Types of fasteners: guidelines for selecting the correct fasteners

What is a fastener?

Fastener is the general name of a kind of mechanical parts used for fastening and connecting two or more parts (or components) into a whole. Fasteners are widely used in various industries, including energy, electronics, electrical appliances, machinery, chemical industry, metallurgy, mold, hydraulic and other industries. All kinds of fasteners can be seen in various machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, chemicals, instruments and supplies. They are the most widely used mechanical basic parts.It is characterized by a wide range of varieties and specifications, different performance and uses, and a high degree of standardization, serialization and generalization. Therefore, some people also call a class of fasteners with existing national standards standard fasteners, or simply standard fasteners.

Types of fasteners

Let’s take a closer look at the different types of fasteners available and your choices.
There are many ways to classify fasteners, but the common ways include:

• According to material: steel fasteners, aluminum alloy fasteners, stainless steel fasteners, copper fasteners, zirconium fasteners, etc.
• According to shape:Bolt、Nut, nuts, screws, screws, retaining screws, fasteners, etc.
• According to the mode of use: fixed fasteners, adjustable fasteners, removable fasteners, etc.
• According to the function: support fastener, support fastener, fixed fastener, contact fastener, etc.
• According to size: small fasteners, medium fasteners, large fasteners, etc.

These classification methods are based on the characteristics and functions of fasteners, which can facilitate the organization and use of fasteners.

It usually includes the following 12 types of parts：

1. Bolt

What is a bolt?

Bolt: machine part, cylindrical threaded fastener with nut. It consists of head and screw (cylinder with external thread)A type of fastener consisting of two parts, which needs to be matched with a nut, is used 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.
Working principle of bolt
The purpose of bolt tightening is to make the two connected bodies have enough compression force, which is reflected on the bolt as its axial preload. Whether it is the compression force between two connected bodies or the axial preload on the bolt, it is difficult to detect and control it directly at the work site. The following are three common methods of bolt tightening

• （1）The torque control method refers to the control method of stopping tightening immediately when the tightening torque reaches a set target value. However, the tightening error of the torque control method is large. When the error of the tightening torque z is 0, the maximum error of the bolt axial preload can reach ± 27_2%. Therefore, the torque control method is only used in situations where the control accuracy of the bolt axial preload is not high
• (2) The yield point control method is a high-precision tightening method developed by using the data yield phenomenon. The tightening accuracy of this control method is very high, and its accuracy mainly depends on the yield strength of the bolt itself, but it is rarely used in actual tightening operations.
• （3）The torque angle control method is based on a certain angle, which makes the bolt produce a certain axial extension and the connector is compressed, resulting in a certain axial preload of the bolt. Therefore, the torque angle control method has been widely used in tightening operations with high requirements; in actual application, one of them is selected according to the different tightening requirements.The control and detection system of automatic tightening machine is mainly divided into three-phase transformer, control and display, main control unit, shaft control unit, motor driver and tightening head.

Classification of bolts

• 1. According to the connected stress pipes, there are ordinary and reamed holes. The bolts for reaming holes should match with the size of the holes, which are used when subjected to transverse force
• 2. According to the head shape, there are hexagon head, round head, square head, countersunk head, etc. Generally, countersunk head is used in the place where the surface is smooth without protrusion after the connection, because the countersunk head can be screwed into the part. The round head can also be screwed into the part. The tightening force of square head can be larger, but the size is large. Hexagon head is the most commonly used

In addition, in order to meet the need of locking after installation, there are holes in the head and in the rod, which can prevent the bolt from loosening when subjected to vibration. Some bolts have no thread, and the polished rod should be made thin, called slim waist bolt. This bolt is conducive to the connection under variable force. There are special high-strength bolts on the steel structure. The head will be made larger, and the size will also change
In addition, there are special uses: T-shaped slot bolts are used most frequently on machine tool fixtures, with special shapes, and both sides of the head should be cut off. Anchor bolts, which are used to connect and fix the machine and the ground, have many shapes, U-shaped bolts, etc. There are also special studs for welding, with one end having a thread and the other end not, which can be welded on the parts, and the other side can be screwed directly.
Selection Guide of Bolts

• 1. The selection principle is that the bolt length should expose 2-3 turns of threads of the nut. If there is no suitable length, the bolt must expose the nut in principle.The bolt length is generally a multiple of 5, and the length is 15mm, 20mm, 25mm… When the calculated length is inconsistent with the standard length, the closer length should be selected. For example, when the calculated length is 26mm or 27mm, the 25mm length should be selected, and when the calculated length is 28mm, 29mm, the 30mm length should be selected
• 2. The direction of bolts shall be consistent, and the nuts shall be placed at the side convenient for maintenance
• 3. Flat washers shall be provided on both sides of the fixed objects connected by bolts, and spring washers or lock nuts shall be installed on the side close to the nuts.
• 4. Discard bolts shall not be used. Discard standard: bolts with obvious cracks, broken threads, sliding threads, disordered threads, tensile deformation of screws, shear marks, etc., and other bolts that can not be repaired as determined by the site.

Maintenance of bolts

• 1. Anchor bolts, stud bolts, always keep the vibration exciter vent unblocked (easy to cause oil leakage due to blockage). If there is still oil leakage after unblocked, replace the oil seal.
• 2. The normal operation of the bearing should not exceed 75 ℃. The temperature of the new vibration exciter may be slightly higher because of a running in process, but after 8 hours of operation, the temperature should stabilize. If the temperature continues to be too high, the oil level, oil level and oil cleanliness should be checked.
• 3. Make sure that the labyrinth groove is full of grease. When working in dusty situations, grease should be added more frequently.
• 4. When replacing the V-belt, the anchor bolt of the motor should be completely loosened to put the V-belt into the pulley groove conveniently. It is not allowed to pry the V-belt with a stick or other objects. The tension of the V-belt must be suitable, and the pulley must be aligned. After the tension is adjusted for the first time, work for 48 hours and readjust it again.
• 5. The bolt connecting the vibration exciter and the screen box is. It is not allowed to use ordinary bolts instead. The fastening must be checked regularly, at least once a month. If any bolt is loose, it will also cause other bolts to cut off, causing damage to the screen machine.
• 6. Where ring groove rivets are used for connection, high-strength bolts can be used instead. All contact surfaces or holes shall be free of iron filings, ash, oil, rust and burrs.
• 7. The high-strength bolts, nuts and washers used must meet the requirements of Technical Conditions for High Strength Large Hexagon Bolts, Large Hexagon Nuts and Washers for Steel Structures.

