JP4180039B2 - Raising tap - Google Patents

Description

  The present invention relates to a raised tap that plastically deforms a pilot hole of a workpiece material to form a female screw, and intends to improve the machining accuracy of the female screw crest and absorb the variation of the pilot hole diameter.

  One of the tools for forming the female screw is a raised tap, and a radial portion corresponding to the female screw to be formed is arranged on the outer circumference of the raised tap in a screw shape to form a male screw. On the other hand, the material to be processed is provided with a pilot hole substantially equal to the effective diameter of the female screw. By screwing the raised tap into the pilot hole, the inner peripheral surface of the pilot hole is plastically deformed to form the female screw. When forming the female thread using the raised tap, there are advantages that no chip is generated and the machining margin is small and the machining accuracy is stable as compared with the cutting tap.

  However, the raised tap forms a female thread by raising a screw thread on the inner peripheral surface of the workpiece, and as shown in FIG. 4, when tapping with the raised tap 10, a normal male screw 10 a having a deep valley is used. In this case, there is a problem that the seam portion 12 is generated at the peak of the female screw 11a in the material to be processed.

  The seam portion 12 may cause “burrs” and “beards”, and may be a target of defective products, and may drop off due to screwing with a male screw and adversely affect the product. Further, when a part on which a female screw is formed is plated, the plating solution may remain in the seam portion 2 and cause rust. Further, when tightening the male screw, if the male screw is chucked in a bent (tilted) state and tightened, one side may enter the normal thread groove, but the other side may enter the seam portion 12 at the summit. In some cases, the parts to be tightened in a screwed state are not fixed (this phenomenon is called “screw floating”).

  Therefore, conventionally, as shown in FIG. 4, by tapping with a male screw 10b having a valley formed shallower than usual, the peak of the female screw 11b is forcibly copied to the shape of the valley of the male screw 10b, that is, plastic deformation. The generation of the seam portion 12 is suppressed as much as possible by not providing a free flowing space for the fiber flow at that time.

  In addition, the inventors of the present invention previously described in Patent Document 1 that the trough of the chamfered portion at the tip of the threaded portion of the rising tap is formed shallower than the trough of the adjacent parallel threaded portion so that the trough diameter is approximately equal to the inner diameter of the female screw. Then, a technique for cutting out the seam portion as a burnish portion that can be finished by pressing the valley portion against the top portion of the female screw during drawing by reverse rotation of the raised tap has been proposed.

JP-A-9-272016

  However, as described above, when the male thread valley is formed shallowly, there is no room on the male thread side when tapping, so it is not possible to absorb the variation in the diameter of the prepared hole, and the large diameter female thread hole Then there was a problem of puncture. In addition, since the contact area with the thread of the female screw is increased, the tapping torque is increased, and it is easy to process a female screw hole with a small diameter (for example, a nominal size of about 4 mm), but a large diameter (for example, a nominal size of about 10 mm). There is also a problem that it is not suitable for machining of female screw holes.

  Therefore, an object of the present invention is to provide a raised tap that can improve the machining accuracy of the female screw crest and can effectively absorb variations in the diameter of the prepared hole.

In order to achieve the above object, according to the present invention, there is provided a raised tap in which a plurality of radial portions are arranged in a screw shape on the outer periphery of a main body to form a male screw, and the inner peripheral surface of the material is rotated by rotating the main body. In a raised tap that forms a female screw by plastic deformation by a portion, the valley of the male screw is shallowly formed to suppress the generation of a seam portion at the top of the female screw during the plastic deformation , and the bottom of the valley or An escape groove is formed on the slopes on both sides of the valley bottom.

  Further, the relief groove formed in the bottom of the valley is formed between arcuate surfaces for converging the fiber flow at the time of plastic deformation of the female screw to the central part of the pitch.

  Further, the relief groove formed in the bottom of the valley is formed between inclined surfaces for converging the fiber flow at the time of plastic deformation of the female screw to the central portion of the pitch.

  The escape groove formed at the bottom of the valley is formed in a semicircular cross section.

  Further, the relief groove formed in the slope portion is formed in a substantially arc shape in cross section.

  According to the present invention having the above-described configuration, the valley of the male screw is formed shallow so that the fiber flow is concentrated at the center of the pitch when the female screw is plastically deformed. The seam part is as small as possible. Further, the clearance groove allows a space and can absorb the variation in the diameter of the prepared hole effectively. Therefore, even if it is applied to a large-diameter female screw hole, it does not puncture.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a boosting tap according to the present invention will be described in detail with reference to the drawings by way of examples.

  FIG. 1 is a side view of a raised tap showing a first embodiment of the present invention.

  As shown in the drawing, a plurality of radial portions (not shown) are arranged in a screw shape on the outer peripheral portion of the main body 1 of the rising tap to form the male screw 2. The male screw 2 has a biting portion 3 whose tip side (right side in the drawing) gradually decreases in diameter toward the tip, and a parallel screw portion 4 is continuous with the rear end side of the biting portion 3. A plurality of oil grooves (not shown) extending in the axial direction of the main body 1 are formed in the circumferential direction of the main body 1.

