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Socket Fasteners for Manufacturers

What are Socket Screws or Socket Fasteners?

Socket screws are a family of externally threaded mechanical fasteners designed with an internal drive recess, most commonly a hexagonal Allen® style drive, that allows installation using a hex key, hex bit, or related driving tool.


Unlike most commercial fasteners that utilize a standard 2A thread fit, socket products are commonly manufactured with a more restrictive 3A thread fit for improved strength, precision, and performance in critical assemblies where close tolerances matter. Their efficient design, compact head styles, and reliable torque transmission make socket fasteners ideal for installations in tight or recessed spaces while maintaining a clean, professional appearance.


Socket fasteners are commonly manufactured to standards including ASME B18.3, ASTM, SAE, DIN/ISO/JIS (metric), with many products available in aerospace and military-grade configurations (AN, MS, NAS). Major domestic manufacturers include Holo-Krome and American Socket.


Check out our Socket Fasteners Buyer's Guide!

Buy Socket Fasteners from MF Supply

Select a product group below to explore available materials and sizes. Our socket family of fasteners includes: Socket Head Cap Screws, Low Head Socket Cap Screws, Flat Head Socket Cap Screws, Button Head Socket Cap Screws, Stripper Bolts (aka Socket Shoulder Screws or Hex Socket Shoulder Bolts), Socket Set Screws, Socket Pipe Plugs, Precision Shoulder Screws, Security Screws and Holo-Krome and American Sockets USA-Made branded sockets products.

Socket Fasteners - Quick Navigation

    1. Why Buy Socket Fasteners from MF Supply?
    2. Socket Fastener Types, Styles, Sizes and Materials Available
    3. How to Choose the Right Socket Fasteners for Your Application
    4. Socket Fasteners Frequently Asked Questions (FAQ)
    5. Cross-Reference Tables
    6. Additional Resources
    7. Why Buy DFARS-Compliant Socket Fasteners From MF Supply vs. a National Distributor?

Why Buy Socket Fasteners from MF Supply?

For over 50 years, MF Supply (RL Supply Inc. dba MF Supply) has helped industrial, aerospace, defense, and precision manufacturers source socket fasteners faster, smarter, and with the documentation their teams require. We supply and source inch, metric, Mil-Spec, DFARS-compliant, USA-made, commercial, and custom socket fasteners from trusted domestic manufacturers, recognized brands, and qualified functional-equivalent sources.

Many buyers already know the part number, print, brand, or specification they need. The bigger challenge is often finding it at the right cost, with a workable lead time, and with documentation that supports purchasing, quality, and audit requirements. MF Supply acts as an extension of your purchasing department, helping you evaluate available socket fastener options without creating unnecessary sourcing delays, wrong-part substitutions, or compliance risk. We help manufacturers keep production moving with:

Mil-Spec, DFARS & USA-Made Support: We support aerospace, defense, and precision manufacturing buyers with Mil-Spec socket fasteners, DFARS-compliant and USA-made sourcing options.

    • OEM Brands & Functional Equivalents: We can help with Holo-Krome, American Sockets, domestic manufacturers, legacy catalog callouts, OEM part numbers, and functional equivalents. When alternatives are appropriate, we focus on matching form, fit, and function based on the part number, print, material, finish, dimensions, thread type, tolerance, head style, drive style, point style, or applicable specification.
    • Compliant & Certified Documentation & Paperwork: Manufacturer Certificates of Conformance (CoC), Material Test Reports (MTRs), DFARS statements, heat/lot traceability, plating certifications, passivation certifications, and related paperwork may be available where applicable. Documentation requirements should be stated at the time of RFQ.
    • Hard-to-Find, Non-Standard & Custom Sourcing: We help buyers source non-stock, backordered, modified, obsolete, special, and custom socket fasteners, including special threads, non-standard dimensions, exotic materials, special finishes, short runs, and parts made to print. If an item is not listed online, our team can help you find it.
    • Domestic & Import Options: Source USA-made socket fasteners alongside approved import options to balance cost, compliance, lead time, and availability requirements.
    • Fast Quotes & Responsive Service: Most RFQs are answered on the same business day by experienced fastener specialists. Providing a part number, print, sample, specification, certification requirement, quantity, and deadline helps our team quote faster and more accurately.
    • Easy Online Search & RFQ Tools: Our website helps buyers filter by size, material, thread, finish, specification, and other attributes. If you cannot find the exact part, quantity, brand, or certification requirement online, submit an RFQ and our sourcing specialists will review it.
    • Support Beyond Order Fulfillment: We support repeat orders, backorders, urgent RFQs, blanket orders, and BOM sourcing.

