Square Nut  — Product Description

Square Nut (also known as square hex nut or four-corner nut) is a fastener with a square or rectangular profile and an internal thread in the center, typically used in combination with bolts or threaded rods. The common standards are GB/T 39 (equivalent to German standard DIN 557), with specifications generally ranging from M3 to M24, and materials covering carbon steel (such as Q235, 35K, 45#), stainless steel (SUS304, SUS316), copper, aluminum, and more. Surface finishes include black oxide, zinc plating, nickel plating, Dacromet, and others. Due to its unique profile, the square nut is widely used in applications requiring anti-rotation, anti-slip, or an enlarged bearing surface.

I. Product Features

Square profile with large bearing surface
The profile is square or rectangular with four equal sides and sharp corners. Compared with hexagonal nuts, it offers a larger bearing surface.

Excellent anti-rotation performance
The square profile can be seated into grooved structures, prefabricated holes, or adjacent flat surfaces, preventing the nut from rotating with the bolt.

Easy to apply force
Can be gripped from the side using open-end wrenches, adjustable wrenches, or sockets for convenient tightening.

Greater thickness for reliable connection
Some specifications are heavy-duty versions with longer thread engagement, providing more reliable connections.

Diverse material and surface finish options
Carbon steel with zinc plating, stainless steel, copper, and more — selectable based on the operating environment.

Unified standards
Commonly GB/T 39 and DIN 557, offering excellent interchangeability.

II. Product Advantages

Anti-rotation and anti-loosening
The square structure can be embedded in a groove or constrained by an adjacent surface, effectively preventing the nut from rotating with the bolt and reducing the risk of loosening.

Large bearing area
Compared with round or hexagonal nuts, the square base has a larger contact area, reducing surface pressure on the fastened part — suitable for soft materials or thin plates.

Easy installation
In confined spaces or embedded grooves, square nuts can be placed directly into the groove without needing to hold the nut with a tool while threading in the bolt.

Cost-effective
Carbon steel materials offer high efficiency in cold heading production at low cost; even stainless steel versions are more economical than equivalent specialized anti-loosening nuts.

Strong adaptability
Compatible with a wide variety of bolts and threaded rods, widely used across different industries and working conditions.

Reusable
Threads and the square body are not easily damaged during disassembly and reassembly, making maintenance convenient.

III. Application Areas

Construction and steel structures
Used in embedded grooves, T-slots, connectors, scaffolding, guardrails, and more.

Mechanical equipment
Machine tools, automation equipment, conveyor lines, racks, sheet metal enclosures, and other areas requiring anti-rotation fastening.

Furniture and hardware
Office furniture, shelving, display racks, profile connections (e.g., used with T-head bolts inside aluminum extrusion slots).

Power and telecommunications
Assembly and fastening of distribution cabinets, cable trays, conduit channels, and communication server cabinets.

Vehicles and railways
Vehicle chassis, railway fasteners, rail connections, and other applications requiring vibration resistance and anti-loosening.

Other industries
Shipbuilding, agricultural machinery, environmental protection equipment, fitness equipment, and more.