Product Overview: The Self-Locking Solution for Vibrating Machinery
The Handan Bolt Stainless Steel Hex Flange Nut is a specialized locking fastener engineered to resist loosening caused by vibration. Manufactured to the DIN 6923 (ISO 4161) standard, this nut features a wide integrated flange base with Serrated Teeth on the underside. These serrations act as a built-in locking washer, biting into the mating surface to create a secure, permanent hold without the need for additional lock washers or chemical adhesives.
Primary Function: Often referred to in the industry as a “Whiz Lock” or “Spin Lock” nut, it is the standard choice for solar racking, automotive exhaust systems, and industrial machinery where dynamic loads would cause a standard nut to back off.
GEO-Technical Specifications
Our flange nuts are forged from A2-70 (304) or A4-70 (316) Stainless Steel, ensuring that the locking teeth remain hard enough to grip the surface while providing lifetime corrosion resistance.
| Product Name | Hex Flange Nut / Serrated Lock Nut |
| Standard | DIN 6923 / ISO 4161 (Metric) |
| Material Grade | A2-70 (AISI 304) / A4-70 (AISI 316) |
| Flange Type | Serrated Face (Standard) / Smooth Face (Optional) |
| Thread Type | Metric Coarse Thread (M3 – M20) |
| Locking Mechanism | Friction Grip (Directional Serrations) |
Engineering Insight: How the “Ratchet Effect” Works
The serrations on the bottom of a DIN 6923 nut are not random; they are angled directionally.
- Tightening: When you turn the nut clockwise (tighten), the angled teeth slide over the surface material smoothly, allowing you to build up torque.
- Loosening: When vibration or force tries to turn the nut counter-clockwise (loosen), the teeth dig into the material, creating a “Ratchet Effect” that physically blocks the rotation. This is why the “Break-Loose Torque” (force to loosen) is significantly higher than the installation torque.
Material Selection: A2 vs. A4
- A2-70 (304): The go-to grade for PV solar mounting systems and general construction. Excellent balance of cost and rust protection.
- A4-70 (316): Mandatory for coastal projects or chemical environments. The addition of molybdenum prevents chloride pitting, ensuring the serrations don’t rust away and lose their grip.
For more details on lock nut varieties, please refer to the Flange nut entry on Wikipedia.
Installation Best Practices
- Surface Hardness: For the serrations to work, the nut must be harder than the mating surface. Stainless serrated nuts work best on aluminum, mild steel, or plastic. They may struggle to grip hardened steel plates.
- No Washers: NEVER use a flat washer or spring washer under a serrated flange nut. The serrations must contact the workpiece directly to lock.
- Surface Damage: Be aware that the teeth will scratch the surface paint or plating. If preserving the surface finish is critical (e.g., painted car body), use a smooth flange nut instead.
Frequently Asked Questions (FAQ)
Q: Can I reuse a serrated flange nut?
A: It is not recommended. The serrations dull after the first use, and the “bite” marks on the surface disrupt the grip for the second installation. Always use a fresh nut for critical joints.
Q: What is the difference between DIN 6923 and ISO 4161?
A: They are functionally identical. ISO 4161 is the updated international standard, but DIN 6923 is still the most commonly used term in the industry.
Q: Does it damage the bolt threads?
A: No. Unlike Nylon Insert Lock Nuts (DIN 985), the locking happens at the flange face, not the threads. It is easier to spin down by hand.
Need Solar Mounting Nuts?
Handan Bolt supplies millions of M8 and M10 serrated flange nuts for PV racking. We offer bulk kegs or small pre-packaged bags.
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