JPH0212023Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a raised tap that plastically deforms the surface of a pilot hole provided in a workpiece to form an internal thread, and in particular, it involves cutting and finishing the inner diameter of the formed internal thread. The present invention relates to a raised tap equipped with a reamer for reaming.

Prior Art Taps are often used as tools for forming internal threads. One type of such a tap has a male threaded portion on which a thread corresponding to the female thread to be formed is formed, and the male threaded portion is inserted into a pilot hole of approximately the same size as the effective diameter of the female thread previously provided in the workpiece. There is a build-up tap that plastically deforms the surface of the prepared hole by being screwed into it to form the female thread. This is mainly used for malleable workpieces, and by biting the thread of the tap into the surface of the prepared hole, the female thread is formed by the plastic flow generated on the surface, and the chips are removed. It has the excellent feature of not emitting any.

By the way, in such a build-up tap, the root diameter of the male thread part becomes the inner diameter dimension of the female thread to be formed, but in order to build up the necessary and sufficient amount of meat in the valley of the male thread part, it is necessary to prepare the workpiece in advance. It was necessary to strictly control the diameter of the pilot hole provided in the hole. In other words, if the diameter of the pilot hole is too small, the amount of meat that bulges due to plastic flow will increase, so there will be nowhere for the meat to go, and the tap setting torque will become excessive, leading to the tap breaking or causing frictional heat. If the diameter of the pilot hole is too large, the build-up of the material due to plastic flow will be insufficient, resulting in a female thread with an appropriate inner diameter. is not obtained. For this reason, when forming a pilot hole with a press punch or the like with high dimensional accuracy, it is possible to tap it as is, but when using a cutting tool such as a drill, the enlargement amount by the tool is unstable and the pilot hole can be tapped. Since the diameter of the tap varies, it is necessary to perform complicated work to obtain a predetermined dimensional accuracy, such as reaming the tap prior to tapping.

In addition, the top of the thread of the female thread formed in this way has a dent at the boundary between the flesh raised from both sides due to plastic flow, so it is not always possible to obtain a fully satisfactory female thread. It was hard to say.

On the other hand, a reamer that has a root diameter of the male thread portion smaller than the inner diameter dimension of the female thread to be formed and has a cutting edge on an outer circumference equal to the inner diameter dimension in the opposite direction to the screwing direction is used for the male thread portion. is integrally provided at the tip of the female thread on the same axis as the male thread, and when the male thread is rotated in the opposite direction and pulled out from the prepared hole after the female thread is formed, the inner diameter of the formed female thread is cut and finished. For example, raised taps designed to
It is disclosed in Publication No. 30041, etc.

A raised tap (hereinafter simply referred to as a tap) 30 shown in FIGS.
2, and a male threaded portion 36 in which a thread 34 is formed. The thread 34 has a shape corresponding to the female thread to be formed, but the diameter of the male thread 36 gradually decreases at the tip end thereof to form a chamfered portion. Further, the thread 34 is provided with projections 38 at four locations per lead, and these projections 38 are used to perform plastic working. Note that one oil groove 40 for supplying lubricating oil is provided in the axial direction in the male threaded portion 36.

FIG. 3 shows a state in which the male threaded portion 36 of the tap 30 is screwed into a pilot hole 44 provided in a workpiece 42, and the surface of the pilot hole 44 is plastically deformed to form a female thread 46. It is. here,
Since the root diameter d ₁ of the male threaded portion 36 is smaller than the inner diameter D ₁ of the female thread to be formed, the inner diameter of the female thread 46 formed in this way is also smaller than the desired inner diameter D ₁ . There is. Note that the diameter dimension D ₂ of the pilot hole 44 is approximately equal to the effective diameter of the female thread to be formed.

On the other hand, a reamer 48 is integrally connected to the tip of the male threaded portion 36 on the same axis as the male threaded portion 36 . The outer diameter d ₂ of the reamer 48 is equal to the inner diameter dimension D ₁ , and six straight grooves 50 are formed in the axial direction on the outer periphery of the reamer 48 .
Six cutting blades 52 are provided in the direction opposite to the screwing direction. Further, a chamfered portion 54 having a chamfered slope with a second angle is formed at the end of each of these cutting blades 52 on the male threaded portion 36 side.

When making a tap using such a tap 30, the male threaded portion 36 is first screwed into the prepared hole 44 from the tip side, and the outer diameter d ₂ of the reamer 48 is the diameter dimension of the prepared hole 44. Since D is smaller than ₂ ,
The reamer 48 is inserted into the pilot hole 44 prior to the male threaded portion 36 without interfering with the pilot hole 44. Therefore, as shown in FIG. 3, the inner circumferential surface of the prepared hole 44 has a female thread 46 whose inner diameter is smaller than the desired inner diameter _D1 due to the thread 34 of the male threaded portion 36. is formed.

