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.