Washer (hardware)

Thin plate with a hole, normally used to distribute the load of a threaded fastener

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Assorted washers: flat, split, star and insulating

A washer is a thin plate (typically disk-shaped, but sometimes square) with a hole (typically in the middle) that is normally used to distribute the load of a threaded fastener, such as a bolt or nut. Other uses are as a spacer, spring (Belleville washer, wave washer), wear pad, preload indicating device, locking device, and to reduce vibration (rubber washer).

Washers are usually metal or plastic. High-quality bolted joints require hardened steel washers to prevent the loss of pre-load due to brinelling after the torque is applied. Washers are also important for preventing galvanic corrosion, particularly by insulating steel screws from aluminium surfaces. They may also be used in rotating applications, as a bearing. A thrust washer is used when a rolling element bearing is not needed either from a cost-performance perspective or due to space restraints. Coatings can be used to reduce wear and friction, either by hardening the surface or by providing a solid lubricant (i.e. a self-lubricating surface).

The origin of the word is unknown. The first recorded use of the word was in ; however, the first time its definition was recorded was in .[1]

Rubber or fiber gaskets used in taps (or faucets, valves, and other piping connections) as seal against water leaks are sometimes referred to colloquially as washers; but, while they may look similar, washers and gaskets are usually designed for different functions and made differently.

Washer types

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Most washers can be categorized into three broad types;

• Plain washers, which spread a load, and prevent damage to the surface being fixed, or provide some sort of insulation such as electrical
• Spring washers, which have axial flexibility and are used to prevent fastening or loosening due to vibrations
• Locking washers, which prevent fastening or loosening by preventing unscrewing rotation of the fastening device; locking washers are usually also spring washers.

Plain washers

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Name(s) Image Description Plain washer (or "flat washer") A flat annulus or ring, often of metal, used to spread the load of a screwed fastening. Additionally, a plain washer may be used when the hole is a larger diameter than the fixing nut.

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Fender washer (US), penny washer, mudguard washer, or "repair washer" (UK) A flat washer with a particularly large outer diameter in proportion to its central hole. These are commonly used to spread the load on thin sheet metal, and are named after their use on automobile fenders. They can also be used to make a connection to a hole that has been enlarged by rust or wear. In the UK, the name originally comes from the size of the old British penny. In the UK, most industries refer to all large OD washers as penny washers, even when the OD is as much as twice the size of the old penny.

An archaic form of this washer was sold as a "pot mender", usually in small quantities through a retail ironmonger. This included two washers, a nut, and bolt, and a sealing washer of rubber, cork, or fibre sheet. They could be used for sealing small holes, rust spots or removed pipe connections in water tanks or large cooking vessels.

Spherical washer nut and screw Part of a self-aligning nut; it is a washer with one radiused surface, which is designed to be used in conjunction with a mating nut in order to allow for up to several degrees of misalignment between parts.

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Anchor plate or wall washer A large plate or washer connected to a tie rod or bolt. Anchor plates are used on exterior walls of masonry buildings, for structural reinforcement. Being visible, many anchor plates are made in a style that is decorative.

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Torque washer Used in woodworking in combination with a carriage bolt; it has a square hole in the centre into which the carriage bolt square fits. Teeth or prongs on the washer bite into the wood, preventing the bolt from spinning freely when a nut is being tightened.

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Spring and locking washers

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Lock washers, locknuts, jam nuts, and thread-locking fluid are ways to prevent vibration from loosening a bolted joint.

Gaskets

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The term washer is often applied to various gasket types such as those used to seal the control valve in taps.

Name Image Description Shoulder washer A plain washer type with integral cylindrical sleeve. Used as a barrier between differing metals and as a seal.

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This term is also used for electrically insulating grommets.

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Crush washer A washer made of soft metal such as aluminium or copper. Used to seal fluid or gas connections such as those found in hydraulic systems and in internal combustion engines.