  In this embodiment, the valley 5 (see the virtual valley bottom 5a) of the male screw 2 is formed at the peak of the female screw 9 in the material to be processed (by the plastic deformation during tapping), and the seam portion is as small as possible. For example, it is formed shallower than H / 6 (about H / 4), and a relief groove 5b is formed at the center of the virtual valley bottom 5a.

In the illustrated example, the clearance groove 5b is formed between the arcuate surfaces 5c for converging the fiber flow (fiber flow) at the time of plastic deformation of the female screw 9 at the center of the pitch. The arcuate surface 5c is preferably formed by, for example, an R surface of a circle inscribed in the virtual valley bottom 5a . The escape groove 5b has a semicircular cross section.

  Due to such a configuration, when the female thread 9 is formed on the material to be processed by a final tap that is attached to a tapping machine or the like (not shown), the valley 5 of the male thread 2 is formed shallow so that the female thread 9 is plastically deformed. Since the flow of the fibers is focused on the center of the pitch, the seam portion formed by the plastic deformation at the top of the female screw 9 becomes as small as possible, and the processing accuracy is improved.

  As a result, the problem that the seam portion causes “burrs” and “whiskers”, becomes a target of a defective product, and falls off due to screwing with a male screw (bolt) to adversely affect the product. Further, when the part on which the female screw 9 is formed is plated, the plating solution does not remain in the seam portion and does not cause rust. Furthermore, the above-described “screw floating” when tightening the male screw (bolt) can be avoided, and the component can be securely fixed.

  Further, a relief groove 5b is formed in the central portion of the virtual valley bottom 5a of the male screw 2, and the contact area with the thread of the female screw 9 is reduced, so that the tapping torque is reduced, and therefore it is easy even for a large-diameter female screw hole. Can be applied to. In addition, since the clearance groove 5b provides a space for the fiber flow, it is possible to effectively absorb variations in the diameter of the prepared hole, and it can be punctured even when applied to a large-diameter female screw hole. Absent.

  FIG. 2 is a side view of a raised tap showing a second embodiment of the present invention.

  This is because the escape groove 5b in the first embodiment is formed between the inclined surfaces 5d for converging the fiber flow at the time of plastic deformation of the female screw 9 to the central portion of the pitch, and the sectional shape of the escape groove 5b is trapezoidal. This is an example of formation.

  Also in this embodiment, the same actions and effects as those in Embodiment 1 can be obtained.

  FIG. 3 is a side view of a raised tap showing a third embodiment of the present invention.

  This is an example in which the relief groove 5b in the first embodiment is formed in a substantially arc shape in cross section (at least the groove bottom portion may be arc-shaped) on the slopes on both sides of the valley bottom 5a.

  Also in this embodiment, the valley 5 of the male screw 2 is formed as shallow as about H / 4, and the flow of fibers at the time of plastic deformation of the female screw 9 is focused at the center of the pitch. The seam portion formed by deformation becomes as small as possible, and the processing accuracy is improved. Further, since the clearance groove 5b can provide a space for the fiber flow, the variation in the diameter of the prepared hole can be absorbed effectively, and even when applied to a large-diameter female screw hole, it does not puncture. .

  Furthermore, since a substantially arc-shaped protruding portion 9a is formed on both sides of the top of the female screw 9 formed by the raised tap (male screw 2) of this embodiment, the tightening torque of the male screw screwed with the female screw 9 is large. On the other hand, the loosening torque also becomes large and difficult to loosen, and since the protruding portion 9a is substantially arc-shaped, there is no particular adverse effect on the screwing operation as compared with the case where it protrudes in a mountain shape (by the V-shaped escape groove). There are advantages.

  Needless to say, the present invention is not limited to the above embodiments, and various modifications such as a change in the cross-sectional shape of the valley 5 are possible without departing from the scope of the present invention.

It is a side view of the rising tap which shows Example 1 of this invention. It is a side view of the raising tap which shows Example 2 of this invention. It is a side view of the raising tap which shows Example 3 of this invention. In the side view of the conventional tap, the defect is indicated by a balloon.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Body of rising tap 2 Male thread 3 Chamfered part 4 Parallel thread part 5 Valley 5a Virtual valley bottom 5b Escape groove 5c Arc surface 5d Inclined surface 9 Female screw 9a Arc-shaped protruding part

Claims (5)

In the raised tap that forms a plurality of radial parts on the outer periphery of the main body to form a male screw by forming a male screw, and plastically deforms the inner peripheral surface of the material by the radial part by rotating the main body,
The male screw valley is shallowly formed to suppress the generation of a seam portion at the peak of the female screw during the plastic deformation, and a relief groove is formed on the bottom of the valley or on both sides of the valley bottom. Raised tap characterized by that.   2. The rising tap according to claim 1, wherein the relief groove formed in the bottom of the valley is formed between arcuate surfaces for converging the fiber flow at the time of plastic deformation of the female screw to the center of the pitch.   The rising tap formed in the said valley bottom part is formed between the inclined surfaces which converge the fiber flow at the time of plastic deformation of the said internal thread to the center part of a pitch, The rise tap of Claim 1 characterized by the above-mentioned.   4. The raised tap according to claim 1, wherein the relief groove formed in the bottom of the valley is formed in a semicircular cross section.   The relief tap according to claim 1, wherein the relief groove formed in the slope portion is formed in a substantially arc shape in cross section.

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