Washers are essential components in bolted connections, helping distribute loads, reduce friction, and prevent damage to surfaces. However, proper washer placement is crucial for ensuring a secure and long-lasting connection. Understanding where washers go on bolts and their specific functions can improve fastening reliability in industrial, construction, and mechanical applications.

Where to Place Washers on Bolts

1. Between the Bolt Head and the Surface

In most applications, a washer is placed directly under the bolt head before inserting the bolt into the material. This helps in:

Distributing the load evenly to prevent surface damage.

Reducing friction between the bolt head and the surface.

Providing a smoother tightening process, especially in high-torque applications.

2. Between the Nut and the Surface

A washer is also commonly placed between the nut and the surface being fastened. This placement serves to:

Protect the material from damage caused by nut rotation.

Improve load distribution, reducing stress concentration.

Enhance the grip of the nut, preventing loosening due to vibrations.

3. Both Under the Bolt Head and Under the Nut

In critical applications, washers are used on both sides of the bolted connection—under the bolt head and under the nut. This is recommended when:

The materials being fastened are soft or prone to deformation.

High vibration or movement might cause the bolt to loosen.

The load needs to be evenly distributed across both surfaces.

Types of Washers and Their Placement

Flat Washers – Used under either the bolt head or the nut to distribute force and protect surfaces.

Lock Washers – Typically placed under the nut to prevent loosening due to vibrations.

Spring Washers – Installed under the nut or bolt head to apply tension and maintain tightness.

Spherical Washers – Used in misalignment applications to ensure proper force distribution.

Fender Washers – Placed under the bolt head when securing thin materials to prevent damage.

Summary

Proper washer placement enhances the stability and reliability of bolted connections. In most cases, washers go under the bolt head, the nut, or both, depending on the application’s requirements. By selecting the right type of washer and ensuring correct positioning, fasteners can maintain strength, resist loosening, and protect surfaces from damage, ultimately improving the performance of mechanical assemblies.