Need a specific socket fastener, domestic option, DFARS-compliant equivalent, certification package, or hard-to-find part? Send us your part number, print, sample, or specification, and we will help you source the right socket fastener.

Socket Fastener Types, Styles, Sizes and Materials Available

The socket fastener category typically includes inch and metric versions of the fastener categories listed below. Most socket caps come with a standard hexagonal socket drive, often referred to by the trademarked name Allen drive. Other options include six-lobe, the non-trademarked equivalent to Torx. and security/anti-theft specific drives including pin-in-hex and pin-in-Torx. Despite the category name “socket”, certain styles are offered with slotted or other drives.


Socket Head Cap Screws

Socket head cap screws, often called Allen screws, socket cap screws or SHCS, are externally threaded cap screws with a cylindrical, flat-chamfered head and a hexagonal recess for internal wrenching. They are a standard choice for applications requiring high strength, compact head geometry, and internal-drive installation. Their design makes them especially useful where wrench clearance is limited and a strong threaded fastener is needed in a smaller footprint. Common standards include ASME, ASTM (inch), ISO, DIN (Metric), MS, NAS (Mil-Spec), USA & DFARS-compliant options. Standard inch sizes range from 0-80 through 1-1/2-6, while metric sizes range from M2 through M64.


Available Styles

    • Standard Head Socket Cap Screws: They have a cylindrical head with a flat chamfered top and a hexagonal recess. Common standards for socket head cap screws include ASTM A574, F835, DIN912, MS16995, MS16996, MS16997, MS16998, NAS1351, and NAS1352.
    • Button Head Socket Cap Screws: Low-profile rounded head with larger bearing surface and cleaner appearance. For use in materials too thin to countersink (ASTM F835, F879, DIN7380).
    • Flat Head Socket Cap Screws: Countersunk design allowing the head to sit flush with the mounting surface. Countersunk heads at 82 degrees provide maximum flushness and side-wall contact (ASTM F835, F879, DIN7991, MS24671, MS24672).
    • Low Head Socket Cap Screw: Reduced head height for clearance-restricted applications. Use in parts too thin for standard height heads and where clearance is limited (DIN7984).

Shoulder Screws

Hex socket shoulder screws, often called shoulder screws, stripper bolts, or shoulder bolts, are precision fasteners with three distinct sections: a hex socket head, a smooth unthreaded shoulder, and a threaded end. The shoulder usually acts as a shaft, axle, pivot point, guide, or bearing surface for moving components within assemblies. Common standards include ASME, ASTM (inch), ISO, DIN (Metric), MS, NAS (Mil-Spec), USA & DFARS-compliant options. They are available in three categories: commercial, precision, and Mil-Spec.


Available Styles

    • Commercial Shoulder Screws, aka Stripper Bolts or Socket Shoulder Cap Screws: are made to the inch standard ANSI/ASME B18.8.2. The size range for the shoulder diameter is from 1/8 to 2”. Metric sizes range from M4 through M24 and come in a variety of length configurations. The thread class is 3A and the tolerance on the shoulder is +.005 / -.005.
    • Precision Shoulder Screws: are sometimes referred to as “tight tolerance” shoulder screws. They are not governed by any official ANSI or ASME standard. The size range for the shoulder diameter is from 3/32 to ½ (metric sizes vary). The thread class is generally 2A and the tolerance on the shoulder diameter varies from +.000/-.001 to -.0005 to -.0015 depending upon the manufacturer.
    • Mil-Spec Precision Shoulder Screws: are available in hex socket drives (MS51576) and slotted drives (MS51575). Their shoulder diameters range from 1/8" to 1/2" for the MS51575 series, and 4-40 through 3/8-16 for the MS51576 series. Both are available in various length configurations and are made of 300 series stainless steel.

