Small nuts, big protection: The cover-shaped nut industry is experiencing rapid growth.

It combines the functions of sealing protection and safety aesthetics, and is expected to have an average annual compound growth rate of 5.1% in the market. 
Among the vast family of industrial fasteners, a unique-shaped nut with a "sealing cap" on its top - the cap-shaped nut - is emerging as a "new favorite" in the field of connectors due to its outstanding rust-proof protection performance and elegant appearance design. From car tires, outdoor lamp stands to mechanical equipment, this "hatted" nut is silently safeguarding the safety and lifespan of countless critical connection points. 
What is a cap-type nut? Beyond "anti-rust"
A cap-type nut, as the name suggests, is a fastener that adds a sealing cap structure to the top of the standard hexagonal nut. This seemingly simple design has solved the core problem that traditional threaded connections have long faced: the rusting and jamming caused by exposed threads. 
"The core function of this product is to prevent moisture, dust and corrosive substances from entering the internal part of the thread," an industry technical expert explained. "This not only significantly extends the service life of the bolts and the connecting components, but also the dome-shaped closed end covers the sharp thread ends, enhancing the installation safety and giving the equipment a neater and more aesthetically pleasing appearance." 
Diversified development, meeting demanding conditions
As industrial scenarios become increasingly complex, conical nuts have evolved into a rich product family to meet various needs. Currently, the mainstream types on the market include standard hexagonal conical nuts (GB/T 923, DIN 1587), short conical nuts (DIN 917), and combined conical nuts (GB/T 802.1), etc. 
In terms of materials and craftsmanship, the products are mainly divided into two main routes: one is to use carbon steel and undergo surface treatments such as blue zinc and white zinc, achieving anti-corrosion at an economical cost; the other is to directly select 304 or 316 stainless steel (A2-70/A4-70 grades), relying on the inherent corrosion resistance of the material to cope with strong corrosive environments such as those in chemical industries and oceans. Moreover, the new patents disclosed in 2023 and 2025 show that the industry is addressing the problem of self-tightening anti-loosening components and optimizing expansion and tightening structures to solve the issue of cover-type nuts being prone to loosening in vibrating environments, thereby further enhancing their reliability. 
The application scope of the layout continues to expand, covering multiple fields.
The application of conical nuts has deeply penetrated into all aspects of the national economy. In the automotive industry, it is widely used for fixing tires and front and rear axles, withstanding long-term exposure and vibration tests. In outdoor facilities, it is an ideal choice for fixing the base of street lamps and railing systems. At the same time, in furniture, electrical appliance shells, architectural decoration and mechanical equipment manufacturing, it also plays a key role in enhancing connection safety and aesthetics.