JP2012066369A - Tap with guide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tap with a guide suitable for forming a female screw of a nut with a groove causing burr in a screw prepared hole such as a hexagonal nut with a groove.SOLUTION: In the tap 1 with the guide, a guide piece 3 fitted to the screw prepared hole is attached to the axially front end of a tap body 2 including a plurality of threads 4 formed to be gradually smaller in their outer diameters to the axially forward direction, and the groove 9 dividing the threads 4 in a circumferential direction. A notch 15 narrower than the groove 9 is formed in the outer periphery of the guide piece 3, and a cutting edge 16 for removing the burr in the screw prepared hole is formed in the edge of the notch 15.

Description

  The present invention relates to a guided tap suitable for forming a nut having a groove that causes a burr in a screw hole, for example, a female screw of a grooved hex nut.

  A hex nut with a groove is used as a nut to be used when reliability of locking prevention is particularly required. The grooved hex nut has a radial groove on its axial end face. Then, in a state in which the male screw member is screw-engaged, a split pin is inserted through the groove of the grooved hex nut and the radial through hole formed in the male screw member.

  When manufacturing this grooved hex nut, first, as shown in FIG. 5, a nut blank B having a screw pilot hole H penetrating in the axial direction and a radial groove G formed in the axial end surface is prepared. Next, the inner periphery of the screw pilot hole H is cut with a tap to form a female screw. Here, when the female screw is formed by a tap, if the tap bites diagonally with respect to the screw pilot hole H, the direction of the screw becomes diagonal and the nut becomes a defective product.

  Therefore, in order to prevent the tap from biting diagonally with respect to the screw hole H, it is conceivable to use the guided tap described in Non-Patent Document 1. This guide-equipped tap is obtained by integrally providing a columnar guide portion at the front end of the tap body in the axial direction. When this guided tap is used, the cylindrical guide portion is fitted into the screw pilot hole H immediately before the tap body bites into the screw pilot hole H, and the axis of the nut blank B and the axis of the tap main body Since the misalignment of the heart is corrected, the tap can be prevented from biting diagonally with respect to the screw pilot hole H.

Japanese Industrial Standard "Threading Tool Terminology-Part 1: Tap" (B0176-1: 2002)

  However, the use of the guided tap has the following problems. That is, when making a nut blank, burrs may occur in the screw pilot hole. In particular, in the nut blank B of a hex nut with a groove, the groove G intersects the screw pilot hole H as shown in FIG. Burr b is likely to occur. If an internal thread is to be formed with the guide tap in the screw pilot hole H where such a burr b exists, the cylindrical guide portion interferes with the burr b and does not pass through the screw pilot hole H. There is a problem that the pilot hole H does not bite.

  In view of this, it is conceivable to use a reamer-type tap as shown in FIG. 8 so that a female thread can be smoothly formed even when the burr b exists in the screw prepared hole H. The tap with reamer includes a reamer part 20 and a tap part 21 provided integrally with the reamer part 20 in the axial rearward direction. The tap portion 21 includes a plurality of screw threads 22 formed so that the outer diameter gradually decreases toward the front in the axial direction, and a groove 23 that divides the screw threads 22 in the circumferential direction. The reamer part 20 is provided with a groove 23 common to the tap part 21, and a cutting edge 24 is formed at the edge of the groove 23. When this reamer-equipped tap is used, since the burr b of the screw hole H is scraped off by the reamer part 20 immediately before the tap part 21 bites into the screw hole H, it is possible to form a highly accurate internal thread. .

  However, when the above-mentioned tap with reamer is used for the nut blank B of the grooved hex nut, the portion of the cutting edge 24 of the reamer 20 may interfere with the edge of the groove G of the nut blank B as shown in FIG. There is. That is, since the groove 23 of the reamer part 20 is a common groove with the groove 23 of the tap part 21, the groove width is relatively large. For this reason, the axis of the reamer 20 and the axis of the nut blank B are misaligned and the portion of the cutting edge 24 of the reamer 20 easily interferes with the edge of the groove G of the nut blank B. May expand or the screw pilot hole H may be cut into an irregular shape.

