Countersunk washers are specialized washers designed to be used in conjunction with countersunk screws or bolts. Unlike ordinary flat washers, countersunk washers have a unique shape. They are raised on the sides, and the center is relatively flat, with a conical recess in the middle. This conical recess is designed to match the angle of the countersunk screw or bolt head, usually 82° or 90°.

The main function of countersunk washers is to ensure a smooth and level finish. When a countersunk screw is tightened, without a countersunk washer, the tapered head of the screw may cause the material to compress or even crack due to the concentrated force. The countersunk washer, with its flat - surface side in contact with the material and the tapered - surface side matching the screw head, can evenly distribute the load of the screw or bolt, reducing the risk of damage to the material. At the same time, it allows the screw or bolt head to sit flush with the surface of the material, creating a more aesthetically pleasing and professional appearance.

Countersunk washers are made of various materials. Common metal materials include stainless steel, which has good corrosion - resistance and is suitable for use in humid environments; carbon steel, which is cost - effective but usually requires anti - rust treatment; and brass, which is often used for its good appearance and electrical conductivity. In addition, there are non - metal materials such as nylon, which has the characteristics of insulation and chemical corrosion resistance, and rubber, which can provide functions such as anti - slip and sealing.

They are widely used in many fields. In woodworking, when installing furniture, countersunk washers can make the surface of the furniture smooth and prevent the wood from being damaged by screws. In metalworking, they are used to ensure the flatness of the metal surface after assembly. In the construction industry, for some decorative parts, countersunk washers can also play a role in both beauty and protection. In addition, in the assembly of precision equipment, because they can avoid protrusions and do not affect the operation and appearance of the equipment, they are also widely used.

In general, countersunk washers are an important fastener accessory, which not only plays a role in protecting materials and distributing loads, but also has a significant impact on the overall aesthetics and performance of the assembly.