Washers are broadly categorised into three main types based on their function: plain, spring, and locking. They are essential for distributing load, preventing loosening from vibration, and protecting surfaces.
Plain (Flat) Washers
Their primary job is to spread the fastener's load over a wider area to prevent damage to the material being joined.
- Standard Flat Washers: Simple discs used for general load distribution and surface protection.
- Repair Washers (Penny Washers): These have a much larger outside diameter compared to the hole, making them ideal for thin or weak materials like sheet metal or timber
Spring Washers
These act like a spring under compression to maintain consistent tension, which helps prevent loosening due to vibration or thermal expansion.
- Common spring Washers: These are split and twisted; when tightened, they flatten and exert a spring force to resist rotation.
- Belleville Washers (Disc springs): A cone-shaped washer that flattens under load to provide high spring force.
- Wave Washers: Curved discs used to apply moderate pressure or take up play in an assembly.
Locking Washers
Specifically designed to "lock" a fastener in place through mechanical resistance or increased friction.
- Shakeproof Washers: Feature internal or external teeth that bite into the surface and the fastener head.
- Wedge Lock (Nord-Lock) Washers: Use a pair of cam-faced washers that use tension instead of friction to prevent loosening in high-vibration environments.
- Tab Washers: Metal discs with one or more bendable tabs. After tightening, the tabs are bent against the nut or into a slot to physically block rotation.
Common Materials & Their Uses
The material choice depends on the environment where the fastener will be used:
- Steel/Stainless Steel: Strong and durable; stainless is preferred for wet or corrosive environments.
- Copper/Brass: Excellent for electrical conductivity and creating seals in plumbing or hydraulic systems.
- Nylon/Fibre: Used for electrical insulation and light sealing in non-conductive applications.