Socket Set Screws

Socket set screws, sometimes called grub screws, are headless threaded fasteners designed with an internal hex socket drive and no protruding head above the surface. Their fully threaded design allows them to secure one component within or against another, making them well suited for holding collars, pulleys, gears, knobs, and other machine components in place on shafts or within assemblies. They are available in multiple point styles depending on holding power and surface engagement requirements. Standards include ASME, ASTM (inch), ISO, DIN (Metric), MS, NAS (Mil-Spec), USA & DFARS-compliant options. Set screws are most commonly available in inch sizes from 2-56 through 1″ diameter and M2 through M24 in metric diameters with a hex socket drive on one end and a cup point on the other.


Available Point Styles

Socket Pipe Plugs

Socket pipe plugs are threaded sealing fasteners with an internal hex socket drive, designed to close tapped pipe openings and ports. Their compact internal-drive design makes installation and removal easier in confined areas where external wrench clearance is limited. Socket pipe plugs are commonly used in hydraulic, pneumatic, fluid-handling, and industrial piping systems where a secure threaded seal is required. They are available in inch sizes from 1/8-27 through 3/4-14 with NPT pipe threads.


Available Styles

    • Flush Seal Type: Features a full-length tapered thread with a 0.875-inch diametral taper per 12 inches, designed to sit flush in a standard tapped hole with a 0.750-inch taper per 12 inches. Both ends are flat and approximately 45° chamfered. Identification grooves distinguish the style, with six grooves standard and three permitted on 1/16-27 plugs. The difference in taper creates a higher sealing load near the large end of the plug, making this design well suited for high-pressure applications where minimal protrusion is required.
    • Dry Seal Type: Features a full-length tapered thread with a 0.750-inch diametral taper per 12 inches and closely controlled root and crest truncation to create metal-to-metal thread contact. This helps prevent spiral leakage and form a positive seal without sealing compounds. Dry seal plugs may be used in American Standard Taper Dryseal Pipe Thread (NPT) tapped holes, but for maximum leak resistance, they should be installed in dryseal tapped holes that are taper reamed before tapping.

Holo-Krome Socket Products

MF Supply also supplies Holo-Krome socket products for customers that require a recognized premium domestic socket fasteners brand for approved-vendor, repeat-buy, or replacement applications. Common Holo-Krome product lines include:

If you are trying to match an existing Holo-Krome part number, branded callout, equivalent, or legacy bill of material, we can help identify the correct family and sourcing option. Send us your RFQ and our sourcing experts will review it ASAP.

American Sockets

MF Supply also supplies American Sockets, a 100% domestically manufactured line of socket fasteners and related precision hardware for customers that require U.S.-made, DFARS-compliant products with manufacturer certifications. Certifications are available to verify the manufacturer, country of origin, and applicable test results. Common American Sockets product lines available include:

American Sockets also serves as a current domestic sourcing option for many applications that previously specified Blue Devil® socket products. If you are trying to source an American Sockets part number, replace a legacy Blue Devil® item, or identify the correct domestic socket fastener for an existing specification or bill of material, send us your RFQ below and our sourcing team can help identify the appropriate product and availability.

Materials and Platings Options

Commercial socket fasteners are commonly stocked in alloy steel and stainless steel , while Mil-Spec socket fasteners are typically available in alloy steel, stainless steel, and A286 stainless steel, depending on the specification.

Standard “steel” socket head cap screws are most often manufactured from heat-treated alloy steel with a black oxide finish and a light oil coating. Stainless steel options commonly include 300-series/18-8, 316, and metric A2 and A4 grades. Specialty materials such as brass, 416 stainless steel, A286 stainless steel, Inconel® 718, nickel-copper alloys, and Monel® may also be available by special order, often with additional lead time.

Additional finishes and platings may be available when greater corrosion resistance, a different appearance, or specific performance characteristics are required. Zinc plating, for example, may be specified as an alternative to black oxide on alloy steel fasteners. When selecting a plated socket fastener, coating thickness should be considered because it can affect thread fit and dimensional tolerances.

How to Choose the Right Socket Fastener for Your Application

Socket fasteners are used across a wide range of industries, including defense, aerospace, industrial manufacturing, and precision manufacturing. Choosing the right socket product starts with understanding how the part will function within the assembly. Socket fasteners are available in several product types, each designed for a specific purpose, from clamping and alignment to shaft retention, spacing, or sealing threaded ports.

