Mil-Spec Explained

Mil-Spec Department of Defense

A common phrase you might come across when searching for fasteners is “Mil-Spec”. While seemingly simple at face value, Mil-Spec is an all-encompassing term used to describe a massive set of specifications, standards, and procedures that make up the US Government’s expectations for military-grade hardware. Here we will help break down the elements that you’ll need to be familiar with when seeking out Mil-Spec fasteners.

By Definition

The term Mil-Spec is shorthand for Military Specification, a broad term that describes a component to be compliant with the US Department of Defense standards of sourcing, fabrication, material, quality, and supply. Fasteners and hardware that fall under Mil-Spec are intended for use in military applications, as well as for use in tangential industries or services that support military interests. Our DoD wants to see the same level of Mil-Spec quality and reliability used everywhere in the defense chain where failures might risk lives or wellbeing.

Agency Distinctions

Perhaps in the future, all military specifications will be consolidated into a single category. Unfortunately, we’re not there yet! Many separate agencies under the DoD have a separate and unique series of specifications. Half of the battle in specifying into the defense chain is knowing which agency spec you’re to comply with, or to cross reference against. Some agencies have their own unique nomenclature for their specs, while others will refer to existing specs written by external technical organizations.
Generally speaking, a military specification reference number takes the form of an agency abbreviation followed by a spec number. For example, “MS35202” is a Military Standard used across multiple agencies, and describes flat countersunk head, aluminum alloy machine screws.
Likewise, “AN3C” is specific to the Department of Air Force and Navy, and describes corrosion-resistant steel, hex cap bolts.

Example Military Spec Abbreviations:

  • AN – Department of Air Force and Navy
  • FF – Federal Specification
  • GSA – General Services Administration
  • MIL – Military Specification
  • MS – Military Standard
  • NAS – National Aerospace Standard
  • NSN – National Stock Number

Example External Organization Abbreviations:

  • ANSI – American National Standards Institute
  • ASME – American Society of Mechanical Engineers
  • ASTM – American Society for Testing and Materials
  • BA – Boeing Standard
  • SAE – Society of Automotive Engineers

A great resource for looking up military specifications, Every Spec, is found here.

Scope of Specification

A typical commercial fastener only has a few details governed by technical specifications, and would only be evaluated for quality in these few areas. A Mil-Spec fastener instead has considerably more details governed by specifications, making the quality requirements on that fastener exponentially higher than their commercial counterpart.

Here are a few examples of additional requirements outlined by Mil-Specs that go above and beyond normal commercial fasteners:

  • Manufacturing of the fastener occurs in an approved and audited facility, typically located within the US or in a partnering country
  • Materials used in fabrication are sourced from approved suppliers
  • Preparation of the materials, cleaning, and any post-fabrication treatment such as passivating, are all performed per approved procedures
  • Quality testing is performed on multiple properties of the fastener, such as hardness, thread dimensions, stamps or markings applied, and finish characteristics
  • The entire lifecycle of the fastener is documented, from raw material sourcing through delivery to the purchaser
  • Not only are the fastener’s fabrication processes governed by written specifications, but the manufacturing plant’s operations themselves are governed by quality programs such as ISO 9001

As a leading distributor of Mil-Spec fasteners and hardware, E&T Fasteners is extremely well versed in the documentation and compliance requirements expected by the Department of Defense and its suppliers. We can help you select and specify Mil-Spec fasteners for your missions, as well as cross-reference between agencies to assure compliance. See more about our Mil-Spec fastener offerings here.

Material Sourcing and More Information

Another important detail involved when selecting Mil-Spec fasteners is material sourcing. DFARS, or Defense Federal Acquisition Regulation Supplement, is a regulation set that outlines sourcing for specialty materials used in defense chain and related Federal initiatives. DFARS intends to protect US interests from shortages or strategic concerns of specialty materials, such as titanium, tungsten, unique steel alloys, and other exotic alloys. It is important to confirm if your Mil-Spec project includes DFARS requirements. Full DFARS information can be found here: https://www.acquisition.gov/dfars.

To look-up a direct military specification number and to find a history of documents pertaining to that spec (such as cancellations, revisions, or supplemental instructions), the Defense Standardization Program’s Assist site is quite helpful, found here https://quicksearch.dla.mil/qsSearch.aspx.

Full Mil-Spec part catalogs can be found on the Defense Logistics Agency website here https://www.dla.mil/TroopSupport/IndustrialHardware/.

Helping you find detailed information for your Mil-Spec application is our specialty! Speak with an E&T sales representative for more information, stock availability, pricing, and more.

About E&T

With sales and support teams spanning the Continental US, E&T Fasteners is here to serve your hardware, fastening, and component needs both domestically and internationally. We are a stocking distributor of metallic, plastic, and exotic alloy fasteners, backed by our technical staff directly experienced in your unique applications. We can assist your specifying and selection efforts, providing engineered solutions, record-fast lead times, and stellar customer service from quote through delivery. Please let us know how we can help!