“D125a Washers” in this mechanical sense (as opposed to meaning “one who washes”) first appeared in English around 1346. … The washer’s smooth surface would allow free movement back and forth, a motion which might plausibly be compared to the scrubbing movement used in washing something. Threaded fasteners do a more reliable job when accompanied by washers. Washers protect the surface from damage during installation. They distribute the pressure and prevent the fastener from moving or corroding. Skipping on washers can dramatically reduce the lifespan of how your product is put together.

General:

Metric DIN 125 Flat Washers are standard metric flat washers – a circular metal disc with a central hole. Typically used to distribute the load over a larger bearing surface either positioned below the head of a bolt or below the nut. This even distribution over a larger area reduces the chance of damaging the bearing surface. A washer could also be used if the outer diameter of a mating nut is smaller than the hole through which the screw is placed. Aspen Fasteners offers over 500,000 unique fastener products from stock in inch and metric standard in a variety of materials and finishes. The following sizes of DIN 125 Flat Washers are available for immediate shipping from stock: Diameters ranging from M3 to M72 in aluminum, brass, nylon, steel as well as stainless steel A2 and A4.