JPH08101Y2 - Tap - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a tap for thread cutting, specifically, for smoothing the thread cutting work and improving the accuracy of a female screw to be cut.

<Prior Art> FIG. 5 shows a typical tap used for processing an internal thread. This is a straight groove tap in which the groove 1 is straight, the cutting tooth part 2 consisting of a biting part 3 and a complete thread part 4 following it.

When the internal thread is cut by such a tap, the biting portion 3 performs a cutting action to gradually create a thread groove, and the complete thread portion 4 meshes with the groove and serves as a guide when the tap itself moves.

<Problems to be solved by the invention> By the way, when cutting a female screw with a tap, the rake angle of the cutting tooth at the chamfered part, the clearance angle of the cutting tooth outer periphery and its inclination angle, and the screw applied to the flank surface of the cutting tooth In addition to the difference in clearance angle with respect to the regular twisting direction, there is the magnitude of the thrust applied to the tap itself. Therefore, there is a problem that the axial progress of the tap varies and a reaction force due to cutting resistance acts, and in the created female screw, the end on the side where the tap bites expands and the surface accuracy decreases. It was happening.

In order to deal with such a problem, for the spiral groove tap, either the leading side or the trailing side of the chevron-shaped tooth surface formed along the line of intersection between the inner wall surface of the tooth groove and the flank surface of the incisor tooth. With a flat second negative cut from the root of the screw to the peak of the screw (Shokai Sho 60-194
425) is proposed. However, as a matter of course, in these improvement plans, the negative second angle causes plastic working instead of cutting, which results in great resistance during cutting. As a result, the same frictional welding phenomenon as that of the constituent cutting edge of the cutting tool is likely to occur in the portion, and as the number of times of use (machining) increases, the finish accuracy of the flank surface of the female screw decreases and the life of the tap itself decreases. Was there.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tap in which the accuracy of a created internal thread and the life of the tap are improved.

<Means for Solving the Problem> Therefore, in order to solve this problem, in the present invention, a plurality of cutting teeth on the rear end side of the bite portion and a plurality of cutting teeth on the complete thread portion following the cutting tooth are provided. In the above, there is a relief that is formed below the tooth flank of at least one of the leading flank and the trailing flank and converges to the tooth groove bottom from the tooth flank toward the heel side, and On the other hand, the present invention proposes a tap characterized in that a relief having a height equal to or lower than the tooth height of an incisal tooth on the tip side adjacent to the lead is formed.

<Action> The creation of the internal thread is performed in the remaining part of the relief in the incisal line,
In addition, the guide of the tap itself is provided in the remaining part of the escape in the flank.

<Embodiment> An embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a partial perspective view of a tooth portion of a tap according to an embodiment of the present invention, and FIG. 2 is a side view thereof.
Further, FIGS. 3 and 4 show the AA cross section and B in FIG.
-B cross section is shown respectively. The tap according to this embodiment is one in which the present invention is applied to a straight groove tap having three grooves, and FIG. 5 is referred to for the entire configuration.

As shown in these figures, in the incisor 5 of the bite-in portion 3 and the incisor 6 of the full thread portion 4 following it, reliefs 7 and 8 are formed below the flanks 5a and 6a on the trailing side. ing.
In the case of the present embodiment, as shown in FIG. 3, the relief 7 of the cutting tooth 5 of the bite part 3 has the apex P on the cutting tooth line 5b side, and is smoothly located at the lower end of the cutting tooth 5, that is, the tooth groove bottom 9. It has converged. The apex P of the relief 7 has a height approximately equal to the tooth height of the cutting teeth 5 on the tip side adjacent to each other along the lead. Therefore, in the flank on the trailing side of the female screw, the portion cut by the cutting tooth 5 on the tip side is located at the escape 7 portion in the next cutting tooth 5.

On the other hand, the relief 8 on the incisal tooth 6 of the complete thread portion 4 is also smoothly converged on the tooth groove bottom 9 with the incisal line 6b side as the apex P ', similarly to the escape 7 on the incisal tooth 5 of the bite-in portion 3. However, the relief 8 has a height substantially equal to that of the last incisor 5 of the bite part 3. Incidentally, the complete thread portion 4 in this embodiment
Has reliefs 8 on the first three incisors 6 adjacent along the lead.

