Understanding NAS and NASM Aircraft Part Numbers
NAS and NASM part numbers are common across aircraft hardware, fasteners, fittings, and aerospace components. This guide explains where these standards came from, how the numbers are structured, what common series can mean, and why each dash number, suffix, and revision must be verified before ordering.
What Do NAS and NASM Mean?
NAS generally refers to National Aerospace Standard. These standards were developed for aerospace parts where consistent dimensions, materials, performance, quality, and interchangeability matter across aircraft programs and suppliers.
NASM is commonly seen when older military standard hardware documents were transferred or converted into aerospace-standard control while preserving much of the legacy part-number structure. Many NASM numbers look similar to older MS numbers because they often continue the same standard family with a new document prefix.
NAS and NASM Numbers Are Document-Specific
There is no universal decoder that works for every NAS or NASM product family. The base number identifies the standard drawing or document, and the dash number or suffix must be interpreted using that specific standard.
- Do not decode NAS bolts using NAS nut, washer, or fitting rules.
- Do not assume an NASM number is identical to an old MS number without checking the current document.
- Verify all dash numbers, suffixes, material codes, finish codes, and configuration details.
- Use approved technical data or the applicable standard before substituting parts.
Why NAS Standards Matter
NAS and NASM standards help the aerospace industry specify precise components for critical assemblies, often where strength, weight, tolerance, vibration, corrosion resistance, or service environment matters.
Aerospace Consistency
Standards help define the same item consistently across manufacturers, distributors, repair stations, and aircraft programs.
Higher Detail Control
NAS standards frequently define close tolerances, strength levels, head styles, materials, finishes, and inspection requirements.
Long-Term Support
Aircraft remain in service for decades, so stable standard numbers help procurement and maintenance teams find controlled replacements.
Legacy Continuity
NASM standards help preserve continuity when older MS or military documents move into newer aerospace-standard systems.
How NAS and NASM Part Numbers Are Usually Built
The exact format depends on the standard. A number may include a base standard, dash code, size code, length code, material option, finish, drilling, locking feature, grip code, or other configuration detail.
NAS / NASM + STANDARD NUMBER + DASH CODE + SUFFIX
This is a concept only. The correct breakdown must be checked against the controlling NAS or NASM standard for that exact part family. Sneaky little dash numbers like to ruin everyone’s day.
Common NAS and NASM Families and Their Uses
These examples are for orientation. They do not replace the controlling standard, aircraft manual, engineering data, or approved substitution record.
NAS Bolts
Many NAS bolt families are used where higher strength, close tolerance, special head style, or controlled grip requirements matter.
- Structural joints and high-load assemblies
- Close-tolerance and shear applications
- Grip, length, material, finish, and drilling must be verified
NAS Screws
NAS screw families can include machine screws, structural screws, countersunk styles, close-tolerance screws, and specialty aerospace configurations.
- Access panels, structures, brackets, and equipment mounting
- Head style and drive style may be encoded
- Thread, length, material, and finish must be confirmed
NAS Washers and Spacers
NAS washer and spacer families may control thickness, inside diameter, outside diameter, hardness, material, or special geometry.
- Load distribution and spacing
- Controlled stack-up and grip adjustment
- Thickness and material can be critical
NAS Nuts and Locking Hardware
NAS and related aerospace standards include nuts, nutplates, inserts, and locking devices used throughout aircraft assemblies.
- Self-locking and fixed-nut applications
- Temperature, material, and locking style vary
- Reuse and torque requirements should be checked
NASM Legacy Fasteners
NASM numbers often appear where older MS standards were converted or maintained under aerospace-standard control.
- May resemble older MS numbers
- Used for bolts, nuts, washers, pins, and related hardware
- Current document status should be verified
NAS Pins, Rivets, and Special Hardware
NAS families can also include pins, rivets, bushings, retainers, clamps, and special-purpose aerospace hardware.
- Control-system and structural applications
- Diameter, grip, head style, and retention method matter
- Substitution requires approved data
NASM and Older MS Numbers
NASM numbers are important because many buyers see both MS and NASM numbers while sourcing the same or related part family. In many cases, the NASM number exists because an older military standard was transferred into a newer standard-management system.
