The four elements of the thread of the triangle screw
The four elements of the thread of the triangle screw
The thread profile, pitch, number of threads and direction of rotation are called the four elements of the triangular screw thread. Only the internal and external threads with the same four elements can be screwed together.
1. Tooth type
On the section passing through the thread axis, the profile shape of the thread is called the tooth profile. The angle between two adjacent flanks is called the profile angle. Commonly used common thread has a triangular profile with a profile angle of 60°.
2. Number of lines
The number of spirals forming a thread is called the number of threads. There are single-thread and multi-thread threads. Multi-thread threads are evenly distributed in a section perpendicular to the axis.
3. Lead
The axial distance between two adjacent teeth on the pitch line corresponding to two points is called the pitch. On the same spiral line, the axial distance between two adjacent teeth corresponding to two points on the median diameter line is called the lead.
4. Rotation
Viewed along the axis, the thread that rotates clockwise becomes a right-hand thread, and the thread that rotates counterclockwise is called a left-hand thread.
Self-tapping screws are used for non-metallic or softer metals
Self-tapping screws are used for non-metallic or softer metals, and do not need to drill and tap.
Self-tapping screws are pointed, so that they can be "self-tapping"; ordinary screws are flat-headed, and the thickness is the same.
Self-tapping screw means: the drilled hole is a chipless tapping hole. The screws used are different from the general ones. The head is pointed and the pitch is relatively large. It is a bit like a chipless tapping. It can be directly screwed without tapping. Go in, metals and plastics usually use this method.
Self-tapping screws are screws without nuts.
It can "tap-drill, squeeze, and press" the consolidated body into corresponding threads on the material to be consolidated by its own threads, so that they can be closely matched with each other.
The dimensions, mechanical properties and functional performance of self-tapping screws have the following standards
American National Standards Institute (ANSI)/ASME B18.6.4─Thread forming and thread cutting self-tapping screws and metal drive screws (inch series)
SAE J933─Mechanical and quality requirements, self-tapping screws
J81 screw thread rolling─SAE
SAE J1237─Metric thread rolling screw
SAE J78─steel self-tapping screws
FIP 1000─Performance specifications of self-tapping screws
DIN 7500─Thread Rolled Screw ISO Metric Screw Line
DIN 7504─Dimensions, requirements and tests of self-tapping and self-tapping screws
ISO 2702─Tapp heat-treated steel
How to choose the material of bolts and nuts?
Many customers ask such questions: How to choose the material of bolts and nuts?
The difference between the mechanical function requirements of bolts and nuts is:
① The mechanical function of the nut mainly depends on the hardness of the nut, the height of the nut, and the wall thickness of the nut. Therefore, the requirements for materials are not high. Of course, if the nut has a resistance requirement, higher-level materials should also be used, such as chemical industry Fasteners and nuts have requirements for durability, which rules higher-level data.
②The higher the functional level of the plastic target required by the bolt, the higher the level of material can be reached. The lower level of material only needs to reduce the tempering temperature to reach the strength requirements, but it cannot meet the requirements of plasticity and resistance. In fastener testing , Brittle fracture is judged to be unqualified. Steel structure bolts are also regulated with higher tensile strength, in order to ensure the plastic resistance of the bolts.
How to install flat head rivets
Flat-head rivets need to be driven with a rivet gun. First, punch holes in the object to be connected, then insert the rivet, and then pull the rivet with the rivet gun.
Rivet: In riveting, a part that uses its own deformation or interference to connect the riveted parts. There are many types of rivets, and they are informal. Common rivets are round head rivets, flat head rivets, countersunk rivets, semi-tubular rivets, solid rivets, composite rivets, step rivets and so on. Flat head rivets are used for riveting occasions with general loads.
For example, if you want to rivet two iron plates with a 3.2X10 flat-head aluminum rivet, first use a 3.3 drill bit to drill through holes in both iron plates, and then insert the thick end of the rivet into the aligned holes on the two plates. Then use the guide nozzle of the rivet gun to insert the thin end of the rivet exposed outside the two iron plates, and pull the handle of the rivet gun until the thin end of the rivet is broken, so that the thick end of the rivet has been deformed. The boards are firmly connected together
The use of non-standard screws
Hexagonal non-standard screws, also known as blind rivet nuts, pull caps, instant pull caps, are used in the fastening fields of various metal sheets, pipes and other manufacturing industries. They are widely used in automobiles, aviation, railways, refrigeration, elevators, switches, and instruments. , Furniture, decoration and other electromechanical and light industrial products assembly. It was developed to solve the shortcomings of thin metal plate and thin tube welding nuts, such as easy melting, easy welding deformation of the base material, and easy slipping of internal threads when tapping. It does not require tapping internal threads, welding nuts, and the riveting is firm and efficient, and easy to use.
Stainless steel nut
Types of non-standard screws
Flat head small head hex half hex rivet nuts, with through holes, blind holes, knurled and non-knurled.
The use of non-standard screws
If the nut of a certain product needs to be installed on the outside, and the space inside is small, the indenter of the sub-riveter cannot be allowed to enter for pressure riveting and methods such as sprouting cannot meet the strength requirements, then pressure riveting and expansion riveting are not feasible. Must use pull riveting. It is suitable for the fastening field of various thickness plates and pipes (0.5MM-6MM). The use of pneumatic or manual riveting guns can be rivetted at one time, which is convenient and firm; it replaces the traditional welding nut to make up for the shortcomings of thin metal plate, thin tube welding, and welding nuts are not smooth.
