JPH078107Y2 - Tap with Inner Diameter Finishing Blade - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tap for cutting an internal thread, and more particularly to an improvement on a tap with an internal diameter finishing blade for simultaneously performing internal diameter finishing of the internal thread.

BACKGROUND ART Conventionally, taps have been frequently used as processing tools for forming internal threads, but one type of such taps has a male thread part with a root diameter larger than the prepared hole diameter, and at the same time cutting the internal thread. There is a tap with an inner diameter finishing blade that performs inner diameter finishing for female threads. For example, Jikho Sho 57
The tap described in Japanese Patent Publication No. -50177 is an example, and in such a tap, a cutting burr is not generated at the top of the thread of the internal thread, and the variation in the prepared hole diameter is corrected to correct the internal diameter of the internal thread. There are advantages such as improvement of the size system.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a tap with an inner diameter finishing blade, since the inner diameter of the female screw is finished at the tip of the male screw portion, the cutting resistance at the beginning of tapping is large and the biting is poor, and the mountain is thin. There is a drawback that the inner diameter tends to be thin.

The present invention has been made in view of the above circumstances, and the purpose thereof is to improve the bite at the beginning of tapping and prevent the thinning of the mountain and the thinning of the inner diameter.

Means for Solving the Problems In order to achieve the above object, the present invention has an inner diameter finish having a male thread portion having a root diameter larger than the prepared hole diameter, and cutting the female thread and finishing the inner diameter of the female thread at the same time. In the bladed tap, the root diameter of the tip side portion of the male screw portion is set to a constant dimension smaller than the prepared hole diameter.

Action and effect of the invention In such a tap with an inner diameter finishing blade, the root diameter of the tip side of the male thread is smaller than the prepared hole diameter. Only the bite bites into the inner peripheral surface of the pilot hole to machine the thread groove of the female screw, and then the inner diameter of the female screw is finished at a portion where the root diameter is larger than the pilot hole diameter.

Therefore, according to such a tap with an inner diameter finishing blade of the present invention, the biting at the beginning of tapping is improved, and the mountain lean and the inner diameter lean are reduced. Moreover, since the thread thinness and the inner diameter thinness at the beginning of tapping are generated near the top of the thread ridge of the female screw, they are satisfactorily cut and removed in the subsequent inner diameter finishing.

On the other hand, since the above-mentioned valley diameter is a constant dimension, for example, as compared with the case where the valley diameter is gradually reduced toward the tip end side of the tap corresponding to the change in the outer diameter of the bite portion, the valley diameter at the tap tip side is Can be maintained at a relatively large value, a decrease in strength can be suppressed, and a cutting edge or the like due to cutting resistance can be prevented.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front view showing a tap with an inner diameter finishing blade (hereinafter, simply referred to as tap) 10 which is an embodiment of the present invention.
The tap 10 is composed of a male screw portion 12 on the front end side and a shank portion 14 on the base end side, and the male screw portion 12 is provided with a thread 16 corresponding to a female screw to be formed. Also,
The female screw portion 12 is composed of a tapered biting portion 18 in which the height of the screw thread 16 is gradually reduced, and a cylindrical complete ridge portion 20 in which the height of the screw thread 16 is substantially equal. Then, such a male screw portion 12 is provided with four grooves 22 at equal angular intervals in parallel with the axis of the tap 10, and a cutting edge 24 is provided at one end of the thread 16 divided by the grooves 22. The chips formed and cut by the cutting edge 24 are discharged through the groove 22.

On the other hand, the root diameter of the male screw portion 12 is the bite portion 18 and the complete mountain portion 20.
And is different. That is, as shown in FIG.
The root diameter d ₁ of the bited portion 18 is smaller than the diameter dimension D of the prepared hole in which the internal thread is to be formed, whereas the root diameter d ₂ of the complete crest portion 20 is larger than the prepared hole diameter D. Further, the prepared hole diameter D is smaller than the inner diameter of the female screw to be formed, and the root diameter d ₂ of the complete crest portion 20 is approximately the same as the inner diameter of the female screw to be formed, strictly speaking considering the elastic deformation of the work material. The size is set so that a female screw having a desired inner diameter can be obtained after cutting. The dimension S in FIG. 2 is an effective diameter.

