Lock Washers Vs Flat Washers Vs Spring Washers: What to Choose?

The difference between lock washers, flat washers, and spring washers lies in how they distribute load, prevent loosening, and support fastener performance—each type serving a specific mechanical role in an assembly.

When working with fasteners, selecting the right washer is often overlooked but critically important. 

This article compares lock washers vs flat washers and spring washers vs flat washers, helping you understand which one fits best for your application. 

Whether you’re dealing with vibration-heavy environments, looking for even load distribution, or needing extra resistance against loosening, this guide breaks down everything, including spring washer use and proper installation tips, like whether to install a lock washer or washer first.

Key Differences Between Lock Washers, Flat Washers, and Spring Washers

What is a Washer and Why Use One?

Washers are thin plates with a hole in the middle used in conjunction with fasteners such as bolts and screws. 

Their primary purpose is to distribute the load of the fastener evenly and prevent surface damage. 

However, washers also help secure the fastener in place and protect against vibration loosening, depending on the type.

There are 3 common types:

• Flat Washers
• Lock Washers
• Spring Washers (also referred to as sp washers)

Flat Washers: Load Distribution Experts

Flat washers are the most basic type. They are smooth, round discs that sit between the fastener head and the surface.

Key Functions:

• Evenly distribute force to prevent material damage
• Reduces friction during tightening
• Protect delicate or soft surfaces like aluminum or plastic
  

Flat washers are ideal for applications that require stability but don’t experience much vibration or movement. 

If you’re dealing with a softer material or just need to space a bolt or screw head properly, a flat washer is likely your best choice.

Use Case:

Used in furniture assembly, electronics, and basic structural fastening where torque is moderate and vibrations are minimal.

Lock Washers: Preventing Loosening

When it comes to security, flat lock washers are designed to prevent fasteners from backing out under vibration or dynamic loads.

How They Work:

They deform as the fastener is tightened, biting into both the bolt head and the surface. This resistance makes it harder for the bolt to rotate on its own.

Types of Lock Washers:

• Split (Helical) Lock Washers – A twisted design that compresses and grips
• Toothed Lock Washers – Internal or external teeth to bite into surfaces

Benefits:

• Excellent for vibration-prone environments like automotive, aerospace, or industrial equipment
• Helps maintain torque and prevent loosening

Lock Washer or Washer First?

The lock washer should always go directly under the nut or bolt head. 

In setups that include both types, the flat washer should sit beneath the lock washer, resting against the surface of the material.

This ensures the lock washer can grip properly and perform its intended function.

Spring Washers: Energy-Absorbing Action

Now, what is a spring washer? A spring washer is a type of lock washer with elasticity. Its job is to absorb shock, maintain tension, and reduce vibration.

Common types include:

• Belleville Washers (Conical) – Cone-shaped to provide high load in limited space
• Wave Washers – Wavy-shaped to offer moderate deflection
• Split Spring Washers – Also classified under lock washers due to their split coil design

Spring Washer Use:

Spring washers are particularly useful where bolt pre-load is critical. The washer maintains tension between bolt threads and the mating material, making it less likely for the joint to loosen.

They are widely used in:

• Circuit boards (wave washers)
• Compressors
• Construction joints exposed to vibration

Can You Use Multiple Washers?

In some applications, combining a lock washer with a flat washer is not only acceptable—it’s encouraged. 

The flat washer protects the surface and spreads load, while the lock washer adds anti-loosening functionality. 

Just be sure to stack them in the correct order: material → flat washer → lock washer → bolt/nut.

Common Misconceptions

Do You Always Need a Washer?

Not necessarily. Washers add benefits, but in some engineered fastener systems, like flange bolts or pre-threaded inserts, they may not be needed.

Are All Washers Universal?

Not all washers are interchangeable. An sp washer may refer to a specific spring washer configuration and isn’t equivalent to a standard flat washer. 

Always match the washer type and material with the application’s mechanical and environmental requirements.

Material and Coating Considerations

Washers are available in various materials, such as:

• Stainless Steel – Corrosion-resistant and ideal for outdoor or marine use
• Carbon Steel – Durable for heavy-duty applications
• Brass – Non-sparking and used in electrical systems
• Nylon/Plastic – For non-metallic, lightweight, and corrosion-sensitive setups
  

Special coatings like zinc plating or black oxide offer added resistance to rust or wear. Choosing the right material helps extend washer and fastener life.

Final Tips for Washer Selection

• Identify the load type – Shear, tension, or dynamic movement? Let that guide your washer selection.
  
• When selecting a spring washer, consider the thickness since it directly influences the deflection behavior. For flat washers, thickness impacts load spread.
  
• Consider the environment – Corrosive? Wet? Choose a washer material that withstands the conditions.
  
• Use proper torque – Overtightening can crush washers, especially spring or plastic ones.

Conclusion: Lock Washers Vs Flat Washers Vs Spring Washers

The washer type you choose plays a crucial role in how well your fastening system holds up over time.

Whether you’re comparing lock washer vs flat washer or exploring the benefits of spring washer vs flat washer, understanding the differences ensures optimal results. 

From distributing load to resisting vibration, washers are small components that carry big responsibilities.