JPH0612126B2 - Special taper screw and its forming method - Google Patents

Description

The present invention relates to a special taper screw and a method for forming the same, and more specifically, to a special taper screw and a screw connection which are general parts such as industrial parts such as machine parts and everyday sundries, And it relates to the molding method.

(B) Conventional technology There are male and female screws as screws, and generally, two objects are fastened by screwing them together. Male threads are usually made using a rolling or cutting die, and female threads are usually made by tapping.

On the other hand, there are also fastenings that do not require a female screw part in advance, for example,
These include wood screws, drive screws, and tapping screws. Of these, the tapping screw is formed by screwing a female screw into the prepared hole when it is fastened to cut the female screw by plastic deformation.

(C) Problems to be Solved by the Invention However, the work of cutting the female screw, so-called tapping, requires a large screwing torque, and the work is complicated and the productivity is poor. In particular, in the case of long or deep female tapping work, machining with tools and visibility are poor. This is because the smaller the diameter, the harder the blade edge can reach and the operator's eyes are hard to reach, and the inspection is not easy. Further, in the conventional operation of tapping into the prepared hole, since it is cut with a blade, the natural flow (fibers) of the metal structure is cut and the strength is lowered, which is not preferable. There is also a taper screw for the pipe end, but since it is slightly inclined and it is generally difficult to make a large taper, it is unavoidable to use parallel threads. Therefore, there are some problems that it is difficult to expect a large tightening force.

(D) Means for Solving the Problem The present invention is intended to solve the above-mentioned problems, and is a screw thread having a relatively sharp corner portion, and press shaving the outer circumference of the material or the inner circumferential surface of the hole. (Light cutting by pressing), the screw shape is formed into a taper taper toward the tip and the volume of the screw groove is formed so as to be gradually expanded toward the tip. By the molding method, a special taper screw having a taper shape in which the screw shape is tapered toward the tip and the volume of the screw groove is gradually expanded toward the tip is produced.

(E) Action Hereinafter, the taper screw of the present invention and the method for forming the same will be described with reference to the drawings.

In FIG. 1, a male screw 1 of the special taper screw has a head portion 2 at the upper portion and a screw shaft 3 at the lower portion. The tip of the screw shaft 3, that is, the screw threads 4 tapering toward the bottom in the drawing are formed at the same pitch. A thread groove 5 is provided between the thread 4 and the thread 4, and the volume of the thread groove 5 is formed such that the volume of the thread groove 5 is gradually increased toward the tip, that is, in the downward direction in the drawing.

Next, as shown in FIG. 2, the female thread 6 of the special taper screw has a thread crest 7 that is screwed into the thread groove 5 of the male thread 1 on the inner peripheral surface, that is, as it goes downward in the figure. They are tapered and provided at equal pitches. Further, a thread groove 8 that is screwed into the thread 4 of the male screw 1 is formed between the thread 7 and the volume of the thread groove 8 goes to the tip, that is, downward in the drawing. In accordance with the above, it is sequentially enlarged and formed.

Next, a method of forming the special taper screw will be described.