Matters needing attention

• 1. During the storage and use of screws, product protection should be strengthened to ensure a dry environment. Electroplated iron screws should not be placed in damp places. Reasonable protection means reasonable internal and external packaging
• 2. In order to prevent damage to the product, screw teeth from being damaged, resulting in failure to pass the go no go gauge, and nuts from being matched, we need to handle with care during transportation
• 3. We need to pay attention to the correct use of the screw to ensure that the product will not be damaged due to improper use. For example, the torque should not exceed the minimum breaking torque. The rust proof layer on the screw surface should not be damaged during use. If it has been damaged or needs to be damaged before use, the rust proof layer should be added after assembly.
• 4. Before using self tapping screw products, it is necessary to understand their performance and precautions.
• 5. During the use of screw products, the performance of products matching the products should be understood to achieve reasonable cooperation.

Troubleshooting of bolts

• 1. Material problems, processing defects and heat treatment process problems can also lead to fracture of connecting rod bolts during engine operation.
• 2. If the diesel engine has runaway fault or the piston burns in the cylinder during operation, the connecting rod bolt will be pulled off. If the engine has runaway fault during operation, a comprehensive inspection should be carried out for the engine, and it is better to replace the connecting rod bolt. If some cylinders have serious cylinder pulling during operation, the connecting rod bolt should also be replaced when replacing the cylinder piston assembly.
• 3. The connecting rod of diesel engine can be divided into several levels. During maintenance, it should be noted that connecting rods of different levels should not be replaced. If the connecting rod cap is disordered or incorrectly installed due to carelessness during maintenance, it will cause the joint surface of the connecting rod big end not to fit closely, and it will cause the connecting rod cap to loosen during engine operation, resulting in the fracture of connecting rod bolts. The connecting rod big end of WD615 series diesel engine is of bevel cut typeThe cutting angle is 45 °, and the connecting rod cap and connecting rod big end joint surface adopts a 60 ° zigzag positioning structure. This structure has the characteristics of close fitting, accurate positioning, reliability, and compact structure. If the connecting rod cap is disordered and wrongly installed during maintenance, it will inevitably lead to poor zigzag positioning of the joint surface, which is very likely to cause the loosening of the connecting rod cap during engine operation, resulting in the fracture of the connecting rod bolts.
• 4. During assembly, the tightening torque is too large and the force is uneven. Since there is no strict use of torque wrench in the assembly, and the specific tightening torque is not well understood, it is believed that the tighter the better; the connecting rod bolt is fastened with a longer force rod, and the tightening torque is too large, which exceeds the yield limit of the bolt data, causing the connecting rod bolt to yield deformation and excessive elongation under the impact loadHowever, fracture. It should be emphasized that connecting rod bolts must be tightened according to the standard, and the tighter the force, the better.

2. Nut

What is?Nut？

Nuts are nuts, which are screwed together with bolts or screws to play a fastening role. One element that must be used in all production and manufacturing machinery can be divided into carbon steel, stainless steel, non-ferrous metals (such as copper) and other types according to different materials.
Application of nuts

• Automobile industry: cars, trucks, buses
• compressor
• construction machinery
• Wind power generation equipment
• Agricultural machinery
• a fastening
• a fastening
• Foundry industry
• Drilling equipment
• Shipbuilding industry
• Mining equipment
• Oil drilling rig (onshore or offshore)
• Utilities
• rail transit
• drive system
• Metallurgical equipment
• Rock hammer

Classification of nuts
(1) Stainless steel nut
Self locking nut, lock nut, lock nut, four jaw nut, screw in nut safety nut, thin rod screw connecting nut, self-locking hexagon cap nut special anchor screw nut, hexagon crown thin nut eyebolt nut.
Fine tooth all metal hexagon flange lock nut、All metal hexagon flange lock nut、Hexagon flange lock nuts with fine pitch non-metallic inserts、Fine pitch hexagon flange nuts.
Welding square nut Welding hexagon nut、Tighten the nut and insert the round nut.
Round nut with slot Round nut with hole on the side、Round nut with hole on end face Small round nut.
Round nut、Ring nut、Butterfly nut。
(2) Copper nut
Copper nut, inlaid copper nut, knurled copper nut, inlaid copper nut, injection molded copper nut, etc.
(3) Alloy nut
Zinc copper alloy nuts, etc.
Selection Guide for Nuts
For many sizes, you need M to remember the nut parameters, which is the basic logical relationship in the mechanical aspect (to be more specific, it is also related to the free tolerance of force and structural design):

• The bolt specifications selected first are standard specifications: M4, M5, M6, M8, M10, M12, (M14), M16, etc.
• Next, the other side leaves a hole. The bolt you choose must be smaller than the hole. The other side leaves a hole of 14. You can only choose a bolt smaller than 14. According to the specification, the nearest bolt is M12. So this is your only choice.

Of course, you can also choose M10 or M8 bolts under the condition of satisfying your mechanics, but you can check whether the M10 or M8 bolt spring pad can not be completely larger than the flange hole and can not work completely. This is called unreasonable structure. Generally speaking, the hole does not match the bolt.
The structural relationship of general mechanical design is that the hole is one level larger than the bolt, and the diameter of the hole is generally 1 to 2 mm larger than the bolt, which is convenient for assembly.
However, there are exceptions. When the bolt is too small, it is generally smaller than M6, and the empty space is selected to be larger than 0.5 mm. This is also determined according to the free tolerance of assembly;
There is only one tenth of the difference between holes and bolts in the complete matching relationship, which is called reamed bolt connection;
When the bolt is larger than M20 or above, the hole can also be appropriately relaxed by 3 mm, even up to 4 mm. This is generally the case. The main consideration is to facilitate installation and reduce installation difficulty. When the bolt hole is in a place where it is particularly difficult to install, the designer also considers relaxing the requirements. When there are many bolts, the requirements can also be relaxed.
Maintenance of nuts
1. In order to keep the surface of stainless steel anti-theft nuts gorgeous and clean, it is necessary to periodically wash and manage the stainless steel used for a long time.
2. Washing method shall be determined according to the surface state: in general, please pay attention not to scratch the surface during washing, and avoid using bleaching ingredients, detergent containing abrasives, steel wire balls (brush roller balls), grinding tools, etc. In order to remove the detergent, clean water shall be used to wash the surface after washing.
matters needing attention