Specialised types

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Name(s) Image Description Keps nut or K-lock nut A nut with an integral free spinning washer; assembly is easier because the washer is captive. Self-aligning washer A two-part washer: one part has one convex spherical surface, which mates with a concave surface on the other part, to allow tightening to a surface which is not perpendicular to the axis of the screw or nut fastener, in a similar manner to a spherical washer and self-aligning nut Top hat washer A shoulder washer type used in plumbing for tap fitting. Insulating shoulder washer Used to electrically isolate a mounting screw from the surface it secures. Often made of nylon, these are also made of teflon, PEEK or other plastics to withstand higher temperatures. Keyed washer A washer with a key to prevent rotation, and is used to lock two nuts in place, without allowing the torque applied to the top nut to cause the bottom nut to also rotate (such as in a threaded headset on a bicycle). Torque-limiting washer A type of washer used in a variety of torque sensitive applications, designed to limit torque to a predetermined level and not beyond. Dowty washer Has a central rubber ring to provide a strong seal against high pressure liquid or gas.

The DIN 125 metric washer standard refers to subtypes A and B. ISO calls these Form A and ISO calls them Form B. They are all the same overall size, but Form B is chamfered on one side.

Materials

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Washers can be fabricated from a variety of materials including, but not limited to:[22]

Corrosion resistance

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A number of techniques are used to enhance the corrosion resistant properties of certain washer materials:

• Metallic coatings &#; Typical coatings used to produce corrosion resistant washers are zinc, cadmium, and nickel. Zinc coating acts as a sacrificial surface layer that falls victim to corrosive materials before the washer's material can be harmed. Cadmium produces a high-quality protective surface but is toxic, both biologically and environmentally. Nickel coatings add protection from corrosion only when the finish is dense and non-porous.
• Electroplating &#; This method involves coating the washer by electrolytic deposition using metals such as chromium or silver.
• Phosphating &#; A resilient, but abrasive surface is achieved by incorporating a zinc-phosphate layer and corrosion-protective oil.
• Browning or bluing &#; Exposing the washer (typically steel) to a chemical compound or alkali salt solution causes an oxidizing chemical reaction, which results in the creation of a corrosion-resistant, colored surface. The integrity of the coating can be improved by treating the finished product with a water-displacing oil.
• Chemical plating &#; This technique utilizes a nickel-phosphor alloy that is precipitated onto the washer surface, creating an extremely corrosion- and abrasive-resistant surface.

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Type and form

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A plain washer and a spring washer are placed on a bolt between the nut (on the threaded end) and the bolt head.

The American National Standards Institute (ANSI) provides standards for general use flat washers. Type A is a series of steel washers at broad tolerances, where precision is not critical. Type B is a series of flat washers with tighter tolerances where outside diameters are categorized as "narrow", "regular" or "wide" for specific bolt sizes.[26]

"Type" is not to be confused with "form" (but often is). The British Standard for Metric Series Metal Washers (BS), written in , coined the term "form". The forms go from A to G and dictate the outside diameter and thickness of the flat washers.

• Form A: Normal diameter, normal thickness
• Form B: Normal diameter, light thickness
• Form C: Large diameter, normal thickness
• Form D: Large diameter, light thickness
• Form E: Normal diameter, normal thickness
• Form F: Large diameter, normal thickness
• Form G: Largest diameter, larger thickness.
  Washer 'form' when comparing different washer material types is used quite freely by stockists. In relation to BS specifically, washer forms 'A' to 'D' inclusive are designated 'bright metal' washers and are supplied self-finished in various metals including: steel alloys, brass, copper, etc. Whereas, BS washer forms 'E' to 'G' inclusive are designated 'black' (uncoated) mild steel washers, which normally are specified with a supplementary protective coating supply condition.