4 Structural rivet nuts are mainly used in non-structural bearing bolt connections, such as the connection of interior parts such as rail passenger cars, highway buses, and boats. The improved rivet nuts that can prevent spin are more excellent than the pallet nuts for aircraft. The advantages are lighter weight, no need to fix the pallet nuts with rivets in advance, and the base material can still be used without operating space on the back.
The specifications of rivet nuts in the national standard are M3, M4, M5, M6, M8, M10, and M12. In fact, M6 and M8 are recommended, because small threads can be directly tapped on the base material. If the threads are large, the weight of the bolt will increase greatly. The increase in connection strength is limited, that is, the matching is unreasonable.
12 common fastener classifications
Fasteners usually include the following 12 types of parts:
1. Bolt: A type of fastener consisting of two parts, a head and a screw (cylinder with external threads), which need to be matched with a nut to fasten and connect two parts with through holes. This type of connection is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection.
2. Stud: There is no head, only a type of fastener with threads on both ends. When connecting, one end of it must be screwed into the part with internal threaded hole, the other end must pass through the part with through hole, and then the nut is screwed on, even if the two parts are tightly connected as a whole. This type of connection is called a stud connection, which is also a detachable connection. It is mainly used where one of the connected parts has a large thickness, requires a compact structure, or is not suitable for bolt connection due to frequent disassembly.
3. Screw: It is also a type of fastener composed of two parts: head and screw. According to the purpose, it can be divided into three categories: machine screws, set screws and special purpose screws. Machine screws are mainly used for a tightening connection between a part with a threaded hole and a part with a through hole, without the need for a nut to fit (this type of connection is called a screw connection, which is also a detachable connection; it can also be Cooperate with nut, used for fastening connection between two parts with through holes.) Set screw is mainly used to fix the relative position between two parts. Special purpose screws such as eyebolts are used for lifting parts.
4. Nut: With internal threaded holes, the shape is generally flat hexagonal column, and also flat square column or flat cylinder. It is used with bolts, studs or machine screws to fasten and connect two parts. It becomes a whole.
5. Self-tapping screws: similar to machine screws, but the thread on the screw is a special self-tapping screw thread. It is used to fasten and connect two thin metal components into one piece. Small holes need to be made in the component in advance. Because this kind of screw has high hardness, it can be directly screwed into the hole of the component. Form a responsive internal thread. This type of connection is also a detachable connection.
6. Wood screw: It is also similar to machine screw, but the thread on the screw is a special rib for wood screw, which can be directly screwed into the wooden component (or part) to use a metal (or non-metal) with a through hole. The parts are firmly connected to a wooden component. This connection is also a detachable connection.
7. Washer: A type of fastener with an oblate ring shape. It is placed between the supporting surface of bolts, screws or nuts and the surface of the connected parts, which increases the contact surface area of the connected parts, reduces the pressure per unit area and protects the surface of the connected parts from damage; another type of elastic washer, It can also prevent the nut from loosening and shockproof.
8. Retaining ring: It is installed in the shaft groove or hole groove of the machine and equipment, and plays a role of preventing the parts on the shaft or hole from moving left and right.
9. Pin: Mainly used for parts positioning, and some are also used for connecting parts, fixing parts, transmitting power or locking other fasteners.
10. Rivet: A type of fastener composed of two parts, a head and a nail shaft, used to fasten and connect two parts (or components) with through holes to make them into a whole. This type of connection is called rivet connection, or riveting for short. Belong to and non-detachable connection. Because to separate the two parts connected together, the rivets on the parts must be broken.
11. Assembled parts and connection pairs: Assembled parts refer to a type of fasteners supplied in combination, such as a combination of machine screws (or bolts, self-supplied screws) and flat washers (or spring washers, lock washers); connection; The secondary refers to a type of fastener supplied by a combination of certain special bolts, nuts and washers, such as the connection of high-strength large hexagonal bolts for steel structures.
12. Welding nails: Because of the heterogeneous fasteners composed of light energy and nail heads (or no nail heads), they are fixedly connected to a part (or component) by welding so as to be connected with other parts.
Application range of related screws
There are many names for screws, and everyone's name may be different. Some people call them screws, some people call them screws, some people call them standard parts, and some people call them fasteners. Although there are so many names, they all mean the same thing. They are all screws. Screws are the general term for fasteners. The principle of the screw is to use the physics and mathematics principle of the oblique circular rotation of the object and the friction force to gradually tighten the utensils and parts.
Screws are indispensable in daily life and industrial production. Screws are also called the rice of industry. It can be seen that screws are widely used. The scope of application of screws are: electronic products, mechanical products, digital products, electrical equipment, electromechanical products. Screws are also useful in ships, vehicles, water conservancy projects, and even chemical experiments. Anyway, screws are used in many places. Such as precision screws used on digital products. Mini screws used in DVDs, cameras, glasses, watches, electronics, etc.; general screws used in televisions, electrical products, musical instruments, furniture, etc.; large screws and nuts are used in engineering, construction, and bridges; transportation equipment, airplanes, trams, and automobiles And so on, use both large and small screws. Screws have important tasks in industry. As long as there is industry on the earth, the function of screws will always be important.
There are many types of screws, whether they are very small screws for glasses or large screws for large-scale heavy electrical engineering. The accuracy of screws is usually 6g (level 2, American standard "IFI" is 2A thread), and the rough screw used in construction engineering is 1g.
The application range of screws is so wide, so the screw market must be relatively large, the demand must be relatively huge, and there must be more screw manufacturers in the screw industry. When purchasing a professional screw purchasing manufacturer, they must first understand some professional basic knowledge of screws, such as screw classification standards and American screw specification tables.
