Washers are typically made through a manufacturing process that involves cutting, stamping, or machining metal or plastic materials into circular discs with a hole in the centre. They come in various types, such as flat, lock, and spring washers. Each is designed to provide specific features like load distribution, locking ability, or spring tension.
Various fixings use washers. Washers are thin, disk-shaped plates with holes that fit over screws, nuts, and other threaded fasteners.
Industrial applications require them for different purposes and requirements. Although most of these components have similar basic features and designs regardless of their intended use, certain washers are better suited to specific jobs.
People often wonder: what are washers used for, and are they necessary?
Learn all about washers, including how they are used, the different types that exist, the washer manufacturing process and their applications.
Did You Know? The top three exporters of metal washers are China with 24,853 shipments, Vietnam with 22,252 shipments, and Japan with 19,834 loads. The US, Germany, and the UAE are the top three export destinations for Indian metal washers.
What Are Washers?
Washers are perforated plates or discs made from various materials that sit between two surfaces subject to rotary friction. In a bolt or screw installation, for example, a gap exists between the threaded fastening and the inserting surface.
Metal disc washers have many uses in different applications, such as penny washers.
In this context, the word 'washer' has no known origin. Still, its usage has existed since the 14th century under the spelling 'whasher', and people say this as "an iron hoop."
Gunners used this hoop to prevent the axle-tree pin from wearing through the nave." The reference indicates the usage of washers in guns or canon axle assemblies to avoid wear.
Types of Washers
Washers are available for an infinite number of uses. Whenever two surfaces need to be connected securely, washers play an essential role. Many types of washers are commonly used.
These are made from various metals and materials specifically designed for special applications.
Specialised washers are available in three basic types: spring, lock, and plain.
1. Spring Washer
Metal spring washers have slightly raised ends that create tension in the metal. Over or below a bolt or nut, they are placed.
Levelling the raised and lowered ends of nuts or bolts prevents them from loosening when tightened.
Spring Washers Types
- Conical – Conical washers can hold tension during thermal expansion and contraction while supporting heavy forces. Height and thickness determine the deflection rate of a conical washer.
- Dome – Dome washers have rounded sides instead of conical ones. With slight deflection, they can carry high loads.
- Wave – Wave spring washers have a unique structure that allows them to rotate in two directions. Cushion springs and spacers are ideal applications for them.
- Finger – Finger washers have three curved flanges that reduce damping, noise, wear, vibration, and skidding. Wave washers have similar load points.
- Crescent – Crescent washers resemble flat washers with a bend in the middle. With the washer's curve, minimal pressure is applied while maintaining flexibility.
Flexible and load-cycling products use these springs because they have uniform rates throughout the deflection range.
2. Lock Washer
A lock washer is a device that locks nuts and bolts in place, which is its purpose. Lock washers come in various forms, but split and teeth washers are the most common.
Locking in the split or teeth prevents the bolt or nut from loosening.
Types of Lock Washers
- Split – Split lock washers consist of a metal ring and a hole in the centre, similar to flat washers. An example of a split washer is a ring with a slit that makes the metal take on the shape of a spring with one section above the other.
A divided washer resembles a spring, so it is called a spiral washer.
- External Teeth – An external teeth lock washer comprises evenly spaced teeth around its circumference. During tightening, bolt or nut teeth dig into the material's surface.
- Internal Teeth – Internal teeth washers have teeth but are located inside the ring's diameter, unlike external teeth washers. These internal teeth serve to absorb shocks and vibrations and effectively secure the lock washer in place.
3. Plain Washers
A hole in the centre of a plain washer has a metal ring surrounding it. As with other washers, flat washers have variations to meet the needs of applications, though they are familiar and have been used for many years.
Types of Plain Washers
- Torque – Torque washers have square holes surrounded by pointy forks. During torque washer tightening, the torque washer's forks bite the material's surface to prevent the bolt or nut from spinning.
- Flat – Flat washers have a hole in the middle and are thin and round. The screws are designed to support small heads. Flat washers are used when there is a need to spread the load.
- Fender – Fender washers have the same shape as flat washers. Their hole size and circumference differ from flat washers. A fender washer's outside diameter is disproportionately larger than its hole diameter. There is a large area of metal surface to support the load.
- Countersunk – These are designed for flat-head screws. Screws and washers form flat surfaces when tightened.
- Shoulder – Shoulder washers have a shoulder around their hole. They protect a wire, screw, or assembly.
- C-Washer – C-washers are plain flat washers with a large section of the metal diameter removed to form the letter C. Slots on C-washers are cut from the edges of the central hole to the edge of the washer. It is not necessary to move or loosen the fastener to position or place it.
Washer Manufacturing Process Explained
A variety of materials are available for washers. Aluminium, copper, galvanised carbon steel and stainless steel are also used.
Choosing a metal washer depends mainly on its intended use. Stamping is the primary method for manufacturing washers.
The washer die is a specially designed form for manufacturing washers. And the gauge determines the washer thickness.
Here are the steps for the manufacturing process of washers.
1. Metal Stamping
The stamping process carried out on a power press, produces washers. During stamping or power pressing, a die determines the washer form.
Metal stamping involves punching a shape or form out of flat metal with a die. A ram comes down with significant force on the bolster plate, punching out shapes from flat sheets of metal, known as blanks.
There are two types of stamping machines: mechanical with flywheels and hydraulic.
2. Washer Dies
A washer die is a customised form used to manufacture washers. A single metal sheet is used for multiple washers since washers are small items.
Using stamping technology, large amounts of washers can be produced while maximising the use of metal sheets.
3. Gauge of Metals
A washer's thickness is determined by its gauge, which also determines its spacing. As early as the industrial revolution, there wasn't a single method for determining viscosity, so gauges were used to measure it.
Each metal type has its own gauge chart because gauges are not uniform.
Applications of Washers
Washers are used in various applications like load distribution, spacer usage, and sealing.
1. Load Distribution
When fasteners are driven into or connected to materials, washers are designed to distribute the load. Fasteners often cause cracks, impressions, and other deformities without washers.
As a result, metal washers prevent such damage by distributing the load evenly and reducing stress on the fastener. Materials other than wood that are soft do not require stress relief.
2. Using as a Spacer
A metal washer can also be used as a spacer for fasteners too long to fit into a hole. Space exists between the head of some fasteners and the material's surface when used.
Four inches long bolts cannot be tightened if connected to materials three inches deep. The bolt surface and head can be filled with metal washers before the bolt is connected to fill the one-inch space between them.
Sealing washers are metal washers with a bonded layer of material, like neoprene, on top. By combining the strength of the metal washer with the sealing power of the material, a tight seal can be created that prevents leaks and drips.
Sealing washers are highly resilient and robust yet very soft and smooth, so the surface is not damaged. Bolt joints are best sealed with sealing washers.
Overtightening sealing metal washers can result in leaks if not done carefully and precisely. It would help to place the washer so it is not concave or convex.
In addition to cushioning the bolt head and sealing the joint, the bonding of the sealing material creates a corrosion-resistant surface. Sealing washers also serve as vibration dampeners in addition to sealing leaks.
Metal washers are small flat pieces of metal with holes in the centre. They are used as spacers, shock absorbers, or to distribute the load of fasteners.
Washers can be manufactured from a variety of materials. Speciality washers are made for unusual and unique applications, with endless uses for metal washers.
Metals are also available in a wide variety of washer configurations. Regarding all products produced for public and industrial use, washer manufacturers adhere to the standards published by the International Organization for Standardisation (ISO).
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