MIL-N-25027 Self-Locking Nuts — 250°F / 450°F / 800°F (Legacy)
The legacy specification for MIL-N-25027 self-locking nuts covered the original military requirements for high-temperature fastening applications rated to 250°F, 450°F, or 800°F depending on base material. Through its final revision, MIL-N-25027G, it was superseded by MIL-DTL-25027, which was itself later superseded by NASM25027 — the specification's active governing document for these Federal Specification fasteners today.
At a Glance
MIL-N-25027 Self-Locking Nuts Overview
The original MIL-N-25027 legacy military specification governed the production and quality assurance of high-performance self-locking nuts. It laid the foundation for defining acceptable base materials for three distinct temperature classes. Fasteners milled from copper-base and aluminum alloys with non-metallic inserts were strictly limited to 250°F, while non-corrosion-resistant steel reached 450°F, and all-metal corrosion resistant steel (CRES) components were capable of reaching 800°F continuous service.
The specification systematically went through revisions lettered A through MIL-N-25027G before the Department of Defense converted it to the "DTL" detail-specification format as MIL-DTL-25027. That document was in turn officially superseded on December 14, 1999, by NASM25027. This pivotal transition transferred the active maintenance of the standard to the Aerospace Industries Association's NAS/Military document family, where it remains closely governed today.
A highly specified companion sheet, MIL-N-25027/1, covered a nickel-copper alloy (Monel) plate-nut variant specifically used in marine hardware. That companion sheet has since been superseded by the MIL-DTL-32258 standard.
Performance Criteria and Torque Testing
To qualify under the original MIL-N-25027 parameters, these locking nuts underwent severe mechanical testing. Standard testing required the nut to exhibit specific prevailing torque resistance—meaning it must resist being backed off the bolt threads without the use of a wrench, ensuring it will not unthread during severe vibration in aircraft or heavy machinery. Modern equivalents must still pass rigorous vibration simulation, axial tensile strength tests, and high-temperature baking to ensure the locking mechanisms do not fail. For historical data or to verify current active standards, engineers rely on the Defense Logistics Agency (DLA) ASSIST portal.
Full Specification Lineage
| Document | Status |
|---|---|
| MIL-N-25027 (through Rev. G) | Superseded by MIL-DTL-25027 |
| MIL-DTL-25027 (Rev. H, 1997) | Superseded by NASM25027 |
| NASM25027 (1999–present) | Active, current governing document |
| MIL-N-25027/1 (Monel plate nut sheet) | Superseded by MIL-DTL-32258 |
MIL-N-25027 is superseded. Current and future procurement should reference NASM25027. If your drawing specifically references the Monel plate-nut sheet MIL-N-25027/1, the applicable current document is MIL-DTL-32258.
Frequently Asked Questions
What's the relationship between MIL-N-25027, MIL-DTL-25027, and NASM25027?
They form a single lineage of regulatory governance: MIL-N-25027 was the original specification, MIL-DTL-25027 was its "DTL"-format successor, and NASM25027 is the current active document after maintenance transferred to the Aerospace Industries Association in 1999.
What was MIL-N-25027/1?
It was a companion sheet specification within the overarching MIL-N-25027 family, detailing a nickel-copper alloy (Monel) plate-nut variant. It has since been directly superseded by MIL-DTL-32258.
Need Self-Locking Nuts to NASM25027?
Ananka Fasteners manufactures current NASM25027 self-locking nuts with full material traceability and Mill Test Certification.
Prefer email? sales@anankafasteners.com
