Types of Washers

A Comprehensive Guide

The following are the main types of washers:

1. Plain Washers

Flat Washers: These are the most basic type of washer, designed to distribute the load of a bolt or screw over a larger area, preventing damage to the surface being fastened. They come in various types, such as Type A (standard flat washers with a smaller outer diameter for general use) and Type B (larger outer diameter and thickness for heavier loads or larger fasteners) .

Fender Washers: These have a thin, large outer diameter with a small inner diameter. They are commonly used in automotive fenders and body panels to distribute the load over a broad area and prevent damage to thin or fragile materials .

Countersunk Washers: Also known as finishing washers, these are designed to conform to the shape of a countersunk screw, providing a flush finish. They are commonly used in cabinetry and furniture .

C-Washers (C-Shaped): These have a split design resembling the letter "C" for easy side installation. They are ideal for applications that require frequent adjustments or rapid part changes, such as machinery maintenance or assembly lines .

Square Washers: These have a square shape and a central hole for bolts or screws. They are larger and thicker than standard round washers, providing enhanced strength and stability. They are commonly used in heavy-duty applications such as structural steel connections, timber frames, or other load-bearing situations .

2. Lock Washers

Split Lock Washers (Helical Spring Washers): These have a helical ring that splits at one point, creating two raised ends. This design creates friction and a mechanical grip as the ends of the washer bite into the fastener and the surface, preventing loosening due to vibration or torque .

External Tooth Lock Washers: These have teeth protruding outward from the outer edge. The teeth dig into the fastener head/nut and the mating surface, preventing rotation. They are easy to install and provide strong resistance to rotation, but may damage soft surfaces or coatings .

Internal Tooth Lock Washers: These have sharp teeth along their inner edge that grip the fastener head or nut. They are particularly useful for compact assemblies or small-headed fasteners, such as those in electrical panels .

Torque Washers (Wedge Lock Washers): These have four prongs that dig into the material, anchoring the bolt in place and preventing it from loosening over time. They are commonly used in woodworking projects .

3. Spring Washers

Belleville Washers: These are disc springs with a conical shape. They are designed to provide a high load-bearing capacity in a small axial space. When compressed, the washer acts like a spring, exerting a force and resisting deformation. They are commonly used in limited-space applications but require a strong spring force .

Dome Spring Washers: These have a convex or domed shape, designed to act as a spring when compressed. They are similar to Belleville washers but typically less aggressive in spring action. The washer's curvature allows it to absorb and maintain tension .

Wave Spring Washers: These have a wavy or sinusoidal shape, which gives them a spring-like action. When compressed, the waves in the washer create a spring effect, allowing it to maintain tension and absorb shock or vibration .

Finger Spring Washers: These consist of several metal "fingers" arranged in a circular pattern, each bent slightly outward. These fingers provide spring action by flexing when compressed, allowing the washer to absorb vibrations and prevent loosening .

Crescent Spring Washers: These have a crescent shape (partially curved). Like other spring washers, they provide tension and can resist loosening under vibration or movement. This type of washer is used in applications that require a low profile with consistent spring force .

4. Sealing Washers

Gasket Washers: These are crafted from materials that create an effective seal, making them essential in plumbing and automotive systems to prevent leaks .

Rubber Washers: Made from elastomeric compounds, these provide excellent sealing properties and help reduce vibrations .

5. Specialty Washers

Shoulder Washers: These insulate fasteners or provide precise spacing and alignment .

Keyed Washers: These have a slot that prevents rotation, ensuring secure alignment of parts .

Wedge Lock Washers: These consist of two interlocking pieces that resist loosening under vibration, offering high reliability in critical assemblies .

Keps Nuts: These are hexagonal nuts with an integrated lock washer attached to the top of the nut, providing a locking mechanism to prevent the nut from loosening due to vibrations or movement .

Top Hat Washers: These have a "top hat" appearance (a flat top and a flared bottom). The wide flange makes them ideal for applications where it is essential to prevent material damage, especially in softer or thinner materials .

Insulating Washers: These are also called shoulder washers or insulating bushings. The "shoulder" part of the washer refers to a raised, cylindrical portion that protrudes from the flat washer. This shoulder acts as a spacer between the fastener and the base material, ensuring there is a gap that isolates the two surfaces .

Retaining Push Nuts: These are designed to quickly and securely retain components on a shaft or stud. They are typically made from spring steel, and the internal design features teeth or serrations that create a firm grip when the nut is pushed on, resisting loosening .

Spherical Washers: These have a concave spherical cap on one side and a flat surface on the other. The spherical cap allows for limited angular or rotational adjustment, ensuring proper contact and even load distribution even when components are not perfectly aligned .

Structural Washers: These are thick and heavy-duty, designed for use with high-strength fasteners. They often have a slightly conical or beveled surface and are used to construct steel structures such as buildings, bridges, and industrial facilities .