The Correct Selection of Flat Washers and Spring Washers

In everyday life, one often observes that in bolted and nutted connections, there is a flat, ring-shaped component present-the washer. A washer is a fastener placed between the bearing surface of a bolt, screw, or nut and the surface of the component being joined; the most commonly used types are flat washers and spring washers.

 

I. Flat Washers

The principle behind flat washers is to increase the contact surface area between the joined components, thereby reducing the pressure per unit area and protecting the surfaces of the joined parts from damage. Their primary functions include pressure distribution, friction enhancement, sealing, vibration damping, and securing.

 

For instance, a single automobile may utilize hundreds of different types of fasteners, totaling thousands of individual pieces; flat washers-particularly when integrated into pre-assembled screw units-are widely applied within the automotive fastener sector. With the increasing demands for vehicle lightweighting, lightweight connection technologies and structural designs are being extensively adopted in vehicle bodies and even chassis structural components. To reduce the compressive stress on the bearing surfaces of the joined parts within a bolted joint-thereby preventing crushing or permanent plastic deformation-the inclusion of flat washers is generally required.

 

II. Spring Washers

Spring washers primarily serve to increase the frictional force between the nut and the bolt. Essentially, they act as a protective measure designed to prevent the loosening of fastening bolts caused by vibration during equipment operation, thereby providing anti-vibration and anti-loosening effects.

 

For example, bolts connecting an electric motor to its base typically require the addition of spring washers. Because motors generate vibration, the absence of a spring washer would likely result in the nut becoming loose. As a general rule, fasteners used on equipment that generates vibration are fitted with spring washers.