What is washer

Washers are indispensable auxiliary components in the fastener system, mainly used for the supporting installation of threaded connectors such as bolts and screws. Their core function is to optimize the connection effect, protect connected components, and enhance the overall fastening reliability. They are widely applied in almost all fields requiring fastening connections, including machinery, automobiles, construction, and electronics.

A washer is typically a thin, annular component with a central hole (non-annular designs are also used in special scenarios). It is mostly made of metals, rubber, plastic, asbestos, or composite materials. During installation, it is fitted over the shank of a bolt/screw, positioned between the "nut/screw head" and the "surface of the connected part". Through physical contact and structural properties, it addresses inherent issues in threaded connections (such as pressure concentration, loosening, and insufficient sealing).

Translated as "distribute pressure" (not "disperse pressure"), which is the standard term in mechanical engineering to describe the uniform transmission of compressive force.Consistently rendered as "connected parts" to align with industry terminology, distinguishing it from "components" (which usually refer to integral parts of a machine).

"Thin-sheet metal" is more accurate than "thin metal" here, as it specifically refers to flat, thin metal sheets commonly used in manufacturing.Retained as "machining errors" (with "machining" in lowercase) because it is a widely recognized engineering term; no additional translation is needed for clarity.

Classification by Function

Plain Washers: With no special structure, they are only used for pressure distribution and error compensation, serving as the most basic type of washer (e.g., plain washers conforming to GB/T 97.1).

Lock Washers: Equipped with anti-loosening structures, such as spring washers (GB/T 93), toothed washers (GB/T 861.1), wave washers, and double-stack self-locking washers.

Sealing Washers: Focus on leak prevention, such as O-rings (GB/T 3452.1), flange washers, and gaskets (e.g., spiral-wound gaskets).

Special-Function Washers: Including insulating washers, heat-insulating washers, and anti-slip washers (with rubber coating), etc.

Washers are highly standardized fasteners, and the main global standard systems include:Chinese Standards (GB): Such as GB/T 97 (Plain Washers), GB/T 93 (Spring Washers), and GB/T 3452 (O-Rings);International Standards (ISO): Such as ISO 7089 (Plain Washers) and ISO 8750 (Spring Washers);German Standards (DIN): Such as DIN 125 (Plain Washers) and DIN 127 (Spring Washers);American National Standards (ANSI): Such as ANSI B18.21.1 (Plain Washers).These standards specify washers' dimensions (inner diameter, outer diameter, thickness), material requirements, and mechanical properties (e.g., hardness, elasticity), ensuring the interchangeability of products from different manufacturers.

When selecting a washer, it is necessary to match the application scenario

1. Matching Connector SpecificationsThe inner diameter of the washer must be consistent with the nominal diameter of the bolt/screw (e.g., an M8 bolt should be paired with a washer with an 8mm inner diameter). The outer diameter should be selected based on the area of the connected part-avoid making it too large (which may interfere with other components) or too small (which fails to effectively distribute pressure).

2. Adapting to Operating Conditions

High-temperature / High-pressure Scenarios: Choose metal washers or high-temperature-resistant composite washers;Humid / Corrosive Environments: Select stainless steel, copper, or corrosion-resistant rubber washers;Vibration-prone Scenarios: Lock washers are a must.

The Uses of Washers

Piping systems

For flange connections in water supply pipes, gas pipes, and chemical pipelines, washers are needed to fill tiny gaps on flange surfaces (even precision-machined flange surfaces have microscopic irregularities). This prevents leakage of water, gas, corrosive liquids, or gases. For example:

Rubber washers are often used at the interface between household gas water heaters and pipes to seal gas.

For high-pressure pipelines in chemical equipment (e.g., those transporting sulfuric acid or ammonia water), corrosion-resistant washers like polytetrafluoroethylene (PTFE) washers or metal washers are required to prevent chemical medium leakage.

Mechanical assembly

When bolts connect metal parts (e.g., motor bases to frames, automobile engine cylinder heads to cylinder blocks), directly tightening the bolts may concentrate pressure locally, causing dents or deformation on the part surface. Adding a metal washer (e.g., a flat washer) distributes the bolt pressure evenly over a larger contact area, protecting the part surface.

Vibration scenarios: Rubber or elastic washers are often used for connectors in automobile chassis and fixed parts of washing machine motors. Their elasticity absorbs vibrations during equipment operation, reducing noise and preventing bolts from loosening due to long-term vibration.

Anti-loosening washers

For example, "spring washers" (metal, in the shape of an open spiral) are compressed when bolts are tightened, generating continuous elastic reaction force to counteract the "loosening tendency" of bolts caused by vibration. Another example is "toothed washers" (with fine teeth on the surface); the teeth can embed into the surface of connected parts to increase friction and avoid relative sliding.

Anti-slip scenarios: Rubber washers are commonly used in furniture assembly (e.g., screw connections for tables and chairs) and adjustable parts of medical equipment (e.g., knobs of operating tables). Their high friction coefficient prevents components from accidentally loosening during use, ensuring safety.

Precision equipment:

For guide rail connections in machine tools and shell assembly of instruments, metal washers with uniform thickness (e.g., copper washers, stainless steel washers) are needed to adjust gaps, ensuring the coaxiality or parallelism of parts and avoiding jamming during equipment operation.

Home improvement scenarios: When installing faucets or shower heads, if there is a slight deviation between the wall interface and the faucet base, thicker or thinner rubber washers can be used to adjust the position. This ensures the faucet is installed without tilting while maintaining a seal. Washers can fill these gaps through their thickness or elasticity.

Hebei Sanwei Fastener Co., Ltd

Our company is mainly engaged in the manufacturing and sales of fasteners, metal products, metal structures, hardware products, metal materials, safety and fire - fighting metal products, and building metal accessories. It also sells railway accessories, industrial and mining accessories, construction accessories, traffic facility accessories, auto parts, rubber products, plastic products, steel - structure accessories, power fittings, mechanical equipment and accessories, rigging, steel, building materials, hardware electrical materials, lifting equipment, decorative materials, stainless - steel products, etc. In addition, the company is involved in import and export business.