Washers are thin plates of metal or non-metallic material with a hole, usually in the middle. These parts are normally used to relieve friction, prevent leakage, isolate, prevent loosening or distribute pressure of a nut, an axle bearing, or a joint.
The primary method used to manufacture washers is stamping and, in addition, processing may include many types of heat treating and surface coating.
Washer Classification and Standards
There is a huge quantity of sort of washers with different shapes and works. So, in order to define a washer with any degree of accuracy, we can make the following basic classification:
- Plain Washers
Or “Flat washers”, it is the most common washer group. Depending of the function they may be round, symmetrically square, hexagonal, rectangular…Some examples are fender washers (DIN 9021), washers for steel structures (DIN 7989), round washers for structural steel (DIN 6916), washers for clamping devices (DIN 6340), spherical washers and conical seats (DIN 6319), penny washers (DIN 9021, 9054), washers for hexagon bolts (DIN 125), washers for cheese head screws (DIN 433), washers for bolts with heavy clamping sleeves (DIN 7349)…
- Spring Washers
Which have axial flexibility, this group is used to prevent fastening loosening due to vibrations and thermal expansion. There are three basic types: Belleville washers (DIN 6796, DIN 2093), curved spring washers (DIN 137) and wave washers (DIN 137B).
- Locking Washers
This group is designed to secure fasteners that have a tendency to rotate or lose friction. Examples: helical lock washers or split lock washers (DIN 127), curved and wave spring lock washers (DIN 128), Toothed lock washers (DIN 6797), Serrated lock washers (DIN 6798), Lock washers (retaining washers) for shafts (DIN 6799), Spring lock washers with square ends for cheese head screws (DIN 7980)…
- Other common types
Shoulder washers (DIN 34816, DIN 34815), C-washers (DIN 6371), tab washers (DIN 432, DIN 463, DIN 93, DIN 462)...
Washers are available in a lot of materials, such as steel, stainless steel, copper, brass, titanium, aluminium, rubber, plastic, nylon, Teflon, zinc, ...