Then, such a tap 10 is attached to a tapping machine or the like, and is screwed into the prepared hole previously formed in the workpiece from the tip side thereof, whereby the internal thread of the internal thread is finished simultaneously with the cutting of the internal thread. Figure 3 shows
FIG. 3 is a view for explaining a cutting process of the female screw 26 by the tap 10, and first, a biting part is formed in the prepared hole 28 shown by a chain line.
When the 18 is screwed in, the root diameter d ₁ of the bite part 18 is smaller than the prepared hole diameter D, so that only the thread 16 is prepared in the prepared hole 28.
The thread groove 30 of the female screw 26 is cut into the inner peripheral surface of the female screw 26 in order. The thin lines shown in the thread groove 30 are the
3 illustrates a biting shape with respect to a prepared hole 28 of the cutting edge 24 in 18. Then the thread groove so formed
When the thread 16 of the complete ridge 20 is screwed into the thread 30, the valley diameter d ₂ of the complete ridge 20 is larger than the prepared hole diameter D, so that the crest 32 of the female thread 26 in the valley of the thread 16 is 32. Is cut and the inner diameter is finished.

As described above, in the tap 10 of the present embodiment, after the thread groove 30 is cut by the biting portion 18, the inner diameter finish is performed by the complete crest portion 20, so that a cutting burr may occur at the crest 32 of the female screw 26. In addition, the dimensional accuracy of the inner diameter of the female screw 26 is improved regardless of the dimensional accuracy of the prepared hole 28.

Further, in the bite portion 18, only the screw thread 16 bites into the prepared hole 28 to cut the thread groove 30, so that the bite is good at the beginning of tapping and the thread thinning and the inner diameter thinning are reduced. Moreover, such a mountain thinness or inner diameter thinness at the beginning of tapping is usually generated only in the vicinity of the inner peripheral surface of the prepared hole 28, that is, in the inner peripheral side of the crest 32 of the female screw 26, so that the complete mountain portion 20 It is excellently cut and removed when finishing the inner diameter by.

Further, the valley diameter d ₁ is constant regardless of the change of the outer diameter, and the groove depth of the screw thread 16 becomes shallower toward the tip of the tap, so that, for example, when the outer diameter of the chamfered portion 18 changes. Screw thread 16 has a small overall diameter, and the valley diameter on the tap tip side is maintained at a relatively large value compared to the case where the valley diameter gradually decreases toward the tap tip side. The chipping of the blade due to the resistance is prevented.

Next, the test results conducted by the present inventors using the above-described tap 10 and four types of conventional taps 34, 36, 38, 40 shown in FIGS. 5 to 8 respectively. explain.

First, the four types of taps 34, 36, 38, 40 will be described. The tap 34 (conventional product I) is a normal tap having no inner diameter finishing blade, and the root diameter d of the male screw portion is larger than the prepared hole diameter D. The diameter D of the prepared hole is small and is set to be substantially the same as the inner diameter of the female screw 26 to be formed. Therefore, in the tap 34, as shown in FIG. 9, the inner peripheral surface of the prepared hole 28 becomes the peak 32 as it is, and the thread groove 30 is cut on the inner peripheral surface by the cutting edge of the bite portion. Internal thread 26
Is formed.

The tap 36 (conventional product II) has a reamer 42 provided at the tip of the tap 34. The prepared hole diameter D is smaller than the diameter R of the reamer 42, and the diameter R is substantially the same as the inner diameter of the female screw 26. They are set to the same size. Therefore, in such tap 36, as shown in FIG.
The inner surface of the prepared hole 28 is cut by 42, and then the thread groove 30 is cut by the cutting edge of the bite portion, whereby the female screw 26 is formed.

