Property Class 12.9 Steel Aerospace Two-Lug Floating Self-Locking Nutplates are supplied to ISO 898-1 property class 12.9. Corrosion behaviour is requires plating or black-oxide protection, the material is magnetic, and the usable service range is commonly limited to approx. +300 °C; confirm against the coating and the load. In practice this grade is the highest common strength class, for high-load machine assembly.
- Grade
- ISO 898-1 property class 12.9
- Corrosion resistance
- Requires plating or black-oxide protection
- Magnetic response
- Magnetic
- Service temperature
- commonly limited to approx. +300 °C; confirm against the coating and the load
Property values are typical for the grade. Certified mechanical test data is available on request for production orders.
For aerospace two-lug floating self-locking nutplates in Property Class 12.9 Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for Property Class 12.9 Steel (ISO 898-1 property class 12.9) is summarized below together with every size supplied.
Why Choose Property Class 12.9 Steel for Aerospace Two-Lug Floating Self-Locking Nutplates
The highest common strength class, for high-load machine assembly. For aerospace two-lug floating self-locking nutplates, this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 12.9 |
|---|
| Magnetic response | Magnetic |
|---|
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
|---|
| Corrosion characteristic | Requires plating or black-oxide protection |
|---|
Corrosion Behavior in Service
Carbon and alloy steel aerospace two-lug floating self-locking nutplates require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Galvanic & Galling Considerations
For aerospace two-lug floating self-locking nutplates in steel, the dominant compatibility issue is hydrogen embrittlement at high property classes (10.9 and above) when electroplated. Plating must be followed by an appropriate baking treatment, or a non-electroplated finish (mechanical zinc, zinc flake) should be substituted.
Sizes of Aerospace Two-Lug Floating Self-Locking Nutplates Available in Property Class 12.9 Steel
| Thread size | Overall length A (in) | Width B (in) | Mounting-hole spacing J (in) | Nut height (in) | Material options | Reference standard |
|---|
| 4-40 | 0.948 | 0.416 | 0.688 | 0.175 | cadmium-plated alloy steel or stainless steel | MS21059 and NASM25027 |
| 6-32 | 0.948~1.292 | 0.416~0.680 | 0.688~1.000 | 0.175~0.344 | cadmium-plated alloy steel or stainless steel | MS21059 and NASM25027 |
| 8-32 | 0.948~1.292 | 0.416~0.680 | 0.688~1.000 | 0.175~0.344 | cadmium-plated alloy steel or stainless steel | MS21059 and NASM25027 |
| 10-32 | 0.948~1.292 | 0.416~0.680 | 0.688~1.000 | 0.175~0.344 | cadmium-plated alloy steel or stainless steel | MS21059 and NASM25027 |
| 1/4-28 | 0.948~1.292 | 0.416~0.680 | 0.688~1.000 | 0.175~0.344 | cadmium-plated alloy steel or stainless steel | MS21059 and NASM25027 |
| 5/16-24 | 0.948~1.292 | 0.416~0.680 | 0.688~1.000 | 0.175~0.344 | cadmium-plated alloy steel or stainless steel | MS21059 and NASM25027 |
| 3/8-24 | 0.948~1.292 | 0.416~0.680 | 0.688~1.000 | 0.175~0.344 | cadmium-plated alloy steel or stainless steel | MS21059 and NASM25027 |
Applications & Industries
Where Aerospace Two-Lug Floating Self-Locking Nutplates are used, and what decides the specification in each case. Stocked from 4-40 to 3/8-24 (screw size).
Industries that specify Aerospace Two-Lug Floating Self-Locking Nutplates
-
Aerospace access panels
Two-lug floating nutplates that absorb accumulated panel-hole tolerance.
-
Aircraft interiors
Removable trim and equipment panels with many closely spaced fixings.
-
Avionics enclosures
Self-locking captive threads installed behind a finished panel.
-
Motorsport bodywork
Lightweight panels removed and refitted without losing the nut.
-
Building services
Threaded rod, channel and suspension assemblies.
-
Machine building & OEM
The clamping counter-face on studs and bolts throughout an assembly.
Typical applications
- providing a self-locking thread that floats between two riveted lugs
- absorbing two-axis hole-position variation across a panel
- keeping the nut captive when the screw is removed
- selecting overall length, width, spacing and nut height from MS21059
- joints re-torqued at a service interval
- completing a bolted joint on a stud, rod or bolt
Service conditions to specify against
- Marine and coastal
- Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- High load
- Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
- Vibration
- Specified where cyclic load would loosen a plain nut or screw — rotating plant, rail, mobile equipment and anything that is not re-torqued in service.
- Match the class
- A nut below the bolt property class strips before the bolt reaches its own limit — pair class 8 nuts with 8.8 bolts, class 10 with 10.9.
Where to use something else
- Do not treat the float as permission to ignore the specified rivet-hole spacing or thread engagement.
Full application guide: where Aerospace Two-Lug Floating Self-Locking Nutplates are used, how to specify them, and the cases they are wrong for
