How Does A Lock Washer Work: A Simple Overview
Lock washers work by creating tension that resists loosening, making them essential for securing fasteners in assemblies subject to vibration or movement.
In many mechanical systems, fastening stability is critical.
Whether it’s in automotive builds, aerospace applications, or home repairs, nuts and bolts can loosen over time due to movement, temperature shifts, or vibration.
That’s where lock washers—also called locking washers—come in.
In this article, we’ll explain how a lock washer works, its types, its applications, and key installation tips.
If you’ve ever wondered what a locking washer is, when to use one, or even how to remove a lock washer, we’ve got you covered with a straightforward breakdown.
What is a Locking Washer?
A locking washer is a specialized type of washer designed to prevent threaded fasteners, like bolts or nuts, from loosening over time.
While flat washers mainly distribute load, locking washers provide added grip and friction to hold the fastener in place.
This is especially important in assemblies exposed to continuous motion, vibration, or thermal cycling.
Lock washers are used across many industries, including automotive, electronics, heavy equipment, and even household appliances.
They come in various forms, each offering different levels of locking power.
How Does a Lock Washer Work?
The key mechanism of a lock washer lies in its ability to maintain tension and resist rotation.
When tightened, the lock washer bites into the mating surfaces—either through its split shape, serrations, or teeth—creating resistance that keeps the bolt or nut in place.
This locking action works in one of two ways:
- Friction: By increasing friction between the washer and the surface.
- Tension: By maintaining a spring-like force that holds the fastener tightly.
For example, an external tooth lock washer features teeth that dig into the bolt head and the mating surface. These teeth resist loosening by interfering with rotation.
4 Common Lock Washer Types
Understanding the different lock washer types helps you choose the right one for your needs. Here are the most common:
1. Split Lock Washer
Also called a helical washer, this type has a single split with a slight twist. When compressed, it exerts a spring force that prevents loosening.
2. External Tooth Lock Washer
This washer has serrated edges that bite into the surface material. Ideal for larger diameter fasteners, the external tooth lock washer maximizes grip.
3. Internal Tooth Lock Washer
With teeth on the inside, this type is best used under a screw or bolt head where external teeth would not make proper contact.
4. Flat Lock Washer
Though technically a flat washer, it’s called a flat lock washer when used in conjunction with another locking mechanism like a split washer.
When to Use a Lock Washer
Knowing when to use a lock washer is just as important as knowing how it works. Use locking washers when:
- The assembly is subject to vibration (e.g., engines, HVAC systems).
- Bolts or nuts need to stay secure over long periods.
- There’s a risk of thermal expansion or contraction.
If you’re choosing between a lock washer or washer first, the general rule is that the lock washer goes against the nut or bolt head, while the flat washer—if used—sits between the lock washer and the material surface.
Lock Washer vs Flat Washer: What’s the Difference?
A flat washer spreads the load and protects surfaces. A lock washer, on the other hand, provides anti-rotation features.
If both are required in one assembly, it’s essential to get the order for the lock washer and flat washer correct to ensure maximum effectiveness.
Where to Put Locking Washer
Install the locking washer directly under the bolt head or the nut. If using a flat washer as well, place it between the lock washer and the material.
This ensures the lock washer has a solid surface to grip against, boosting performance.
Correct installation order:
- Material surface
- Flat washer (if used)
- Lock washer
- Nut or bolt head
Are Lock Washers Directional?
In general, most locking washers—like split and toothed types—are not directional, but for maximum performance, you should still install them in a way that ensures proper grip.
For instance, the sharp side of a split washer should face the bolt or nut for better bite.
Are Lock Washers Reusable?
Are lock washers reusable? Not typically. Once compressed or deformed, their locking ability is compromised.
Reusing them may reduce their effectiveness and increase the risk of loosening. For high-stakes applications, always opt for a new washer during reassembly.
How to Remove Lock Washer
To remove a lock washer, you’ll need to:
- Loosen the fastener (nut or bolt) with a wrench or appropriate tool.
- Slide the washer off the bolt or screw shaft.
- If the washer has deformed or is stuck due to its teeth or compressed shape, you may need pliers to gently work it loose.
Always inspect the washer after removal. If it shows wear or damage, discard it and use a new one.
Installation Tips for Lock Washers
Here are a few expert pointers to make sure your locking washer does its job:
- Match materials: Use stainless steel lock washers with stainless steel bolts to avoid galvanic corrosion.
- Use the correct size: The washer must match the diameter of your fastener.
- Apply torque properly: Overtightening can flatten or damage the washer, while under-tightening reduces locking ability.
- Avoid mismatched surfaces: Uneven surfaces can prevent the washer from sitting flush, reducing its performance.
Final Thoughts: Lock Washers Offer Reliable Anti-Loosening Performance
In summary, how does a lock washer work? It prevents bolts and nuts from loosening due to vibration or stress by either creating tension or increasing friction.
Whether you’re using a flat lock washer, an external tooth lock washer, or a split washer, knowing how and when to use them makes your assembly more secure and reliable.
From understanding what a locking washer is to knowing where to put a locking washer and whether lock washers are reusable, this guide provides a comprehensive overview for DIYers and professionals alike.
Resources
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