the threading surface 12 is formed by a protrusion 12a and a valley groove 12b. The lower end moves in an arc shape to the approaching portion 13, and the tip portion 3 is sharpened at the tip end and the thread 5 can be processed on the outer peripheral surface thereof.

One die, in the illustrated case, a fixed die 11a, is provided with a groove forming portion 14 of the cutting groove 6 at a position on the rear end side of the thread machining surface 12, and the final stage from the latter half of the thread formation to the screw material. Immediately before, the thread 5 is divided to reach the trough 5a to form a groove 6 having a depth to be recessed.

The groove forming portion 14 has a groove processing portion 15 disposed at a position near the sharp tip 3 with respect to the shaft portion 2 along the rolling direction of the thread material of the thread processing surface 12, and the groove processing portion 15. A relief groove 16 that is arranged in parallel at a position on the head 4 side of the screw material and is recessed with respect to the groove machining surface 15a in the groove machining portion 15, and a position on the head 4 side of the screw material with respect to the relief groove 16 The lower grooved portion 15 and the upper grooved portion 17 are separated in the axial direction of the screw material with the escape groove 16 interposed therebetween.

The groove processed portions 15 and 17 and the relief groove 16 therebetween are integrally formed from the same material to form a square block shape as a whole, and a recessed portion or a square hole 18 provided at the rear portion of the fixed die 11a. The recessed portion or the square hole 18 is fixed in a state in which it fits inside, so that a part of the fixed die 11a is left on the rear end side, thereby suppressing a decrease in strength of the fixed die 11a.

  The groove forming protrusions 19 of the groove processed portions 15 and 17 in the groove forming portion 14 have a trapezoidal shape in the cross section similar to the protrusion portion 12a and a mountain shape with an arc at the top, and are inclined with respect to the vertical direction of the fixed die 11a. The top of the groove forming projection 19 has a height protruding from the threaded surface 12 of the fixed die 11a, and this protruding height determines the depth of the cutting groove 6 with respect to the valley 5a.

  As shown in FIG. 2 (c), the groove machining surfaces 15a and 17a are formed on the upward inclined portion a, the intermediate flat portion b, and the downward inclined portion c along the rolling direction of the screw material from the upstream side to the downstream side. The upward inclined portion a is set in the range of 1 to 2.5 °, the intermediate flat portion b is set in parallel with the rolling direction of the screw material, and the downward inclined portion c is set in the range of 2 to 4 °. The starting end of the inclined portion a and the rear end of the descending inclined portion c coincide with the thread machining surface 12 of the fixed die 11a.

  Furthermore, when the length along the rolling direction of the screw material on the groove machining surfaces 15a and 17a is 1 when the length of the downward inclined portion c is 1, the upward inclined portion a is 1.5 to 2 times longer. The flat part b is set to 2.4 to 3 times the length.

By setting such conditions from the upstream side to the downstream side, the generation of the impact of the screw material indentation when the cutting groove 6 is formed by the groove forming protrusion 19 is mitigated, and the load on the groove forming portion 14 and the fixed die 11a is reduced. Can be mitigated.

The width of the escape groove 16 along the axial direction of the screw material is set to be not less than 1 pitch and less than 3 pitches of the thread 5 in the self-piercing screw 1 to be rolled, and the surface height of the relief groove 16 is When the shaft portion of the screw material passes through the groove forming portion 14 and is set to be equal to or lower than the valley groove 12b on the thread machining surface 12 of the fixed die 11a, the thread machining surface 12 of the die 11 When the formed thread 5 is not deformed or damaged, the rolling pressure of the die 11 is not applied to the portion of the shaft portion 2 facing the escape groove 16, and the groove forming protrusion 19 bites into the shaft portion 2. The portion of the shaft 2 facing the relief groove 16 facilitates the flow of the screw material and reduces the flow amount of the screw material to the pointed tip 3, thereby forming the pointed tip 3 of both dies 11a and 11b. Excessive Do not apply pressure, die 11a and 11b increase and cracks generation and durability of sharpness will prevent molding defects occurrence of tip 3.

