10 Types of Washers: Everything You Need to Know

Washers are thin plates used to distribute loads, prevent loosening, or seal joints. Uneven load distribution can cause fasteners to loosen, rust, or even break. Washers are usually made of metal or plastic

Now, let’s explore the types of washers, their uses, and how to choose the right one

What is a Washer?

A washer is a thin disk or ring placed between a nut and a bolt or beneath a screw head. It distributes load, prevents damage, resists vibration, and seals surfaces. Washers are essential in CNC machining, where tight tolerances, like ±0.01 mm, must be maintained for stability and safety. They are used across industries such as aerospace, automotive, medical, and electronics.

10 Types of Washers

Washers are crucial components in hardware and industrial applications, serving various purposes such as load distribution, surface protection, and fastening security. Below are the most widely used 10 types of washers, each tailored to specific needs and environments:

1. Plain Washers

Plain washers are the most common type used for general load distribution and surface protection. They are often CNC-machined to precise thickness for consistency in assembly.

Used where large clamping force is required, they help avoid damaging materials such as aluminum or plastic. Also known as hardware washers, they help improve torque without increasing surface pressure.

2. Torque Washer

A torque washer is designed with external tabs or ribs that lock into soft materials like wood or plastic. Often used with carriage bolt torque washer assemblies, they resist rotation and maintain clamping force. CNC stamping processes are often used to form their serrated shapes.

3. Flat Washer

The flat washer is a simple round disk with a hole in the center, used for load distribution. It’s frequently used in CNC assemblies requiring high flatness. They come in various materials and sizes including 2 inch inside diameter washers, 1 8 washer, 5/8 washer dimensions, and washer size chart specifications.

4. Fender Washer

Fender washers are characterized by their significantly larger outer diameter relative to the central hole. This design provides an extended surface area, making them ideal for applications requiring greater load distribution. They are commonly used with soft, thin, or brittle materials, such as wood, plastic, or fiberglass, to prevent pull-through and ensure a secure fastening.

Unlike standard flat washers, fender washers excel in spreading stress evenly across oversized holes or delicate surfaces, reducing the risk of material damage. They are widely utilized in automotive, construction, and DIY projects where additional support is necessary.

5. Countersunk Washer

The countersunk washer fits flush with countersunk screws for smooth finishes and load-bearing capacity. Available in various finishes like countersunk washer 1/2 diameter galvanized steel, they’re ideal in aerospace, optics, and electronics where clean surfaces are critical.

6. Shoulder Washer

Shoulder washers are also called insulating washers. They are used in electrical assemblies where the washer with screw prevents metal-to-metal contact. These are commonly made from nylon, PTFE, or PEEK, and are often CNC-machined to tight tolerances for high-performance assemblies.

7. Conical Washer

Conical washers, also known as Belleville washers, are engineered with a conical shape that allows them to function like a spring under load. Their design provides the ability to apply pre-load to a bolted assembly, ensuring that the connection remains secure even under dynamic conditions. These washers are particularly effective at absorbing shocks, vibrations, and thermal expansion, making them ideal for high-stress environments such as automotive, aerospace, and industrial machinery.

8. C-Washer

Crescent washers, commonly referred to as C-washers, feature a unique design with an open slot resembling the shape of the letter “C.” This slot enables the washer to be installed or removed without the need to fully disassemble the bolt or fastener it supports. This design makes C-washers particularly useful in applications requiring frequent adjustments, maintenance, or quick assembly and disassembly.

They are often utilized in heavy machinery, automotive systems, and industrial equipment where efficiency and accessibility are paramount. Additionally, they provide stability and load distribution while allowing for enhanced flexibility in dynamic setups.

9. Lock Washers

Lock washers prevent fasteners from loosening under vibration. Common types include split rings, internal teeth, and external teeth. CNC production of lock washers is essential in automotive and industrial machinery to ensure reliable assembly.

To clearly understand the assembly sequence, users often ask the installation order of nut washers, bolts, flat washers or lock washers first – usually, flat washers close to the surface, followed by lock washers under the nut or bolt.

10. Spring Washers

Spring washers include wave washers and curved washers and are used in axial load applications. The comparison of spring washers and flat washers shows how spring washers provide resilience and how flat washers distribute the load. Spring washer combinations are used when components experience frequent load transfers or temperature changes.

Washers are essential components in fastening systems to increase stability, protect surfaces and prevent loosening. Each washer is designed to meet specific functional needs, from load distribution and insulation to shock absorption and quick installation. The following table summarizes the 10 most common types of washers, their unique functions and typical use cases: