NASM25027 — Self-Locking Nut, 250°F / 450°F / 800°F
NASM25027 covers self-locking nuts qualified for sustained service at 250°F, 450°F, or 800°F depending on material. Adopted by the Department of Defense on December 14, 1999, it directly supersedes the earlier MIL-N-25027 and MIL-DTL-25027 military specifications.
At a Glance
Overview
NASM25027 sets the requirements for self-locking nuts intended to resist loosening under vibration without a separate locking device such as a cotter pin. It replaced MIL-N-25027 and MIL-DTL-25027 as part of the broader 1990s effort to convert military nut and bolt specifications into industry-maintained NASM ("NAS/Military") documents.
The temperature rating a given nut can carry depends on its base material: copper-base alloy, aluminum alloy, and nickel-copper alloy nuts are rated to 250°F; non-corrosion-resistant steel to 250°F or 450°F; and corrosion resistant steel to 250°F, 450°F, or 800°F. Coatings, lubricants, or non-metallic locking elements can lower the effective temperature limit below the base-material rating.
- Qualification testing is based on a 15-cycle install/removal reusability test.
- Two torque values govern acceptance: a maximum torque that must never be exceeded through all 15 cycles, and a minimum breakaway torque that must still be met on the 15th removal.
- Noncorrosion-resistant steel nuts heat treated to 36 HRC or greater, in thread sizes 0.164"-32 and above, are limited to 0.050% sulfur or phosphorus content by weight.
- Manufacturers must maintain a certified test report on file showing conformance to the qualification requirements.
Temperature Rating by Material
Select a base material to see its rated service temperature under NASM25027.
Material Temperature Ratings
| Material | Max Rated Temperature |
|---|---|
| Copper-Base Alloy | 250°F |
| Aluminum Alloy | 250°F |
| Non-Corrosion-Resistant Steel | 250°F or 450°F |
| Corrosion-Resistant Steel | 250°F, 450°F, or 800°F |
| Nickel-Copper Alloy | 250°F |
NASM25027 is the direct successor to MIL-N-25027 and MIL-DTL-25027. It is also referenced by related nut standards including NASM21052 (plate nuts) and NAS1727 (self-aligning nuts) — confirm which downstream document governs your specific nut configuration.
Manufacturing & Quality Notes
A new mating screw is used for every reusability test, with the same screw/nut pair carried through all 15 cycles.
Test screws must match the material of the nut under test — steel screws for steel nuts, stainless for stainless, aluminum for aluminum.
Products previously qualified through certified government qualification tests and reports are considered qualified to this specification without retesting.
Coatings, lubricants, and non-metallic locking elements can reduce the effective service temperature or reusability cycle count below the base-material rating.
NASM25027 — Frequently Asked Questions
Is NASM25027 the same as MIL-N-25027?
NASM25027 is the direct successor document. It was adopted by the DoD on December 14, 1999, superseding both MIL-N-25027 and MIL-DTL-25027 Revision H, Amendment 1. Products qualified under the older military specs can be considered qualified under NASM25027.
How many times can an NASM25027 nut be reused?
The standard qualification test is a 15-cycle install/removal reusability test, though certain material and lubricant combinations are limited to fewer cycles per the applicable footnotes in the specification.
What determines the temperature rating of a specific nut?
Base material sets the ceiling: copper, aluminum, and nickel-copper alloys top out at 250°F; steel can reach 250°F or 450°F; corrosion-resistant steel can reach up to 800°F. Coatings and lubricants may lower the practical limit.
Need NASM25027 Self-Locking Nuts to Print?
Ananka Fasteners manufactures NASM25027 self-locking nuts with full material traceability and Mill Test Certification on every lot.
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