Socket head cap screw strength - Eng-Tips

18 Aug.,2025

 

Socket head cap screw strength - Eng-Tips

I have an application in development that uses 1.375-12 socket head cap screws. The calculated maximum load for the beast puts a stress of about 119 ksi on each one of these. (The estimated load may be high, I plan to strain gauge the beast and find out what the real load is.) Since nominal yield of a grade 8 is 120 ksi, I've been trying to research high-strength bolts. I've come across a couple of places now that seem to be saying that SHCS's are normally higher strength than grade 8. I'm getting confused.

This is a really critical application, and this bolted assembly is one of the most critical parts of it. Of course, we're going to prototype and test the beast very thoroughly, but I want to be testing my other components without the distraction of these bolts turning out to be the weak link.

So is it true that these SHCS's are already high-strength? Anyone have definite data on the strength? Do I need to specify a certain type?

I'm also going to have to make some custom shoulder screws that will go in some of the same holes and see the same loading. I'm thinking 17-4PH looks good for those, does anyone have any rocks to throw at that idea? Thanks for the references, TVP, that's exactly what I needed. The BOM (which I recently inherited) called the screw out as a grade 8, which was throwing me off. I'll make sure to specify ASTM A574 so I'll know what I'm getting.

What was bothering me was that, although the ultimate strength for grade 8 is 150 ksi, its yield is 120 ksi and I'm just a sneeze away from that. Am I wrong thinking if it yields, it's failed? Won't it at least be losing some of the preload?

The shoulder bolt is a custom design; the diameter and height of the cylindrical body are very specific, and the head is truncated to just enough to hold a spring down. The internal hex goes down inside the body of the bolt. (The original design was a SHCS through a sleeve, but I had to put in a taller spring and ran out of headroom.) But the same ASTM A574 material makes sense for these too. No need to get unduly exotic.

Thanks again, you've been very helpful. Thanks to all for the thoughtful inputs.

As engineers, we always have constraints, and they usually preclude doing what we would ideally choose. If I had my druthers, I'd use more bolts or bigger ones or both. But I've got space constraints, and I've got the available space packed full of the biggest bolts that will fit. The only variable left to work with is the strength of the bolts.

On the tightening method, I'm just being realistic. I can specify how this gets put together initially, but out in the field they're going to use whatever tools they have.

I could use load-indicating bolts to verify the preload, but in operation this is all inside a heavy steel housing. Directly measuring the load on the bolts in operation will not be practical.

If it turns out the maximum load is significantly less than the theoretical, I'll have a lot less to be concerned about. And I have very good places to strain gage the whole unit and a very good strain gauge guy to set that up. I can effectively make the whole thing a big load cell, and calibrate it with well-quantified known loads. I will know with high confidence what my loading is before the total design is finalized.

Ultimately there will be extensive testing of the final product as specified by industry standards, and additional tests for our own comfort. Horstr1,

My misspent youth was 25 years in the bolting service and tooling business. I have seen several applications similar in concept to what I think you are proposing. At the very least, I would suggest that you specify for field installation and maintenance the following:

1. Use hardened washers under the head of your SHCS's to reduce friction and increase bearing area (make sure there is no more than 0.63" clearance in the hole),

2. Ensure that the SHCS does not bottom out in a tapped hole,

3. Service dependent, specify the best lubricant you can use, but because these are 12UNF threads, too much can be a detriment,

4. If nothing else, specify that a calibrated torque tool - manual, pneumatic, hydraulic, or electric be used, and that some means of limiting tool-induced angularity/side loads is employed.

5. Make yourself a test block, with umpty whatever 1.375-12 tapped holes, and use this to develop your installation procedures/torque values.

hope this rambling helps. good luck

Socket Head Cap Screw | mfsupplyblog - MF Supply's

Domestic Socket Products at www.mfsupply.com!

Greetings to our precision manufacturing community!

For more information, please visit Hebei Bentley Technology.

We are reaching out with an important announcement regarding our domestic sockets product lines. As we continuously strive to bring you the best in quality and service, we want to inform you of a significant change in our offerings.

Firstly, we want to address a key change: the Blue Devil® brand, a name many of you have come to trust and rely on for your domestic socket products needs, will no longer be produced. This marks the end of an era, but also the beginning of an exciting new chapter.

