Flat washers and spring washers are well-known and often used washers. Due to their different characteristics, they must be distinguished in practical application, otherwise they will not play their due role, and may lead to some unnecessary trouble.
In the process of bolt use, flat pad and spring pad play an indispensable role respectively, so how to choose flat washers and spring washers correctly? Let’s talk today.

What is a flat washer?

The flat washer is mainly stamped out of an iron plate. The shape is generally a flat washer with a hole in the middle.

The role of flat washer

Flat washers are usually thin pieces of various shapes used to reduce friction, prevent leakage, isolate, prevent loosening or distribute pressure. Many materials and structures have such components, which are used to perform various similar functions. Limited by the material and technology of threaded fasteners, the supporting surface of bolts and other fasteners is not large, so in order to reduce the compressive stress of the pressure-bearing surface to protect the surface of the connected part, washers are used.　In order to prevent loosening of the connection pair, anti-loosening spring washers, multi-tooth lock washers, round nut stop washers, and saddle, wave, and cone elastic washers are used.
Flat washers are mainly used to reduce the pressure. When some parts are tightened with a large axial force, the washers are easy to be pressed into a dish shape. At this time, materials can be used and the hardness can be improved to solve the problem.
The locking effect of the spring washer is general, and the important parts are used as little or not as possible, and the self-locking structure is adopted. For spring washers used for high-speed tightening (pneumatic or electric), it is better to use surface phosphated washers to improve their wear-reducing performance, otherwise they will easily burn out or open due to friction and heat, or even damage the surface of the connected part. For the connection of thin plates, spring washer structure shall not be adopted. According to statistics, spring washers are used less and less in cars.
Because of the large and uniform locking force, the connecting tooth shape in the tooth-shaped elastic washer is used more in the automobile industry, while the spacing tooth shape is less.

• 1. Increase the contact area between the screw and the machine.

• 2. Eliminate the damage to the surface of the machine when the spring pad is unloading the screw. When used, it must be a spring pad and a flat washer. The flat washer is next to the surface of the machine, and the spring pad is between the flat washer and the nut.

Advantages and disadvantages of flat washers

Advantage:

• ①By increasing the contact area, parts can be protected from damage;

• ②By increasing the contact area, reducing the pressure between the nut and the device, so as to play a protective role.

Disadvantages:

• ①The flat washer cannot play the role of earthquake resistance;

• ②The flat washer does not prevent loosening.

How to choose a flat washer?

Flat washer is used as a part to prevent bolts and nuts from locking. Flat gaskets are used where fasteners are used. How to choose a suitable flat gasket? The flat washer is a kind of flat washer, which mainly serves to increase and tighten the contact area between the screw and some large equipment. When using the flat washer, it is often suitable for the nut and the nut to cooperate with each other. It must have the necessary important characteristics within the most effective sealing time:

• 1. In the case of a harsh environment, the flat gasket should be sealed. When a certain temperature and pressure are in operation, it is not easy to leak.

• 2. When the flat gasket is connected to the contact surface, it is necessary to better ensure the tightness, just like the good effect.

• 3. When the gasket is under pressure, the anti-wrinkle ability should be better under the influence of temperature, otherwise the screw will be damaged and hard gas leakage will occur.

• 4. Don’t get infected when using flat washers.

• 5. The flat washer can be used to disassemble well. This is the biggest effect of choosing a flat washer.

• 6. Remember to ensure normal use at the relative temperature when using the flat washer.

In order to better use flat washers, when choosing flat washers, try to choose flat washers made of anti-rust and anti-corrosion materials, which not only saves time and effort, but also can play a good role in flat washers.

When used with bolts and nuts, the selection criteria for flat washers:

• 1. When selecting gasket materials, attention should be paid to the problem of electrochemical corrosion when different metals are in contact. The material of the flat washer is generally the same as that of the connected parts, usually steel, alloy steel, stainless steel, aluminum alloy, etc. When electrical conductivity is required, copper and copper alloys can be used.

• 2. The inner diameter of the flat washer should be selected according to the larger value of the thread or screw diameter, and the outer diameter of the connected material should be relatively soft (such as composite material) or matched with the spring washer.

• 3. When choosing to place the W washer under the bolt or screw head, in order to avoid interference between the fillet under the head and the washer, a flat washer with a chamfered inner hole can be used.

• 4. For important bolts with larger diameters, or in order to increase the ability to resist extrusion, steel washers should be used. Steel washers should be used for tension bolts or tension-shear composite bolt connections.

• 5. Special gaskets are used in special requirements. For electrical conductivity, copper gaskets can be used; sealing gaskets with air tightness requirements can be used.

What is a spring washer?

Spring washers are often called spring washers in the screw industry. Its materials are stainless steel and carbon steel, and carbon steel is also iron. Commonly used spring washers are M3, M4, M5, M6, M8, M10, M12, M14, M16. These specifications are more commonly used. Spring washers are widely used in load-bearing and non-load-bearing structures of general mechanical products. They are characterized by low cost, convenient installation, and are suitable for parts with frequent assembly and disassembly.

