JPH06238518A - Cold forming tap - Google Patents

Abstract

PURPOSE:To provide a cold forming tap with high durability even when it is used for machining without using tapping oil. CONSTITUTION:A male screw part 2 of a cold forming tap 1 made of high hard steel, is coated with TiN (titanium nitride). To the TiN, TiCN (titanium carbonitride) is applied to coating. On a chamfer part 2a of the tip of the male screw part 2, five screw threads 5 are provided. A boundary of a flank face 2d of a thread 2b and a top 2e of the thread 2b is chamfered and machined. On the male screw part 2, a certain number of grooves 4 are provided in the axial direction of the cold forming tap 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a build-up tap for plastically working a female screw hole on a workpiece such as a metal plate or a metal block.

[0002]

2. Description of the Related Art Screws are used for fastening members in a wide range of fields such as automobiles, general machinery and electric equipment. Fastening of a member with a screw is performed by drilling a prepared hole in a workpiece for fixing the member with a drill or a reamer and screwing the screw into the prepared hole. However, especially when the work piece is hard like a metal plate or a metal block, if a female screw that matches the male screw portion of the screw is formed in the prepared hole in advance, the male screw and the female screw will mesh accurately, Highly stable tightening can be performed. Therefore, it is indispensable to form an accurate internal thread in the prepared hole formed in the workpiece in order to improve the quality of the product.

A tap is used as a tool for forming such an internal thread. For this tap, a cutting tap that forms an internal thread while shaving the inner surface of the pilot hole,
There is a raised tap that plastically deforms the inner surface of the prepared hole to form a female screw. The cutting tap has a drawback that a lot of chips are generated during processing and the finished surface becomes rough. On the other hand, the raised tap has less chips generated during processing,
The finished surface is smooth. Further, the resistance applied to the raised tap at the time of processing is large and almost double that of the cutting tap, but the processing speed is fast and the manufacturing efficiency is good. The raising tap is
Since it has the above advantages, it has been widely used in various fields.

An example of such a conventional raising tap will be described below with reference to the drawings. It should be noted that the numbers less than or equal to M indicate the outer diameter of the male screw portion. For example, if M1, the outer diameter is 1.
It is 0 mm. As shown in FIG. 5, the conventional thread forming tap 1 is formed by processing high-speed steel into a shaft shape and providing a male screw portion 2 at one end thereof. High-speed steel is a steel material suitable for processing a workpiece by high-speed rotation because it has high toughness and is unlikely to break. Male thread 2
A tapered biting portion 2a is formed at the tip of the so that it can be smoothly inserted into the prepared hole. This bite 2
The number of threads 2b in a is usually four or two. The thread 2b is generally shaped as shown in FIG. The cross section in the diametrical direction of the male screw portion 2 is not a perfect circle, and the raised portions 2
c is provided. As shown in FIG. 7, the raised tap 1 having four protrusions 2c larger than M2.6 is provided with four protrusions 2c. Further, in the build-up tap 1 of M2.6 or less, as shown in FIG. 8, three raised portions 2c are provided. On the other hand, an end portion on the opposite side of the male screw portion 2 is provided with a shank square portion 3 processed into a prismatic shape.

The work of plastic working an internal thread on a workpiece by the above-mentioned build-up tap 1 is as follows.
That is, first, a prepared hole is formed in the workpiece, but since the build-up tap 1 builds up the internal thread by plastic flow, the prepared hole has a slightly larger diameter than that of the cutting tap. next,
The shank square portion 3 of the build-up tap 1 is attached to the head of a machine for drilling work such as a drilling machine. Then, the heap tap 1 is fed in the axial direction while rotating the head, and the male screw portion 2 is inserted into the prepared hole of the workpiece set on the table. Then, the raised portion 2c provided on the male screw portion 2
Screw thread 2b of abuts on the inner wall of the prepared hole. At this time, M
In the build-up tap 1 having a size larger than 2.6, since the four raised portions 2c are provided, there are four portions in contact with the prepared hole in one cross section. On the other hand, in the build-up tap 1 of M2.6 or less, since the three raised portions 2c are provided, there are three portions in contact with the prepared hole in one cross section. In this way, the abutment of the screw thread 2b causes the inner wall of the prepared hole to plastically flow, and the female screw is plastically worked. It should be noted that it is indispensable to inject tapping oil for lubrication and cooling of the male screw part 2 and the pilot hole during processing.

