- A plain washer (or 'flat washer')
is a flat annulus or ring, often of
metal, used to spread the load
of a screwed fastening.
Additionally, a plain washer may
be used when the hole is a
larger diameter than the fixing
nut. Plain washers, which
spread a load, and prevent
damage to the surface being
fixed, or provide some sort of
insulation such as electrical
- Washers are usually metal High quality bolted joints require hardened steel washers to prevent the loss of pre-load after the torque is applied.