A washer is a thin plate (typically disk-shaped, but sometimes square) with a hole (typically in the middle) that is normally used to distribute the load of a threaded fastener, such as a bolt or nut. Other uses are as a spacer, spring (Belleville washer, wave washer), wear pad, preload indicating device, locking device, and to reduce vibration (rubber washer). Washers often have an outer diameter (OD) about twice their inner diameter (ID), but this can vary quite widely.
Washers are usually metal or plastic. High-quality bolted joints require hardened steel washers to prevent the loss of pre-load due to brinelling after the torque is applied. Washers are also important for preventing galvanic corrosion, particularly by insulating steel screws from aluminium surfaces. They may also be used in rotating applications, as a bearing. A thrust washer is used when a rolling element bearing is not needed either from a cost-performance perspective or due to space restraints. Coatings can be used in attempt to reduce wear and friction either by hardening their surface, or providing a solid lubricant (i.e. a self-lubricating surface).
ASTM Specifications for Washers
- Specification for Hardened Steel Washers , carbon steel, steel, washers, weathering steel, Hardened steel washers
· - Standard Specification for Washers, Steel, Plain (Flat), Unhardened for General Use
· - Standard Specification for Compressible-Washer-Type Direct Tension Indicators for Use with Structural Fasteners
- M6 (6mm)
- M8 (8mm)
- M10 (10mm)
- M12 (12mm)
- M16 (16mm)
- M20 (20mm)
- M24 (24mm)
Do nuts need washers?
Washers are important. They ensure that a nut is installed properly and prevent softer materials from damage by distributing the pressure over a greater surface area. Are washers necessary? Washers are not always necessary but it is common practice to use them anyway.
What does a washer do for a nut?
Washer, machine component that is used in conjunction with a screw fastener such as a bolt and nut and that usually serves either to keep the screw from loosening or to distribute the load from the nut or bolt head over a larger area. For load distribution, thin flat rings of soft steel are usual.
What goes first nut or washer?
If there is only one washer used with a nut/bolt, it usually goes on the nut side. The nut in most circumstances is more movable, and is more commonly turned to tighten the assembly. The washer helps prevent damage to the surface of the object being fastened.