TW201334899A - Cutting tap - Google Patents

Abstract

This invention provides a cutting tap capable of stably forming high-precision inner threads. The cutting tap of this invention comprises a leading part (1) including a plurality of threads (10) formed in a manner that the outer diameter of the threads gradually becomes smaller toward the axial front side; and a complete thread part (2) including a plurality of threads (20) with a constant outer diameter in the axial direction. In this cutting tap, the complete thread part (2) comprises a valley floor uniform-diameter part (2A) having threads (20A) of which the effective diameter (d2) and the valley diameter (d1) are the same relative to the threads (10) of the leading part (1); and a valley floor large-diameter part (2B) disposed continuously at the axial rear side of the valley floor uniform-diameter part (2A) and having threads (20B) of which the effective diameter (d2) is the same as that of the threads (10) of the leading part (1), and the valley diameter (d1') is larger than that of the threads (10). A valley floor cutting edge (6) is formed at the front side edge of the rotation direction in the valley floor portion of the valley floor large-diameter part (2B) .

Description

Cutting screw tap

This invention relates to a cutting screw that forms an internal thread by cutting.

As a screw tap for forming a high-precision internal thread, a tapping with a reamer as shown in Fig. 8 is known (Non-Patent Document 1). The tapping with the reamer includes: a squeegee portion 100 that processes the inner diameter of the guide hole of the internal thread; and a tapping portion 101 that is integrally disposed behind the axis direction of the reamer portion 100.

If the internal thread is formed by the tapping with the reamer, the inner diameter of the guide hole of the internal thread is processed by the reamer portion 100 before the internal thread is formed by the tapping portion 101, so even in the original guide hole When there is unevenness in the inner diameter, a high-precision internal thread can be formed.

For example, in the case of manufacturing a nut, first, a nut base having a guide hole having an internal thread is formed, and secondly, an internal thread is formed in an inner diameter of the guide hole. Here, since the guide hole of the internal thread is generally formed by pressing or pressing, the inner diameter of the guide hole existing in the internal thread generates a shear surface and a fracture surface, and due to the portion of the shear surface and the fracture surface Part of the case where the inner diameter of the pilot hole is slightly different. Therefore, if the internal thread is formed by the ordinary tap without the knives portion 100, the inner diameter of the internal thread is different due to the portion of the shear surface and the portion of the fracture surface, and the precision of the internal thread is not obtained. Hey. On the other hand, if the internal thread is formed by the above-mentioned screw with the reamer, even if the inner diameter of the guide hole of the internal thread is slightly different due to the portion of the shear surface and the portion of the fracture surface, the formation is caused by the formation. Before the internal thread, The reamer portion 100 processes the inner diameter of the guide hole of the internal thread, so that it is easy to obtain the internal thread precision as a purpose.

[Previous Technical Literature] [Patent Literature]

[Non-Patent Document 1] Japanese Industrial Standard "Threading Tool Terms - Part 1: Screw Attack" (B0176-1: 2002)

However, even in the case of using the screw with the reamer, there are the following problems. That is, even if the inner diameter of the guide hole of the internal thread is machined by the squeegee portion 100, when the internal thread is formed by the tapping portion 101 in the inner diameter of the machined guide hole, a burr is generated at the top of the thread of the internal thread. The situation. In this case, since the height of the thread of the internal thread becomes high due to the burr, the inner diameter of the internal thread becomes too small, and the purpose of the internal thread precision cannot be obtained.

The problem to be solved by the invention is to provide a cutting screw that can stably form a high-precision internal thread.

In order to solve the above problems, a cutting screw tap is provided, comprising: an indentation portion including a plurality of threads formed in such a manner that an outer diameter thereof gradually becomes smaller toward the front in the axial direction; a full thread portion including the axial direction The outer diameter is a fixed number of threads; and the cutting screw tapping adopts the following structure: the full thread portion includes: a valley bottom same diameter portion, and the thread includes a thread having the same effective diameter and small diameter with respect to the thread of the inverted tooth portion; Large diameter section of the valley, which continuously Provided in the axial direction rear of the same diameter portion of the valley bottom, and comprising a thread having the same effective diameter but a small diameter with respect to the thread of the inverted tooth portion; and forming an edge on the front side in the rotation direction of the bottom portion of the large diameter portion of the valley bottom portion There is a bottom knife.

