Seven structural forms of screw connection
Screw connection is used to connect two thin parts. There is a through hole on the connected part, and the parts are tightly connected through the screw connection of bolt and nut. For the convenience of practical operation, there is a certain gap between the screw and the hole. The structure is simple, and the loading and unloading is convenient. It is a common connection method in the automobile industry.
According to the structural form, material differences, functional requirements and other screw joint structural forms are mainly divided into seven kinds.
In this structure, bolts, nuts and connected parts are independent at the beginning, which is convenient for disassembly, and the selection of bolts and nuts is more flexible.
Screw connection structure diagram
Sheet metal opening: generally, the opening size of the first layer of sheet metal is bolt diameter + 0.5, and the second layer is increased by 1 mm based on the opening size of the first layer（ There are some differences in the production capacity of different main engine plants.)
Screw connection section
Projection welding nut + bolt
In this structure, the projection welding nut and the sheet metal pre form a component, as shown in the section below, the projection point of the projection welding bolt will be integrated with the sheet metal, and then connected with the bolt.
This kind of structure is mainly used in the areas where there is no space on one side or where it is difficult to install on one side, such as the fourth floor of the top cover, the seat cross beam and so on. The opening mode of sheet metal is the same as that of structural form 1.
Projection welding bolt and section
The opening mode of sheet metal is the same as that of structural form 1
Projection welding bolt + nut
Convex welding bolt is divided into end convex welding bolt and bearing surface convex welding bolt. The bearing surface convex welding bolt needs opening, and the bottom hole system of convex welding bolt must be (M + 0.5), which is suitable for the parts with tight fitting and sheet metal of mounting parts. The end convex welding bolt does not need sheet metal opening, which is suitable for the parts without tight fitting and sheet metal of mounting parts. Projection welding bolts are used in the front panel and front longitudinal beam of some vehicles.
Projection welding bolt drawing
With the application of aluminum body, the hot connection can not be realized, and then for aluminum structure, at present, the screw connection can not be realized by projection welding.
Blind rivet nut + bolt
The nut is pressed into the sheet metal preset hole in advance by pressure, and the diameter of the preset hole is slightly smaller than the embossed tooth of the rivet nut. Then the combination of the bolt and the rivet nut makes the sheet metal connection a structural way, and the connection strength is greatly affected by the form of the rivet nut.
Features: one side of the sheet metal is flat, and the other side is protruding (thread side)
Detail drawing of blind rivet nut
Rivet nut + bolt
Riveted nut is a structural form which is composed of components in advance with sheet metal through Hooke’s law, and then combined with bolts to realize connection. The sheet metal hole of riveted nut is usually m-0.5mm, which is applied in various parts of aluminum body.
Features: both sides of the sheet metal are uneven, and the screw side protrudes about 1.5mm.
Rivet bolt + nut
The structure is the same as structure 4, but the pressed rivet nut is replaced by pressed rivet bolt. The choice of bolt and nut mainly depends on the functional requirements and the requirements of hand parts
Detail drawing of rivet bolt
Rivet bolt + nut
The structure is the same as structure 5, but the rivet nut is replaced by rivet bolt. The choice of bolt and nut mainly depends on the functional requirements and the requirements of hand parts.
Detail drawing of rivet bolt
In automotive applications, the number of pull rivets is always greater than that of press rivets. Why?
The main reason is that pull riveting can be applied to finished products and semi-finished products, while press riveting must be applied to thin plates, which can not be used after finished products. In the process of car body assembly, pull riveting has fewer restrictions, more convenient operation and function satisfaction, and the number of pull riveting is always more than that of press riveting（ The differences between pull riveting and press riveting will be introduced in detail later.)
The common screw connection is not affected by the material, but it needs sufficient space on both sides, which is mainly used in the large space part of the anti-collision beam.
For projection welding fasteners, they are widely used in steel areas, and only one side space is needed to meet the requirements, which is convenient for the installation of various parts in the final assembly process. With the development of body materials, the application of press riveting fasteners and pull riveting fasteners is gradually increasing, but press riveting needs more space, while pull riveting only needs one side space, For the closed structure or space under the narrow small area riveting occupies a particularly important position.
According to the function, material, production, space and other factors, the seven structural forms are applied in different areas.
Source: China Bolts Manufacturer – Yaang Pipe Industry Co., Limited (www.ugsteelmill.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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