JPH0214903Y2 - - Google Patents

Description

[Detailed description of the invention] Technical Field This invention relates to a raised tap that forms a female thread on the inner circumferential surface of a female thread material by plastic working, and in particular has a function of removing the top of the raised internal thread. This is related to the raised tap.

Conventional technology In general, a build-up tap is equipped with a threaded part for processing.
By being screwed into the inner peripheral surface of the female thread material,
A female thread is formed on the inner peripheral surface by plastic working. The raised part along the opposing flank surfaces of the threaded part for processing becomes the thread of the female thread, and the top of the female thread has a raised part as shown in Figures 6 and 7. There is a tendency for underfills, or imperfections 40, which are not completely filled with plastically flowed metal and create recesses.

By the way, it is possible to specify the effective height (height of the thread) without including the incomplete part 40 at the top of the thread of the female thread, but in that case, the screw thread with the male thread product may be In this case, the incomplete portion 40 of the female thread crest interferes with the male thread root, making it impossible to screw together, or the gap between the male thread root and the female thread crest becomes smaller than the appropriate value. Therefore, the effective height of the female thread includes the incomplete portion 40 at the top of the female thread, but it is desirable to avoid this from the viewpoint of the strength of the female thread. For example, when machining a JIS metric coarse screw with a nominal M10 and a pitch of 1.5 mm, the height of the incomplete part 40 at the top of the thread, which is insufficiently raised, is usually about 0.3 mm. teeth
This corresponds to 37% of the effective thread height (height of the thread; approx. 0.81 mm) of the female thread according to the JIS standard, and the complete portion accounts for the remaining 63%, which is considered a slight consideration in terms of the strength of the female thread. Can not do it. It is said that internal threads formed by building up machining are about 10 to 20% stronger than those formed by cutting because the fiber structure of the material (fiber flow) is not cut, but this is due to the effective thread height. This is the case where the thread does not include the imperfection 40, and if the imperfection reaches one-third or more of the thread, such strength cannot be expected.

For this reason, it is conceivable to remove the incomplete portion of the top of the internal thread formed by the build-up. The present applicant previously proposed, in Utility Model Application No. 57-18927, a build-up tap with an inner diameter finishing blade for finishing the inner diameter of an internal thread by cutting off the top of the plastically worked internal thread. As shown in Figs. 8 and 9, this means that the highest part 42 of the root diameter of the external thread of the tap is located between the highest parts (protrusions) 44 of the mountain diameter, and that there is a line parallel to the axis. A groove portion 46 extending in the direction (or twisting direction) is provided, whereby the highest portion 42 of the groove diameter serves as a cutting edge.

On the other hand, Japanese Utility Model Application Publication No. 58-184226 discloses that because the diameter of the pilot hole of the female thread material is smaller than the specified value, the female thread bulges out more than necessary, causing interference between the thread and the tap. Disclosed is a tap equipped with a cutting portion for removing wrinkles, etc. that occur at the top of the internal thread due to such interference. As shown in Fig. 10, this has a groove 48 in the threaded part of the tap in a direction parallel to the axis (or in the twisting direction), thereby forming a cutting edge corresponding to the cross section of the external thread. .

Problems that the invention aims to solve According to the tap with an inner diameter finishing blade proposed in Utility Model Application Publication No. 57-18927, the incomplete top of the female thread can be removed at the same time as plastic working to obtain an appropriate inner diameter dimension. Can be done.

However, as described above, since the tap has a structure in which the cutting edge is formed at the bottom of the thread, it is troublesome to determine the cutting radius of the cutting edge with high precision. In other words, in the threaded part of a threaded tap, the top and valley of the threaded part of the threaded part are generally machined at the same time using a general-forming tool, so the effective diameter and root diameter of the threaded part are dimensioned separately. Unable to manage. Therefore, if you try to improve the accuracy of the root diameter in order to improve the machining accuracy of the cutting edge, you will need to increase the machining accuracy of the entire threaded part, which may require a high-precision model or tap tap. After forming the threaded portion, only the root diameter must be finished with high precision using a crusher roll (shaping roll made of a grinding wheel, etc.), which raises the problem of high processing costs.

On the other hand, the type disclosed in Japanese Utility Model Application Publication No. 58-184226 has the function of removing wrinkles, etc. of the internal thread caused by excessive buildup and removing surface defects, but this is different from the present invention. The purpose is different, and even if we ignore this fact, it has the same problem as the tap mentioned above in that it is troublesome to achieve the precision of the cutting edge because the cutting edge is formed on the threaded part of the tap. It is inherent.

Means for Solving the Problems The present invention was made in order to solve these conventional problems, and as mentioned above, the processing thread part that is screwed into the inner circumferential surface of the female thread material. In the built-up tap provided with the above, a wiper blade section is provided adjacent to the rear side of the threaded part for processing in the relative spiraling direction with respect to the female thread material, for cutting off the top of the thread that is raised by the threaded part for processing. It is characterized by this.

Effects of the invention In this way, the wiper edge is provided adjacent to the back side of the heaping tap instead of the thread for processing, so that the precision of the cutting edge of the wiper edge is different from the dimensional accuracy of the thread for processing. It can be specified separately, which makes it easy to process the wiper edge portion with high precision. If you use this type of threading tap with a further blade, the top of the female thread where the threading is insufficient will be removed with the wiper blade, making it possible to obtain a female thread that is sound in terms of dimensions and strength. be.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 shows a raised tap 2 which is an embodiment of the present invention. This build-up tap 2 has a processing thread part 4, a wiper blade part 6,
It includes a guide threaded portion 8 and a shank 10, and has a male threaded shaft shape as a whole. Processing thread part 4
comprises a chamfered threaded portion 12 whose outer diameter gradually increases as it moves away from the tip end surface of the tap 2, and a parallel threaded portion 14 whose outer diameter is constant following the chamfered threaded portion 12, The chamfered threaded portion 12 is screwed into the inner circumferential surface of the prepared hole of the female thread material prior to the parallel threaded portion 14, and this chamfered threaded portion 12 performs plastic working of a substantial female thread on the inner circumferential surface based on build-up forming. , the parallel threaded portion 14 plays the role of finishing the raised internal thread.

These chamfered threaded portions 12 and parallel threaded portions 14
As is clear from FIG. 2, four protrusions 15 protruding outward in the radial direction are formed on the screw thread at predetermined periodic intervals (equally spaced in this embodiment). These protrusions 15 are directly acting parts for plastic working of the female thread, and the protrusions 15 of adjacent threads are connected in a direction parallel to the axial center of the tap 2 or in a spiral shape centered on the axial center. It is being done.

The wiper blade portion 6 is provided adjacent to the rear side of the processing thread portion 4 (particularly the parallel thread portion 14) in the relative spiraling direction to the female thread material. The wiper blade portion 6 includes a chamfered portion 16 on the side of the parallel threaded portion 14 whose outer diameter gradually increases as the distance from the chamfered portion 16 increases, and a finished portion 18 having a constant outer diameter following the chamfered portion 16. As is clear from FIG. 3, four grooves 20 extending in a direction parallel to the axis of the abutting tap 2 are formed across the chamfered portion 16 and the finished portion 18 at equal angular intervals. There is. As a result, these grooves 20
Four cutting edges 22 are formed at the boundary between the land and the remaining land. A flank 24 having a predetermined relief angle is formed on the land following each cutting edge 22, and a rake surface 26 following the cutting edge 22 is formed in the groove 20, and each cutting edge 22 is given by the intersection line of these rake face 26 and flank face 24.

In the chamfered portion 16, the diameter of the cutting edge, that is, the diameter of the circle drawn by the cutting edge 22, increases along the conical surface with the finishing portion 18 side as the bottom surface, but in the finishing portion 18, The cutting edge 22 extends along the generatrix of the cylindrical surface, and the diameter of the cutting edge is constant.
Further, the cutting edge diameters of both the chamfered portion 16 and the finished portion 18 are larger than the diameter of the valley of the external thread of the parallel threaded portion 14 and smaller than the diameter of the crest, that is, the outer diameter. As shown in FIG. 5, the chamfered portion 16 of the wiper blade portion 6 gradually removes an incomplete portion 40 at the top of the female thread 28 which is raised by the threaded portion 4 for processing. It plays the role of excision. In addition, in the finishing part 18, when the female thread to be plastic-processed is, for example, a metric coarse thread, when the height of the peak ABC is H, the height of the peak cut is H/4 (defined in JIS B 0205).
The diameter of the cutting edge is determined so that In addition, in such a wiper edge part 6, it is desirable that the axial length of the chamfered part 16 is set to about 1 to 5 times the thread lead of the parallel threaded part 14, and the axial length of the finished part 18 It is sufficient if it is approximately equal to the above screw lead.

Further, the aforementioned guide screw portion 8 is provided adjacent to the wiper blade portion 6 on the shank 10 side. The guide thread part 8 has a thread lead equal to and on the lead line of the parallel thread part 14, and the outer diameter and diameter of the thread are slightly smaller than those of the parallel thread part 14, It is screwed into a female thread formed through the processing thread part 4 and the wiper blade part 6, and guides the relative spiral movement between the female thread material and the tap 2.

The raised tap 2 as described above can be suitably used not only as a hand tap but also as a machine tap such as an automatic tapping machine, for example, for tapping a female nut. When used as a machine tap, the tap 2 is normally given a rotational motion, while the nut blank 30 as a female thread blank shown in FIG. 4 is fed in the axial direction.

