A Guide to Different Types of Lock Washers and Their Uses

In any bolted joint, washers play a more significant role than many people realize. They help distribute load, protect mating surfaces, and support consistent clamp force. But when vibration, movement, or dynamic loads are involved, standard flat washers are often not enough. That’s where lock washers come in.

Lock washers help fasteners stay tight over time. Whether you’re working on industrial equipment, automotive assemblies, electrical systems, or general maintenance and repair, choosing the right lock washer makes the difference between a reliable joint and one that loosens prematurely.

This guide breaks down the most common types of lock washers, how they work, and when to use each. By the end, you’ll be able to make confident, informed fastening decisions.

What Are Lock Washers and How Do They Work?

A lock washer is a type of washer used with bolts, screws, or nuts to help prevent loosening after installation. Unlike flat washers, which mainly distribute load and protect surfaces, lock washers add resistance to the fastener assembly to actively resist loosening. They work in a few different ways, depending on the design:

• Spring force creates tension that helps maintain the clamp load.
• Serrations or teeth bite into mating surfaces for mechanical locking.
• The wedging action resists rotation under vibration.

This added resistance helps counteract the effects of vibration, thermal expansion, and repeated movement, which are common causes of fastener loosening. In many applications, both flat and lock washers are used together, but lock washers are essential when joint integrity matters under dynamic conditions.

Common Types of Lock Washers

There’s no one-size-fits-all lock washer. Different designs solve distinct problems, and understanding how each works helps ensure you choose the right type for the job:

Split Lock Washers (Helical Spring Lock Washers)

Split lock washers are the most widely used and recognized type of lock washer. They:

• Are made with a helical, split-ring design
• Act like a spring when compressed under a bolt head or nut
• Apply continuous tension to help resist loosening

These washers are commonly used in general-purpose bolted joints where moderate vibration is present. While simple and cost-effective, they are best suited for applications where loads and vibration are not extreme.

Tooth Lock Washers (Serrated Washers)

Tooth lock washers feature serrations that bite into the mating surfaces to prevent movement. There are two types:

• Internal tooth lock washers: Teeth face inward toward the bolt or screw, which are ideal where a clean outer appearance is important.
• External tooth lock washers: Teeth extend outward for a stronger locking effect. They provide greater holding power than internal tooth designs.
• Internal/External tooth lock washers: Teeth face inward as well as extend outward for a specialized design.

Because the teeth create metal-to-metal contact, these washers are commonly used in electrical grounding applications and light-duty assemblies exposed to vibration. They are especially effective where maintaining electrical continuity is critical.

Belleville Washers (Disc Spring Washers)

Belleville washers have a conical shape that acts like a spring under compression. These washers:

• Maintain consistent tension as loads change
• Compensate for thermal expansion and material settling
• Perform well in high-load and dynamic environments

These washers are frequently used in automotive, industrial, and heavy equipment applications, where maintaining clamp force over time is critical.

Wave Washers

Wave washers are designed for applications that need a light spring force in a compact space. They:

• Have wavy profiles that provide preload without excessive force
• Are ideal for assemblies with limited axial space
• Help absorb vibration and reduce play

They’re often used in small mechanical assemblies, enclosures, and applications where components need to stay snug without high clamp loads.

Wedge Lock Washers (Nord-Lock Style)

Wedge lock washers use a two-piece cam system that creates a wedge-locking effect. These cam angles resist rotation under vibration, while the bolt tension increases before loosening can occur. Additionally, these are extremely dependable in high-vibration environments, making them common in:

• Heavy-duty, safety-critical applications
• Construction equipment
• Transportation
• Industrial machinery

Lock Washer Materials and Finishes

Lock washers are available in a range of materials and finishes, and choosing the right combination is critical for long-term performance. The material affects strength and durability, while the finish determines how well the washer holds up against corrosion, moisture, and environmental exposure:

• Stainless steel: This material offers excellent corrosion resistance for outdoor, marine, and food-related environments.
• Carbon steel: This is a strong, cost-effective option for dry, controlled environments, such as industrial machinery, structural assemblies, and general-purpose fastening applications.
• Zinc-plated: This finish provides basic corrosion protection for indoor or light moisture exposure. Zinc-plated lock washers are frequently used in commercial and light industrial applications.
• Galvanized finishes: These finishes create a thicker zinc coating for outdoor or high-humidity environments, including construction, agricultural equipment, and infrastructure projects where long-term durability is essential.

In addition to material and finish, proper sizing is essential. Lock washers are manufactured in both Imperial (inch) and metric sizes, and they must match the fastener system being used. Mixing metric washers with imperial bolts, or vice versa, can compromise fit, preload, and locking performance.

By selecting the right material, finish, and size, you ensure your lock washers deliver consistent clamping force and resist environmental damage. This ensures they perform as intended throughout the life of the assembly.

Choosing the Right Lock Washer for Your Application

Selecting the right lock washer for your application depends on where the fastener will be used. Key factors to consider include:

• Vibration level: Is the application subjected to light, moderate, or severe vibration?
• Dynamic loads: Is there constant movement, shock, or load cycling?
• Environment: Will the washer be exposed to moisture, corrosion, chemicals, or temperature changes?
• Fastener type: Is the washer attached to hex bolts, cap screws, machine screws, or socket head fasteners?
• Mating surface material: Is the application surface steel, aluminum, composites, or plated?

Matching the washer type to both the fastener and the application ensures long-term joint reliability.

Lock Washers vs. Lock Nuts vs. Threadlocker

Lock washers are just one option for preventing fastener loosening. In some cases, other solutions may be more effective.

• Lock washers work well for moderate vibration and general-purpose assemblies.
• Lock nuts (such as nylon inserts or all-metals) provide built-in resistance and are ideal for repeated vibration.
• Threadlocker compounds chemically bond threads and are often used in high-vibration or permanent assemblies.

For critical joints, the best practice often involves combining methods. You can use a lock washer with a lock nut or threadlocker to strengthen the connection.

Fasteners Etc., Inc. Has the Right Lock Washer for Every Application

Choosing the correct lock washer helps ensure bolted joints stay tight, safe, and reliable over time. From split lock washers to advanced wedge-lock designs, understanding how each type works allows you to select the best solution for your specific application. Fasteners Etc., Inc. brings deep industry knowledge, a wide inventory of fastener types, and personalized service to every customer. Whether you need corrosion-resistant washers, high-strength industrial solutions, or help selecting the right fastener combination, our team is here to help. Contact us today to request a quote or get expert guidance for your next project.