Flange Nuts

What Are Flange Nuts?

Flange nuts are hex nuts with an integrated wide bearing surface at the base that acts like a built-in washer. The flange distributes clamp load over a larger area, speeds installation, and protects the joint surface. Flange nuts are available in serrated and non-serrated styles, in inch and metric threads, and in corrosion-resistant materials and finishes.

Serrated vs. Non-Serrated Flange Nuts

• Serrated flange nuts – locking teeth bite into the mating surface to resist loosening from vibration. Best for permanent assemblies on metal where surface marring is acceptable.
• Non-serrated flange nuts – smooth bearing surface for evenly distributed clamping without surface scoring. Ideal when you want washer-like load spread and easier removal/reuse.

Materials & Finishes

• Stainless steel (18-8 / 304) – general corrosion resistance for indoor/outdoor use.
• 316 stainless steel – enhanced resistance for marine, chemical, or coastal environments.
• Zinc plated steel – economical protection for dry indoor and light outdoor exposure.
• Hot-dip galvanized steel* – heavy zinc layer for rugged exterior/structural applications.

*Availability varies by size/series. Check product grid for current options.

Common Applications for Flange Nuts

• Automotive, powersports, and machinery assemblies subject to vibration
• Sheet-metal fastening where a separate washer is undesirable
• Racking, frames, and structural brackets that benefit from wider load spread
• HVAC, electrical, and MEP support systems
• General fabrication, maintenance, and repair work

How to Select the Right Flange Nut

• Thread system & size – match inch (UNC/UNF) or metric (coarse/fine) plus diameter and pitch.
• Locking need – choose serrated for vibration resistance; non-serrated when surface finish matters.
• Environment – pick the material/finish that meets corrosion and code requirements.
• Bearing diameter – confirm flange O.D. fits the contact area and any pocket/recess.

Installation Tips for Flange Nuts

• Hand-start to avoid cross-threading; tighten with the correct wrench or socket.
• For serrated styles, seat on clean metal; avoid use with separate washers, shims, or soft coatings you don’t want marked.
• Follow project torque specs for the bolt grade/size and lubrication condition.
• Where galling is a risk (stainless-to-stainless), consider compatible anti-seize and follow spec guidance.

Standards & Fit

Flange nuts are produced to common commercial and DIN/ISO specifications with standard internal thread classes (e.g., 2B inch / 6H metric). Always verify thread, flange O.D., and height against drawings before assembly.