As the chamfered threaded portion 12 and the parallel threaded portion 14 are screwed into the pilot hole formed in the nut material 30, a female thread is formed on the inner peripheral surface of the pilot hole by plastic working. That is, the portion of the inner circumferential surface of the pilot hole corresponding to the thread of the chamfered thread portion 12 is recessed to form the valley of the female thread, and the excess thickness is raised along the opposing flank surfaces to form the female thread 28. However, at the top of the thread 28, an incomplete portion 40, which is insufficiently raised as described above, occurs. However, when this incomplete portion 40 is passed through the wiper blade portion 6, it is first gradually removed by the chamfered portion 16 and reaches the finished portion 18, and then is completely completed by cylindrical cutting in the finished portion 18. , and as shown in Figure 5, the peak cut height is H/4 as described above.
It is said that In this way, the incomplete portion 40 is gradually removed by passing through the chamfered portion 16, and is finally finished by cutting the finished portion 18, so that the tap torque required for the removal and cutting is small, and there is no need for cleaning. It has the advantage of high surface smoothness and the final height of the female thread can be finished with high precision. After the top of the female thread 28 is finished with high precision as described above, the female thread portion is screwed into the guide thread portion 8 and sent further rearward.

With such a wiper blade part 6, the female thread 2
8 is reliably cut off and the remaining portion gives the female thread 28 its normal dimensions, ensuring the original strength of the raised internal thread and also improving its dimension. It is also possible to obtain a suitable internal thread. Moreover, since the wiper blade part 6 is formed not on the processing thread part 4 but adjacent to the rear side thereof, the dimensional accuracy of the processing thread part 4 can be the same as that of general conventional heaping taps. Furthermore, the wiper blade portion 6 can be easily machined with high precision from its outer circumferential side, and its manufacturing cost and tap cost can be reduced.

Note that the chips of the incomplete portion 40 of the female thread 28 are accommodated in the groove portion 20 of the wiper blade portion 6;
In the case of hand tapping, since each nut material 30 is tapped, there is almost no problem with clogging, and even when used in an automatic tapping machine, the nut materials 30 are tapped with chamfered screws at regular intervals. The structure that is sent to section 12 is normal,
Since there is a certain interval before the next nut material 30 is supplied, the chips stored in the groove 20 naturally fall to the outside of the groove 20 together with the cutting oil, and the groove 20 becomes clogged with chips. Moreover, there is no problem in setting up the tap.

Further, when the nut material 30 is forged with a nut former, the diameter of the screw hole in the nut material has a slope of driving with a punch, and one end of the hole diameter is tapered larger than the other end. Although there is a tendency, if the diameter of the screw hole is set to be small, there will be no problem in applying the tap 2.

Further, in the embodiment described above, the wiper blade portion 6
Although the groove portion 20 is formed in a direction parallel to the tap axis, it may be formed in the form of a twisted groove in the opposite direction to the twisting direction of the threaded portion 4 for processing.
Furthermore, it may be formed so as to pass through the guide screw portion 8 on the rear side and reach the shank 10.

Further, although the guide threaded portion 8 is generally necessary in the case of a hand tap, it is not indispensable in the case of a machine tap because it is fed in the axial direction by a mechanical feeding means.

In addition, it goes without saying that the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a front view of a raised tap which is an embodiment of the present invention, and FIG. 2 is a -
A cross-sectional view, and FIG. 3 is a - cross-sectional view in FIG. 1. FIG. 4 is a diagram illustrating a state in which an internal thread is formed in a nut material using the raised tap shown in FIG. 1, and FIG. 5 shows a state before the top of the internal thread in FIG. 4 is removed. It is an enlarged sectional view. FIGS. 6 and 7 are enlarged cross-sectional views showing examples of imperfections at the tops of female threads that occur during plastic working of female threads using a general build-up tap. FIG. 8 is a front view showing a specific example of a conventional raised tap, and FIG. 9 is a cross-sectional view thereof. FIG. 10 is a front view showing another conventional example. 2: Raising tap, 4: Processing thread part, 6: Wiper blade part, 8: Guide thread part, 10: Shank,
12: Chamfered thread part, 14: Parallel thread part, 16:
Biting part, 18: Finishing part, 20: Groove part, 2
2: cutting edge, 28: female thread, 30: nut material (female thread material), 40: incomplete part (top of female thread).

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a build-up tap that is provided with a threaded portion for processing and is screwed into the inner circumferential surface of an internally threaded material to form an internal thread on the inner circumferential surface by plastic working, A build-up tap characterized in that a wiper blade section is provided adjacent to the rear side of the working thread part in the relative spiraling direction with respect to the female thread material, for cutting off the top of the thread that is raised by the working thread part. . (2) The wiper edge portion has a chamfered portion in which the diameter of the cutting edge gradually increases as it moves away from the threaded portion for processing, a finishing portion where the diameter of the cutting edge is constant following the chamfering portion, and the chamfered portion and the finishing portion. The raised tap according to claim 1 of the utility model registration claim, which is provided with a groove portion formed across the ridge.