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 (DIN7984)
  • Flat Head– Countersunk heads at 82 degrees provide maximum flushness and side wall contact (ASTM F835, F879, DIN7991)
  • Button Head – For use in materials too thin to countersink (ASTM F835, F879, DIN7380)

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 MS16995, MS16996, NAS1351 and NAS1352 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 MS16995, MS16996, NAS1351 and NAS1352.

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.

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Newsletter – January / February 2016

 

Newsletter
Volume 18
February 12, 2016
January / February News
Greetings and Happy February!  We started 2016 fast out of the gate and are ramping up for a strong Q1, despite a PMI index of 48.2%, reports of contraction in the manufacturing sector and the volatility that sometimes occurs during election years.  I hope you are experiencing growth!
Today, I am continuing our discussion on thought leadership within the American Manufacturing community. Additionally, I am glad to get back to our “What the Heck Is that” roots and put the spotlight on one of our best-selling products, the Socket Head Cap Screw.
INSIDE THIS ISSUE
1.    SBA EMERGING LEADERS
2.    WHAT THE HECK IS A SOCKET HEAD CAP SCREW?
3.    MANUFACTURING ROUNDTABLE AND THE NJMEP
4.    MF SUPPLY JOINS DPA
5.    GOING LEAN?
Since graduating on October 27, I have been introduced to many amazing resources.  One exciting development I wanted to share with you is that MF Supply was selected as a case study class for Rutgers Business School. What does that mean, you ask?  Well, between now and April 20th, a group of smart and creative Rutgers MBA candidates are analyzing MF Supply and our marketplace. They will use BIG DATA and other tools, and present recommendations including an ROI on where we should focus our energies to grow. One of their initial thoughts was that MF Supply should be targeting companies with Set-Aside needs or Diverse buying initiatives.  If you hadn’t heard, MF Supply is a WBE and WOSB certified business, which means if your customer has Set Aside needs, we should be talking!  I am so excited for this project and am thankful to the SBA for connecting me to Rutgers and other resources.
If you are curious to know more about the SBA-EL program (in NJ or your state), or think you or someone you know might benefit from participating, please check out these two articles about the program inNJBIZ and American Entrepreneurship Today to find out more. To apply, please email Dominick.Belfiore@sba.gov and tell him I sent you!

 
Socket Head Cap Screws or socket caps, which are sometimes referred to by their trademarked name “Allen” screws, have become the standard among high strength fasteners needed to withstand the faster speeds and higher pressure of today’s machines, instruments and assemblies.  They are externally threaded, with a cylindrical head with a flat chamfered top, and a hexagonal recess for internal wrenching.
Who uses Socket Head Cap Screws?
Because of their cylindrical shaped heads and internal wrenching installation method, socket cap screws need less space than alternative fasteners.  This makes socket caps ideal for precision assembly work with close tolerances and applications that need a well tooled appearance.
Common uses include machine parts, die fixtures and assemblies.
Why use a Socket Cap vs a Hex Head Cap Screw?  
We don’t want to play favorites, but here are a few advantages of using socket caps:
Size matters– The smaller socket head enables driving where there is not sufficient space for wrenches or sockets. In addition, Socket caps are available off the shelf starting as small as 0-80 diameter and are commonly available to diameter 1-1/2-6.  Hex Head Cap screws start at 1/4-20 diameter.
Strength – Alloy Steel Socket Caps, though not measured in grades, provide greater tensile strength than equivalent size Grade 5 or Grade 8 steel Hex Head Cap screws.  i.e. 1/4-20 Socket cap=180k psi min, 1/4-20 Hex Head Grade 5 =120k psi min,  1/4-20 Hex Head Grade 8 =150k psi min.
Torque  – The 6 flat surfaces within the recess allow for high torquing without damaging the head,  and with no side clearance restrictions or additional wrench space.
Thread fit- Socket products generally have a 3A thread fit.  3A threads have restrictive tolerances often used where safety is a critical design consideration. Hex Head Cap Screws are generally class 2A.  2A threads offer a combination of performance, economy, and convenience. Nearly 90% of all commercial and industrial fasteners have a 2A fit.
Economy –  Socket Cap heads are smaller, hence, the size of the component parts can be reduced, reducing material costs.  Smaller parts cost less to drill and tap, take less energy to drive, and weigh less than alternatives.
What options are available?
The most common variables are the head style, diameter and thread, length, material and plating or finish.  Socket caps can also be captivated, vented, patched or pelleted.  Below are some of the most common options:
 
HEAD STYLES
There are 4 main available head styles, and each serves a slightly different purpose. All commercial Socket Caps conform to ASME B18.3.
 
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 (DIN7984)
Flat Head  – Countersunk heads at 82 degrees provide maximum flushness and side wall contact  (ASTM F835, F879, DIN7991)
Button Head – For use in materials too thin to countersink (ASTM F835, F879, DIN7380)
DRIVES
The most common and readily available drive style is a hexagonal socket drive, however, Socket Caps may also be available in security pin-in-hex, pin-in-torx, or six-lobe torx versions in certain sizes and materials.
Are there other factors to consider?
Of course!  “Steel” Socket Caps off the shelf are alloy steel black oxide through heat treatment and come oiled. If you need greater corrosion resistance or a different look than black, consider stainless steel or zinc plating.
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.
Beyond color and plating, there are always other factors to consider, such as: domestic or import, commercial or mil-spec, with or without sprinkles :). And remember, Socket Head Cap Screws can also show up under their most popular domestic brand names (Holo-krome) and mil-spec number (MS16995, MS16996, NAS1351 and NAS1352).    If you have any questions, please reach out and ask!
Socket Head Cap Screws available at MF Supply
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 (Holo-krome), 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).
For more detailed information on Socket Head Cap Screws, visit us at http://www.mfsupply.com/category_s/1869.htm
MANUFACTURERS ROUNDTABLE – NJMEP
Did you ever get an invitation that piqued your interest, and show up at an event wondering if it would be worth your time?  On January 27, I said yes to an NJMEP invitation to a Manufacturers Roundtable, hosted by Bergen Community College. I am so glad I went!
Assemblyman Gary Schaer, along with 30 manufacturers, educators and other advocates discussed ways we can support manufacturing in NJ.  Many connections were made, and last week, a group of 10 of the students from Bergen’s current CNC training class visited MF Supply to learn more about the Supply chain. They were a bright, motivated and very impressive group of students.  If you are hiring, great!  I’d love to connect you to the team at Bergen Community College.
And get yourself on the NJMEP (or if you are outside of NJ, contact your state’s MEP) email list to find out about relevant events and programs that just might be a difference maker for your business.
On November 1, 2015  we were officially welcomed into the DPA Industrial family.  What does this mean for our customers?  We can now help you with more product categories and pass along fabulous savings on many more items including:
  • Industrial
  • Safety Equipment & Clothing
  • Packaging
  • Janitorial/Sanitorial
Please contact me to set up a meeting to see if we can help save you time and money by becoming a single source for more of your industrial needs.
GOING LEAN
Since our core values include striving for achievement, self improvement and growth, we are exploring Lean certification. Is being Lean one of your initiatives? Check out this inspirational video about how Lean processes lead to immediate improvements in a NYC foodbank.   Enjoy the video by clicking here!
Regards,
Robin Lieberman
President
P.S. We are closed on February 15 in observance of President’s Day. Wishing you and yours a happy and healthy long weekend and Valentine’s Day from the entire team here at MF Supply.