First, a method of forming the female screw 6 will be described. FIG. 3 (a) schematically shows a female screw molding device, in which a die holder 10 is placed on 9 presses, and a material having a hole for female screw molding on the die holder 10. 11 is set. On the other hand, a punch holder 12 is installed on the upper piece of the press 9, and a rotary holder 13 is installed under the punch holder 12. A male screw punch 14 for molding the material 11 is set on the rotation holder 13. The rotation holder 13 is for allowing the male screw punch and the material to rotate relative to each other in order to remove the male screw punch 14 from the material 11 after forming the screw on the material 11, and even when mounted on the material 11 side. Good. Material
In order to mold 11, it is first necessary to design the male screw punch 14. In order to design the male screw punch 14, it is necessary to determine the length of the screw portion, the shape of the screw thread, the shape of the screw groove, the depth, the screw pitch, the degree of taper, etc., but the screw thread has a relatively acute angle. Good to have a corner. It is important that, as shown in FIG. 4, the shaving waste Wn of the material 11 at the time of molding must be accumulated in the thread groove Gn by the thread Mn of the male screw punch 14, preferably the male screw and the female screw. In order to make the screw engagement good, it is necessary that W = G, that is, the volume of the shaving waste matches the volume of the thread groove of the male screw. The male screw punch 14 designed in this manner is manufactured by using tool steel, which is a hard material, by techniques such as numerical control lathe, powder metallurgy, and precision casting, and then set in the molding apparatus of FIG. 3 (a). Next, the press 9 is operated to lower the upper piece of the press 9 in the direction of the arrow, and the male screw punch 14 is strongly pressed into the hole of the soft material 11, and the inner peripheral surface of the material 11 is pressed by shaving. A thread 7 and a thread groove 8 are formed on the inner peripheral surface. The screw shape is formed at the tip, that is, tapered as it goes downward in the figure, and the volume of the screw groove 8 is formed so as to expand at the tip, that is, as it goes downward in the figure. At this time, as shown in FIG. 4, the volume of the shavings of the material 11 coincides with the volume of the thread groove of the male screw punch 14, so that the male screw and the female screw can be brought into contact with each other without any gap and the meshing is completed. Next, when removing the male screw punch 14, the press 9 is unloaded and the rotary holder 13
At the same time, the male screw punch 14 is rotated to remove the male screw punch 14 from the material 11.

Next, a method of forming the male screw 1 will be described. FIG. 3 (B) schematically shows a male screw forming device, but it is the same device as the device shown in FIG. 3 (A), and includes a female screw punch 15 and a male screw forming material 16 However, it is needless to say that the female screw punch 15 is also manufactured in the same manner as the male screw punch 14 and that the male screw can be formed by the same procedure as the female screw forming procedure described above. is there.

The press for installing the tool set for forming the special taper screw according to the present invention may be a normal press, and may be a mechanical press, a hydraulic press, or any other type of press. Then, in order to facilitate the screw molding, the edge of the molding material may be heated and softened before press shaving. Furthermore,
As the material of the male screw punch, almost any kind of material can be used as long as it is a hard material, and metal, ceramics, plastics and composite materials thereof (FRM, FRC, FRP, etc.) are preferable. Of course, the material of the female screw die can be selected in a wide range as long as it is a hard material.

The press placed with the tool set described above may be a normal press. The type of mechanical press, hydraulic press, and other presses does not matter.

Theoretically, the amount of shaving should be large enough to cause plastic deformation, but in reality, there is a crack in the material, the forming load becomes too large, etc. A shaving allowance of several mm or less is preferable.

(F) Examples Hereinafter, examples of experiments conducted in the present invention will be described.

[Example 1] An existing NC lathe and a male screw punch were manually attached to a tool steel (S
It was manufactured in K3), quenched and tempered. On the other hand, after drilling a pilot hole of 20.0 mm in inner diameter on a mild steel round bar (SS41) (outer diameter 50.0 mm, length 30.0 mm), which is a material for female thread molding,
Using a 20 ton hydraulic press, the male screw punch was pushed into the prepared hole of a mild steel round bar with a load of about 20 tons, and a female screw was formed by press shaving. Next, the press was gradually loaded and the male screw punch was rotated to release the female screw after molding.
Then, when the internal thread was cut in half and the profile was observed, it was confirmed that the thread and the groove of the internal thread were almost completely formed.

[Example 2] The mild steel round bar, which is a material for forming an internal thread, was heated to about 800 ° C using a high frequency induction heating device with an output of 3 kw, and then
In the same manner as in Example 1, press shaving was performed to form a female screw. The press shaving molding force could be reduced to 13-15 tons. Graphite oil was used for lubrication of the male screw punch and the inner surface of the hole. When the formed female screw was cut in half and the cross-section of the female screw was observed, it was confirmed that the screw groove of the male screw was completely filled with shavings and that the female screw had no defect.

