Flange Nuts, Marine Grade
What are marine grade flange nuts? Flange nuts have a wide flange built into the base of the nut, acting as an integrated washer that spreads the clamping load over a larger area and removes the need for a separate washer. Many have a serrated flange that bites the surface to resist loosening. In marine service they come in 316 stainless and metric 316 (A4), keeping the flange corrosion free in salt. AlbanyCountyFasteners.com stocks these in marine materials.
Why a built-in flange helps on marine work
The flange does two jobs a plain nut needs a washer for. It spreads the clamp load over a wider bearing area, protecting softer material and bridging a slightly oversized hole, and it removes a loose component from the assembly, which on a boat or a windy dock means one less thing to drop or fumble during installation. Where the flange is serrated, the teeth bite into the bearing surface as the nut tightens, adding resistance to vibration loosening on top of the load spreading. That combination suits marine hardware that both sits on finished surfaces and shakes in service. The trade with a serrated flange is that it marks the surface, so on a visible finish a plain flange or a flange nut with a washer suits better. In 316 the flange, the part in closest contact with the surface, does not corrode and streak the joint.
Why choose marine flange nuts
- Built-in flange spreads load like an integrated washer
- Removes a separate washer from the assembly
- Serrated flange versions bite to resist loosening
- 316 stainless keeps the flange corrosion free in salt
- Metric 316 (A4) option for metric assemblies
Common applications
- Marine hardware on finished surfaces
- Joints needing load spread without a separate washer
- Vibrating connections (serrated flange)
- Brackets and fittings on soft or thin material
- Metric marine equipment (A4)
- Any clamped joint in salt where a washer would otherwise be needed
Marine Flange Nut FAQs
Do I still need a washer with a flange nut?
Usually not, since the flange acts as an integrated washer spreading the load. On very soft material or a large hole you may still add one, but for most joints the flange replaces the separate washer.
What does a serrated flange do?
Its teeth bite into the bearing surface as the nut tightens, resisting rotation and helping prevent vibration loosening. It adds a locking action on top of the load spreading.
Will a serrated flange mark the surface?
Yes, the teeth deliberately bite and leave marks, which is how they lock. On a visible or finished surface, use a non-serrated flange nut or add a washer to protect the face.
Why 316 for a flange nut?
The flange is in close contact with the surface, where a corroding nut streaks and weakens the joint fastest. 316 resists salt so the flange stays sound and the bearing surface protected.
Is the metric option the same grade?
Yes, metric flange nuts are 316-equivalent A4 stainless, matching the inch 316 corrosion resistance. Only the sizing standard differs.
Can a serrated flange nut be reused?
The teeth dull and the locking action weakens with reuse, so for a reliable lock fit new. A plain flange nut reuses more readily since it does not rely on biting teeth.