When the internal thread is formed by the cutting screw, the internal thread is formed in the inverted portion, and the top of the thread of the internal thread is machined by the bottom cutter of the large diameter portion of the valley, so that even within the guide hole of the internal thread When the diameter is uneven, the inner diameter of the internal thread is also fixed, and a high-precision internal thread can be formed. Further, even when the internal thread is formed by the inverted portion, the burr is generated at the top of the thread of the internal thread, and the burr can be cut by the bottom cutter of the large diameter portion of the bottom.

In the cutting screw of the present invention, since the internal thread is formed by the inverted portion, the top of the thread of the internal thread is machined by the bottom cutter of the large diameter portion of the bottom portion, so that the high-precision internal thread can be stably formed.

Hereinafter, the cutting screw attack of the embodiment of the invention will be described. The cutting screw is tapped on a nut tapping used in the manufacture of a nut by a tapping machine. As shown in Fig. 1, the nut tapping has an inverted tooth portion 1 which includes a front outer diameter toward the axial direction. a plurality of threads 10 formed in a gradually smaller manner; a fully threaded portion 2 comprising a plurality of threads 20 having a fixed outer diameter along the axial direction; and a cylindrical handle 3. The full thread portion 2 is continuously provided rearward in the axial direction of the inverted portion 1, and the handle 3 is provided continuously behind the axial direction of the full thread portion 2.

In the screw tapping, the groove 4 which passes through the fully threaded portion 2 from the front end in the axial direction of the inverted portion 1 to the shank 3 is formed, and by the groove 4, the tooth can be inverted The respective threads 10 of the portion 1 are divided into the circumferential direction, and the respective threads 20 of the completely threaded portion 2 are also divided into the circumferential direction. Further, as shown in FIG. 2, a cutter 5 is formed in a portion where the inner surface of the groove 4 intersects the surface of the screw 10, and the cutting debris generated by the cutter 5 can be discharged through the groove 4. In the inverting portion 1, a retracting portion (a so-called retracting portion of the inverted portion) in which the height of the thread 10 is gradually lowered is attached to the rear side in the rotation direction from the cutter 5. The grooves 4 are formed in plural at intervals in the circumferential direction at a fixed interval.

As shown in FIG. 3, the inverted portion 1 includes a plurality of threads 10 that obliquely remove the incomplete shape of the top of the thread 10 so as to be inclined toward the front in the axial direction. Although the outer diameter d _c of each thread 10 of the inverted portion 1 gradually decreases toward the front in the axial direction, the effective diameter d ₂ and the small diameter d _{1 of} each thread 10 are fixed along the axial direction.

Here, the effective diameter d _{2 of} the thread 10 is fixed along the axial direction, and is not necessarily strictly defined as a fixed, but to reduce the cutting resistance when the internal thread is formed, and also includes the effective diameter d _{2 of the} thread 10 from the axial direction. The inverted cone with a slight inclination (1/1000~3/1000 tilt) slightly smaller toward the rear. Further, the effective diameter d ₂ of the thread 10 is the diameter of the virtual cylinder whose width of the thread groove is equal to the width of the thread 10. The small diameter d ₁ of the thread 10 is the diameter of the virtual cylinder that is in contact with the bottom of the thread. The outer diameter d _c of the thread 10 is the diameter of the virtual cone that meets the top of the thread 10.

The number of threads of the inverted portion 1 can be set to be in the range of 13 to 25. When the number is set to 13 or more, the cutting load of each of the threads of the inverted portion 1 when the internal thread is formed is lowered, so that the internal thread having a good surface roughness can be formed. Moreover, if it is set to 25 or less, the guide hole H for the internal thread can be prevented (see According to Figure 4), the cutting is poor.

The thread 20 constituting the fully threaded portion 2 includes fully shaped threads 20A, 20B. Further, although the complete thread portion of the respective screw 2 20A, 20B of the outer diameter d and the effective diameter d ₂ along the axial direction are fixed, but the diameter _{d. 1} along the axial direction to vary halfway. That is, the full thread portion 2 includes a valley bottom same diameter portion 2A including a thread 20A having the same effective diameter d ₂ and small diameter d ₁ as the inverted portion 1, and a valley large diameter portion 2B including the inverted teeth The thread 10 of the portion 1 has a thread 20B having the same effective diameter d ₂ but a small diameter d ₁ '. The valley bottom large diameter portion 2B is continuously disposed rearward in the axial direction of the valley bottom same diameter portion 2A.

Here, the outer diameter d of the threads 20A, 20B of the full thread portion 2 is the diameter of the virtual cylinder contacting the top of the thread 20A (or 20B). The small diameter d _{1 of the} thread 20A and the small diameter d ₁ ' of the thread 20B are the diameters of the virtual cylinder contacting the bottom of the thread. The effective diameter d ₂ of the threads 20A, 20B is the diameter of the virtual cylinder such that the width of the thread groove is equal to the width of the thread 20A (or 20B).