1. Standard Socket Head Cap Screw: Ideal for precision assembly work with close tolerances and applications needing a well-tooled appearance. provides greater tensile strength than equivalent sizes of Grade 5 or Grade 8 hex head cap screws while requiring less surface area or counterbore since the fastener is internally wrenched. For general fastening and high-strength assembly, standard socket head cap screws are often the best choice. They provide strong clamping force and are commonly used in machinery, equipment, tooling, and precision assemblies where a secure, recessed-drive fastener is required.

2. Button Head Socket Cap Screw: Ideal for light-duty fastening applications where a wider bearing surface, lower-profile head, and smoother finished appearance are preferred. The domed head is wider and lower than a standard socket head cap screw while using a similar threaded design and internal hex socket drive. Button head socket cap screws are commonly used in machinery, equipment, panels, guards, and assemblies where appearance and reduced head height are important. Because the lower-profile head provides less strength than a standard socket head cap screw, button head screws are best suited for light to moderate fastening applications and are generally not recommended for critical, high-strength joints.

3. Socket Shoulder Screws: Ideal for applications requiring controlled rotation, sliding movement, precision spacing, or accurate alignment. Precision shoulder screws and commercial hex shoulder screws (also called shoulder bolts or stripper bolts) both feature an enlarged, unthreaded cylindrical shoulder beneath the head, but they may differ in dimensional tolerances, available sizes, and intended applications. The smooth shoulder acts as a bearing, pivot, guide, or spacing surface, making these fasteners well suited for pulley shafts, linkages, sliding components, punch-and-die work, fixtures, locating features, and other precision assemblies. Precision shoulder screws are typically selected where tighter dimensional control and more accurate positioning are required, while commercial shoulder bolts are commonly used for general-purpose movement, spacing, and fastening applications.

4. Socket Set Screws: Ideal for shaft-based assemblies where collars, pulleys, gears, knobs, or similar components need to be secured in position without a protruding screw head. Socket set screws are headless fasteners with an internal hex drive and are available in multiple point styles, including cup point, flat point, cone point, dog point, oval point, and knurled cup point. Each point style provides a different balance of holding power, surface contact, penetration, and shaft engagement, making set screws a common choice for machinery, tooling, power transmission components, and precision mechanical assemblies.

5. Socket Pipe Plugs: Ideal for sealing threaded ports and openings in hydraulic, pneumatic, fluid-handling, and mechanical systems. Socket pipe plugs use an internal hex drive and are designed to provide a compact, secure closure where external wrench clearance may be limited. When selecting a socket pipe plug, factors such as thread type, material, pressure rating, corrosion resistance, and sealing performance should be matched to the application. Common configurations include NPT, dry seal, and flush seal pipe plugs for industrial equipment, manifolds, valves, pumps, and other fluid or pressure systems.

6. Material and finish should be selected based on the environment and performance requirements. Stainless steel is commonly used when corrosion resistance is important. Alloy steel is often selected for higher-strength applications. Brass may be used in more specialized applications where conductivity, corrosion resistance, or non-sparking properties are needed. Finish options also matter: zinc plating can provide general corrosion protection, while black oxide is often used for light protection, reduced glare, and appearance.

7. Compatibility is just as important as durability. Buyers should confirm the required thread type, thread pitch, length, diameter, head style, drive style, point style, tolerance, and applicable inch, metric, or Mil-Spec requirements before ordering. Matching the existing system specification helps prevent fit issues, installation problems, and production delays.

For faster sourcing and quoting, provide the part number, print, sample, or specification whenever possible. MF Supply can help identify the right socket product, review functional equivalent options, and source parts that meet your application, material, finish, and documentation requirements.

Popular Socket Fasteners Questions (FAQs)

1. What is a socket fastener?

A socket fastener is a threaded mechanical fastener with an internal drive recess, most commonly a hex or Allen®-style socket. Socket fasteners are commonly used where strength, compact installation, reliable torque transfer, or a clean appearance is required.

2. What are the most common types of socket fasteners?

Common types include socket head cap screws, button head and flat head socket screws, set screws, shoulder screws, socket pipe plugs, and tamper-resistant socket screws. Each style is designed for different strength, clearance, fastening, or assembly requirements.

3. What industries commonly use socket fasteners?

Socket fasteners are widely used in aerospace and defense, precision manufacturing, robotics and automation, medical equipment, hydraulics, electronics, industrial machinery, tool and die, and automotive applications.