  The problem to be solved by the present invention is to provide a guided tap suitable for forming a nut having a groove which causes a burr in a screw pilot hole, for example, a female screw of a grooved hex nut.

  In order to solve the above-mentioned problem, the axial front end of the tap body having a plurality of screw threads formed so that the outer diameter gradually decreases toward the front in the axial direction and a groove for dividing the screw threads in the circumferential direction. A guide piece that fits into the screw hole is attached, a notch narrower than the groove is formed on the outer periphery of the guide piece, and a cutting blade that removes the burr of the screw hole is formed on the edge of the notch Adopted a tap with guidance of the configuration.

  When this guided tap is used, the guide piece fits into the screw pilot hole just before the tap body bites into the screw pilot hole, and the misalignment between the nut blank axis and the tap body axis is corrected. It is possible to prevent the tap body from biting diagonally with respect to the screw prepared hole. Even when burrs are present in the screw pilot holes, the cutting edges on the outer periphery of the guide piece scrape off the burrs, so that the female threads can be formed smoothly. In addition, when forming a female thread on a grooved hex nut with this guided tap, the width of the notch on the outer periphery of the guide piece is narrow, so the axis of the guide piece is not easily displaced from the axis of the nut blank, and the guide piece The outer peripheral cutting edge hardly interferes with the nut blank groove.

  As the cutting edge, it is preferable to employ a cutting edge that does not provide a circumferential relief. If it does in this way, when a guide piece is inserted in a nut blank, the axis center of a guide piece and the axis center of a nut blank will not shift easily. Therefore, it can prevent more effectively that the cutting edge of a guide piece and the groove | channel of a nut blank interfere.

  The outer periphery of the guide piece is composed of a cylindrical surface and a tapered surface having a small diameter from the cylindrical surface toward the front in the axial direction, and the notch extends axially rearward from the axial front end of the tapered surface. It can be formed to reach the cylindrical surface. If it does in this way, since the said cutting edge is formed over the whole radial direction range which a taper surface exists, it becomes possible to remove an excessive burr | flash smoothly.

  In the case where the notch is formed so as to extend rearward from the front end in the axial direction of the tapered surface and reach the cylindrical surface, it is preferable that the rear end in the axial direction of the notch is positioned at substantially the center in the axial direction of the cylindrical surface. . If it does in this way, since the cylindrical surface is not divided in the circumferential direction by the notch, the guiding action of the nut blank by the cylindrical surface becomes more stable.

  In the guided tap according to the present invention, the guide piece is fitted into the screw hole so that the axis of the nut blank and the axis of the tap body coincide with each other, so that the female screw is formed straight with respect to the screw hole. be able to. Moreover, since there is a cutting edge on the outer periphery of the guide piece, a female thread can be formed smoothly even when burrs are present in the screw pilot hole. In addition, the notch on the outer periphery of the guide piece is narrow so that it does not easily interfere with the groove of the nut blank of the grooved hexagon nut, and as a result, it prevents the expansion of the screw pilot hole and irregular cutting of the screw pilot hole. Can do.

The front view which shows the tap with guidance of embodiment of this invention FIG. 1 is an enlarged sectional view of the vicinity of the guide piece Sectional view along line III-III in FIG. FIG. 2 is an exploded perspective view of the guided tap shown in FIG. Perspective view showing nut blank of hex nut with groove Sectional drawing which shows the process in which a female thread is formed in the screw pilot hole of the nut blank of FIG. 5 with the tap with a guide of FIG. Sectional view of nut blank and guided tap shown in FIG. Sectional drawing which shows the process in which a female thread is formed in the screw pilot hole of the nut blank of FIG. 5 with the conventional tap with a reamer. Sectional drawing which shows the state which the cutting edge of the reamer part shown in FIG. 8 interfered with the edge of the groove | channel of the nut blank

  Hereinafter, the guided tap 1 according to the embodiment of the present invention will be described. This guided tap 1 is a nut tap used for manufacturing a nut by a tapping plate. As shown in FIG. 1, the tap 1 includes a tap body 2 and a guide piece 3 attached to the front end of the tap body 2 in the axial direction. Become.

