Serrated Flange Nuts
What Are Serrated Flange Nuts?
Serrated flange nuts are hex nuts with a wide, built-in bearing surface (the flange) and radial teeth on the underside. The flange spreads clamp load like a washer, while the serrations bite into the mating surface to provide vibration-resistant locking without a separate lock washer.
Key Benefits of Serrated Flange Nuts
- Integrated washer – wider bearing surface protects the joint and speeds assembly.
- Vibration resistance – serrations create prevailing torque to help prevent loosening.
- Fewer parts – eliminates separate washers/lock washers in many applications.
- Fast installs – hex drive works with standard wrenches and sockets.
Materials & Finishes
- 18-8 / 304 Stainless Steel – general corrosion resistance for indoor/outdoor use.
- 316 Stainless Steel – enhanced corrosion resistance for marine or chemical exposure.
- Zinc Plated Steel – economical corrosion protection for dry or sheltered environments.
- DIN/ISO Metric Series – common metric flange nut standards with serrated bearing faces.
When to Use Serrated vs. Non-Serrated
- Choose serrated for metal-to-metal joints where vibration resistance is required and minor surface marking is acceptable.
- Choose non-serrated when you need smooth bearing action, plan to remove/reuse hardware, or must protect coatings/finishes.
Common Applications
- Automotive, powersports, and machinery subject to vibration
- Racking, frames, guards, and equipment brackets
- Sheet-metal fabrication and light structural assemblies
- HVAC, electrical, and MEP supports
Selection Guide
- Thread system – match inch (UNC/UNF) or metric (coarse/fine), diameter, and pitch.
- Flange diameter – confirm O.D. covers slots/oversize holes and fits any recess.
- Surface – serrations require clean metal (avoid use on soft materials or delicate finishes).
- Environment – pick stainless or 316 for corrosion; zinc plated for economical indoor use.
Installation Tips
- Hand-start to prevent cross-threading, then tighten with the correct wrench/socket.
- Seat serrated faces directly on metal—do not place a washer between serrations and the joint surface.
- Follow torque specs for the fastener grade, size, and lubrication condition.
- For stainless-to-stainless assemblies, consider anti-seize per spec to mitigate galling.
Standards & Fit
Serrated flange nuts are produced to common commercial and DIN/ISO specifications with standard internal thread classes (e.g., 2B inch / 6H metric). Verify thread, flange O.D., and height against your drawings or bill of materials before assembly.
FAQs about Serrated Flange Nuts
Use the accordion below for quick answers to sizing, material, installation, and best-practice questions.
They combine a hex nut, a built-in washer, and locking serrations. The flange spreads load; the serrations create prevailing torque to resist loosening from vibration.
They can. The teeth bite into the surface and may mar paint or plating. If finish protection matters, use non-serrated flange nuts or a standard nut with a washer.
Not recommended. A washer isolates the serrations from the joint and defeats the locking action. Serrated faces should seat directly against the mating surface.
Stainless steel is preferred outdoors; 316 stainless is recommended for marine/coastal or chemical exposure. Zinc plated steel is best for dry, sheltered environments.
Match thread system (inch or metric), diameter, and pitch to the bolt or stud. Also confirm the flange outside diameter and nut height fit your design clearances.
Often yes. The serrations provide prevailing torque, so a separate lock washer is typically unnecessary.
They are often reusable, but locking performance can diminish after multiple cycles. Inspect for wear or rounding of serrations and follow your maintenance policy.
Follow the job specification or fastener torque chart for the bolt grade/size and lubrication condition. The serrations add friction—use values specified for your application.
Generally no. The teeth can gouge soft substrates. Use non-serrated flange nuts with appropriate washers or inserts when fastening into softer materials.
Standards differ in dimensions (flange O.D., nut height) and marking. Always match the required standard in your drawings (DIN6923, ISO specs, etc.) before ordering.