Classification of spring washers

Internal tooth elastic washer, external tooth elastic washer
There are many sharp elastic warped teeth on the circumference, which are pressed against the supporting surface to prevent the loosening of the fastener. Internal tooth elastic washers are used under screw heads with smaller head sizes; external tooth elastic washers are mostly used under bolt heads and nuts. Toothed elastic washers are smaller than ordinary spring washers, and the fasteners are evenly stressed and reliable in preventing loosening, but they are not suitable for frequent disassembly.

Wave spring washers

Wave washers are divided into WG type, WL type, WN type:

WG wave washer:

The WG wave washer is an open-type elastic washer, which can usually be installed in a small space, such as prestressing the bearing, reducing the noise of the bearing operation, and improving the accuracy and stability of the bearing. In addition, there are also a large number of electronic appliances. The applied materials include carbon steel, stainless steel, copper alloy, etc.

WL wave washer:

The WL wave washer is a lap type elastic washer, which can usually be installed in a small space, such as prestressing the bearing, reducing the noise of the bearing operation, and improving the accuracy and stability of the bearing. In addition, there are also electronic appliances. A large number of applications. Materials include carbon steel, stainless steel, copper alloy, etc.

WN wave washer:

WN type wave washer is a multi-layer wave crest overlap type elastic washer. Compared with the WL type, this series is composed of multiple layers of materials. Therefore, the K value curve under the same compression stroke is gentler than that of the WL type. It is suitable for larger elasticity. In the case where the elasticity release of the entire working stroke is required to be more uniform. The materials used are carbon steel, stainless steel, copper alloy, etc.

Disc spring washer:

The disc spring washer is also known as the Belleville spring washer, the inventor is the French Belleville. DIN6796 disc spring washer (HDS series) is a lock washer designed for bolt and screw connection. It is designed and manufactured according to DIN 6796 and is used for the connection of medium or high strength bolts and screws. The large supporting load and elastic recovery make the HDS series very effective. The bolt tension can withstand the slack due to the following reasons: wear, creep, slack, thermal expansion, contraction, or compression of seals. The HDS series increases the elasticity of the screw several times. It can effectively replace the ordinary spring washer, but it is not suitable for the combination of lock washer and flat washer. Because the HDS series are disc springs that can be aligned or stacked. The combination of the inversion method can increase the deformation of the disc spring group, and the combination of the superposition method can increase the spring force of the disc spring group. The ideal installation method is to flatten as much as possible, the closer the flattened state, the faster the tension torque increases, and the proper bolt tension can be obtained without a torque wrench.

The role of spring washer

• 1. The function of the spring washer is that after the nut is tightened, the spring washer gives the nut an elastic force to tighten the nut to make it not easy to fall off. The basic function of the spring is to give a force to the nut after the nut is tightened to increase the friction between the nut and the bolt.

• 2. Generally, flat washers are not used when spring pads are used (except for protecting the surface of fasteners and the mounting surface, use flat washers and spring pads).

• 3. flat washers are generally used in connecting parts. One is soft and the other is hard and brittle. Its main function is to increase the contact area, disperse the pressure, and prevent the soft texture from being crushed.

The spring washer is installed under the nut to prevent the nut from loosening.
The bolts connecting the motor and the machine base generally need spring washers, because if the motor vibrates without spring washers, the nuts will loosen. Generally, the fasteners on the vibration equipment are equipped with spring washers, and the flanges generally do not need to be added. . The addition of spring gaskets on the flange is related to the medium flowing in the pipeline. If it is easy to produce pulses, it is best to add spring gaskets, and there are high-speed fluids, and the diameter changes frequently. Do not generalize. On some valves, the stuffing box gland All flanges require spring gaskets.

Advantages and disadvantages of spring washers

Advantage:

• ①The spring washer has a good anti-loosening effect;

• ②The spring washer has good seismic effect;

• ③Low manufacturing cost;

• ④The installation is very convenient.

Disadvantages:
Spring washers are greatly affected by the material and process. If the material is not good, the heat treatment is not well grasped, or other processes are not in place, it is easy to crack, so you must choose a reliable manufacturer.

The difference between spring washers and flat washers

The spring washer can prevent loosening and increase the pre-tightening force. The flat washer does not have this function. It can be used to increase the fastening contact area, prevent the friction between the bolt and the workpiece, and protect the surface of the connector from the bolt. The surface of the workpiece is scratched when the nut is tightened.
However, some important connections, such as the place where the power is transmitted by the friction force generated by compression, cannot be used with spring pads. If the rigidity of the connection is reduced, accidents may occur. The spring washer can be omitted. When the strength of the connected parts is low, flat washers or flange bolts are used to increase the contact area, and spring washers must be used when there is vibration, pulse, and medium temperature fluctuations.

When to use flat washers and when to use spring pads?

• 1. Under normal circumstances, only flat washers can be used when the load is relatively small and the load is not subject to vibration.

• 2. In the case of relatively large loads and vibration loads, a combination of flat washers and spring pads must be used.

• 3. Spring washers are basically not used alone, they are all used in combination.

In the actual use process, due to the different emphasis of flat washers and spring washers, in many occasions they are used in conjunction with each other, so as to protect the parts, prevent the nut from loosening, and reduce the advantages of vibration, which is great choice.