JPH042806B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing metal bolts and/or nuts (hereinafter referred to as bolts and nuts) coated with synthetic resin that have excellent rust prevention, sealing effects, and loosening prevention effects, and manufacturing methods using the method. related to bolts and nuts. (Prior Art) Metal bolts and nuts are commonly used. Further, bolts and nuts made of hard vinyl chloride or nylon resin reinforced with glass fiber or the like are used. There are also metal bolts and nuts that are plated. Furthermore, in view of the frequent occurrence of accidents caused by loosening of bolts and nuts in recent years, we have introduced products that fit nylon molded at right angles to the threads of bolts, and nylon molded to part of the threads of nuts. Various types are available, such as those fitted with screw threads and those fitted with springs. In addition, a bolt in which part of the bolt is coated with nylon by the fluidized dipping method is disclosed in Japanese Patent Application Laid-Open No. 49-130941.
It is described in. (Problem to be solved by the invention) Metal bolts and nuts have the disadvantage of being susceptible to corrosion. Bolts and nuts made of hard vinyl chloride, etc. have one-third to one-tenth the tensile strength and other physical properties of bolts and nuts made of metal, so they cannot be used in places that require strong fastening force. Can not. Plated metal bolts and nuts are an attempt to increase rust prevention, but the effect is not sufficient and salt spray tests show that rust develops in a short period of time, so they cannot be used in corrosive environments. It is dangerous to use. Generally sold locking bolts and nuts have insufficient rust prevention and can be expected to have a loosening effect to some extent, but their initial torque is high, such as M
Even when compared with -10, the result is 25 to 40 kg-cm, and many of them are difficult to fasten. These are Nippon Giken's NS high-speed screw loosening testers, which are considered optimal for testing the locking effect, with a frequency of 1780 times/min and an amplitude of 11.
When tested at m/m, there is almost no product that does not come loose after 100,000 cycles. The bolt disclosed in JP-A-49-130941 is theoretically thought to be effective in preventing loosening, but in reality, the threaded part is not coated with nylon uniformly with the same thickness, that is, some thread grooves are coated with nylon. Since the bottle is buried, it cannot be expected to have much of a tightening or loosening effect, and when a bottle equivalent to JIS Class 2 is processed, the initial torque is abnormally high and it cannot be used in reality. Furthermore, since the coating is a part of the screw thread, it has no anti-rust properties. (Means for solving the problem) In order to make resin-coated metal bolts and nuts of the desired standard dimensions, the metal bottles and nuts are processed in advance to a size equivalent to the thickness of the resin coating, and then heated. After the entire surface is coated with plastic resin, for bolts, use a normal rolling machine, and run the rolling machine at a temperature higher than the heat deformation temperature of the coating resin and lower than its melting point, preferably at an additive temperature of both temperatures. Constantly heated within the average temperature range of ±15℃,
The rolling pressure is set to 1/4 to 1/9 of the design pressure used for general structural rolled steel materials, and the nuts are reshaped by rolling. or more, preferably 1.2 to 1.5 times the height, and smaller than the JIS grade 2 accuracy inner diameter of the nut, preferably,
Attach a guide made of a round bar without a cutting edge with a diameter that is one-eighth to one-tenth of the inner diameter.
The starting point of the cutting edge of the tap is a tapered shape with a blade height of about 1/4 of the height of the screw thread of JIS grade 2 precision, and the end is the blade height of the height of the thread of JIS grade 2 precision. Reshape by thread cutting using a tap with a blade height of 100 lbs., so that the coating resin has approximately the same thickness on the threaded surface. (Function) Reduce the thickness of the coating resin in advance, and
When the metal bolt 1 and nut 2, which have been machined by an amount equivalent to 1/8th to 1/10th of the height of the threaded peak, are coated with thermoplastic resin.
The coating resin 3 is thinly applied at the top of the thread 4 and becomes thicker toward the bottom 5 of the thread groove. When pressure is applied with a rolling machine, the resin at the bottom of the thread groove is pushed toward the top of the thread. However, since a portion equivalent to 1/8 to 1/10 of the height of the threaded ridge at the top of the thread has been cut, the coating resin 3 is shaped so as to cover the entire surface of the thread with approximately the same thickness as desired. You can get the standard. In the case of reshaping by thread cutting, the thick part of the resin in the thread groove is scraped off so that the entire surface of the threaded part has approximately the same thickness, and the thread is reshaped. (Example) Using rolled steel for general structure, rolling diameter 8.85m/m
A steel bar with a length of 50m/m below the neck is made into a hexagonal head with a header,
Pressure 2850Kg with round die rolling machine (JIS class 2 equivalent)
After rolling, the metal bolt 1 is made by lathe processing again so that the outer diameter is 9.5 m/m. Next, the Japanese patent No. owned by Atochem in France.
Using the method in No. 896275, the entire surface of the product is coated with nylon resin manufactured by the same company. As shown by the dotted line in FIG. 3, this coating film is thin at the thread crest 4;
The thickness increases toward the bottom 5 of the thread groove. This is heated and kept at 160°C using the rolling machine mentioned above, and is rolled and formed by applying a pressure of 570 kg. In addition, using the same steel grade, a JIS class 2 hexagonal nut 2 was made using a header, and the effective diameter
Threads were cut using an automatic thread tapping machine at 8.75 m/m, and the entire surface was coated with resin using the method described above.
A guide with a length of 10 m/m and a length of 10 m/m was held at the tip, and the screw was shaped using a tap with an effective diameter of 9.026 m/m and a tapered blade height of 0.2 m/m to 0.812 m/m. For bolts that have been reshaped by rolling after being fully coated, the resin is pressed toward the top of the thread by the pressure of the rolling machine during rolling and reshaping, so when the rolling machine is removed, the resin will move to the desired position at the top of the thread. It swells even more. In order to prevent this bulge, it is necessary to apply an amount equivalent to 1/8 to 1/10 of the height of the threaded peak 3 of the metal bolt and nut before coating (6
It is preferable to make the part ) small. In addition, the rolling pressure for reshaping is 1/4 to 1/4 of the pressure for rolling metal bolts and nuts of the same shape.
It is preferable to reduce it to one-ninth. The coating resin 3 that has been reshaped by rolling may be pushed up from both ends of the thread crest 4, causing wrinkles, and the surface of the coating resin 3 that has been reformed by thread cutting is rough, so the temperature is 20° higher than the melting point of the resin. It is preferable to shape the resin surface by remelting at a temperature higher than 40°C.
In the above example using Atochem's nylon 11 resin, the melting point is 186°C, so the melting point is 205 to 210°C.
The mixture was heated for 3 to 4 minutes at an ambient temperature of . The bolts and nuts of the above examples and the bolts and nuts on the market were subjected to a salt spray test and a loosening test using an NS high-speed screw loosening tester manufactured by Nippon Giken Co., Ltd. The results were as follows.