Example 3 A male screw punch was fastened to the female screw obtained in Example 2 above.
A torsional breaking torque of 52 kgf · m was obtained. When a tensile force was applied, the male screw punch was pulled out with a load of about 25 tons. In all experiments, the root portion of the thread of the female screw was broken.

Example 4 After heating the pure aluminum bar (A1016) having a diameter of 26.0 mm, which is softer than the mild steel round bar (SS41), to 500 ° C. by using the female screw obtained in the above Example 1 as a die Then, the male screw was formed by pushing the female screw die and press-shaving the outer peripheral surface thereof. After the molding, the pure aluminum rod removed by rotating the male screw had a satisfactory rectangular taper screw. On the other hand, it was also confirmed that copper, softened thermoplastic plastin, hard clay, and SiC ceramics before sintering could be molded by the molding method of the present invention.

(G) Effect of the Invention As described above, according to the present invention, the outer circumference of the material or the inner peripheral surface of the hole is simply press shaving (light cutting by pressing) with a screw thread having a relatively sharp corner. Compared with the conventional thread cutting work (tapping), the load and speed can be increased and the workability and productivity can be improved.
Also, because the female screw is molded at the time of fastening with only the male screw, the fastening of both can be completed at the same time as molding, and two objects can be fastened while molding the screw, and when used in an automobile production line etc., two objects can be fastened with high production. It is useful. Moreover, the molding method is simple. On the other hand, it can be removed, unlike assembly by welding or the like. Further, since it is press shaving, the shaving waste is deposited in the screw groove of the male screw to form the female screw thread, and the material yield is good. Furthermore, since the screw shape is tapered toward the tip and the volume of the thread groove is gradually expanded toward the tip,
Coupled with the above-mentioned shaving waste accumulated in the thread groove of the male screw to form the female screw thread, the male screw and the female screw can be contacted with each other without a gap, and complete fitting can be realized. Further, since the screws of the metal parts, particularly the female screw, are tapered, they can be conveniently used together with a wood screw or the like. Further, the male and female screws have the above-described special shapes whose shape design is difficult, and therefore do not cause screw differences. Furthermore, by changing the taper shape, thread groove volume, thread shape, etc., it is possible to make an infinite number of different male and female screw pairs, which can be used for fastening to prevent mistakes in the screw, and because the shape is special, it can be personalized. It can also be used for fashion screws. In addition, it can be used for a wide range of machines, structures such as buildings and mechanical parts, tools, metal fittings, piping parts, electronic parts, and other screw forming and fastening. There is a great one.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a male screw of special taper screws, FIG. 2 is a sectional view showing an example of a female screw of special taper screws, and FIG. FIG. 3 is a schematic view of the external thread forming device, and FIG. 4 is a partially cutaway enlarged sectional view showing a state during internal thread forming by press shaving. In the figure, 1 ... Special taper screw (male screw), 4 ...
Screw thread, 5 ... Screw groove, 6 ... Special taper screw (female screw), 7 ... Screw thread, 8 ... Screw groove, 9 ... Press, 10
...... Die holder, 11 …… Material for female screw molding, 12 ……
Punch holder, 13 …… Rotating holder, 14 …… Male screw punch, 15 …… Female screw punch, 16 …… Material for forming male screw.

Claims (3)

[Claims] Claim: What is claimed is: 1. A special taper screw having a taper shape in which the screw shape is tapered toward the tip, and the volume of the screw groove is gradually expanded toward the tip. 2. A screw thread having a relatively sharp corner, the outer periphery of the material or the inner peripheral surface of the hole is press-shaving to form the screw shape into a taper taper toward the tip and the volume of the screw groove is formed at the tip. A method of forming a special taper screw, which is characterized by forming so as to gradually expand as it goes. 3. The special taper screw forming method according to claim 2, wherein two objects are fastened while forming a screw by press shaving.