Further, the tap 38 (conventional product III) is a conventional tap having an inner diameter finishing blade as described in Japanese Utility Model Publication No. 57-50177, in which the root diameter d of the male thread portion is larger than the prepared hole diameter D. The root diameter d is set to be approximately the same as the inner diameter of the female screw 26.
Therefore, in such a tap 38, as shown in FIG. 11, from the beginning of tapping, the thread crest 30 is machined and the crest 32 is machined at the same time, and then the thread groove 30 is completely machined. By doing so, the internal thread 26 is formed.

In addition, the final tap 40 (conventional product IV) has the shape of the thread of the chamfered portion similar to that of the complete thread as described in, for example, British Patent Application Publication No. 1584771 (1977). The valley diameter d ₁ of the bite portion is continuously increased from the tip toward the complete peak portion, like the outer diameter, and the prepared hole diameter D is larger than the valley diameter d ₂ of the complete peak portion. The size is set to be large and substantially the same as the inner diameter of the female screw 26. Therefore, in such tap 40, as shown in FIG. 12, the inner peripheral surface of the prepared hole 28 becomes the peak 32 as it is, and the thread groove 30 is cut on the inner peripheral surface by the cutting edge of the bite portion. By doing so, the female screw 26 is formed. The chips in this case have a substantially similar shape.

Table 1 shows the results of examining these five taps for these taps. As is clear from the test results, all of the conventional products have advantages and disadvantages and are not always sufficiently satisfactory.
In No. 10, good results were obtained for all of the above five test items. In the table, ⊚ indicates that there is no problem and is good, ○ indicates that it is normal, and x indicates that there is a problem.

Although one embodiment of the present invention and the test results have been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, in the above embodiment, the root diameter d ₁ of the bite part 18 is set to the prepared hole diameter D.
It is designed to be smaller than that, and after the thread groove 30 is completely cut by the cutting edge 24 of the bite portion 18, the inner diameter is finished in the complete mountain portion 20, which is shown in FIG. Like the tap 50, it is possible to change the root diameter in the middle of the biting portion 18, and it is also possible to change it in the middle of the complete mountain portion 20.

Further, in the above-mentioned embodiment, a step is formed between the valley diameters d ₁ and d ₂ , but the valley diameter is continuously changed, and the prepared hole diameter D
It is also possible to intersect with.

Further, although four linear grooves 22 are provided in the above-described embodiment, the number of the grooves 22 can be appropriately changed, and of course, a twist groove that is inclined with respect to the axis of the tap 10 can be provided. .

Although not illustrated one by one, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a front view of a tap with an inner diameter finishing blade according to an embodiment of the present invention. FIG. 2 is a diagram showing the tip of the tap shown in FIG. 1, and is a diagram for explaining the relationship between the root diameter of the male screw portion and the prepared hole diameter. FIG. 3 is a view for explaining the cutting process of the tap shown in FIG. FIG. 4 is a view showing a tip portion of another embodiment of the present invention. 5, FIG. 6, FIG. 7, and FIG. 8 are views showing the tip portion of the conventional tap, respectively, corresponding to FIG. 9, 10, 11 and 12 are respectively FIG. 5, FIG. 6, FIG. 7 and FIG.
It is a figure explaining the cutting process of the tap of a figure, and is a figure corresponding to the said each FIG. 10,50: inner diameter finish bladed taps 12: external thread portion, 26: female thread 28: pilot hole D: hole diameter, d _1, d _2: minor diameter

Claims (1)

[Scope of utility model registration request] 1. A tap with an inner diameter finishing blade, which has a male thread portion having a valley diameter larger than the prepared hole diameter, and at the same time finishes the inner diameter of the female thread by cutting and processing the female thread. A tap with an inner diameter finishing blade having a constant diameter smaller than the prepared hole diameter.