Standard metric flat washers sizes

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Washers of standard metric sizes equivalent to BS Form A are listed in the table below. Measurements in the table refer to the dimensions of the washers as described by the drawing. Specifications for standard metric flat washers were known as DIN 125 (withdrawn) and replaced with ISO . DIN (Deutsches Institut für Normung - German Institute for Standardization) standards are issued for a variety of components including industrial fasteners as Metric DIN 125 Flat Washers. The DIN standards remain common in Germany, Europe and globally even though the transition to ISO standards is taking place. DIN standards continue to be used for parts which do not have ISO equivalents or for which there is no need for standardization.[27]

Nominal screw
sizes, M (mm) Screw pitch
thread, P (mm) Diameter (mm) Thickness,
H (mm) 1st
choice 2nd
choice Coarse Fine Internal
hole, d1 External,
d2 1 0.25 1.1 3 0.3 1.2 0.25 1.3 3.5 0.3 1.4 0.3 1.5 4 0.3 1.6 0.35 1.7 4 0.3 1.7 1.8 4.5 0.3 1.8 0.35 2 0.4 2.2 5 0.3 2.5 0.45 2.7 6 0.5 2.6 2.8 7 0.5 3 0.5 3.2 7 0.5 3.5 0.6 3.7 8 0.5 4 0.7 4.3 9 0.8 5 0.8 5.3 10 1 6 1 0.75 6.4 12 1.6 7 1 7.4 14 1.6 8 1.25 1 8.4 16 1.6 10 1.5 1.25 or 1 10.5 20 2 12 1.75 1.5 or 1.25 13 24 2.5 14 2 1.5 15 28 2.5 16 2 1.5 17 30 3 18 2.5 2 or 1.5 19 34 3 20 2.5 2 or 1.5 21 37 3 22 2.5 2 or 1.5 23 39 3 24 3 2 25 44 4 27 3 2 28 50 4 30 3.5 2 31 56 4 33 3.5 2 34 60 5 36 4 3 37 66 5 39 4 3 40 72 6 42 4.5 3 43 78 7 45 4.5 3 46 85 7 48 5 3 50 92 8 52 5 4 54 98 8 56 5.5 4 58 105 9 60 5.5 4 62 110 9 64 6 4 66 115 9 68 70 120 10 72 74 125 10 76 78 135 10 80 82 140 12 85 87 145 12 90 93 160 12 100 104 175 14

See also

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Notes

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   Bowmans Fastener Technical Fast of on page 32 and 33 has SAE recommendation from that lock washers not be used in any critical application. BMW motorcycles experienced a series of broken lock washers and BMW then disallowed their use in U-joints due to the damage of loss of the spacer and nut loosening.

References

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Further reading

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If you want to learn more, please visit our website Hebei Bentley Technology.

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• Parmley, Robert. (). "Section 11: Washers." Illustrated Sourcebook of Mechanical Components. New York: McGraw Hill. ISBN  Drawings, designs and discussion of various uses of washers.

Washers are commonly used small components in mechanical connections, typically flat metal rings. Their main function is to provide cushioning, isolation, and sealing between two fastened objects to ensure the stability and reliability of fasteners.In daily life, we often encounter various types of washers, including flat washers, spring washers, locking washers, retaining washers, etc. Each type can be further classified based on their shapes.

This article compiles 14 types of washers. Let's take a look!

 

 

The standard spring washer is the most widely used type in the market. It is commonly referred to as a spring washer in the bolt industry. These washers find extensive application in both load-bearing and non-load-bearing structures of general mechanical products. They are known for being cost-effective, easy to install, and suitable for frequently assembled/disassembled parts.

Material options include stainless steel and carbon steel, with common specifications such as M3, M4, M5, M6, M8, M10, M12, M14, M16. The national standard GB/T 94.1-87 specifies the technical conditions for standard spring washers with sizes ranging from 2-48mm.

 

  Standard Spring Washer  

 

 

The saddle-shaped spring washer, resembling a horseshoe, is primarily used to prevent loosening of bolts. Its unique structure increases friction, preventing fasteners from coming loose. It shares the anti-loosening functionality with other wave spring washers and stainless steel spring washers.

 

 

The wave spring washer, a common mechanical sealing component, is typically made of metal with a wavy shape. Its excellent elasticity and sealing performance allow it to deform under stress, returning to its original state to maintain tight contact. This makes it suitable for various static and dynamic sealing applications.