  The tap body 2 includes a biting portion 5 composed of a plurality of threads 4 formed so that the outer diameter gradually decreases toward the front in the axial direction, and a plurality of threads 6 having a constant outer diameter along the axial direction. A complete mountain portion 7 and a cylindrical shank 8. The complete mountain portion 7 is provided continuously behind the bite portion 5 in the axial direction, and a shank 8 is provided continuously behind the complete mountain portion 7 in the axial direction.

  The tap body 2 is provided with a groove 9 extending from the front end in the axial direction of the biting portion 5 to the shank 8 through the complete peak portion 7. The groove 9 divides the threaded portions 4 and 6 of the bite portion 5 and the complete thread portion 7 in the circumferential direction. A cutting edge 10 is formed at the edge of the groove 9 to cut the inner periphery of the screw pilot hole H (see FIG. 6) to form a female thread. A plurality of grooves 9 are provided at regular intervals in the circumferential direction and have a circular arc cross section.

  As shown in FIGS. 2 and 4, a screw shaft 11 to which the guide piece 3 is attached is integrally formed at the axial front end of the tap body 2. The guide piece 3 is formed in a cylindrical shape having a screw hole 12 that engages with the screw shaft 11 as a center.

  The outer periphery of the guide piece 3 includes a cylindrical surface 13 and a tapered surface 14. The outer diameter of the cylindrical surface 13 is set to be slightly smaller than the reference dimension of the inner diameter of the female screw corresponding to the tap body 2 so as to fit into the screw pilot hole H. The standard dimension of the inner diameter of the female thread is a dimension that serves as a standard for thread tolerance. For example, for a metric thread, it is defined in Japanese Industrial Standard “General Metric Thread-Part 4: Standard Dimension” (B0205-4: 2001). Has been. Specifically, the standard dimension of the inner diameter of the metric screw can be obtained by (nominal diameter of screw) −1.0825 × (screw pitch). The unified screw is defined in the Japanese Industrial Standard “Unify coarse screw” (B0206: 1973). Specifically, {(nominal diameter of screw) −1.082532 / (per 25.4 mm The number of threads)} × 25.4.

  The tapered surface 14 is formed in a conical shape having a small diameter from the cylindrical surface 13 toward the front in the axial direction. The inclination angle of the tapered surface 14 is preferably set in a range of 5 to 20 ° with respect to the axial direction. If it is 5 ° or more, excessive burr b can be removed smoothly when removing burr b with a cutting edge 16 described later. If it is 20 ° or less, secondary burr is generated when burr b is removed. Can be reliably prevented.

  As shown in FIG. 3, notches 15 are formed on the outer periphery of the guide piece 3 at regular intervals in the circumferential direction, and cuts for removing burrs of the screw pilot holes H are formed at the edges of the notches 15. A blade 16 is formed. The cutting edge 16 is not provided with a circumferential relief. That is, the flank of the cutting edge 16 is a tapered surface 14 on the outer periphery of the guide piece 3, and the radius from the axial center of the guide piece 3 to the tapered surface 14 does not change along the circumferential direction and is constant. Yes.

  The width W1 of the notch 15 shown in FIG. 3 is narrower than the width W2 of the groove 9 shown in FIG. 2, and is preferably a portion sandwiched between adjacent grooves G of the nut blank B shown in FIG. It is formed narrower than the width W3. Moreover, the notch 15 is formed in the V-shaped cross section inclined with respect to the radial direction so that the rake angle of the cutting edge 16 becomes positive even with the narrow width W1. In this embodiment, the notch 15 has a V-shaped cross section. However, the present invention is not limited to this, and any cross section other than the V-shaped cross section may be used as long as the rake angle of the cutting edge 16 is positive. A shape may be adopted.