[0006]

However, the above-mentioned conventional tapping tap has the following drawbacks. That is, although a small amount of protective oil is applied to the workpiece, it is indispensable to positively inject tapping oil during processing for lubrication and cooling of the processed portion. However, this tapping oil needs to be washed off from the work piece after processing, and the solvents suitable for this washing off, such as CFCs and trichloroethane, have a negative impact on the environment and the human body. Is not desirable for use.

In order to deal with this, if processing is performed without using tapping oil, the raised tap 1
Temperature rises, wear and welding occur, resulting in extremely low durability. The present invention has been proposed in order to solve the above problems, and an object thereof is to provide a build-up tap having high durability even when processed without using tapping oil.

[0008]

In order to achieve the above object, the present invention according to claim 1 is a build-up tap having a male screw portion, wherein the male screw portion plastically works a female screw on a workpiece. The male screw portion is coated with a material having a hardness higher than that of the male screw portion.

The present invention according to claim 2 is characterized in that the male screw portion is coated with titanium nitride, and the upper layer of the titanium nitride is coated with titanium carbonitride.

The present invention according to claim 3 is characterized in that the male screw portion is coated with a cobalt compound.

The present invention according to claim 4 is characterized in that the male screw portion is fluorinated.

The present invention according to claim 5 is characterized in that a tapered biting portion is provided at the tip of the male screw portion, and the number of threads in the biting portion is five or more.

The present invention as set forth in claim 6 is characterized in that, in the raised tap having an outer diameter of the male screw portion of 2.6 mm or less, four or more ridges are provided in the axial direction around the male screw portion. And

Further, the present invention according to claim 7 is characterized in that the angle formed between the flank surface and the crest of the thread of the male thread portion is chamfered.

Furthermore, the present invention according to claim 8 is characterized in that a groove is provided around the male screw portion in the axial direction or in a direction oblique to the axis.

[0016]

The operation of the present invention having the above construction is as follows. That is, according to the first aspect of the present invention, since the male screw portion is coated with a substance having a hardness higher than that of the male screw portion itself, wear due to contact with the workpiece is reduced.

According to the second aspect of the present invention, the male screw portion is coated with titanium nitride, and the surface thereof is coated with titanium carbonitride having a higher hardness. Wear is reduced.

According to the present invention of claim 3, since the male screw portion is coated with the cobalt compound, wear due to contact with the workpiece is reduced.

According to the present invention of claim 4, since the surface of the male screw portion is subjected to fluorination treatment, wear due to contact with the workpiece is small.

Further, according to the present invention as set forth in claim 5, since the number of threads in the bite portion is 5 or more, the number of places in contact with the workpiece during machining increases, and the force applied to one thread is increased. Is reduced.

Further, according to the present invention of claim 6, even in a build-up tap having an external diameter of a male screw portion of 2.6 mm or less,
Since four or more ridges are provided in the same manner as the ones larger than 2.6 mm, the number of places that come into contact with the workpiece during machining is increased, and the force applied to one screw thread is reduced.

Further, according to the present invention, the angle formed by the flank surface and the crest of the thread of the male thread portion is chamfered, so that the work piece hits the corner of the thread portion. The coating peeling or wear of the male thread itself is reduced.