 

  Wave Spring Washer  

 

 

Also known as a plain washer, the flat washer is the most commonly used type. It is typically round, though square washers can also be used as needed for assembly. Flat washers serve to increase the contact area, improving the load distribution on connected components and protecting their surfaces. Specific variations include flat washer-C class, large washer-A and C class, extra-large washer-C class, small washer-A class, flat washer-A class, flat washer-chamfered-A class, square washer, etc.

     Flat Washer    

 

The saddle-shaped elastic washer, also known as a saddle washer, is commonly used in applications requiring anti-loosening. When used in conjunction with bolts, it prevents loosening by providing additional force to the nut after tightening, increasing the friction between the nut and bolt.

 

 

The wave elastic washer, also known as a wave washer or double wave washer, is a common mechanical sealing component made of metal with a wavy shape. Its elastic deformation provides anti-loosening capabilities, with a relatively small spring force that evenly distributes stress, avoiding damage to connected surfaces.

   Wave Elastic Washer   

 

 

The internal tooth lock washer is a common fastening component widely used in mechanical equipment. Its internal gear structure allows for the fastening and securing of parts, achieved through the interplay of locking and unlocking steps. During normal operation, the internal tooth lock washer maintains a tightened state, preventing loosening and thread sliding, ensuring the normal operation of mechanical equipment.

 

 

The external tooth lock washer is commonly used in mechanical component connections, with a working principle similar to the internal tooth lock washer. It prevents loosening of threaded connections by relying on the engagement force between the tooth tips and the flat surface of the connected component. External tooth lock washers are typically made of high-strength materials such as stainless steel, aluminum alloy, or copper alloy, offering good mechanical and corrosion resistance properties.

 

  Internal/External Tooth Lock Washer 

 

 

As the name suggests, the internal serrated lock washer features serrations on the inside, commonly used for connecting fasteners and other components. Its special design allows it to provide higher locking force when subjected to vibration or external forces.

 

 

The external serrated lock washer is used for small parts to provide spring action. Its dimensions are similar to those of self-tapping screws used with three-dimensional stamped parts. The serrated washer is mainly used for anti-loosening in parts where the bolt head or nut is locked down, presenting as a standalone circular washer with staggered openings.

 

 

The I-beam steel angle washer is a mechanical component used for connecting I-beam steel. It typically consists of a set of square angle washers and nuts. I-beam steel is a commonly used building material, widely employed in various construction structures. To ensure the safety and stability of I-beam steel, angle washers are introduced as crucial connecting elements. Standard specifications guide the use of angle washers, playing a significant role in ensuring the quality and reliability of I-beam steel structures.

 

  I-beam Steel Angle Washer  

 

 

The single ear retaining washer is a common mechanical sealing device designed to prevent leakage of liquids or gases while providing axial and radial fixed support. Comprising an inner ring, outer ring, and a single-side ear, it clamps onto the shaft with a specific radial gap, allowing lubricating oil or sealing medium to enter during operation, serving both lubrication and sealing purposes.

 

 

The double ear retaining washer, also known as a double ear snap ring, is a metal circular ring often made of spring steel or stainless steel. Based on its structural characteristics, the double ear retaining washer can be divided into internal ear and external ear types. As a commonly used component in mechanical equipment, its primary function is to prevent axial displacement of bearings during operation.

 

    Retaining Washer    

 

 

The circular nut retaining washer, also known as a retaining washer, is a washer designed to prevent circular nuts from loosening. It achieves this by utilizing the cooperation of retaining ears, the circular nut opening, and the keyway on the shaft. Typically used in conjunction with circular nuts, it finds widespread applications in electrical appliances, elevators, and mechanical assemblies, effectively fixing rolling bearings to prevent loosening.

 

   Circular Nut Rtaining Washer   

 

In summary, these are common types of washers frequently used in the market, each offering specific performance advantages suited for particular applications. When selecting washers, it is essential to consider specific requirements, usage scenarios, and performance criteria to determine the most suitable washer type.

 

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