  As shown in FIG. 2, the notch 15 extends axially rearward from the front end in the axial direction of the tapered surface 14 to reach the cylindrical surface 13, and the rear end in the axial direction is located at substantially the center in the axial direction of the cylindrical surface 13. It is formed as follows. As shown in FIG. 1, the notch 15 is preferably formed so as to be inclined with respect to the axial direction so that the rear side in the axial direction is shifted to the front side in the rotational direction. It can be discharged forward.

  As shown in FIG. 2, the outer diameter of the cylindrical surface 13 is set to be the same as or slightly larger than the outer diameter of the front end of the tap body 2 in the axial direction. Therefore, when the burr b (see FIG. 6) of the screw pilot hole H is scraped off with the cutting edge 16 of the guide piece 3, even if the root part of the burr b slightly remains, the remaining part remains the tap body. It is possible to prevent interference with the outer diameter portion of the front end of the second axial direction.

  Next, the usage example which manufactures a slotted hexagon nut using this tap 1 with a guide is demonstrated.

  As shown in FIG. 5, a nut blank B having a screw pilot hole H penetrating in the axial direction and a radial groove G formed in the axial end surface is formed. At this time, the burr | flash may arise in the part where the groove | channel G crosses the screw pilot hole H. FIG. Next, as shown in FIG. 6, the nut blank B is fed into the front end of the guided tap 1 that rotates at a fixed position. Then, the screw pilot hole H of the nut blank B is guided by the taper surface 14 of the guide piece 3 and is fitted to the cylindrical surface 13, and by this fitting, the axis of the nut blank B and the axis of the tap body 2 are aligned. In this state, the screw thread 4 of the biting portion 5 bites into the screw pilot hole H to form a female screw, and the nut blank B is a screw portion in which the biting portion 5 and the complete screw portion 7 are combined. Through the whole, a slotted hexagon nut is completed.

  Here, when the nut blank B is fitted to the guide piece 3, the burr b of the screw pilot hole H may interfere with the guide piece 3. In this guided tap 1, Since the cutting edge 16 scrapes off the burr b, the nut blank B is smoothly fitted to the guide piece 3.

  By the way, when the nut blank B is fed into the front end of the guided tap 1, the nut blank B is either in the direction in which the side with the groove G faces the guide piece 3 or the side without the groove G faces the guide piece 3. It is not decided whether it will be sent. Then, there is no problem when the side without the groove G is sent in the direction facing the guide piece 3, but when the side with the groove G is sent in the direction facing the guide piece 3, as shown in FIG. The groove G and the notch 15 of the guide piece 3 are likely to interfere with each other, and this interference may enlarge the screw pilot hole H or cut the screw pilot hole H into an irregular shape.

  However, since the guided tap 1 of this embodiment has a width W1 (see FIG. 3) of the notch 15 smaller than a width W2 (see FIG. 2) of the groove 9, as shown in FIG. The shaft center of the nut blank B and the shaft center of the nut blank B are difficult to shift, and the portion of the cutting edge 16 of the guide piece 3 does not easily interfere with the edge of the groove G of the nut blank B. Further, since the width W1 (see FIG. 3) of the notch 15 is narrower than the width W3 (see FIG. 7) of the portion sandwiched between the adjacent grooves G of the nut blank B, the notch 15 is sandwiched between the adjacent grooves G of the nut blank B. It is possible to reliably prevent the portion to be dropped into the notch 15. Therefore, even when the nut blank B is fitted to the guide piece 3 in a tilted state, the guide of the cylindrical surface 13 and the taper surface 14 ensures the misalignment between the axis of the nut blank B and the axis of the tap body 2. It can be corrected.

  As described above, the guide tap 3 has the guide piece 3 fitted into the screw hole H immediately before the biting portion 5 bites into the screw pilot hole H, and the axis of the nut blank B and the tap body 2. Therefore, the female screw can be formed straight with respect to the screw pilot hole H. Even when the burr b exists in the screw prepared hole H, the cutting edge 16 on the outer periphery of the guide piece 3 scrapes off the burr b, so that a female screw can be formed smoothly. Further, since the notch 15 on the outer periphery of the guide piece 3 has a narrow width W1, it is difficult to interfere with the groove G of the nut blank B. As a result, the expansion of the screw hole H and the irregular cutting of the screw hole H are prevented. can do.