That does not mean every MS-to-NASM reference is automatically acceptable for installation. The current standard, revision, aircraft manual, procurement requirement, and customer quality rules still control what may be purchased and used.
- MS often identifies the older Military Standard number.
- NASM often identifies the current aerospace-managed version of a similar or successor standard.
- The item may look the same, but document revision, scope, material, finish, or qualification rules can matter.
- Use the applicable standard and approved records before treating numbers as interchangeable.
What Each Part of the Number Can Change
A single dash code or suffix may change the physical part, installation fit, strength, material, finish, or acceptance requirements.
| Number Element | What It May Identify | Why It Matters |
|---|---|---|
| NAS / NASM Prefix | The standard system or document-control family. | NAS and NASM are related but not identical labels; the controlling document must be checked. |
| Base Standard Number | Specific drawing or product family such as a bolt, screw, washer, nutplate, pin, or specialty item. | A nearby base number can be a different part family, not just another size. |
| Dash Number | Diameter, length, grip, thread, class, style, size, or other standard-defined option. | The same dash code can mean different things in different NAS families. |
| Material Code | Alloy steel, corrosion-resistant steel, aluminum alloy, titanium, or another permitted material. | Material affects strength, corrosion resistance, weight, compatibility, and temperature capability. |
| Finish Code | Cadmium, passivation, anodizing, dry-film lubricant, primer, or another finish when defined. | Finish can affect corrosion resistance, torque, bonding, and environmental performance. |
| Configuration Suffix | Drilled head, drilled shank, oversize shank, locking feature, countersunk head, or special option. | The configuration must match the assembly design and approved maintenance data. |
NAS Compared with AN and MS
AN, MS, NAS, and NASM numbers all appear in aviation sourcing because aircraft programs and standards evolved over decades.
- AN is tied to the older Army-Navy standard system.
- MS is tied to the Military Standard system.
- NAS is tied to National Aerospace Standards.
- NASM often preserves or continues military-standard hardware under aerospace-standard management.
Why NAS Numbers Are Still Everywhere
NAS hardware remains common because modern and legacy aircraft both rely on controlled aerospace hardware standards for structural, mechanical, and system assemblies.
- Large installed base across civil and military aircraft
- Used in aircraft design, repair, procurement, and maintenance records
- High confidence when sourced with proper documentation and verification
- Useful for cross-reference research when a program lists older numbers
Similar NAS Numbers Are Not Automatically Interchangeable
Two NAS or NASM numbers can look close while representing different size, grip, thread, material, finish, oversize, drilling, head style, or qualification requirements.
- Verify the complete number, including every dash and suffix.
- Check the current standard, revision, and supersession status.
- Review dimensions, material, finish, class, and configuration.
- Do not substitute based on appearance, partial number, or “close enough” catalog logic.
Where NAS and NASM Parts Are Used
- Airframe structural joints
- Close-tolerance bolt installations
- Control-system linkages
- Engine, accessory, and equipment mounting
- Fuel, hydraulic, pneumatic, and environmental systems
- Electrical, avionics, and support assemblies
What to Review Before Ordering
- Complete NAS or NASM number, including all dashes and suffixes
- Current or superseding standard and revision
- Diameter, thread, length, grip, material, finish, and configuration
- Condition, quantity, and unit of sale
- CoC, trace, manufacturer paperwork, or required test records
- Aircraft eligibility and approved substitution data
How to Search for NAS and NASM Parts
Search the complete NAS or NASM part number first. Include all dashes, spaces, leading zeros, and suffix letters exactly as shown in the manual, purchase order, tag, or packaging label.
If the exact search does not return a match, try the number without punctuation, then search the base standard number to find related listings. Treat superseding and cross-reference numbers as research leads until they are verified against the controlling standard and approved aircraft data.
Need Help Identifying a NAS or NASM Part?
Send AVBOX US the complete part number, aircraft application, dimensions, photos, alternate number, superseding number, or documentation requirement you are working through.