Next, the tap 30 is rotated in the opposite direction and pulled out from the pilot hole 44, but the outer diameter of the reamer 48
Since d ₂ is equal to the inner diameter dimension D ₁ , the above female thread 46
The top of the thread 56 is cut and finished by the cutting blade 52 of the reamer 48 to obtain a female thread 46' having the desired inner diameter dimension _D1 . FIG. 4 is a diagram showing a state in which the inner diameter of the female thread 46 is finished by cutting with the reamer 48 in this manner.

In such a tap 30, there is no need to bulge the surface of the pilot hole 44 so as to sufficiently fill the valley of the male threaded portion 36;
The accuracy required for the diameter dimension D ₂ of is relaxed, and since the top of the thread 56 of the female thread 46 formed by the male thread portion 36 is finished by cutting with the reamer 48, it is not raised. The recess 58 that occurs at the boundary between the two layers is removed, and a good internal thread 46' is obtained.

Moreover, such a tap 30 is provided separately from the external threaded portion 36 where a reamer 48 for finishing the inner diameter is used for tapping, and the cutting edge 52 of the reamer 48 is structurally suitable for simple means such as external surface machining. Therefore, it can be easily formed. Therefore,
There are no manufacturing restrictions even for small-diameter taps, which account for most of the demand, and the present invention can be applied to a wide range of taps, and the accuracy of the internal diameter dimension of the female thread to be formed is also improved.

Problems to be Solved by the Invention However, even with such conventional heaping taps, a portion of the flesh that should be removed by the reamer escapes to the flank side of the thread of the female thread and is not removed.
Sometimes it remained as a burr.

Means for Solving the Problems The present invention was made to solve the above problems, and its gist is to provide a male threaded portion with a thread corresponding to the female thread to be formed. The male threaded portion is screwed into a prepared hole of substantially the same size as the effective diameter of the female thread provided in advance on the workpiece, thereby plastically deforming the surface portion of the prepared hole to form the female thread, A reamer having a root diameter of the male threaded portion smaller than the inner diameter of the female thread to be formed and a cutting edge facing opposite to the threading direction on an outer circumference equal to the inner diameter thereof is provided at the tip of the male threaded portion. A type of embankment that is integrally provided on the same axis as the male thread, and finishes cutting the inner diameter of the formed female thread when the male thread rotates in the opposite direction and is pulled out from the pilot hole after forming the female thread. At the tap, the reamer has a root diameter equal to the inner diameter of the female thread to be formed, an outer diameter smaller than the diameter of the pilot hole, a thread angle equal to the thread of the male thread, and a bottom of the thread. A low thread whose width is equal to the width of the top of the female thread to be formed is provided on the same spiral as the thread of the male thread, and the cutting edge is provided at the bottom of the low thread. It is characterized by

Function and Effects of the Invention In such a build-up tap, when the male threaded portion is rotated in the opposite direction and pulled out from the prepared hole, and the inner diameter of the formed female thread is finished by cutting with a reamer, the reamer has a Since the low thread and the female thread are engaged, the meat to be cut and removed is prevented from escaping to the flank side, and the thread shape is appropriate even for workpieces that are prone to burrs, such as those with high malleability. This makes it possible to obtain a female thread.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings. In the following embodiments, the same parts as those in the conventional example are given the same reference numerals, and the explanation thereof will be omitted.

The raised tap (hereinafter simply referred to as tap) 60 shown in FIGS. 5 and 6 differs in the structure of the reamer 62 from the tap 30 of the conventional example. This reamer 62, as shown in detail in FIG. 7 and FIG.
4 on the same spiral. The root diameter d ₃ of the low thread 64 is equal to the inner diameter dimension D ₁ of the female thread to be formed, and the outer diameter d ₄ is approximately halfway between the diameter dimension D ₂ of the prepared hole 44 and the above-mentioned inner diameter dimension D ₁ . Furthermore, the width W of the root is equal to the width W of the crest of the thread of the female thread to be formed (see FIG. 3). By forming six straight grooves 66 to divide this low thread 64 in the axial direction, the low thread 64 is
A cutting edge 68 is provided at the bottom of the groove 4 in a direction opposite to the screwing direction of the tap 60. In addition, reamer 62
A chamfered portion 70 is formed at the end on the male threaded portion 36 side.