• (1) The washer of slurry pump shall be added under the nut of foundation bolt; the foundation bolt of lifting and transportation equipment shall be locked with locking device.
• (2) Before the foundation bolt is screwed on the nut, it shall be lubricated with oil or grease to prevent rust in the future, which will make disassembly difficult.
• (3) The foundation bolts can be tightened only after the concrete reaches 75% of the design strength.
• (4) The foundation bolt shall be tightened from the middle of the equipment, and then be tightened diagonally at both ends. The assembler shall ensure that the tightening force is uniform. It is forbidden to tighten one side before tightening the other. After tightening the nut, the perpendicularity of the foundation bolt shall be rechecked with a frame level.

3. Screw

What are screws?

Screw refers to the screw (foreign name: Screw), which is a tool that uses the physical and mathematical principles of the oblique circular rotation and friction force of objects to gradually fasten objects and parts. Screw is a general term for fasteners, and is a daily colloquial language.
Metric thread is organized in MM (mm), and its cusp angle is 60 degrees. Both American thread and inch thread are organized in inches. The cusp angle of American thread is 60 degrees, while that of inch thread is 55 degrees.
Due to the different units of measurement, the representation methods of various threads are different. For example, M16-2X60 represents a metric thread. His specific meaning is that the nominal diameter of the screw is 16MM, the pitch is 2MM, and the length is 60MM. For example, 1/4-20X3/4 represents an imperial thread, and his specific meaning is that the nominal diameter of the screw is 1/4 inch(One inch=25.4MM), there are 20 teeth on one inch, and the length is 3/4 inch. In addition, if the American screw is to be represented, UNC and UNF are usually added behind the English screw to distinguish between American coarse teeth and American fine teeth.
Application of screws
Screw The machine screw is mainly used for the fastening connection between a part with a fixed threaded hole and a part with a through hole, without nut matching(This type of connection is called screw connection, which is also a detachable connection. It can also be used with a nut for the fastening connection between two parts with a through hole. It is also the most common screw. Screw set screws are mainly used to fix the relative position between two parts. We call them “stop screws”, acting as a locating pin. Special purpose screws, such as eyebolts, are used for lifting parts.
Classification of screws
1. Slotted common screw
It is mostly used for the connection of small parts. It includes pan head screws, cylindrical head screws, half countersunk head screws and countersunk head screws. The head strength of pan head screws and cylindrical head screws is high, and they are connected to common parts; the head of half countersunk head screws is curved, and its top is slightly exposed after installation, and it is beautiful and smooth, and is generally used for instruments or precision machinery; countersunk head screws are not allowedThe exposed part of the nail head.
2. Hexagon socket and hexagonal socket torx screws
The head of this kind of screw can be embedded in the component, which can exert greater torque, and has higher connection strength, so it can replace the hexagonal bolt. It is often used at the joint with compact structure and smooth appearance.
3. Cross recessed common screw
It is similar to the slotted ordinary screw in use function and can be replaced with each other, but the cross recessed ordinary screw has a high groove strength, is not easy to be unscrewed, and has a beautiful appearance. When used, it must be loaded and unloaded with a matching cross screwdriver.
4. Eyebolt
The eyebolt is a kind of hardware fitting for bearing load during installation and transportation. When using, the screw must be screwed to the position where the bearing surface fits tightly. It is not allowed to use tools to tighten it, nor is it allowed to have a load perpendicular to the plane of the eyebolt acting on it.
5. Set screw
The set screw is used to fix the relative position of the machine part. Screw the set screw into the screw hole of the part to be tightened, and press its end tightly on the surface of another part, that is, fix the previous part on the next part.
The set screw is usually made of steel or stainless steel, and its end shapes include cone, concave, flat head, cylindrical and stepped. The end of the set screw with cone or concave end directly tightens the part, which is generally used at places that are not often disassembled after installation. The end of the set screw with flat end is smooth, which does not damage the surface of the part after being tightened. It is used at the connection where the position needs to be adjusted frequently, and can only transmitSmall load; the cylindrical end set screw is used at the position that needs frequent adjustment and fixation. It can bear large load, but its anti loosening performance is poor, so anti loosening measures should be taken when fixing; the stepped set screw is suitable for fixing parts with large wall thickness.
6. Self tapping screw
When the self tapping screw is used on the connected part, the thread may not be made in advance at the connected part. When connecting, the screw can be used to directly tap the thread. It is often used to connect metal plates with thin thickness. There are two kinds of self tapping screws, namely, cone end self tapping screw and flat end self tapping screw.
7. Self tapping locking screw
The self tapping locking screw not only has the self tapping function, but also has the performance of low screw in torque and high locking. Its thread has a triangular cross section, and the surface of the screw has been hardened with high hardness. Its thread specification is M2-M12.
Selection guide for screws

• Check the head of the screw: whether there is a burst, surface blackening, dark spots, delamination, etc;
• If it is a combination screw, check whether the screw is missing and flat, and spring washer;
• Check whether the tooth lines have teeth and the tail of the bundle is too long;
• Check whether the thread passes the go no go gauge;
• Measure whether the external diameter of the tooth meets the standard;
• Measure whether the head size meets the standard;
• For combination screw, measure whether the size of gasket meets the standard;
• Test whether the screw has removed the hydrogen.

Maintenance of screws

• 1. The process of rinsing the screw is very important and needs to be very careful. During this process, there will be residues left on the surface of the screw. The rinsing step is after the silicate detergent cleaning.
• 2. The screws shall be stacked properly during tempering and heating, otherwise slight oxidation will occur in quenching oil.
• 3. The white residue of phosphide will appear on the surface of high-strength screw, which indicates (point 1) that the inspection is not careful enough during operation.
• 4. There will be blackening on the surface of parts and components, resulting in chemical reverse use, which indicates that the heat treatment work is not complete, and the alkaline residue on the surface has not been completely removed.
• 5. The standard parts of parts will rust during rinsing, and the water used for rinsing should also be replaced frequently.
• 6. Excessive corrosion indicates that the quenching oil has been used for too long, and new oil needs to be added or replaced.