We are thrilled to introduce American Sockets – a new brand of domestic socket products! This transition is more than just a change in name; it’s a reaffirmation of our continued commitment to quality and excellence.

  • Continuity in Quality and Manufacturing: While the brand name changes, what remains constant is the quality of the products. American Sockets are manufactured by the same esteemed US manufacturers that produced the majority of the Blue Devil products. This ensures that the products you’ve trusted for years will continue to be of the same high standards.
  • Seamless Transition: We understand the importance of consistency in your operations. Rest assured, that this transition from Blue Devil to American Sockets will be seamless, with no compromise in the product quality or variety that you have come to expect.

MF Supply is a WBE/WOSB woman owned business, and leading supplier of Domestic Socket Products including major OEM brands, such as American Sockets, and brand equivalents, in various sizes and materials. We offer options when it comes to made in the USA, DFAR compliant Socket Products. Many of our products are available with Certificate of Conformance and full certifications available upon request.

Here are links to the American Socket brand of Inch Domestic Socket Product Lines:

  • Socket Head Cap Screws
  • Button Head Cap Screws
  • Flat Head Cap Screws
  • Low Head Socket Cap Screws
  • Socket Set Screws, Cup Point
  • Socket Set Screws, Oval Point
  • Socket Set Screws, Cone Point
  • Socket Set Screws, Half Dog Point
  • Socket Set Screws, Flat Point
  • Precision Dowel Pins, Bright & Ebony

Here are links to the American Socket brand Metric Domestic Socket Product Lines:

  • Socket Head Cap Screws
  • Flat Head Cap Screws
  • Button Head Cap Screws
  • Low Head Socket Cap Screws
  • Socket Set Screws, Cup Point

In addition to American Sockets brand Socket Products, we offer a vast choice of socket products, including Mil-Spec, OEM branded, standards and custom made specials. To search for what you need, use our Search bar, then filter by size, material, specification, or other qualities you are seeking. Alternatively, you can check out these handy links to view by category:

  • Socket Products | MF Supply
  • Holo-Krome® | MF Supply
  • Mil-Spec Socket Head Cap Screws | MF Supply
  • Leading supplier of mil-spec Socket set screws to precision manufacturers. Request a Quote Today. (mfsupply.com)

Do you still have questions or would like to speak with a representative? Reach out to us, and our MF Supply team of sourcing experts will help you find what you’re looking for. “Finding the right screw for you” is our tag line after all!

Book a one-on-one consultation with our President, Robin, to discuss how MF Supply can help you solve your Industrial Sourcing, Fastener, and Safety concerns.

Six Reasons To Buy From MF Supply

  • Full eCommerce Enabled Website With Technical Manual Available 24/7 – Visit our website and Create a New Account, track online orders, browse our product catalog, check technical specs, subscribe to our blog, or buy online.  We are adding items and improving functionality daily!
  • Same Day Shipping From The USA – Our hardware products are in stock and ship to you directly from our USA based distribution centers.
  • Functional Equivalents To Expensive Brand Names- We stock and source alternatives to brand name fasteners, reducing long lead times and saving you money.
  • Creatively Solve Problems – We are sourcing experts and specialize in hard to find parts. We offer custom manufacturing and reworking solutions at competitive pricing, reducing long deliveries.
  • One-Stop Shopping On Certified Hardware – We stock and source a full line of fasteners including Mil-Spec, DFARS compliant and other industrial products.
  • WBE/WOSB Woman Owned Certified Small Business – To meet your diversity & set-aside needs.

MF Supply is a WBE/WOSB certified supply chain partner to business, industry and government.  We are sourcing experts and stocking distributors of Hardware, Precision & Mil-Spec Fasteners and Safety supplies.  For more than 50 years, we have been supplying manufacturers in the electronics, industrial, commercial, aerospace and military markets with the full range of fastener products and services.  Our Cage Code is 58QG4 and our registered name is RL Supply Inc dba MF Supply. 

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MF Supply Expands Online Product Catalog to 22,189 Unique Items and Counting!

Greetings to our precision manufacturing community!