  In the case of illustration, the self-drilling screw 1 shows a shape in which a cutting groove 6 is formed at a position on the pointed tip 3 side and a position 1 to 3 pitch apart from the thread on the head 4 side. In the die 11 to be manufactured, an example in which the groove forming portion 14 is arranged with the groove processing portions 15 and 17 divided in the axial direction of the screw material with the escape groove 16 interposed therebetween is shown. The groove forming portion 14 provided in the die when the self-drilling screw 1 is rolled may be formed by forming the cutting groove 6 only at one position close to the sharp tip 3. FIG. The upper grooved portion 17 in a) may be omitted, and the lower grooved portion 15 and the relief groove 16 may be formed. The relief groove 16 with respect to the lower grooved portion 15 is formed by the shaft portion 2 of the screw material. Is located on the head 4 side of the portion where the cutting groove 6 is machined, and the portion of the shaft portion 2 Since the rolling pressure of the die 11 is not applied to the die 11, the die 11 of the self-drilling screw 1 having the sharpened tip 3 and the depth of the cutting groove 6 recessed into the valley portion 5a is the same as described above. Rolling is possible.

  The grooved portions 15 and 17 and the relief groove 16 are arranged between the second half of the rolling direction of the screw material and immediately before the final process with respect to the thread machining surface 12 of the die 11. A finishing thread machining surface 20 is provided between the end and the rear end of the thread machining surface 12 of the die 11, and the finishing thread machining surface 20 is formed between the protrusion 12 a of the thread machining surface 12 and the valley groove. 12b remains in the extended arrangement, and the trough 5a and the thread 5 of the portion that has passed through the escape groove 16 at the shaft portion 2 of the screw material are corrected and finished.

  The die 11 of the present invention is configured as described above, and a screw material in which the head 4 is processed in advance between the fixed die 11a and the moving die 11b in a state where the moving die 11b is in the retracted position. When the moving die 11b is moved to the forward movement position, the shaft portion 2 of the screw material sandwiched between the two dies 11a and 11b is subjected to rolling pressure on the threaded surface 12 of both dies 11a and 11b while rolling. The thread 5 is formed by the trough 5a being squeezed and a part of the material flowing into the trough 12b. At the same time, the tip side of the shaft part 2 is squeezed at the lower part of the thread machining surface 12, and the pointed tip 3 is formed. It will be done. In addition, about the axial part, a screw thread, a cutting groove, etc. which are formed in the screw material in the middle of a rolling process, the code | symbol same as the applicable part of the completed self-drilling screw 1 is attached | subjected and demonstrated.

  When the processing of the thread 5 on the screw material is approaching the latter half, the shaft portion 2 of the screw material enters the groove forming portion 14 while rolling and moves to the rear end of the fixed die 11a, and the lower groove processing portion 15 and Groove forming projections 19 forming the groove processing surfaces 15a, 17a of the upper groove processing portion 17 bite into the shaft portion 2 and crush, thereby dividing the middle of the screw thread 5 and forming a cutting groove 6 deeper than the trough portion 5a. Will do.

  The grooved portions 15 and 17 have a height at which the tops of the groove forming projections 19 forming the grooved surfaces 15a and 17a protrude from the threaded surface 12 of the fixed die 11a, and the grooved surfaces 15a and 17a. Are formed in the upward inclined portion a, the intermediate flat portion b, and the downward inclined portion c from the upstream side to the downstream side with respect to the rolling direction of the screw material, so that the groove processing surface 15a is formed by the upward inclined portion a. The thread 5 is divided while mitigating the occurrence of impact when the thread 5 starts to bite into 17a, and then the intermediate flat part b forms a cutting groove 6 deeper than the valley 5a in the part where the thread 5 is divided. Finally, the groove forming projection 19 is moved away from the cutting groove 6 by the downward inclined portion c, whereby the cutting groove 6 is formed smoothly and accurately.

As described above, when the cutting groove 6 is formed on the shaft portion 2 by the groove forming portion 14, the shaft portion 2 is rolled by the upper and lower portions of the groove forming portion 14 by the two dies 11 a and 11 b, and the sharp tip 3 and the screw thread 5. In such a state, when the groove forming projections 19 of the groove processing portion 15 and the upper groove processing portion 17 bite into the shaft portion 2 as described above, the portion into which the screw material is pressed becomes the shaft. It will follow the direction.