Matters needing attention
When assembling screws, bolts, nuts and other standard parts, safety lock pads, washers, cotter pins or brake lead wires should be installed according to the original regulations. The retaining washers, cotter pins and brake lead wires should not be reused after removal. The number of installed washers should not exceed the original number. After the nuts are tightened, the length of the screw extending beyond the nuts should be within the range of 1-3 buckles(excluding adjusting screws or bolts)In case of two nuts with locking effect, they should be installed one by one. First tighten one nut, then tighten the other nut. It is not allowed to tighten the two nuts at the same time. The thickness of the brake lead wire should be able to pass through the hole of the screw head smoothly, but not less than 10% of the hole diameter. The direction of passing through the hole should be such that after the lead wire is tightened, a locking torque should be applied to the screwThe two ends of shall be tightly twisted and cut at about 15 mm from the twisting point.
When installing the cotter pin, the pin head should enter the slot of the slotted nut. At least 2/3 of the diameter of the rod should be embedded in the slot. The long end of the tail should bend up to the upper part of the screw, and the short end should bend down to the nut plane, and should be closely attached. There should be no cracks and breaks at the bend of the pin tail. The diameter of the cotter pin should be consistent with the diameter of the opening pin hole, not too thin, so as not to play a role in safety. When there are multiple bolts in the connected partDuring bolt fastening, all bolts shall be tightened in two or three times. Never tighten one bolt before the other.

4. Expansion screws

What is an expansion screw?

Generally speaking, expansion screws are metal expansion screws. The wedge slope is used to promote expansion to generate friction and wrapping force, so as to achieve the fixed effect. One end of the screw is threaded, and the other end is tapered. It is wrapped with an iron sheet (some are steel pipes) and an iron sheet cylinder (steel pipes)Half of them have a number of notches. Insert them into the holes made on the wall together, and then lock the nuts. The nuts pull the screws outward, and the taper is pulled into the iron cylinder. The iron cylinder is expanded, and then firmly fixed on the wall. Generally, it is used to fasten the guard rails, awnings, air conditioners, etc. on cement, bricks, and other data. However, its fixation is not very reliable. If the load has a large vibration, it canIt can become loose, so it is not recommended to install ceiling fans.
Operating principle of expansion screw
The expansion screw consists of a screw rod, an expansion pipe and other parts. The tail of the screw rod is conical, and the inner diameter of the cone is larger than the inner diameter of the expansion pipe. When the nut is tightened, the screw rod moves outward, and the cone part moves through the axial movement of the thread, thus forming a large positive pressure on the outer peripheral surface of the expansion pipe. In addition, the angle of the cone is small, so that the wall, the expansion pipe and the cone formFriction self-locking, thus achieving a fixed role.
The spring washer on the expansion screw is a standard part. Because its opening is staggered and elastic, it is called a spring washer. The function of the spring washer is to use the sharp corner of the staggered opening to penetrate into the nut and flat washer to prevent the nut from loosening.
The flat washer is also a standard part, and its function is to evenly distribute the pressure of the nut on the connected parts.
Application of expansion screw

• Fasten air conditioners, water heaters, range hoods, etc;
• Fixed frameless balcony windows, anti-theft doors and windows, kitchen, bathroom components, etc;
• Fixation of ceiling screw rod (combined with sleeve and cone cap);
• Other occasions that need to be fixed.

Classification of expansion screws

• 1. Metal expansion screw;
• 2. The elevator is equipped with expansion screws, and the car repair expansion screws;
• 3. Chemical anchor bolt;
• 4. Internal expansion screw;
• 5. Window expansion screw;
• 6. Heavy duty anchor bolts.

Selection Guide for Expansion Screws
It is very important to look at the thickness of the expansion bolt expansion pipe. The thickness of the pipe determines whether the anchoring force is firm or not. It is easy for the master to pull it out. When purchasing, be careful. If you can squeeze the expansion bolt with your hand, you must not buy it! It is absolutely non-standard! When purchasing, be sure to choose the one with the thickness of the pipe, and use the expansion screw that cannot be moved with your hand. Such expansion bolts will greatly increase the anchoring in the wallpower.
According to the matching degree of screw threads and nuts, non-standard expansion bolts have poor matching degree. Bolts and nuts are loose and feel like they will fall off. Such products are easy to be scratched when tightening, which will cause secondary rework and loss of money and time. When purchasing, be sure to buy expansion bolts that have high matching degree with nuts and do not loosen, which will not cause scratch and other phenomena during installation. Safety and qualityThe quantity is also guaranteed.
According to the weight, some non-standard Pengzhan bolts look heavy and thick. In fact, there is a large gap between the screw and the expansion tube, and the rod is thin and the tube is thick. Compared with non-standard expansion bolts, the weight of national expansion bolts may be twice that of non-standard expansion bolts. Like faucets, the heavier the bolts, the better. Only the heavier the bolts, the more materials will be enough.
Maintenance of expansion screw

• 1. The rinsing procedure of the expansion screw should not make any mistakes. Be careful when carrying out the rinsing procedure. In this process, residues will be left on the surface of the screw. In addition, the rinsing must be carried out after the completion of silicate detergent.
• 2. When the screws are tempered and heated, they must be stacked correctly. If there is an error, a small amount of oxidation will occur in the quenching oil.
• 3. If white phosphide appears on the surface of the expansion screw, it indicates that an error occurred during the inspection during rinsing.
• 4. If the skin of the expansion screw turns black, it indicates that the work after the heat treatment is not up to the standard, and the alkaline residue of the skin has not been completely removed.
• 5. The expansion screw may rust during rinsing, so the water used for rinsing must be replaced frequently.

Matters needing attention

• 1. Drilling depth: the relevant data introduces the length of the expansion tube, but I found that this depth is not good in the specific construction, which may be related to the amount of debris left in the hole, so you’d better be 5 mm deeper than the length of the expansion tube. As long as you are greater than or equal to the length of the expansion tube, then the length of the expansion bolt left underground is equal to or less than the length of the expansion tube.
• 2. Of course, the harder the bolt is, the better the ground is. This also depends on the stress of the object you need to fix. The stress strength of the device in concrete (C13-15) is five times that in brick.
• 3. After a M6/8/10/12 expansion bolt accurately installed in the concrete, its non ambitious stop force is 120/170/320/510 kg respectively.