MF Supply is a leading WOSB / WBE Certified distributor of commercial, mil-spec and custom made fasteners. With a legacy of over half a century and a reputation for continuously evolving to meet our customers’ needs, we are thrilled to announce the recent expansion of our online catalog to include a whopping 22,189 unique items! Our updated catalog now includes Holo-Krome branded products, non-standard, domestic and DFAR Socket Cap Screws, an extensive list of Bolts, and more Thread Rolling & Thread Forming Screws.

We are constantly evolving to meet the changing needs of manufacturers. With this strategic expansion, we underscore our commitment to as a comprehensive one-stop shop for commercial and mil-spec fasteners and hardware for industrial and precision manufacturers, ensuring our customers have a seamless and efficient purchasing experience online and offline.

New Product Highlights:

1. Socket Cap Screws:  We have always stocked and sourced a variety of imported, domestic and mil-spec socket cap screws. Our recent expansion in this category include standard and nonstandard sizes, and a variety of standard and exotic materials. We are now offering more Button Head, Flat Head, Flat Head 100 degree, Low Head and Standard Socket head cap screws in a wider choice of materials including: A286, Brass, Inconel, Silicon Bronze, and 316 Stainless Steel, in addition to regular Alloy and 18-8 Stainless Steel. 

2. Bolts: Our selection of bolts has undergone a significant enhancement and now includes 18 Bolt categories, in multiple sizes and materials. Materials offered include Steel, B7 Alloy, Stainless Steel, 316 Stainless Steel, Aluminum, Silicon Bronze, A2, A4, Brass, Inconel and Nickel-Copper. Our 18 bolts’ categories include:

  • Bent Anchor Bolts
  • Carriage Bolts
  • Closed Eye Screws
  • Elevator Bolts
  • Flange Bolts
  • Hanger Bolts
  • Heavy Hex Bolts
  • Heavy Hex Structural Bolts
  • Hex & Square Machine Bolts
  • Hex Head Cap Screw
  • Hex Head Joint Draw Bolts
  • Hex Tap Bolts
  • Open Eye Bolts
  • Plow Bolts
  • Square Head Battery Bolts
  • Step Bolts
  • Timber Bolts
  • Track Bolts

3. Holo-Krome Products: We are proud to announce the inclusion of Holo-Krome brand fasteners to our catalog. Holo-Krome, a reputable domestic OEM, is well known for their extensive offering of quality products within the Socket Products segment. We introduce the following Holo-Krome products that are now available for purchase directly in our website: Dowel Pins, Hex Socket Shoulder Screws, Socket Cap Screws, Allenuts, Socket Jam Screws, Socket Pressure Plugs, and Socket Set Screws. 

4. Thread Rolling / Thread Forming Screws: We also expanded our online offering to now include over 2.7K alternatives to Plastite® & Taptite® Screws. Our recent expansion in this category include more Steel, Black Oxide and Stainless Steel screws. Our off the shelf products are ready to ship from multiple warehouses across the USA, and include:

  • EJOT® PT®-Alternative, Metric
  • Plas-Fix®45 and Plastite®-Alternate, Metric
  • Plastite®-Alternative, Inch Sizes
  • Taptite®-Alternative, Inch Sizes
  • Taptite®-Alternative, Metric Sizes

By bolstering our product offering in these key areas, we aim to be the preferred supplier for manufacturers in various sectors, including: aerospace, OEMS of instrumentation, equipment and machines, architectural metal and glass, sheet metal fabrication, contract manufacturers, lighting, furniture, and elevators.

Manufacturers working with us can expect timely deliveries, competitive pricing, and access to expert guidance to help optimize their fastener choices. Manufacturers eager to explore our product catalog, including our recently expanded product categories, are encouraged to visit our website at www.mfsupply.com, reach out to us at or request a quote. Our MF Supply team of sourcing experts will help find what you need. “Finding the right screw for you” is our tag line after all!

“At MF Supply, we understand the dynamic needs of the manufacturing industry, including the balance of price, quality, availability and certification paperwork. The expansion of our product catalog demonstrates our commitment to being a one-stop solution for all fastener needs. Whether it’s standard fasteners, specialized custom hardware, mil-spec parts or OEM brand names like the trusted Holo-Krome brand, we have it all under one roof.” – Robin Lieberman, President of MF Supply.

Book a one-on-one consultation with our President, Robin, to discuss how MF Supply can help you solve your Industrial Sourcing, Fastener, and Safety concerns.