According to the eighth aspect of the present invention, since the groove is provided around the male screw portion, the chips generated during the machining are discharged from this groove.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the raising tap according to the present invention will be described below with reference to the drawings. The same members as those in the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

(1) Configuration of Embodiments The configuration of one embodiment of the present invention will be described below. That is,
As shown in FIG. 1, there is a build-up tap 1 made of high-speed steel provided with a male screw part 2, and its surface is coated with two layers. First layer 4 on the surface that directly abuts the workpiece
For this, TiCN (titanium carbonitride) is used. This means that TiCN has a Vickers hardness of 2800 to 30.
00, there is sufficient hardness to directly contact the work piece,
Because it is less likely to deteriorate, it is suitable for forming the first layer 4 on the surface. In addition, the second layer 5 that directly contacts the male screw portion 2
For this, TiN (titanium nitride) is used. This is because TiCN, which is suitable for the surface, is difficult to attach to high-speed steel, so it is easy to attach to both high-speed steel and TiCN.
First, attach N to the male screw part 2 made of high-speed steel, and then attach T
The coating of iCN enables the fixing of TiCN. The thickness of this coating is 1.5 to 5 for the first layer 4 and the second layer 5 together.
The thickness is 2.0 microns, and the male screw portion 2 is thinner than the conventional one having the same standard by this thickness.

Further, five threads 2b are provided in the bite portion 2a at the tip of the male screw portion 2. This thread 2b
As shown in FIG. 2, the boundary between the flank surface 2d and the peak 2e is chamfered so that no corner is formed and a flat surface slightly remains on the peak 2e. And M
As shown in FIG. 3, both the build-up tap 1 having a size larger than 2.6 and the build-up tap having a size of M2.6 or less are provided with four or more ridges 2c so that the cross section of the male screw part 2 is substantially rectangular. Further, as shown in FIG. 4, the male screw portion 2 is provided with several grooves 6 in the axial direction of the raised tap 1.
The chamfering may be performed so that the flat portion does not remain on the mountain top 2e.

(2) Operation and effect of the embodiment The operation and effect of this embodiment having the above-mentioned structure are as follows. That is, as in the conventional example, a prepared hole is formed in the workpiece, and the male screw portion 2 of the raised tap 1 is inserted into the prepared hole while rotating. Then, the raised portion 2c around the male screw portion 2 contacts the prepared hole, and the female screw is plastically worked.

According to this embodiment, the male screw portion 2
Since the first layer 4 on the surface of TiCN is coated with TiCN, the advantages of high toughness high speed steel and high hardness TiC
It is possible to combine the advantages of N together. That is, even if the tapping oil is not used, since TiCN having a high hardness directly contacts the prepared hole, the durability is dramatically improved. The TiCN of the first layer 4 is the same as the TiN of the second layer 5.
Since it firmly adheres to the high-speed steel through the medium, the advantage of the high-speed steel that it is less likely to be damaged is sufficiently retained. And
Since tapping oil is not used, it is not necessary to wash the tapping oil after processing, resulting in good manufacturing efficiency. Furthermore, it is safe because it is not necessary to use a solvent such as CFC or trichloroethane for cleaning the work piece.

Further, since there are five or more screw threads 2b of the bite-in portion 2a, the number of places contacting the prepared hole increases, the force applied to each screw thread is reduced, and TiCN and TiN are less likely to peel off. . Therefore, durability is improved.

Further, since the rising tap of M2.6 mm or less is also provided with four or more ridges similarly to those of 2.6 mm or more, there are more places to come into contact with the prepared hole at the time of machining. The force applied to the screw thread 2b of
CN and TiN are less likely to peel off. Therefore, durability is improved.

Further, since the angle formed by the flank surface 2d and the crest 2e of the thread 2b of the male threaded portion 2 is chamfered, Ti due to the corner of the thread 2b hitting the prepared hole
The peeling of CN and TiN or the abrasion of the male screw portion itself is reduced, so that the durability is improved.

Further, since four or more ridges 2c seen in the cross section of the male screw portion 2 are formed, the force applied to the surface of the raised tap 1 at the time of processing can be reduced, and the peeling of TiCN and TiN is small. Therefore, durability is improved.

Further, since the male screw portion 2 is provided with the groove 4, the chips (for example, chips) slightly generated at the time of machining (for example,
The dust such as a protective film formed on the surface of the work piece is the groove 6
Is discharged through. Therefore, chips are not accumulated in the prepared hole, and the manufacturing efficiency is improved.