5. Rivets

What is a rivet?

Rivets are nail shaped objects used to connect two parts (or components) with through holes and caps at one end. In riveting, the riveted parts are connected by their own deformation or interference. There are many types of rivets, and they are not restricted in form.
Working principle of rivet
Riveting is to use a metal cylinder or metal pipe (rivet) with a slightly smaller perforation diameter to pass through the workpiece to be riveted, and knock or pressurize the two ends of the rivet to deform and thicken the metal column (pipe) and form rivet heads (caps) at both endsThe workpiece cannot be detached from the rivet. When the external force that separates the workpiece is applied, the nail rod and nail cap bear the generated shear force to prevent the workpiece from separating. Riveting is divided into cold riveting and hot riveting. Cold riveting is the riveting of rivets at room temperature; hot riveting is used in places with higher connection requirements, such as steel beam riveting of iron bridge. When hot riveting, the rivets need to be preheated. Hot and red rivets need to be penetrated into the rivet holes and punchedAfter the rivet head is fixed, the contraction stress during the cooling process will make the connection closer. Riveting generally requires double-sided operation. The emergence of blind rivets makes single-sided operation a more simple and easy process.
Application of rivets
Rivets are usually used to rivet the connection between objects, and special tools are usually required for operation. There are many kinds of rivets, such as semicircle head rivets, flat cone head rivets, countersunk head rivets, semi countersunk head rivets, flat head rivets, blind rivets, tubular rivets, label rivets, etc., to meet different work needs.
Classification of rivets
Commonly used are R type rivets, fan rivets, pop rivets (pop rivets)Tree rivets, half round head, flat head, half hollow rivets, solid rivets, countersunk head rivets, pop rivets, and hollow rivets are usually used to connect the riveted parts by their own deformation. Generally, cold riveting is used for those smaller than 8mm, and hot riveting is used for those larger than this size. However, there are exceptions, such as the nameplate on some locks, which is riveted by the interference between the rivet and the lock body hole.
R type plastic rivet, also known as expansion rivet, is composed of plastic sub rivet and female buckle. During installation, it does not need to use installation tools. It places the installation base in a smooth hole, and then presses down the head. The specially designed foot expands and stretches after being stressed, and is firmly locked on the installation surface. It is often used to connect plastic shells, lightweight plates, insulating materials, circuit boards, or any other lightThin, lightweight data, beautiful and practical, easy to use.
Fan rivets are specially designed for manual installation. They can be pulled in through the holes in the panel or chassis. They are made with elastomer data and have good toughness. They can be quickly installed even in interference assembly. They are ingeniously designed with elastic function and are not easy to slip out after being pulled in with corresponding holes. Fan rivets are mainly used to fix fans, heat sinks and chips in electronic computer casesIt can prevent vibration and reduce noise.
The core striking rivet is a new type of riveting fastener that is very convenient for riveting. The core striking rivet can show its unique advantages in a relatively narrow space or in an environment where there is no riveting machine or the riveting machine cannot be used. Two or more connected parts can be riveted successfully by hitting the nail core on one side with a hammer and other tools. The core striking rivet can be divided into oblate heads according to the shape of the nail hat brimCore rivets and countersunk core rivets can be divided into all aluminum core rivets, aluminum steel core rivets, all stainless steel core rivets, steel core rivets, aluminum stainless steel core rivets, plastic core rivets, etc. According to the different material combinations, core rivets and countersunk core rivets can be divided into all aluminum core rivets, aluminum steel core rivets, plastic core rivets, etc. Core rivets do not have to use manual riveting machine or pneumatic riveting machine to rivet like core rivets, so they have better riveting performance and convenienceIt can be widely used for riveting various connected parts.
Plastic tree rivets, also known as inverted tooth shaped plastic rivets, are also called Christmas tree shaped plastic rivets. The tooth shaped sheet has good elasticity and can be directly pressed and installed manually in the round hole of interference assembly. The tooth shaped sheet can be adjusted and fixed according to the actual thickness. The inverted tooth shaped design is that the rivet is firmly fixed to the installation surface after installation, which is not easy to be pulled out, and is suitable for foam and woodPlastic tree rivets have excellent insulation, fire resistance, non-magnetic, heat insulation, light weight, high temperature resistance, high strength and corrosion resistance, and are widely used in various industrial fields.
The rivet types can be roughly divided into open type, closed type, double drum type and single drum type series. The following is a brief description of their respective models.
Countersunk blind rivet: riveting of riveted parts with smooth and beautiful surface after riveting.
Double drum blind rivet: when riveting, the rivet core pulls the end of the rivet body into a double drum shape, clamping the two structural parts to be riveted, and reducing the pressure on the surface of the structural parts. Purpose: Mainly used for riveting various thin structural parts in various vehicles, ships, buildings, machinery, electronics and other industries.
Large brim blind rivet: Compared with ordinary blind rivets, this rivet has a significantly larger aluminum cap diameter. When riveting with the connector, this rivet has a larger contact area, a stronger support surface, which can enhance the torque strength and withstand higher radial tension. Applicable industry: it is suitable for fastening soft and fragile surface materials and oversized holes. The new brim diameter is suitable forSoft materials have special protective applications.
Closed blind rivet: It is specially designed to wrap the spindle head after riveting, and is very suitable for various applications with waterproof requirements. It has high shear force, anti vibration and high pressure resistance.
All aluminum blind rivets The rivet body of this rivet is also made of high-quality aluminum wire, which is beautiful and durable after riveting and will never rust. Compared with ordinary blind rivets, the rivet riveting strength is low, and it is suitable for connectors with soft data.
Open stainless steel rivet: This rivet is the best choice for high tensile demand and corrosion resistance.
Semi round head rivets are mainly used in riveting occasions under large transverse loads, and are most widely used.
Flat cone head rivets are usually used for riveting of hull, boiler water tank and other places with strong corrosion due to their large heads and corrosion resistance.
Countersunk rivets, semi countersunk rivets, 1200 countersunk rivets and semi countersunk rivets are mainly used in riveting situations where the surface needs to be smooth and the load is not large.
Flat head rivets are used for riveting under general load.
Flat head and flat round head rivets are mainly used for riveting of sheet metal or non-metallic materials such as leather, canvas and wood.
Large flat head rivets are mainly used for riveting non-metallic materials.
Semi hollow rivets are mainly used for riveting occasions with small load.
Headless rivets are mainly used for riveting of non-metallic materials.
Hollow rivets are light in weight and weak in head. They are used for riveting non-metallic materials with small load.
Tubular rivets are used for riveting of non-metallic materials under no load.
Signboard rivets are mainly used to rivet nameplates on machines, equipment, etc.
The blind rivet is a kind of rivet used for single-sided riveting, but it must be riveted with a special tool – riveting machine (manual, electric, pneumatic). This kind of rivet is especially suitable for ordinary rivets that are inconvenient to use (riveting must be performed from both sides)Therefore, it is widely used in building, automobile, ship, aircraft, machinery, electrical appliances, furniture and other products. Among them, the open type flat round head pop rivets are the most widely used, the countersunk head pop rivets are suitable for the riveting occasions where the performance needs to be smooth, and the closed type pop rivets are suitable for the riveting occasions where high load and certain sealing performance are required.
Core rivet is another kind of rivet riveted on one side. When riveting, hammer the rivet head to expose the rivet core so that it is flush with the end face of the rivet head, which is very convenient. It is especially suitable for ordinary rivets (riveting must be performed from both sides)Or blind rivets. Usually flat round head rivet is used, and countersunk head rivet is suitable for riveting where the surface needs to be smooth.
Some rivets can also be paired with clothes, becoming popular elements today, and most of them are representatives of punk style.
In addition, there is a pair of special rivets. They are divided into two parts. The thicker one has a hole in the center of the cap rod, which is an interference fit with the thinner one. When riveting, the thin rod can be driven into the thick rod.
Rivet selection guide