A bottom cutter 6 is formed at an edge on the front side in the rotation direction of the bottom portion of the valley bottom large diameter portion 2B of the full thread portion 2. Here, the relief surface of the bottom cutter 6 is the surface of the bottom of the valley large diameter portion 2B, and the cut surface of the bottom cutter 6 is the inner surface of the groove 4.

Further, in order to prevent the interference of the thread guide hole H, the small diameter thread portion of the inverted ₁ d 1 (i.e., with the bottom diameter d ₁ of the small diameter portion 2A) is set to be smaller than the inner diameter of the internal thread of the reference size. On the other hand, in order to process the top of the thread 30 (refer to FIG. 5) of the internal thread formed by the inverted portion 1, the bottom cutter 6 is brought into contact with the top of the thread 30 of the internal thread (refer to FIG. 6), and The small diameter d ₁ ' of the large-diameter portion 2B of the valley bottom is set to be the same as the reference dimension of the inner diameter of the internal thread, or is set to be large within the tolerance range of the inner diameter of the internal thread. The reference dimension of the inner diameter of the internal thread is the reference for the thread tolerance. For example, for the metric thread, the Japanese industrial standard "Generally used metric thread - Part 4: Reference size" (B0205-4:2001) As stated. The reference dimension of the inner diameter of the metric thread can be specifically determined (the nominal diameter of the thread) - 1.0825 x (the distance between the threads). In addition, the uniform standard thread is specified in the Japanese industrial standard "Unified standard coarse thread" (B0206: 1973), specifically, {(nominal diameter of thread) -1.082532 / (number of threads per 25.4 mm) )}×25.4 and seek.

The number of threads of the same diameter portion 2A can be set to be in the range of 2 to 8. When the top of the thread 30 of the internal thread is machined by the bottom cutter 6 of the large diameter portion 2B of the valley bottom, the axis of the nut base N (see FIG. 6) of the same diameter portion 2A can be secured. The guiding action of the direction is such that the axial direction of the nut base N when the nut is tapped once is exactly the same as the distance between the threads 20A, and as a result, the shape of the thread 30 of the internal thread can be prevented from being deformed (so-called internal thread) Expanded). By setting it to 8 or less, the number of threads of the full thread part 2 does not become excessive.

The number of threads of the large diameter portion 2B of the valley bottom can be set to be in the range of 2 to 5. When the number is set to two or more, the top of the thread 30 of the internal thread can be surely processed. When the number is five or less, the number of threads of the full thread portion 2 can be controlled as a whole, and the time required for the nut base N to pass through the full thread portion 2 can be short, so that the productivity of the nut is excellent.

Further, in all of the threads 10, 20A, and 20B of the inverted portion 1 and the full thread portion 2, in order to reduce the cutting resistance when the internal thread is formed, the effective diameter d _{2 may be} gradually changed from the front to the rear in the direction of rotation. Small concession (the overall retreat of the thread). In this case, the effective diameter d ₂ and the small diameters d ₁ and d ₁ ' vary in the direction of rotation, but are in the direction of the rotation direction (and the end of the cutter 5 side) directly related to the cutting of the internal thread. The middle path is the benchmark.

The outer circumference of the shank 3 is a cylindrical surface, and the outer diameter d _{s thereof} is set to be the same as or smaller than the small diameter d ₁ ' of the large-diameter portion 2B of the valley bottom.

Moreover, the nut tapping is made of high speed tool steel as a base material. Here, since the screw root of the full thread portion 2 is not provided with a relief portion whose diameter is reduced toward the rear in the rotation direction, or even if it is provided, the relief surface of the bottom cutter 6 is required to have weld resistance. Therefore, in order to prevent the welding of the bottom cutter 6, it is preferable to apply a hard film to at least the portion of the screw root of the entire thread portion 2. Examples of the type of the hard film include metal carbides such as TiC, metal nitrides such as TiN and TiAlN, and metal carbonitrides such as TiCN, or such solid solutions. When the hard film is applied to the entire threaded portion of the combined inverted portion 1 and the full thread portion 2, the wear resistance of the cutter 5 can be improved.