In such a tap 60, by screwing the male threaded portion 36 into the prepared hole 44, the prepared hole 44 can be opened.
The process of forming the internal thread 46 by plastically deforming the surface part of is exactly the same as that of the conventional example, but after that,
When the inner diameter of the female thread 46 is cut and finished by the reamer 62 when the tap 60 is rotated counterclockwise and pulled out, the lower thread 64 and the female thread 46' are engaged as shown in FIG. . Therefore, there is no possibility that burrs or the like due to cutting may be formed on the top of the thread 56 of the female thread 46', and the female thread 46' can have an appropriate thread shape. That is, when a workpiece 42 made of a highly malleable material is tapped using, for example, the tap 30 of the conventional example, a portion of the meat to be cut is removed, as shown in FIG. However, according to the tap 60 of this embodiment, the low thread 64 prevents the meat from escaping, and is not removed by cutting and remaining as a burr 72. It will definitely be removed.

Incidentally, when the tap 60 of this embodiment was attached to a tapping machine and tapped into aluminum alloy and copper alloy, which have high malleability and drawability, the female thread 46 was found to have no burrs and a high accuracy in internal diameter dimension. 'was gotten. The specifications of the tap 60 used are as follows: nominal size is M6, pitch is 1 mm, and the accuracy of the male thread part 36 is for female thread grade 6H according to JIS-B-0209 (allowable limits and tolerances for metric coarse threads). and a reamer 62 provided at the tip.
The root diameter d ₃ is the inner diameter dimension 5.153 to 5.153 in JIS-B-0209 (acceptable limits and tolerances for metric coarse threads).
It was set to 5.000mm within the range of 4.917mm. Also, pilot hole 4
Diameter size D ₂ of 4 has a hit rate of 100%.
It is 5.48mm.

The above-mentioned is only one specific example of the present invention, and the present invention has been modified and improved in various ways without departing from its spirit, for example, the straight groove 66 may be replaced with a twisted groove. It can be implemented in various ways.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an example of a conventional raised tap. FIG. 2 is a view from the tip side of the heaping tap shown in FIG. 1. FIG. 3 is a sectional view of a female thread formed by screwing the raised tap shown in FIG. 1 into a prepared hole. FIG. 4 is a cross-sectional view showing the process in which the inner diameter of the female thread in FIG. 3 is cut and finished by the reamer of the build-up tap in FIG. 1.
FIG. 5 is a front view of a raised tap which is an embodiment of the present invention. FIG. 6 is a view from the tip side of the heaping tap shown in FIG. 5. FIG. 7 is an enlarged front view showing the reamer of the raised tap shown in FIG. 5. FIG.
FIG. 8 is a partially cutaway view of the reamer shown in FIG. 7 from the distal end side. FIG. 9 is a cross-sectional view showing a process in which the internal diameter of the internal thread formed by screwing in the raised tap of FIG. 5 is finished by cutting with a reamer. FIG. 10 is a cross-sectional view illustrating a burr produced at the tip of the thread of a female thread. 60: Raise tap, 34: Thread, 36: Male thread, 42: Workpiece, 44: Prepared hole, 46, 4
6': Female thread, 62: Reamer, 64: Low thread,
68: Cutting edge, d ₁ : Root diameter of male thread, d ₃ : Root diameter of low thread, d ₄ : Outer diameter of low thread, D ₁ : Internal diameter of female thread to be formed, D ₂ : Pilot hole , w: width of the bottom of the low thread, W: width of the top of the thread of the female thread to be formed, θ: thread angle.

Claims (1)

[Claims for Utility Model Registration] A male thread having a thread formed thereon corresponding to the female thread to be formed, the male thread having a diameter substantially the same as the effective diameter of the female thread previously provided on the workpiece. By being screwed into the hole, the surface of the prepared hole is plastically deformed to form the female thread, while the root diameter of the male thread is smaller than the inner diameter of the female thread to be formed, and A reamer having a cutting edge in the opposite direction to the screwing direction on an equal outer circumferential portion is integrally provided at the tip of the male threaded portion on the same axis as the male threaded portion, and after forming the female thread, the male threaded portion is rotated in the opposite direction. In a build-up tap of the type that cuts and finishes the inner diameter of the formed female thread when it is rotated and pulled out from the pilot hole, the reamer is provided with a root diameter equal to the inner diameter dimension of the female thread to be formed and an outer diameter of the female thread to be formed. A low thread that is smaller than the diameter of the prepared hole, has a thread angle equal to that of the male thread, and has a root width equal to the width of the crest of the female thread to be formed is formed on the male thread. A build-up tap characterized in that it is provided on the same spiral as the thread, and the cutting edge is provided at the bottom of the valley of the low thread.