• a. Strength of rivet: including tensile strength and shearing strength。
• b. Riveting thickness (GRIP): measure the thickness to be riveted, and then select according to the recommended riveting range of rivets。
• c. Rivet data (MATERIAL): rivet body data of rivets usually include aluminum, steel, stainless steel, copper, and of course, some special data, such as monel。
• d. DIAMETER: The size of the hole diameter is very important for riveting. It is too small, and it is difficult to insert rivets. It is too large, and the riveting is not tight。
• e. HEAD TYPE: Rivet brim has round head, CSK HEAD and FLANGE, which are most commonly used. If the surface is flat after riveting, use countersunk head. If the riveted object is soft, use large brim.

Rivet maintenance

• First: There are white substances on the surface, which should be some phosphating substances. The main reason for this is that the fasteners were not pickled or rinsed carefully enough during production.
• Second: In the process of quenching fasteners, the impurities on the surface must be cleaned with silicate, and care must be taken not to leave any impurities on the surface.
• Third: After tempering, fasteners need to be soaked in the solution for a period of time. If oily substances are produced, it means that the fasteners are not clean enough. This is mainly because the fasteners are stacked improperly when they are heated, and there may be some small oxidation phenomenon in the quenching oil.

Matters needing attention

• 1. The hole diameter of the rivet should be 0.10 mm larger than the rivet diameter. If it is too small, it will affect the bonding strength. If it is too small, it is difficult for the rivet to penetrate.
• 2. During riveting, the sub hole diameter of the riveting machine head shall be marked according to the diameter of the mandrel, the orientation of the conduit shall be properly adjusted and locked with nuts so that the mandrel can freely penetrate into the pull clamp of the conduit, and then the rivet shall be pierced into the nail hole, the pull button shall be pressed to pull the mandrel off, and the riveting shall be completed.
• 3. When selecting rivets, it is also necessary to pay attention to the following points: when drilling rivet holes, the hole diameter should be straight with the surface of the workpiece; when using rivet to check the rivet, the rivet inspection axis must be the same with the rivet hole axis, and it is not allowed to tilt. When pulling the rivet, the riveter should be slightly pressed to make the rivet tail close to the surface of the workpiece.

6. Retaining ring

What is a retaining ring?

The retaining ring is divided into the retaining ring for hole and the retaining ring for shaft. The limiting effect can prevent the axial movement of other parts. The forming process is mostly plate punching, and the functional section is conical. After assembly, most of the large specifications and models are “linear contact”. The large specifications and models are made by the process of wire winding and punching excess materials. The section is regular rectangular, and after assembly, it is “face contact”.
Application of retaining ring
The fixation of parts on the shaft is divided into axial fixation and circumferential fixation.
Axial fixation methods include: shaft shoulder or collar fixation, shaft end retainer ring or conical surface fixation, shaft sleeve fixation, round nut fixation, and elastic retainer ring fixation.
The retaining ring mainly plays the role of axial fixation, and the cone surface with retaining ring has a high centering degree.
The retaining ring of rolling bearing is equivalent to a movable retaining ring, which is used to protect rollers and is convenient for installation. The structure of the retaining ring includes flat retaining ring, oblique retaining ring and middle retaining ring.
Classification of retaining ring

• Flat retainer ring: a separable basically flat washer whose inner or outer part is used as the outer ring or inner ring flange of the radial cylindrical roller bearing.
• Inclined retaining ring: a separable ring with an L-shaped section, the outer part of which acts as the inner rib of the radial roller ball bearing.
• Middle retaining ring: a separable ring in two or more rows of roller bearings, used to separate and guide each row of rollers.