At this time, since the groove forming portion 14 is provided with the relief groove 16 between the groove processed portions 15 and 17, the two dies 11a and 11b are adjacent to the position where the cutting groove 6 is formed with respect to the shaft portion 2. An unrolled portion is generated, and thus the pushed screw material can easily flow to the portion of the shaft portion 2 that faces the escape groove 16, thereby forming the cutting groove 6 by the groove forming portion 14. The amount of flow of the screw material to the sharp tip 3 side of the shaft portion 2 can be reduced, so that excessive pressure is not applied to both dies 11a and 11b in the molding process of the sharp tip 3, and both dies 11a and 11b It is possible to prevent the occurrence of cracks and the occurrence of defective molding of the sharp tip 3.

  Further, in forming the cutting groove 6 in the middle of the shaft portion 2 by the upper groove processing portion 17, since the head 4 side of the cutting groove 6 is rolled by both dies 11 a and 11 b, the shaft portion 2 is released. The flow of the screw material to the portion facing the groove 16 is facilitated, and the escape amount of the screw material to the head 4 side of the shaft portion 2 can be reduced, and hence the occurrence of fluctuations in the length dimension of the shaft portion 2 is suppressed. be able to.

  Further, in the latter half of the rolling process in forming the thread 5 with the die 11, the thread 5 is formed on the portion facing the cutting groove 6 and the escape groove 16 positioned therebetween by the groove forming part 14 provided on the fixed die 11a. However, only the moving die 11b is used, but by increasing the amount of material that escapes the portion of the shaft portion 2 that faces the escape groove 16, the thread 5 in the portion that faces the escape groove 16 is substantially the same height as the other portions. Can be formed.

  Further, in the formation of the cutting groove 6 by the groove forming portion 14, when the groove processing portions 15 and 17 are processed to a depth that is recessed into the trough portion 5a, the groove processing portion with respect to the thread processing surface 12 of the fixed die 11a. The groove machining surfaces 15a and 17a of 15 and 17 become high, so that there is a concern that when the thread 5 enters the groove machining parts 15 and 17, a large load is applied to the groove forming part 14.

On the other hand, in the present invention, the grooved surfaces 15a and 17a of the grooved portions 15 and 17 have an upward inclined portion a and an intermediate flat portion b extending from the upstream side to the downstream side with respect to the rolling direction of the screw material. By forming the trapezoidal shape by the downward inclined portion c, the upward inclined portion a can reduce the occurrence of an impact when the shaft portion 2 enters, reduce the occurrence of cracks and the like of the groove forming portion 14, and the thread. When 5 leaves | separates from the groove formation part 14, since it becomes the downward inclination part c, it can prevent that the screw thread 5 bites into the die | dye 11. FIG.

Furthermore, the thread material flows into the portion of the finishing threaded surface 20 provided between the rear end of the relief groove 16 and the rear end of the threaded surface 12 of the die 11 a where no rolling pressure is applied by the relief groove 16. However, the diameter of the thread 5 and the valley 5a corresponding to the escape groove 16 can be finally corrected by the processed surface 20.

The completed self-piercing screw 1 discharged from the rear end side of the fixed die 11a described above has a sharp tip 3 at one end of the shaft portion 2 and a head 4 at the other end, as shown in FIG. The middle of the thread 5 is divided into two positions, a position near the pointed tip 3 of the part where the thread 5 is provided on the outer peripheral surface of the part 2 and a position several pitches away from this position on the head 4 side. Thus, it has a structure in which a cutting groove 6 having a depth reaching the valley 5a is formed.

In such a self-drilling screw 1, the sharp tip 3 improves the accuracy of the screwing position and the screwing ability at the initial stage of screwing, and the cutting groove 6 provided in the middle of the screw thread 5 divides the screw thread 5. Since the depth is recessed into the trough 5a, the rear edge of the screwing rotation of the part that divides the thread 5 becomes the cutting edge, and the threaded part of the thread 5 is cut when screwed into the wood member. At the same time, the rear edge of the screwed rotation of the portion recessed in the valley portion 5a becomes the cutting edge, and the entry portion of the shaft portion 2 is cut, so that the amount of cutting can be increased and the cutting groove 6 is cut Since scraps are stored, it is possible to suppress an increase in screwing resistance due to the biting of cutting scraps between the wood member and the self-piercing screw 1.