(3) Experimental Data Experimental data for comparing the durability of the present invention tap and the conventional tap will be described below. This experiment
The build-up taps are M2.6 to 3.0, 1.2 mm thick zinc steel plate is used as the work piece, and nine build-up taps 1 are mounted on the head and rotated by 2150 revolutions per minute for processing. Is. When even one of the nine taps deteriorates below a predetermined standard, it is assumed that the life of all the other taps has expired. First of all, in the conventional tapping tap,
When tapping oil was used, processing was possible about 50,000 times, but when tapping oil was not used, the durability decreased to about 1000 times.

Next, in the raising tap according to this embodiment, even if tapping oil is not used,
It was possible to process it more than 00 times.

(4) Other Examples The present invention is not limited to the above examples, and the shape, material, etc. of each member can be appropriately changed. For example, the coating of high speed steel may be done by liquid or vapor deposition. Further, even if the material for coating the screw portion 2 is a cobalt compound or the screw portion 2 is fluorinated, the durability is improved. Further, the groove 4 of the male screw portion 2 may be oblique to the axis of the build-up tap 1.

Then, like the conventional raising tap 1,
Even if the number of the threads 2b of the bited portion 2a is four, if the number of the raised portions 2c is four or more, the number of the threads 2b contacting the prepared hole increases from 12 to 16 or more. Therefore, the force applied to one screw thread 2b is reduced, and TiCN and T
iN becomes difficult to peel off.

Further, this embodiment can be processed by using tapping oil. When tapping oil was used, it was
It is possible to process more than 000 times.

[0039]

As described above, according to the present invention, the male thread portion is coated with a material having a hardness higher than that of the male thread portion itself. It is possible to provide a rising tap having durability.

[Brief description of drawings]

FIG. 1 is an enlarged view showing a cross section in the axial direction of a thread forming tap which is an embodiment of the present invention.

FIG. 2 is an enlarged view showing an axial cross section of a screw thread in a thread forming tap according to an embodiment of the present invention.

FIG. 3 is an enlarged view showing a diametrical cross section of a build-up tap according to an embodiment of the present invention.

FIG. 4 is a side view showing the groove of the build-up tap which is one embodiment of the present invention.

FIG. 5 is a side view showing an example of a conventional raising tap.

FIG. 6 is an enlarged view showing an axial cross-sectional view of a screw thread in an example of a conventional thread forming tap.

FIG. 7 shows an example of a conventional tap for raising M2.6 or more,
Enlarged view showing diametrical section

FIG. 8 shows an example of a conventional tap of M2.6 or less,
Enlarged view showing diametrical section

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Raised tap 2 ... Male screw part 2a ... Bit part 2b ... Thread 2c ... Raised part 2d ... Frank surface 2e ... Mountain top 3 ... Shank square part 4 ... 1st layer 5 ... 2nd layer 6 ... Groove

Claims (8)

[Claims] 1. A build-up tap having a male thread part, wherein a plastic thread is formed on a workpiece by the male thread part, wherein the surface of the male thread part is coated with a substance having a hardness higher than that of the constituent material of the male thread part. Heap taps that are characterized. 2. The raised tap according to claim 1, wherein the male screw portion is coated with titanium nitride, and the titanium nitride upper layer is coated with titanium carbonitride. 3. The raised tap according to claim 1, wherein the male screw portion is coated with a cobalt compound. 4. The raised tap according to claim 1, wherein the male screw portion is fluorinated. 5. A taper-shaped biting part that tapers toward the tip side is provided at the tip of the male screw part, and the number of threads in the biting part is 5 or more. Heap tap described. 6. The raised tap having an outer diameter of the male threaded portion of 2.6 mm or less, wherein four or more raised portions parallel to the axial direction are provided around the male threaded portion. Heap tap. 7. The thread forming tap according to claim 1, wherein an angle formed by a flank surface and a crest of the thread of the male thread portion is chamfered. 8. A groove is provided around the male screw portion in an axial direction or a direction oblique to the axis.
Heap tap described.