Lock washers are small but critical components in fastening systems, designed to prevent nuts and bolts from loosening due to vibration, dynamic loads, or thermal expansion. While they may seem straightforward, improper selection or installation can lead to serious failures — especially in high-stress environments like machinery, automotive assemblies, or structural connections. In this guide, we’ll explore when to use lock washers, how to choose the right type for your application, and common mistakes to avoid to ensure your fasteners stay secure and your assemblies remain reliable.
What Are Lock Washers?
Lock washers are specially designed washers used to prevent bolts, nuts, or screws from loosening due to vibration, thermal expansion, or dynamic loads. They are typically placed between the fastener (such as a nut or bolt head) and the workpiece surface, enhancing joint stability through friction, elastic deformation, or mechanical interlock.
Features of Lock Washers
| Feature | Description |
| Strong anti-loosening | Effectively resists loosening from vibration or thermal cycling. |
| Diverse designs | Includes spring, toothed, wedge, and disc-shaped styles. |
| Wide applicability | Common in mechanical, automotive, electrical, and construction industries. |
| Easy to install | Installs like a regular washer, no special tools required. |
| Various materials | Made from carbon steel, stainless steel, spring steel, etc., with zinc plating or anti-corrosion finishes available. |
Types of Lock Washers
By Working Principle:
| Type | Working Principle | Features & Applications |
| Split Lock Washer | Uses spring tension to resist loosening | General-purpose, for light loads |
| Tooth Lock Washer | Teeth bite into the surface to increase friction | Used for electrical connections and sheet metal fastening |
| Wedge Lock Washer | Cam-shaped internal faces lock against rotation | Ideal for high-vibration environments; reusable |
| Belleville Washer | Conical shape provides axial preload | Used where preloading or thermal compensation is needed |
| Wave Washer | Wavy shape provides spring-like cushioning | Provides light, continuous tension in assemblies |
By Shape / Tooth Configuration:
- Internal Tooth Lock Washer: Teeth on the inner edge; suitable for tight spaces.
- External Tooth Lock Washer: Teeth on the outer edge; offers greater contact and holding force.
- Internal-External Tooth Washer: Teeth on both edges; ideal for electrical grounding and conductive assemblies.
How Should Lock Washers Be Used?
Lock washers are designed to prevent fasteners from loosening due to vibration, torque, or thermal expansion. They are commonly used in mechanical, automotive, and structural applications where secure and long-lasting fastening is critical.
- Correct Placement
Install the lock washer between the nut (or bolt head) and the surface of the part being fastened.
It should be in direct contact with the surface to create friction.
- Use with Flat Washers (if needed)
If used with soft materials (like aluminum), place a flat washer between the lock washer and the surface to prevent damage.
- Torque Properly
Tighten the bolt/nut to the recommended torque to fully engage the locking action.
- Do Not Reuse Most Types
Many lock washers (especially split or serrated types) lose effectiveness after removal.
When Should Lock Washers Be Used?
- High-Vibration Environments
e.g., engines, heavy machinery, vehicles, HVAC systems. - Critical Joints
Where loosening may cause equipment failure or safety issues. - Thermal Cycling Applications
Where frequent expansion/contraction might loosen fasteners. - Disassembly Is Infrequent
In assemblies not meant to be frequently taken apart.
When Not to Use Lock Washers
- On very hard surfaces where teeth cannot bite.
- In critical aerospace or high-load applications — may need locking nuts or thread-locking compounds instead.
- If frequent disassembly is expected — choose a more durable locking method.
Contact MT.BOLTS
MT.BOLTS specializes in the manufacturing and supply of Steel Fasteners, including screws, bolts, nuts, and washers. Our products conform to international standards (ANSI / ASTM / DIN / ISO / JIS) and are available in various materials, dimensions, and surface finishes.
Contact us today to learn more about fasteners and to procure high-quality products. Our technical team is ready to provide expert support and custom selection solutions.
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