Washers are commonly used in conjunction with threaded fasteners. For instance, bolts are often inserted through the center of a washer. This helps distribute the load of the bolt more evenly across the surface of the object, thereby protecting it from damage.
Although most washers are flat, some are raised. They maintain a circular shape and have a central hole to support a threaded fastener. Countersunk washers, however, are raised rather than flat.
Countersunk washers are washers that dip inward radially, meaning they are raised on the sides. You can see an example in the photo above. The sides of a countersunk washer are raised, but the center is relatively flat and not elevated.
Countersunk washers function by inserting a threaded fastener through their center, as they also have a central hole designed for this purpose.
Like flat washers, countersunk washers can distribute the load of a bolt or other threaded fasteners. However, countersunk washers are particularly suitable for use with flat-head fasteners. Both bolts and screws may have flat heads, which fit perfectly into the countersunk washer's hole. The fastener's head will not protrude but will "sink" into the countersunk washer's hole.
Countersunk washers offer better protection against vibrations compared to flat washers. When installed, they press against the object to resist vibrations. Essentially, countersunk washers act as springs; driving a threaded fastener through the center forces the sides to collapse, pressing against the object and providing greater resistance to vibrations, which could otherwise cause the washers to loosen.
Countersunk washers come in various materials, including stainless steel, bronze, brass, aluminum, and more. When selecting countersunk washers, it's important to check their material composition.
Also, consider the size when choosing countersunk washers, as they are available in different sizes. The diameter of the hole must match the diameter of the fastener for which you intend to use the countersunk washer. If it's too large or too small, it may not properly support the fastener.