【table】

[Table] The bolts used in these tests were M-10 with a neck length of 50 m/m, tightened with a tightening torque of 200 kg-cm, and the number of vibrations when the nut moved through the marked position was measured. In the present invention, either rolling or thread cutting may be used when manufacturing the metal bolts 1 and nuts 2 and reshaping the coating resin 3. The coating resin 3 is not limited to nylon 11 resin manufactured by Atom Co., Ltd., and other thermoplastic resins can be used. Furthermore, the standard dimensions and materials of the metal bolt 1 and nut 2 and the thickness of the coating resin 3 are not limited to those in the above embodiment. Moreover, the shape of the thread is not limited to that shown in the drawings, and various known shapes can be adopted. (Effects) According to the present invention, metal bolts and nuts coated with a resin having a uniform or desired thickness can be obtained, and the bolts and nuts manufactured by this method have an initial torque of about 10 kg- cm, the initial torque is low,
Not only is it easy to fasten and has excellent corrosion resistance, chemical resistance, electrical insulation, and sealing properties, it also has particularly excellent locking and sealing effects, such as power transmission towers, tanks, marine structures, and automobiles. , suitable for bolts and nuts used in railways, etc.

[Brief explanation of drawings]

What is shown in the drawings shows an example of a product manufactured by the method of the present invention. Figure 1 is a sectional view of the main part of a bolt, Figure 2 is a sectional view of the main part of a nut, and Figure 3 is a sectional view of the main part of a nut.
The figure is an explanatory diagram of resin coating of the threaded portion, and FIG. 4 is an explanatory diagram of thread processing. 1...Metal bolt, 2...Metal nut, 3
...Coating resin, 4...Screw top, 5...Screw groove bottom.

Claims (1)

[Claims] 1. The thickness of the coating resin is reduced in advance, and the height of the threaded ridge is 1/8 to 1/8 of the height of the threaded crest.
After coating the entire surface of a metal bolt with a thermoplastic resin that has been cut to a size equivalent to 1/10, the thickness of the thermoplastic resin coating layer on the screw thread is reshaped to be almost uniform by rolling, and the melting point of the coating resin is than 20℃~40℃
A method for manufacturing a metal bolt coated with a synthetic resin, characterized by remelting at a high temperature and reshaping the resin surface. 2. Reduce the thickness of the coating resin in advance, and reduce the thickness to 1/8 to 1/8 of the height of the threaded ridge at the top of the thread.
After coating the entire surface of a metal nut with thermoplastic resin by cutting the equivalent of 1/10th, the thickness of the thermoplastic resin layer on the screw thread is reshaped to be almost uniform by thread cutting, and A method for producing a synthetic resin-coated metal nut, which comprises remelting at a temperature 20 to 40 degrees Celsius higher to reshape the resin surface.