The manufacture of the above-described nut tapping can be performed, for example, in the following manner. First, the outer circumference of the round bar containing the high speed tool is ground to form the groove 4. Next, the threads 10 of the inverted portion 1 and the threads 20A, 20B of the fully threaded portion 2 are formed by grinding. Here, when the threads 20A and 20B are formed by the polishing process, the small diameter d ₁ ' of the screw 20B of the large-diameter portion 2B of the valley bottom is polished so as to be larger than the small diameter d ₁ of the screw 20A of the valley-like diameter portion 2A. Thereafter, the top portion of the thread 10 of the portion of the inverted portion 1 is obliquely cut so that the outer diameter d _c of the thread 10 of the inverted portion 1 gradually decreases toward the front in the axial direction. At this time, at the top of the thread 10, a relief portion whose height toward the rear in the rotation direction is also lowered is also provided. Finally, a hard film is applied to the threaded portions of the combined inverted portion 1 and the fully threaded portion 2.

Next, an example of the use of the nut to make a nut using the nut will be described.

The nut screw is rotated in a fixed position, and the nut base N (refer to FIG. 4) is engaged with the front end of the nut tap. Thus, as shown in FIG. 4, first, the thread 10 of the inverted portion 1 is introduced into the inner diameter of the guide hole H of the internal thread, and the inner diameter of the guide hole H is cut. At this time, the portion existing between the adjacent threads 10 of the inverted portion 1 generates a burr b. Further, since the effective diameter d ₂ of the thread 10 in the inverted portion 1 is fixed along the axial direction, the burr b cannot be removed even if the cutting of the inverted portion 1 is performed. Therefore, as shown in FIG. 5, the nut base N is in the state of being adjacent to the thread 20A of the full thread portion 2, and is also in the state of the residual burr b. At this time, there is a state in which the burr b is present at the top of the thread 30 of the internal thread of the nut base N, and since the height of the thread 30 of the internal thread is increased by the height corresponding to the burr b, the internal thread exists in this state. The inner diameter is too small.

However, thereafter, as shown in FIG. 6, the top of the thread 30 of the internal thread is machined by the bottom cutter 6 formed in the large diameter portion 2B of the full thread portion 2, at which time the thread 30 is cut by the bottom cutter 6. The top edge of the b. Further, when the top of the thread 30 of the internal thread is machined by the bottom cutter 6, the thread 20A of the same diameter portion 2A is threaded into the internal thread, so that the nut base N when the nut is tapped once is rotated. The amount of advancement in the axial direction is completely the same as the distance between the threads 20A, and the internal thread can be prevented from being enlarged. As a result, within the nut base N The diameter forms a high-precision internal thread and completes the nut.

However, in the case where the guide hole H of the internal thread is formed by pressing or pressing, the inner diameter of the guide hole H is generated to generate the shear surface and the fracture surface, and the portion of the shear surface and the fracture surface Part of the case where the inner diameter of the pilot hole H is slightly different. In other words, if the internal thread is formed by the nut tapping, the top of the thread 30 of the internal thread is machined by the bottom cutter 6 of the large diameter portion 2B after the internal thread is formed by the inverted portion 1. Therefore, the inner diameter of the internal thread can be fixed, and a high-precision internal thread can be formed.

As described above, when the internal thread is formed by the nut tapping, the internal thread is processed by the bottom cutter 6 of the large diameter portion 2B of the second half of the full thread portion 2 after the internal thread is formed by the inverted portion 1. Since the inner diameter of the guide hole H of the internal thread has irregularities, the inner diameter of the internal thread can be fixed and a high-precision internal thread can be formed. Further, even when the internal thread is formed by the inverted portion 1, the burr b is generated at the top of the thread 30 of the internal thread, and the burr b can be scraped off by the bottom cutter 6 of the large diameter portion 2B of the bottom.

Further, as the cutting screw tapping of the top of the thread 30 capable of machining the internal thread, it is also conceivable to set the small diameter d ₁ to be larger over the entire length of the inverted portion 1 and the full thread portion 2, but if so, Due to the interference of the screw root of the screw, the cutting torque is too large, and smooth tapping cannot be achieved. On the other hand, since the nut tapping of the above-described embodiment is such that the small diameter d ₁ ' is large in the portion of the large-diameter portion 2B of the full thread portion 2, the cutting torque can be minimized, and the tapping can be minimized. Smooth tapping.

The bottom large diameter portion 2B can be adjacent to the threads 20B, 20B as shown in FIG. The surface of the bottom of the valley is formed in a straight line in a straight line shape, and as shown in FIG. 7( a ), a portion of the side connecting the thread 20B from the bottom of the valley bottom is formed in a circular arc shape. Further, as shown in Fig. 7(b), the surface of the valley bottom between the adjacent threads 20B and 20B may be formed in a circular arc shape in total. If so, when the top of the thread of the internal thread is cut by the bottom cutter 6 between the adjacent threads 20B, 20B, the portion connecting the side from the top of the thread of the internal thread is rounded, so that it is completed. The thread can smoothly perform the thread engagement of the externally threaded part, and becomes an internal thread excellent in the workability of the thread engagement.

