Washer or lock washer: which one is it and why does it matter?

When assembling a bolted joint, the correct order of components is crucial to ensure proper tightening and prevent potential failures. One common question that arises is whether a washer should be placed before or after a lock washer. This blog post will delve into the intricacies of washer and lock washer assembly, providing a comprehensive guide to help you determine the correct order for your specific application.

Washer vs. Lock Washer

Washer: A washer is a thin, flat disk that is placed between a nut or bolt head and the surface being fastened. Its primary function is to distribute the load and prevent damage to the surface.

Lock Washer: A lock washer is a specialized type of washer that is designed to prevent a nut or bolt from loosening due to vibration or movement. It features a split or deformed design that creates friction against the nut or bolt surface.

Determining the Correct Order

The correct order of washer and lock washer assembly depends on several factors, including the type of lock washer being used and the application requirements.

Type of Lock Washer

Internal Tooth Lock Washer: This type of lock washer has teeth on the inside that bite into the bolt or nut. It should be placed between the nut or bolt head and the surface being fastened.

External Tooth Lock Washer: This type of lock washer has teeth on the outside that bite into the surface being fastened. It should be placed between the washer and the nut or bolt head.

Application Requirements

Vibration Resistance: For applications where vibration is a concern, the lock washer should be placed between the nut or bolt head and the surface being fastened. This will provide maximum resistance to loosening.

Load Distribution: If load distribution is the primary concern, the washer should be placed between the nut or bolt head and the surface being fastened. This will help spread the load and prevent damage to the surface.

General Assembly Guidelines

Based on the factors discussed above, the following general assembly guidelines can be followed:

• For internal tooth lock washers, use the order: Bolt/Nut -> Washer -> Lock Washer -> Surface
• For external tooth lock washers, use the order: Bolt/Nut -> Lock Washer -> Washer -> Surface
• When both a washer and a lock washer are required for load distribution and vibration resistance, use the order: Bolt/Nut -> Washer -> Lock Washer -> Surface

Additional Considerations

Multiple Lock Washers

In some cases, multiple lock washers may be used to provide additional resistance to loosening. When using multiple lock washers, alternate between internal and external tooth types.

Lubrication

Lubricating the threads of the bolt or nut can help reduce friction and make assembly easier. However, avoid excessive lubrication, as this can reduce the effectiveness of the lock washer.

Thread Engagement

Ensure that the bolt or nut is sufficiently engaged in the threads of the mating component. Insufficient thread engagement can compromise the strength and stability of the joint.

Key Points: Ensuring Proper Assembly

Following the correct order of washer and lock washer assembly is essential to achieve a secure and reliable bolted joint. By understanding the different types of washers and lock washers, their functions, and the application requirements, you can optimize the performance and longevity of your assemblies. Remember to always consult with the manufacturer’s specifications for specific guidance on the correct order and assembly procedures.

Frequently Asked Questions

1. What is the purpose of a washer?

A washer distributes the load and prevents damage to the surface being fastened.

2. What is the purpose of a lock washer?

A lock washer prevents a nut or bolt from loosening due to vibration or movement.

3. Which type of lock washer should I use?

Internal tooth lock washers are used between the nut or bolt head and the surface being fastened, while external tooth lock washers are used between the washer and the nut or bolt head.

4. Can I use multiple lock washers?

Yes, multiple lock washers can be used to provide additional resistance to loosening. Alternate between internal and external tooth types.

5. Should I lubricate the threads before assembly?

Yes, lubricating the threads can reduce friction and make assembly easier. Avoid excessive lubrication.

6. How much thread engagement is required?

Sufficient thread engagement is crucial for joint strength and stability. Consult the manufacturer’s specifications for specific guidance.