In the thread cutting with the tap having the above structure, first, the internal teeth are created by the cutting teeth 5 of the bite part 3. And as the tap rotates along the lead, 1
Cutting is performed for each cutting amount per cutting tooth 5. At this time, with the tap of this embodiment, escape to the flank 5a on the follower side.
Is provided, the cutting by the cutting tooth line 5b is performed in the remaining portion of the escape 7 on the trailing side.

By the way, in the straight groove tap as in the present embodiment, the reaction force caused by the cutting resistance exerts a force on the cutting tooth 5 to push it toward the trailing side. However, since the flank 5a on the trailing side is provided with the relief 7 as described above, the cutting tooth line 5b does not come into contact with the already cut portion, so that extra cutting, that is, enlargement of the female screw does not occur. On the other hand, as it rotates, the flank surface 5a gradually and continuously abuts the tooth space bottom 9 to guide the tap. As described above, in the tap of the present embodiment, even if there is a variation in the axial direction when biting and a reaction force due to cutting resistance, the angle shape of the created internal thread does not expand and the surface accuracy is ensured.

Cutting progresses from the chamfered portion 3 to the complete thread portion 4 as the tap progresses, but in the present embodiment, the complete thread portion 4 is cut.
Relief 8 on the first 3 incisors 6 along the lead at
Is provided. Therefore, even in this case, even if the cutting tooth 6 is pressed to the trailing side by the reaction force due to the cutting resistance, the cutting tooth line 6b is formed on most of the portion of the biting portion 3 cut by the cutting tooth 5.
Does not touch. Therefore, the angle shape of the female screw does not expand, and the surface accuracy is ensured to be high. Incidentally, since the tap completely meshes with the thread after the cutting is transferred to the complete thread portion 4, there is no variation in the way of progress, and the pressing by the above reaction force is not caused by the fourth and subsequent cutting teeth 6. There is no problem that the value becomes sufficiently small and the mountain shape expands.

Although the description of the embodiment has been completed, the present invention is not limited to this embodiment. For example, the above-described embodiment is not limited to the present invention.
It is applied to the straight groove tap of the main groove, but 4
It may be applied to taps with an even number of grooves such as the main groove,
It may be applied to a spiral groove tap having a spiral groove. In addition, as a result of the experiment, the relief formed on the incisor tooth of the complete thread portion following the bite portion can be created evenly in the circumferential direction to create a good female screw when balanced in the radial direction. confirmed. For example, in the case of a four-groove tap, it is sufficient to form a clearance in at least two facing cutting teeth out of four cutting teeth in one turn along the lead following the biting portion, and in a five-groove, it is possible to form a relief. The relief may be formed on all the incisors of the book. Further, when the present invention is applied to a spiral groove tap, the reaction force applied to the tap depends on the correlation between the winding direction of the screw and the twisting direction of the groove, and when applied to the straight groove tap, the reaction force applied to the tap due to the inclination of the biting part. Therefore, a clearance may be formed on the leading flank surface. Further, in both straight groove taps and spiral groove taps, further improvement in surface accuracy may be required, and flanks may be formed on both the leading side and the trailing side flanks.

<Effect of device> According to the tap according to the present invention, a relief is provided below the flanks of the cutting teeth of the bite portion and the cutting teeth of the complete thread portion, and the once cut portion is cut again by the next cutting tooth. Since this is not done, the surface precision of the created internal thread can be kept good even if a reaction force due to cutting resistance occurs, and the life of the tap itself does not decrease as in the conventional improvement plan.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing a tooth portion of a tap according to an embodiment of the present invention, and FIG. 2 is a side view thereof.
3 and 4 are a sectional view taken along the line AA and a sectional view taken along the line BB in FIG. 2, respectively, and FIG. 5 is a side view of a general tap. In the drawings, 1 is a groove, 2 is an incisal tooth portion, 3 is a toothed portion, 4 is a completely threaded portion, 5 and 6 are incisors, 5a and 6a are flank surfaces, 5b and 6b are incisal lines, and 7 and 8 Is the escape, and 9 is the root of the tooth space.

Claims (1)

[Scope of utility model registration request] 1. At least one of a leading flank and a trailing flank in a plurality of cutting teeth on the rear end side of a chamfered portion and a plurality of cutting teeth of a complete screw thread portion following the cutting tooth. Is a relief that is formed below the tooth surface side of the tooth surface and that converges to the tooth groove bottom from the tooth surface side to the heel side and that is less than or equal to the tooth height of the cutting tooth on the tip side adjacent to the cutting tooth along the lead. A tap formed by forming a relief having a height.