The Ultimate Buyer's Guide for Purchasing Friction Bolt

Whether you&#;re directly involved in supplying the military or engaged in related sectors, understanding Mil-Spec fasteners is essential. This guide will equip you with crucial insights into these specialized components, ensuring you make informed decisions in your procurement process.

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Understanding Mil-Spec

Mil-Spec (Military Standard) is a term used to describe the rigorous standards set by the U.S. Department of Defense for manufacturing military equipment.

Fasteners that meet these standards are designated as Mil-Spec fasteners and are identified by specific prefixes such as AN, MS, NAS, or NASM, followed by a part number (e.g., MSC-4).

These prefixes indicate the standards body or specification type, such as NAS for National Aerospace Standard and MS for Military Standard.

Mil-Spec vs. Commercial Fasteners

While they may look similar to commercial fasteners, Mil-Spec fasteners are manufactured to more precise and stringent specifications. 

These define various attributes of the fastener, including dimensions, tensile strength, material qualities, and plating. 

Mil-Spec fasteners are also traceable back to their manufacturers via lot numbers, ensuring they come from government-qualified sources that adhere to the highest quality control standards. 

This level of lot traceability and quality assurance is what sets them apart from standard commercial fasteners.

Some of the stringent specifications for mil-spec fasteners

• Dimensions &#; Mil-Spec fasteners must conform to specific length, diameter, and head shape dimensions to ensure compatibility and functionality across military equipment.
  • Example standard &#; ANSI/ASME B18.2.1 &#; Covers dimensions for square and hex bolts and screws.
• Tensile strength &#; This measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. The tensile strength of fasteners determines their capability to withstand loads and stress.
  • Example standard &#; ASTM F568M &#; Specifies the mechanical properties of carbon and alloy steel externally threaded metric fasteners.
• Material qualities &#; Mil-Spec fasteners are made from materials that must meet specific chemical and physical properties to ensure durability and resistance to corrosion and wear.
  • Example standard &#; SAE AMS &#; Specifies the requirements for a corrosion-resistant steel with high strength up to 600°F.
• Plating &#; The type of plating used on Mil-Spec fasteners is critical for corrosion resistance, enhancing electrical conductivity, and reducing surface friction.
  • Example standard &#; ASTM B633 &#; Provides specifications for electrodeposited coatings of zinc on iron and steel.

Who Needs Mil-Spec Fasteners?

Mil-Spec fasteners are crucial for anyone manufacturing or servicing military equipment. 

They are typically specified in the bill of materials (BOM) for projects requiring high-grade materials that can withstand the demands of military use. 

Common applications include: 

• Aerospace construction
• Naval vessels
• Defense-related machinery

Comparing Standards and Features

To illustrate, let&#;s compare the Mil-Spec MS-C4 &#; a 4-40 x 3/8 Phillips Flat 100-degree machine screw in 300 series stainless steel &#; with a similar commercial screw:

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Mil-Spec Features:

• Manufactured in a QLSM-approved factory
• Made in the USA or another DFARS-compliant country
• Meets specific military procurement specifications
• Undergoes rigorous cleaning, descaling, and passivation
• Subject to detailed inspections and quality assurance processes
• Offers full lot traceability and certifications

Commercial Screw Features:

• Manufactured according to ASME standards
• Thread dimensions conform to ASME specifications

The Mil-Spec fastener not only meets higher quality standards but also includes specific military-grade processes not found in commercial products.

Certification Requirements

For Mil-Spec fasteners, a Certificate of Conformance (COC) is typically required, certifying that the fasteners meet all relevant military specifications and standards. Full certifications, which provide detailed reports on the chemical and physical properties of the materials used, can often be obtained for an additional fee.

Considerations for DFARS Compliance

DFARS (Defense Federal Acquisition Regulation Supplement) compliance is crucial for materials used in military applications. It specifies that the raw materials, like stainless steel or high-grade alloy steels, must be sourced from the United States or other qualifying countries. This compliance ensures that all materials used in the production of Mil-Spec fasteners meet the highest standards for security and performance.

Final Words on Buying Mil-Spec Fasteners

Understanding and procuring the correct Mil-Spec fasteners are crucial for anyone involved in military supply chains or industries requiring high-specification components. By ensuring you are well-informed about these essential components, you can significantly enhance the reliability and performance of your military-related projects.

Nuts and bolts work together with washers to connect work pieces. You may hear the terms nuts and bolts used interchangeably, but a bolt has a very different function than a nut. We&#;ll discuss different types of each piece of hardware, when you&#;d use them and the basics of how each piece functions to join pieces together.

Bolts have a head with a driving surface (typically hexagonal, to fit a wrench or socket/ratchet combination) and a cylindrical shaft that runs through the work pieces you&#;re assembling. The shaft is threaded but often has an unthreaded portion known as the shank or body near the head. The shank reduces the likelihood of the bolt shearing or snapping as the stronger, unthreaded portion carries most of the load. This unthreaded portion can also make it easier and faster to install longer bolts. 

In most assemblies, you&#;ll need a washer &#; a thin, unthreaded piece that fits onto the bolt shaft. Its function is to spread the load of the connection over a greater area or to help prevent the fastener from loosening once installed. 

A nut pulls the work pieces together along the bolt shaft. A nut is threaded like a bolt, but while a bolt has external threads along the shaft, a nut has internal threads. The nut threads fit the threads on the bolt, allowing the nut to spin along the bolt shaft. A nut designed to work with a bolt will have a driving surface like that of the bolt (a hexagonal nut works with a hex-head bolt). 

One typical application for a bolt, washer and nut is to insert a bolt into matching holes on work pieces you&#;re fastening and then tighten the nut. As you tighten the nut, it cinches the pieces together, forcing the washer against one element and pulling the bolt head tightly against the other element. You&#;ll often need two wrenches so you can hold the bolt head in place while tightening the nut. 

Keep in mind that to properly match a nut and washer to a bolt, you need to consider factors such as material, finish, size and thread type.

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