However, the manual screw tap used in the above-described embodiment is used in order to form the internal thread to make it rotate forward, and then to reverse the internal thread for pulling it out. The tapping is always used to make it rotate forward. The present invention is preferably applied to a screw tap which is used for the forward rotation of the nut as in the above-described embodiment. The reason is as follows. In other words, the screw tap that is always used for normal rotation is used because the full thread portion 2 surely penetrates the guide hole H of the internal thread. Therefore, if the present invention is applied to such a screw tapping, the valley bottom diameter of the entire thread portion 2 can be completely The portion 2B does machine the top of the thread 30 of the internal thread over the entire length of the thread.

Further, in the above-described embodiment, a screw tap for a triangular thread having a bilaterally symmetrical shape will be described as an example. However, the present invention can also be applied to a thread other than a triangular thread (such as a trapezoidal thread) or a special thread that is not bilaterally symmetric. (Sawtooth thread, etc.) Attack with a screw.

1‧‧‧ inverted teeth

2‧‧‧Complete thread

2A‧‧‧ Valley Bottom

2B‧‧‧ Valley Bottom Section

6‧‧‧ Valley cutter

10‧‧‧ thread

20‧‧‧ thread

20A‧‧ thread

20B‧‧ thread

d‧‧‧The outer diameter of the complete thread

d ₁ ‧ ‧ footpath

d ₁ '‧‧‧ Trail

d ₂ ‧‧‧effective trail

d _c ‧‧‧ outer diameter of the inverted tooth

d _s ‧‧‧ outer diameter of the handle

Fig. 1 is a front view showing the cutting screw of the embodiment of the invention.

Figure 2 is an enlarged cross-sectional view taken along line II-II of Figure 1.

Fig. 3 is an enlarged cross-sectional view showing the threaded portion of the cutting screw shown in Fig. 1.

Fig. 4 is an enlarged cross-sectional view showing a state in which the thread of the inverted portion shown in Fig. 3 is engaged with the inner diameter of the guide hole of the internal thread.

Fig. 5 is an enlarged cross-sectional view showing the state in which the nut base shown in Fig. 4 is adjacent to the thread of the full thread portion.

Fig. 6 is an enlarged cross-sectional view showing a state in which the top of the thread of the internal thread is cut by the large diameter portion of the bottom of the full thread portion shown in Fig. 3.

Fig. 7(a) is a view showing a modification of the large-diameter portion of the valley bottom shown in Fig. 3, and Fig. 7(b) is a view showing another modification of the large-diameter portion of the valley bottom shown in Fig. 3.

Fig. 8 is a view showing the screw tap of the prior attached reamer.

1‧‧‧ inverted teeth

2‧‧‧Complete thread

3‧‧‧ handle

2A‧‧‧ Valley Bottom

2B‧‧‧ Valley Bottom Section

6‧‧‧ Valley cutter

10‧‧‧ thread

20A‧‧ thread

20B‧‧ thread

d‧‧‧The outer diameter of the complete thread

d ₁ ‧ ‧ footpath

d ₁ '‧‧‧ Trail

d ₂ ‧‧‧effective trail

d _c ‧‧‧ outer diameter of the inverted tooth

d _s ‧‧‧ outer diameter of the handle

Claims (1)

A cutting screw taper comprising: an indentation portion (1) comprising a plurality of threads (10) formed to gradually decrease in outer diameter (d _c ) toward the front in the axial direction; and a full thread portion (2) And comprising a plurality of threads (20) whose outer diameter (d) is fixed along the axial direction; wherein the full thread portion (2) comprises: a valley bottom diameter portion (2A), which comprises The thread (10) of the tooth portion (1) has a thread (20A) having the same effective diameter (d ₂ ) and small diameter (d ₁ ); and a large diameter portion (2B) of the valley bottom, which is continuously disposed at the same diameter of the valley bottom a portion (2A) rearward of the axial direction and including a thread (20B) having the same effective diameter (d ₂ ) but a small diameter (d ₁ ') with respect to the thread (10) of the above-mentioned inverted portion (1); A bottom cutter (6) is formed at an edge of the front side in the rotation direction of the bottom portion of the valley large diameter portion (2B).