The rib is a narrow shoulder parallel to the rolling direction and protruding from the raceway surface, which is used to support and guide the rolling body and keep it in the bearing.
Selection guide of retaining ring
Because the retaining ring generally uses the data of spring steel 65Mn, its comprehensive mechanical property after heat treatment is better than that of carbon steel, but it has overheating sensitivity and temper brittleness. It is used for small size flat and round springs, cushion springs, spring springs, and can also be used to make spring rings, valve springs, clutch springs, brake springs, and cold drawn steel wire cold coiled coil springs. When the shaft rotates, the circlip can also be usedIt rotates and is tightly clamped. As long as the snap ring does not break, it will not fall off.
Maintenance of retaining ring
The hole is installed in the round hole with a retaining ring, which is used to fix the axial movement of the parts. The outer diameter of this type of retaining ring is slightly larger than the diameter of the assembly round hole. When installing, it is necessary to use a circlip pliers, insert the tong nozzle into the clamp hole of the retaining ring, and clamp the retaining ring, before it can be placed into the pre processed inner groove of the round hole. It is mostly used for bearing holes, which are “blocked” by the outer position of the holeIt is used for bearing outer ring. The stop ring is a single ended ring with constant section, which is installed in the annular groove to make the rolling bearing axial positioning in the housing or on the shaft.
matters needing attention

• 1. The retaining ring for hole generally has two small holes. Because of the small holes, it is easy to assemble and disassemble, and has good eccentric elasticity.
• 2. The stop ring has no small hole and no eccentricity, so it is difficult to assemble, cannot be disassembled, and has poor elasticity.
• 3. The inner diameter and outer diameter of the stop ring can be used as long as the size is appropriate, while the outer diameter can only be used for the hole, because there are two small holes inside.

7. Washer: a type of fastener with flat circular shape. It is placed between the support surface of bolts, screws or nuts and the surface of connecting parts, which plays the role of increasing the contact surface area of connected parts, reducing the pressure of tissue area and protecting the surface of connected parts from damage. Another type of elastic washer can also play the role of preventing the loosening of nuts.
8. Pin: mainly used for positioning parts, and some can also be used for connecting parts, fixing parts, transmitting power or locking other fasteners.
9. Assembly and connecting pair: assembly refers to a type of fastener supplied in combination, such as a combination of a machine screw (or bolt, self supplied screw) and flat washer (or spring washer, lock washer); connecting pair refers to a type of fastener supplied in combination with a special bolt, nut and washer
10. Others: mainly including welding nails. Welding nails, heterogeneous fasteners composed of nail rods and nail heads (or without nail heads), are fixed and connected to a part (or component) by welding to connect with other parts.

Application of fasteners

Fasteners are basic mechanical parts, known as “the rice of industry”. They can be found in space shuttles, trains, ships, wind power and mechanical equipment, tables, chairs, benches, frying pans, mobile phones and watches. It can be said that fasteners are indispensable for flying in the sky, running on the ground and swimming in the water.

Maintenance of fasteners

The following points should be paid attention to in the daily maintenance of fasteners.

• 1. When the fasteners are quenched, silicate cleaning agent shall be used to clean the impurities on them, and then rinse carefully to avoid impurities left on the fasteners, which will affect their normal application.
• 2. After tempering, the fasteners may show signs of discoloration. After soaking the fasteners in the solution for a period of time, there will be oily substances, which indicates that the fasteners are not clean enough. After analysis, it is known that the reason is that the fasteners are improperly stacked during heating, resulting in slight oxidation of the fasteners in the quenching oil.
• 3. If there is white matter on the fastener, it may be some phosphide. The reason for this phenomenon is that the acid cleaner is not used for cleaning and the rinsing tank is not thoroughly inspected.
• 4. The quenching waste heat blackening of high-strength screws has a uniform and flat oil black outer surface. It is detected that it is caused by alkali burn. Therefore, the surface alkali cannot be removed from the quenching oil of steel fasteners, which will burn the surface at high temperature and aggravate the damage during tempering.It is recommended that the fasteners be thoroughly cleaned and rinsed before heat treatment to completely remove the alkaline residues that may cause burns to the fasteners.
• 5. Large fasteners are often quenched with polymer water solution. Before quenching, the fasteners are cleaned and rinsed with an alkaline cleaner. After quenching, the fasteners have rusted on the inside. Therefore, the rinsing water should be changed frequently to ensure that the fasteners will not rust during rinsing.
• 6. High strength fasteners often see some black stripes. This black stripe is a pollutant of surface residues, a baked quenching oil, and an evolution of gaseous substances during quenching. Because the quenching oil is excessively aged, it is recommended to add new oil.

When a fastener fails, it will first affect the performance of the fastener itself, and then it may be the use of the whole mechanical equipment. Therefore, the above problems must be paid enough attention. Just like people, only by paying attention to health care can we reduce the possibility of disease. The key to fastener maintenance is to reduce failures and extend service life.
matters needing attention
Common mistakes in fastener use:
1. Substitute coarse for fine
The bolts of important connecting parts on the machine, such as transmission shaft, flying shaft, etc., mostly use fine thread. When parts are missing during maintenance, someone uses coarse thread bolts to replace them. Because of the large inner diameter of fine thread bolts, small pitch and external angle, they have the advantages of high strength, good self-locking performance, and strong ability to withstand impact, vibration, and load exchange;After the coarse thread bolt is replaced, it is easy to loosen, fall off or break, causing mechanical accidents.
2. Pore mismatch
The bolts (such as transmission shaft bolts and flywheel bolts) on the machine that bear the transverse load and shear force shall be fitted with the bolt holes in a transitional manner. The assembly shall be firm and reliable, and can bear the lateral force. Someone did not pay attention to the inspection during the assembly, and the bolts were still installed when there was a large gap between the bolts and the bolt holes, resulting in bolt loosening or cutting accidents.
3. Thickened nut
Some people often mistakenly believe that the thickened nut can increase the number of working turns of the thread, thus improving the reliability of the connector. In fact, the thicker the nut is, the more uneven the load distribution between the threads of each turn is, the easier it is to cause the connector to loosen.
4. One female with multiple gaskets
During installation, sometimes the bolt after assembly is too long, so someone will install many spring washers on one bolt. In this way, the spring washers are not evenly stressed during the firming process, and some will break, reducing the pre tightening force of the bolt; or generating eccentric load, reducing the connection reliability of the bolt.
5. The washer is too large
Sometimes, due to the lack of suitable washers, someone will replace them with washers with larger inner diameter. In this way, the contact area between the bolt head and the washer is small, the bearing force or locking force of the washer decreases, and the bolt is easy to loosen under vibration and impact loads.
6. Torque discrepancy
Many people think that the bolts should be “tightened rather than loosened”, so they consciously increase the tightening torque of the bolts, which results in bolt slippage. On the other hand, for important bolts that need to be tightened with torque, some people try to save time by using adjustable wrenches to tighten them, which often results in looseness due to insufficient torque, resulting in mechanical failure.
7. Improper locking
After the important bolts are assembled, the locking device shall be used to lock them. When the cotter pin is used for locking, the common error is to lock them with too thin split lock or half split lock; when the spring washer is used for locking, the common error is that the gap between the washer openings is too small and the elasticity is lost; when the lock plate is used for locking, the common error is to lock the lock plate at the corners of the nut;When double nuts are used for locking, the common mistake is to install the thinner nuts outside and not tighten them tightly.
8. False and firm