Six Reasons To Buy From MF Supply

  • Full eCommerce Enabled Website With Technical Manual Available 24/7 – Visit our website and Create a New Account, track online orders, browse our product catalog, check technical specs, subscribe to our blog, or buy online.  We are adding items and improving functionality daily!
  • Same Day Shipping From The USA – Our hardware products are in stock and ship to you directly from our USA based distribution centers.
  • Functional Equivalents To Expensive Brand Names- We stock and source alternatives to brand name fasteners, reducing long lead times and saving you money.
  • Creatively Solve Problems – We are sourcing experts, offer competitive pricing and specialize in finding hard to find parts and reducing long deliveries.
  • One-Stop Shopping On Certified Hardware – We stock and source a full line of fasteners including Mil-Spec, DFARS compliant and other industrial products.
  • WBE/WOSB Woman Owned Certified Small Business – To meet your diversity & set-aside needs.

MF Supply is a WBE/WOSB certified supply chain partner to business, industry and government.  We are sourcing experts and stocking distributors of Hardware, Precision & Mil-Spec Fasteners and Safety supplies.  For more than 50 years, we have been supplying manufacturers in the electronics, industrial, commercial, aerospace and military markets with the full range of fastener products and services.  Our Cage Code is 58QG4 and our registered name is RL Supply Inc dba MF Supply. 

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Mil-Spec Socket Caps for Sale

MF Supply is your one-stop-shop for all of the high-quality hardware you need! In today’s blog, we are discussing our mil-spec socket cap options.

What is a Socket Cap?

A socket cap is the standard among high strength fasteners that are needed to withstand the faster speeds and higher pressure of today’s machines, instruments, and assemblies. They’re also known as their trademarked name, Allan Screws, and they’re used across various applications.

MF Supply Mil-Spec Socket Caps

  • NASC & NASC STAINLESS STEEL SOCKET HEAD CAP SCREWS
  • MS ALLOY STEEL SOCKET HEAD CAP SCREWS
  • NASN & NASN A286 STAINLESS SOCKET HEAD CAP SCREWS

Stainless Steel Socket Head Cap Screws

Our stainless steel socket caps come in both coarse and fine thread.

MS is our fine thread socket cap. Click here for more information!

MS is our coarse thread socket cap. Click here for more information!

Alloy Steel Socket Head Cap Screw

MS Alloy Steel Socket Head Cap Screws come in zinc yellow or with a clad plating. Click here for sizes and more information!

A286 Stainless Socket Head Cap Screws

NASN is our fine thread option. Click here for more details!

NASN is our coarse thread option. Click here for more details!

For more information, please visit Hexagon Socket Head Screw.

Why Choose MF Supply for Mil-Spec Socket Caps?

All of our mil-specs socket head cap screws come with full paperwork and are all DFAR compliant. Many of them are available from drop-ship directly from the factory with no lead time and next day delivery!

Learn More About Mil-Spec Socket Caps

If you are looking for high-quality mil-spec socket cap screws with quick delivery, contact us at MF Supply today!

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Socket Head Cap Screw Buyer’s Guide

7 Things to Know When Buying Socket Head Cap Screws

Socket head cap screws or socket caps, have become the standard among high-strength fasteners needed to withstand the faster speeds and higher pressure of today’s machines, instruments and assemblies.

Also known as their trademarked name, “Allen” screws, these fasteners are broadly used across various applications in many industries, including: aerospace, electrical motors, hydraulic equipment, instrumentation, tooling and fixtures, machinery, military and many more. Common uses include machine parts, die fixtures and assemblies.

1. What is a Socket Head Cap Screw? 

Socket caps are externally threaded cap screws with a cylindrical head with a flat chamfered top and a hexagonal recess for internal wrenching. Hence, socket caps need less space than alternative fasteners.

Whereas nearly 90% of all commercial and industrial fasteners have a 2A fit, which offers a combination of performance, economy, and convenience, socket products generally have a 3A thread fit. 3A threads have restrictive tolerances often used where safety is a critical design consideration.

Because of their efficient design and thread fit, socket cap screws are ideal for precision assembly work with close tolerances and applications that need a well-tooled appearance.