Furthermore, the length direction of the cutting groove 6 is inclined with respect to the axial direction of the shaft portion 2, and the length is set to be 1 pitch or more and 3 pitch or less of the thread 5. If the pitch is 1 pitch or less, a sufficient amount of cutting waste cannot be stored, and if the length is 3 pitches or more, the material escape amount to the portion facing the escape groove 16 of the shaft portion 2 is reduced. It is possible to prevent the problem that the height of the screw thread 5 near the center of the portion is lowered.

As described above, the self-drilling screw 1 manufactured with the die 11 of the present invention has a sharp tip 3 and a cutting provided at a depth at which the thread 5 is divided into the shaft portion 2 and reaches the valley portion 5a to be recessed. Due to the synergistic effect of the grooves 6, the screwing can be performed smoothly and cracking of the wooden member can be effectively prevented.

DESCRIPTION OF SYMBOLS 1 Self-drilling screw 2 Shaft part 3 Sharp tip 4 Head 5 Screw thread 5a Valley part 6 Cutting groove 7 Unthreaded part 11 Die 11a Fixed die 11b Moving die 12 Thread processing surface 12a Protrusion part 12b Valley groove 13 Approaching part 14 Groove Forming part 15 Lower grooved part 16 Relief groove 17 Upper grooved part 18 Square hole 19 Groove forming protrusion 20 Finishing thread machining surface a Up slope part b Intermediate flat part c Down slope part

Claims (7)

  A screw thread is provided on the outer peripheral surface of the shaft portion having a sharp tip at one end and a head portion at the other end from the sharp tip toward the head side, and the screw thread is provided in the middle of the portion provided with the screw thread in the shaft portion. A die for rolling a self-drilling screw in which a cutting groove having a depth reaching a thread valley is formed, the die comprising a combination of a fixed die and a moving die, A forming part of the cutting groove is provided at a position on the rear end side of the thread processing surface in the die, and the forming part is provided with respect to the groove processing part disposed along the rolling direction of the screw material, and the groove processing part. A rolling die for self-drilling screws that is arranged in parallel at a position on the head side of the screw material and is formed by a relief groove that is recessed with respect to the groove processing surface in the groove processing portion.   The molding part is arranged such that the grooved part is provided at the upper and lower positions of the die, and the lower grooved part and the upper grooved part are vertically divided with an escape groove provided therebetween. Item 2. A rolling die for self-drilling screws according to Item 1.   3. The self-drilling screw according to claim 1, wherein a groove processing portion of the forming portion has a height at which a top portion of a groove forming projection forming a groove processing surface protrudes from a thread processing surface of a die. Dies.   The groove machining surface of the groove machining portion is formed in an ascending inclined portion, an intermediate flat portion, and a descending inclined portion from the upstream side to the downstream side with respect to the rolling direction of the screw material. The rolling die for a self-drilling screw according to any one of claims 1 to 3, wherein the die is set in a range of 0.5 °, and the downward inclined portion is set in a range of 2-4 °.   The length along the rolling direction of the screw material on the grooved surface of the grooved part is 1.5 to 2 times longer when the length of the descending inclined part is 1, and the intermediate flat part The rolling die for self-drilling screws according to claim 3, wherein the length is set to 2.4 to 3 times.   The self-drilling screw according to any one of claims 1 to 5, wherein a width along the axial direction of the screw material of the relief groove is set to be not less than 1 pitch and less than 3 pitches of the thread in the self-drilling screw to be rolled. Rolling dies.   The grooved portion and the relief groove are arranged between the latter half of the rolling direction of the screw material with respect to the die and immediately before the final process, and the rear end of the escape groove and the rear end of the thread machining surface of the die are arranged. The rolling die for self-drilling screws according to any one of claims 1 to 6, wherein a finished thread machining surface is provided therebetween.