  In addition, since the guide tap 1 is not provided with a circumferential relief on the cutting edge 16 of the guide piece 3, when the guide piece 3 is inserted into the nut blank B, the shaft center and the nut of the guide piece 3 are arranged. The axis of the blank B is difficult to shift. Therefore, interference between the cutting edge 16 of the guide piece 3 and the groove G of the nut blank B can be more effectively prevented.

  The outer periphery of the guide piece 3 can be configured by only the cylindrical surface 13. However, when the outer periphery of the guide piece 3 is configured by the cylindrical surface 13 and the tapered surface 14 as shown in the above embodiment, the tapered surface 14. Since the cutting edge 16 is formed over the radial range where the burrs exist, excessive burr b can be removed smoothly, which is preferable.

  Further, the notch 15 can be formed so as to reach the axial rear end of the cylindrical surface 13, but the axial rear end of the notch 15 is formed on the cylindrical surface 13 as shown in the embodiment. It is preferable to form it so as to be positioned approximately in the center in the axial direction. In this way, the cylindrical surface 13 is not divided in the circumferential direction by the notch 15, so that the guiding action of the nut blank B by the cylindrical surface 13 is stabilized.

  The guide piece of a general guided tap does not require hardening because it does not have a cutting edge 16, whereas the guide piece 3 of the guided tap 1 of the above embodiment has a cutting edge 16 so that it has a considerable hardness. Need. Therefore, as a material of the guide piece 3 of the above embodiment, it is preferable to employ a material having a hardness equivalent to that of the tap body 2, for example, a high-speed tool steel, and further, when a hard film is coated on the surface of the guide piece 3, The wear resistance of the cutting edge 16 can be improved. Examples of the hard film to be coated on the surface of the guide piece 3 include metal carbides such as TiC, metal nitrides such as TiN and TiAlN, metal carbonitrides such as TiCN, and solid solutions thereof. Further, instead of coating the hard film, an oxide film may be formed on the surface of the guide piece 3 by water vapor treatment or nitriding treatment may be performed.

  In the above embodiment, an example of manufacturing a grooved hexagon nut using the guided tap 1 has been described. However, when this guided tap 1 is used, a nut having an axial groove on the inner periphery of the screw pilot hole H. In addition, female threads can be smoothly formed for all nuts having grooves that cause burrs in the screw hole, such as nuts having a circumferential groove on the inner periphery of the screw hole H.

1 Tap with Guide 2 Tap Body 3 Guide Piece 4 Thread 9 Groove 13 Cylindrical Surface 14 Tapered Surface 15 Notch 16 Cutting Edge H Screw Pilot Hole

Claims (4)

  Tap body (2) having a plurality of threads (4) formed such that the outer diameter gradually decreases toward the front in the axial direction, and a groove (9) for dividing the threads (4) in the circumferential direction. A guide piece (3) that fits into the screw pilot hole (H) is attached to the front end in the axial direction, and a notch (15) narrower than the groove (9) is formed on the outer periphery of the guide piece (3). And a guide tap in which a cutting edge (16) for removing the burr (b) of the screw pilot hole (H) is formed at the edge of the notch (15).   The guided tap according to claim 1, wherein the cutting edge (16) is not provided with a circumferential relief.   The outer periphery of the guide piece (3) is composed of a cylindrical surface (13) and a tapered surface (14) having a small diameter from the cylindrical surface (13) toward the front in the axial direction, and the notch (15) The guided tap according to claim 1 or 2, wherein the tapered surface (14) is formed so as to extend rearward in the axial direction from an axial front end of the tapered surface (14) to reach the cylindrical surface (13).   4. The guided tap according to claim 3, wherein an axial rear end of the notch (15) is positioned substantially in the axial center of the cylindrical surface (13).

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