4. Are DFARS-compliant socket fasteners available?

Yes. Many socket fasteners are available in DFARS-compliant domestic or qualifying-country materials for aerospace and defense applications requiring specialty metals compliance and traceability documentation.

5. Can you buy inch, metric, and Mil-Spec socket fasteners from one supplier?

Yes. MF Supply stocks and sources inch, metric, commercial, aerospace, and Mil-Spec socket fasteners in a range of product types, materials, sizes, and specifications.

6. Can MF Supply help cross-reference or identify socket fasteners?

Yes. MF Supply can help identify socket fasteners from part numbers, prints, specifications, OEM references, and Mil-Spec callouts, and can also review possible functional equivalents when appropriate.


Cross-reference tables' links:

Resources:

Why Buy DFARS-Compliant Socket Fasteners From MF Supply vs. a National Distributor?

MF Supply (CAGE Code 58QG4) is built for buyers who need more than a box of screws. We help confirm that the socket fasteners customers need meet the required Mil-Spec, material, finish, DFARS, domestic-source, certification, and traceability requirements before the order ships. For qualifying in-stock orders, MF Supply can provide same-day shipment and supporting documentation, subject to order timing and document availability.

When sourcing DFARS-compliant socket fasteners, including mil-spec socket head cap screws, product availability is only part of the requirement. Buyers must also confirm material compliance, documentation, traceability, and delivery timing. MF Supply specializes in Mil-Spec and compliance-driven fastener sourcing, helping aerospace, defense, government, and precision manufacturers obtain the correct parts with the required paperwork.

Unlike a general industrial distributor, MF Supply reviews the buyer’s complete requirements, including the applicable military specification, material, finish, country-of-origin restrictions, certification requirements, and traceability level.


MF Supply vs. a National Distributor

Option Best For Advantages Things to know Shipping
MF Supply In-Stock Mil-Spec Socket Fasteners Buyers requiring fast shipment, compliance review, and order documentation for in-stock, bulk Mil-Spec socket fasteners. Manufacturer’s Certificate of Conformance included with all in-stock Mil-Spec socket fastener orders. Knowledgeable staff available to review DFARS, domestic, Buy American, traceability, and other compliance requirements. Personal, responsive service for aerospace, defense, government, and precision manufacturing supply chains. In-stock Mil-Spec socket fasteners include Manufacturer’s Certificate of Conformance, Material Test Reports, and DFARS statement. Buyers with additional documentation or traceability requirements should confirm those needs at time of order. Same-day shipping may be available for MF Supply stock on orders received before 3:00 PM ET.
MF Supply Sourced & Custom American-Made Socket Fasteners Aerospace, defense, government, and critical OEM buyers requiring DFARS-compliant, Buy American, hard-to-find, backordered, or custom-made socket fasteners not readily available through their regular supply chain. Knowledgeable staff understands complex supply-chain and compliance requirements, including Manufacturer’s Certificates of Conformance, DFARS, lot and heat numbers, plating certifications, physical and chemical test reports, First Article requirements, and full traceability. MF Supply helps identify sourcing options based on the buyer’s technical, documentation, and compliance needs. Availability and documentation vary by part number, manufacturer, lot, and order requirements. Full traceability or custom manufacturing may require factory minimums, longer lead times, and higher costs. Lead time and shipping turnaround depend on the manufacturer or upstream source. MF Supply will advise buyers of available options and expected delivery timing during the quotation process.
National Catalog Distributor Buyers prioritizing quick online ordering of standard commercial hardware, often referred to as COTS, or Mil-Spec hardware requiring basic certification only. Broad catalog, easy online ordering, fast shipment on many standard items, and low minimum order quantities. Compliance documentation, traceability, and DFARS support may vary by product and should be verified before purchase when required. Often optimized for rapid shipment of stocked catalog items; availability and shipment timing depend on the specific product and warehouse location.
Industrial Fastener Distributor Buyers purchasing common commercial fasteners without specialized compliance or documentation requirements. May offer local inventory, account pricing, sourcing assistance, and personalized service. Mil-Spec expertise, DFARS review, documentation completeness, and traceability capabilities can vary significantly by distributor. Compliance documentation, if required, should be confirmed before purchase. Shipping speed varies by distributor, inventory position, and supplier network. Same-day or expedited shipment may be available for stocked items.

Can't find what you're looking for? Email us at [email protected] for a custom quote. "We have the right screw for you" is our motto after all!

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