Metric Class 10.9 Zinc Plated Serrated Flange Nuts
Class 10.9 Metric Serrated Flange Nuts in Zinc Plated Steel—also called serrated flange lock nuts, toothed flange nuts, grip lock flange nuts, or serrated hex flange lock nuts—combine high-strength fastening with aggressive vibration resistance in a single, efficient component. These nuts feature an integrated washer flange with serrated teeth on the bearing surface that bite into the mating material during tightening, creating a mechanical lock that resists loosening. The zinc plated finish provides corrosion protection for indoor and moderate outdoor applications while the Class 10.9 steel delivers the strength required for heavy-duty and safety-critical assemblies.
How Serrated Flange Nuts Work
The serrations on a serrated flange nut function as an integrated locking mechanism. As the nut is tightened against the workpiece, the hardened teeth on the underside of the flange dig into the mating surface, creating mechanical interference that resists counter-rotation. Unlike free-spinning nuts that rely solely on thread friction and clamping tension to stay tight, serrated flange nuts physically grip the assembly—providing reliable resistance to back-off even under severe vibration, impact loading, and thermal cycling. This built-in locking action eliminates the need for separate lock washers, reducing part count and assembly time while ensuring consistent performance.
Why Choose Class 10.9 Serrated Flange Nuts?
Class 10.9 steel provides a minimum tensile strength of 1,040 MPa (150,000 PSI) and yield strength of 940 MPa—approximately 25-30% stronger than Class 8.8 fasteners and the metric equivalent of SAE Grade 8. Combined with the aggressive serrated locking feature, these nuts are purpose-built for high-stress, high-vibration environments where both maximum clamping force and secure fastening are non-negotiable. The integrated flange distributes load across a wider bearing surface than a standard hex nut, reducing stress concentration and preventing pull-through on softer substrates—while the serrations ensure the joint stays locked tight.
Material & Specifications
Our Class 10.9 metric serrated flange nuts are manufactured from quenched and tempered alloy steel, heat-treated to achieve the mechanical properties required for safety-critical and heavy-duty fastening applications. The serrations are formed during manufacturing to create consistent tooth geometry that provides reliable grip across the full range of tightening torques. The zinc plated finish provides corrosion resistance for indoor environments and moderate outdoor exposure while meeting RoHS compliance standards. Zinc plating also facilitates smoother installation by reducing friction during the initial threading phase before the serrations engage.
Serrated vs. Non-Serrated Flange Nuts: Which Do You Need?
The choice between serrated and non-serrated flange nuts depends on whether vibration resistance or surface protection is your priority. Serrated flange nuts provide excellent resistance to loosening through mechanical grip—but the teeth will permanently mark or indent the mating surface. This makes them unsuitable for finished, painted, or decorative surfaces, and limits their reusability since the serrations may not seat properly in previously marked material. Non-serrated (smooth) flange nuts spin freely and protect the mating surface from damage but do not provide inherent locking action. Choose serrated when vibration resistance is critical and surface marking is acceptable; choose non-serrated when surface protection matters more than built-in locking.
Serrated Flange Nuts vs. Prevailing Torque Flange Nuts
Both serrated and prevailing torque flange nuts provide vibration resistance, but through different mechanisms with different trade-offs. Serrated flange nuts lock by gripping the mating surface—they're highly effective but mark the material and lose effectiveness if reused on previously marked surfaces. Prevailing torque flange nuts lock through thread interference (either all-metal distortion or nylon insert)—they don't mark the surface and can be reused for multiple installation cycles, but may have temperature limitations depending on design. For applications requiring repeated assembly and disassembly without surface damage, prevailing torque is preferred. For permanent or semi-permanent installations where maximum grip is needed, serrated flange nuts excel.
Important Considerations
Because serrated flange nuts grip by biting into the mating surface, they are best suited for use against bare metal, raw steel, or materials where surface marking is acceptable. Avoid using serrated flange nuts on painted, powder-coated, anodized, or polished surfaces where the serrations would cause cosmetic damage. The serrations also make these nuts less suitable for applications requiring frequent removal and reinstallation, as the teeth may not engage properly with previously marked material. For reusable applications or finished surfaces, consider non-serrated or prevailing torque flange nuts instead.
Common Applications
Class 10.9 zinc plated metric serrated flange nuts are specified across industries where high strength and reliable vibration resistance are essential:
- Automotive & Motorsports: Suspension components, subframes, engine mounts, exhaust hangers, underbody hardware
- Heavy Equipment & Machinery: Structural frames, vibrating equipment, hydraulic system mounts, guards and covers
- Agricultural Equipment: Tillage implements, harvester assemblies, PTO guards, high-vibration attachments
- Industrial & Manufacturing: Conveyors, motor mounts, compressors, pumps, process equipment subject to vibration
- Construction & Infrastructure: Structural connections, equipment anchoring, safety barriers, signage supports
Available Sizes
We stock Class 10.9 zinc plated metric serrated flange nuts in a range of popular thread sizes to cover most heavy-duty and high-vibration applications. Albany County Fasteners offers competitive bulk pricing and same-day shipping on in-stock items to keep your projects moving.
Need a non-serrated version, plain finish, or different strength grade? Contact our team—with over 18 million fasteners in stock, we can help you source the right flange nut for your specific application.