2. What sizes are available?

Commercial socket caps, which conform to ASME B18.3, are available off the shelf in inch sizes starting as small as 0-80 diameter and are commonly available to diameter 1-1/2-6. Metric socket caps, which conform to DIN 912, are available from M1.4 – M48 diameter and are most common in coarse thread. Screw lengths and thread lengths are related to the diameter of the screws and all lengths may not be available in all materials and styles.

3. What materials and platings are available?

“Steel” socket caps off the shelf are alloy steel black oxide through heat treatment and are generally oiled. Stainless steel grades 18-8/303, A2, 316 and A4 are also commonly available. Other exotic materials such as brass, 416, A286 or special finishes may be available for special order with a lead time.

If you need an alloy steel fastener, but require greater corrosion resistance or a different look than black, consider stainless steel or zinc plating.

4. Are there special considerations when plating socket head cap screws?

We are so glad that you asked! If you are considering zinc plated socket caps, proceed with caution! Because of their tight tolerances and 3A fit, zinc plating a socket cap will often change the thread fit to a commercial nut fit. If you need a 3A fit, you must specify that on your purchase order so the factory can meet your thread fit needs when creating and plating your screws.

5. Other than size, material and plating, what other options are available?

The other main considerations when selecting socket caps are the head style and the drive type.

There are four main available head styles, and each serves a slightly different purpose.

  • Standard Head – The standard in socket head cap screws (ASTM A574, F835, DIN912)
  • Low Head – Use in parts too thin for standard height heads and where clearance is limited (DIN)
  • Flat Head– Countersunk heads at 82 degrees provide maximum flushness and side wall contact (ASTM F835, F879, DIN)
  • Button Head – For use in materials too thin to countersink (ASTM F835, F879, DIN)

Most socket caps come with a standard hexagonal socket drive. Other options include security pin-in-hex, pin-in-torx, or six-lobe torx versions in certain sizes and materials.

6. Are there other factors to consider?

We’ve covered the most common variables including head style, diameter and thread, length, material and plating or finish. Here are a few of the other considerations you might be faced with based on the project and the bill of materials:

  • Do you need domestic parts or will imported screws work?
  • Do you require parts that conform to a specific mil-spec number, such as MS, MS, NAS and NAS with their exacting tolerances and traceability, or will standard commercial parts work?
  • Does your bill of materials calls out a specific manufacturer, such as Holo-krome or Blue Devil?

7. What level of certification is required?

Generally, a Certificate of Conformance or a COC is sufficient for your customer. Full certification with material certs, DFARS certification and test reports are often available for USA-made and mil-spec parts for a fee.

Socket Head Cap Screws Available at MF Supply

MF Supply is a leading supplier of Socket Head Cap Screws in alloy and stainless steel, including the brands Holo-krome and Blue Devil. We offer functional equivalents to the most popular national brands such as Fastenal, McMaster-Carr, MSC Industrial and Grainger.

Here at MF Supply, we offer:

  • The full range of commercial and mil-spec parts, including parts that are DFARS and ROHS compliant.
  • Brand names, generic equivalents, domestic and import.
  • Custom made parts per print in non-standard and exotic materials and finishes.
  • Inch and Metric sizes.
  • Stainless steel in 18-8, 316, A286, A2 and A4 (ASTM F837, F879).
  • Mil-spec MS, MS, NAS and NAS.

For more detailed information about socket head cap screws, visit our website. And if you don’t see it listed, as always, ask us. “Finding the right screw for you” is our tag line after all!

For more than 40 years, MF Supply has helped American manufacturers streamline operations, saving them time and money with our sourcing expertise and unique supply chain strategies. We are a WBE/WOSB certified stocking distributor of fasteners and electronic components.

We work with the best-established factories in the United States and DFARS-certified countries, and stock a huge inventory including all major brands and equivalents. MF Supply provides solutions including: same-day drop ship direct from the factory; custom sizes, materials and plating options; and DFARS parts with full paperwork and Certificates of Conformance.

We creatively solve common problems including hard-to-find parts and long lead times. Our sourcing and reworking expertise includes fast turnaround for modification of existing parts, hard to find standards and specials, special threads, non-standard diameters and lengths, exotic materials, special platings and short runs. We provide functional equivalents to expensive brand name fasteners and help our customers save money while reducing lead times.

Follow our blog at http://blog.mfsupply.com/

The company is the world’s best Square Head T Bolt supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

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