smarter fastening

When an engineer specifies a ¼-20 x 2 zinc plated Grade 5 hex cap screw in their design, they are expecting to get a part that meets strength requirements, can be serviced with a 7/16” tool, and will resist corrosion.  But if that engineer’s purchasing team sends that description out to five suppliers would they all supply the same part?  Chances are, all parts would function similarly, but corrosion resistance would be all but guaranteed to vary.

Now what if that engineer specified a Hex Cap Screw per ASME B18.21.1, ¼-20 x 2, Steel per SAE J429 Grade 5, zinc plated per ASTM F1941 Fe/Zn 5AS?  He would receive a 7/16” across flats, 3,800 lb minimum tensile strength, .0002” thick zinc plated fastener with RoHS compliant sealer to meet 96 hours to white rust salt spray resistance.  By simply referencing the appropriate fastener standards, each aspect of this part is now controlled, ensuring the intended part will be supplied regardless of source.  The engineer can be confident that the part will meet dimensional, material, performance and plating requirements without the need for creating documentation such as a print that would need to be maintained.

So who creates and maintains these fastener standards: an exclusive group of manufacturers serving their private interests, a secret society in an ivory tower?  Far from it.  ASME, ASTM and SAE are open to participation by any interested party.  The fastener committees and associated sub-committees ensure a proper balance of producers, users and independent consultants so that the standards produced are truly in the best interests of all involved.  And while fasteners may be a mature industry, standards are constantly under development as materials, manufacturing methods, usage and other aspects continue to change.

The message here is two-fold.  First, referencing standards when specifying and ordering fasteners is a simple way to ensure accurate orders and proper performance.  Years of development and manufacturer and user input have led to the current standards, and they control all of the pertinent aspects of the fasteners.  Second, the continued development of new standards and refinement of existing standards depends upon the participation of all parties involved.  If you find yourself looking to the standards for information, you should consider making a contribution yourself!

Here at Field we also understand that a full understanding of fastener standards can take years to master – time that our customers don’t have to spend.  For that reason we encourage the use of our team as a resource to identify and properly document the best fastener for each application.  Not currently enjoying the benefits of Field’s engineering team?  Contact Engineering@fieldfastener.com with your application and experience the Field difference.


John Medcalf – Applications Engineer, FIELD


About the Author:  John Medcalf has a BSME from Northern Illinois University, and is a four year team member of Field.  While at Field he has held positions in both Quality and Engineering, visiting manufacturers and OEM’s across North America and in Asia.  He is a member of, and active participant in, ASME B18 and ASTM F16 fastener subcommittees, and has represented the US as an ANSI delegate to the ISO TC2 fastener committee meetings.