There are rust stains, scale, iron filings, sand grains and other impurities in the threads of bolts, nuts or screw holes, or there are burrs, sediment and other impurities on the joint surface of the connector, which are not removed before assembly. When tightening the bolts, due to the blocking effect of impurities, the surface is tightened very tightly, and the torque value meets the requirements, but actually the connector is not really compressed;In addition, there is another case that, due to the jacking effect of impurities such as oil sludge and scale in the screw hole, although the bolt torque meets the requirements, the working parts are not compressed. Under such false firmness, vibration, load shock and temperature changes often make the bolts loose quickly.

Selection Guide for Fasteners

When selecting fasteners for industrial applications, it is very important to select the fasteners that are suitable for your needs. This means not selecting specific sizes and types, but also selecting appropriate data, coatings, etc.

Why is the correct fastener important?

Fasteners may be the smallest part in industrial products, but they are one of the most critical parts. You must choose a fastener that can meet the specific needs of your product and use pipes.
Selecting the wrong fastener may result in the product not being durable or under pressure. The wrong fastener may also lead to expensive product redesign at the last minute, or significantly increase the product cost.
Although they may be small, the fasteners you choose need to be of the same or better quality as the products they support. This is not just about choosing the fasteners with the lowest cost, but choosing the most appropriate fasteners to ensure the reliability and lasting success of the products.

How to select the appropriate fasteners according to your needs?

When choosing fasteners for industrial applications, consider these seven questions before making your choice.
1. How to use fasteners?
The first thing to consider is how to use fasteners and the product itself. For example, if fasteners are opened and closed regularly, then durable solid metal fasteners are meaningful. If fasteners are rarely opened, then cheaper alternatives, such as plastic, can be accepted.
2. Where are fasteners used?
Environmental factors will affect the type of fasteners that may be required by the product. Under less stringent conditions, fasteners used indoors may not be as solid as those used outdoors or in more extreme environments. Specific environmental requirements should also be considered. For example, exposure to salt water will result in Grade 18-8 (18% chromium, 8% nickel)Stainless steel fasteners corrode and lose integrity. If salt water is a key environmental factor, fasteners made of 316 grade stainless steel are less likely to rust.
3. What is the correct fastener type?
As you know, many types of fasteners are available – bolts, screws, nuts, washers, rivets, anchors, inserts, rods, clips, pins, etc. – each fastener type has many variations. For example, you can choose from several different types of screw heads, including flat, oval, round, disc, hex, hex washers, trusses, buttons, and sleeve covers.The types of nuts are also diverse, including hexagonal nuts, cap nuts, rubber nuts, locknuts, flange nuts, square nuts, three-way nuts, torque lock nuts, K-lock nuts, slotted nuts, couplings and slotted nuts.
Each type of fastener has its inherent advantages, disadvantages and applications, so some types of fasteners can be better selected under specific circumstances. You need to select the correct fastener type according to specific product requirements, including how to use fasteners, what data will be used, how to match fasteners with the whole product design, etc. You can choose ready-made fastenersYou can also design your own customized fasteners according to specific product requirements. (Of course, off the shelf fasteners are cheaper and easier to obtain, and customized fasteners may be the only way to meet unique product specifications.)
When determining the fastener type, please be familiar with the ASTM fastener standards. You can often use these standards to select the desired fastener type.
4. What is the appropriate data?
Knowing how and where to use fasteners can also help you determine the correct data for fasteners. The data you select affects not only the cost, but also the strength and corrosion resistance of fasteners
You can choose from the following common materials:

• Steel (including stainless steel, carbon steel and alloy steel) is the most commonly used data in fasteners today because of its high tensile strength and durability;
• Although bronze is more expensive, it is superior to stainless steel in highly corrosive marine environment;
• Although brass is softer than steel or bronze, it also has high corrosion resistance;
• Aluminum and brass have many of the same mass, but are relatively light;
• Nylon is light, different from other data, and non-conductive;
• Please note that each data type has a different level. Select the level that best suits your use and environment needs.

5. What is a suitable coating?
Generally, coatings are added to fasteners to improve corrosion resistance. However, in some cases, coatings are purely decorative
The most common fastener coatings include:

• The zinc coating has good corrosion resistance, but if the coating is damaged or exposed to water or extreme humidity, it may rust;
• Although a thicker zinc coating may affect the compatibility of fasteners, the zinc coating will cover the fasteners with a thicker zinc coating to obtain better corrosion resistance;
• Chromium plating also improves corrosion resistance and adds visual appeal to fasteners.

More complex chemical coatings can also be provided for specific applications, including:

• Fluoropolymer resin coating for lubrication and corrosion resistance;
• Molybdenum disulfide (MoS) for high pressure load friction protectiontwo）Coating;
• Impact and abrasion resistant epoxy coating;
• Phenolic coating for high temperature environment.

6. What is the appropriate size?
The pipe and location of fasteners also affect the size of fasteners. Heavier applications may require larger fasteners, while tighter designs may require smaller fasteners
Most fastener types have various industry standard sizes. For example, metric bolts are M5 to M30 in size, and holes are 5.5mm to 32mm in size.

How to select the correct fastener manufacturer?

Several factors need to be considered when selecting a suitable fastener manufacturer:

• Product quality: ensure that the quality of fasteners meets your needs and can meet relevant standards and specifications.
• Price: The price should be reasonable and compatible with the quality.
• Reliability: ensure that the manufacturer can deliver products on time and provide adequate technical support.
• Expertise: The selected manufacturer should have rich expertise and be able to provide suggestions and solutions.
• Customer feedback: ask other customers’ comments on the manufacturer to understand the reliability and quality of the manufacturer.
• After sales service: ensure that the manufacturer can provide timely and effective after-sales service.
• Company history: learn about the manufacturer’s company history and reputation to ensure that it is a stable and reliable partner.

By considering these factors, you can choose a fastener manufacturer.