The Square Nut (commonly known as a four-sided nut, metric square nut, thin square nut, or DIN 557 / DIN 562 fastener) is a classic four-sided internally threaded fastener designed to provide a larger surface contact area than standard hex nuts. This unique square geometry prevents nut rotation when inserted into pre-formed channel slots, aluminum extrusion tracks, or blind square recesses. Manufactured in carbon steel (Property Classes 4 and 8) and austenitic stainless steel (SS304/A2-70 and SS316/A4-80), our square nuts conform strictly to global ISO standards.
Technical Specifications of Square Nuts
We supply both standard height square nuts (DIN 557) and thin low-profile square nuts (DIN 562). The wide flat sides make square nuts ideal for blind assembly applications where a wrench cannot hold the nut, or where blind insertion into structural channels is required.
| Property Class / Grade | Raw Material Base | Proof Stress Rating | Standard Execution | Available Surface Treatments |
|---|---|---|---|---|
| Class 4 / Class 6 | Low Carbon Steel (Q195 / Q235B) | 400 – 600 N/mm² | DIN 557 (Standard) / DIN 562 (Thin) | Electro-Zinc Plated (Blue-White / Yellow) |
| Class 8 (High Tensile) | Medium Carbon Steel (45# Quenched) | 800 N/mm² | DIN 557 (Standard Height) | Black Oxide, Electro-Zinc, Hot-Dip Galvanized (HDG) |
| Stainless A2-70 / A2-80 | Austenitic Stainless Steel SS304 (1.4301) | 700 – 800 N/mm² | DIN 557 / DIN 562 | Passivated Clean Natural / Electropolished |
| Stainless A4-70 / A4-80 | Austenitic Stainless Steel SS316 (1.4401) | 700 – 800 N/mm² | DIN 557 / DIN 562 | Passivated Clean Natural / Electropolished |
Precision Cold Heading and Four-Side Stamping Process
At our manufacturing plant in Handan, China, square nuts undergo multi-station cold forming, precision internal thread tapping, heat treatment, and surface plating:
- Four-Side Cold Heading: High-speed cold formers stamp wire rod into exact four-sided square body dimensions with flat, square bearing faces to maximize surface contact area.
- Precision Internal Tapping: Automated tapping machines thread metric 6H internal pitches to ensure low installation torque and smooth assembly.
- Continuous Thermal Heat Treatment (Class 8): Medium carbon steel nuts are heat-treated in continuous mesh-belt quenching furnaces to achieve uniform hardness and 800 MPa proof strength.
- Surface Coating & Chemical Passivation: Electro-zinc plating (5–12 µm), Hot-Dip Galvanizing (45–85 µm molten zinc dipping), or acid passivation for stainless steel items.
Versatile Industrial Applications of Square Nuts
Square nuts are specified in applications requiring high bearing surface contact or blind channel retention:
- Aluminum Extrusions & Strut Channels: Slid into T-slots or strut channels where the square sides lock against channel walls to prevent spinning during bolt tightening.
- Electrical Switchgear & Busbar Connections: Fastening copper busbars and electrical enclosures where wide surface contact reduces electrical resistance.
- Heavy Machinery & Wooden Pole Hardware: Used in railway ties, timber construction, and utility pole hardware where high surface friction prevents back-off.
Quality Assurance and Export Packaging for Square Nuts
Handan YiHao Fastener enforces strict Quality Assurance (QA) standards for all overseas export orders. Testing procedures include 100% thread plug gauge go/no-go checks, square dimension across flats verification, proof stress testing, and salt spray validation.
All export orders are bulk packed in heavy-duty 25kg inner cartons, neatly stacked on ISPM 15 compliant fumigated wooden pallets, and wrapped in protective stretch film for safe ocean freight.
Request Factory Direct Pricing for Square Nuts
Looking for a trusted manufacturer in Handan, China for carbon steel or stainless steel square nuts (Class 4, Class 8, SS304, SS316, DIN 557 / DIN 562)? Contact Handan YiHao Fastener today for technical datasheets, thin profile options, free samples, and direct bulk export quotes.
