WINTER 2021

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THE DISTRIBUTOR’S LINK
Rob LaPointe AIM TESTING LABORATORY
Avoiding Catastrophic Failure in Plated Socket-
Head Cap Screws by Choosing the Correct Product
Strength and Process for Your Application.
The socket-head cap screw (SHCS) is a wonderfully
engineered fastener that is useful for countless
applications where availability, compactness and strength
are desired. The compact features of this fastener are
found in its head and drive design. Since its drive facets
are inside the head rather than outside the head, the
shape of the head can be round rather than hexagonal.
Also, its diameter can be significantly smaller than a
hex-head screw of comparable strength. A round head
and internal drive feature enable this fastener to be sunk
below the surface of the assembly it is holding together,
leaving no fastener head to obstruct or interfere with the
surface. The internal drive of the socket-head cap screw
makes it possible to drive the screw with smaller tooling
which can be beneficial in many applications that require
compactness and or machine assembly.
Rob LaPointe is a noted authority in materials and fastener technology. With extensive experience
in the management and science of materials testing laboratories combined with master’s degrees in
physics and education, he excels at bringing solutions to the client. Working specifically in the fastener
testing industry, he has developed expertise in mechanical, nondestructive, metallurgical and chemical
testing. With a background of 20 years in physics education, Rob is effective at communicating complex
ideas in a simple and understandable manner, communicating well with clients enabling them to make
informed decisions about their products and business. AIM is located at 1920 Cordell Court #101, El
Cajon, CA, 92020. Tel: 909-254-1278, email: sales@aimtestlab.com or online at www.aimtestlab.com
FASTENER SCIENCE: AVOIDING CATASTROPHIC
FAILURE IN PLATED SOCKET-HEAD CAP SCREWS
The strength of the common alloy-steel SHCS is
FIGURE 1 SOCKET HEAD CAP SCREW (SHCS) PER ASME B18.3
FIGURE 2 SOCKET HEAD CAP SCREW WITH BLACK OXIDE FINISH
legendary and is often the deciding factor for an engineer
in choosing this fastener for a particular application.
Products made to the ASTM A574 specification for inch
sizes and to ISO 898-1, Class 12.9 for metric sizes are
capable of withstanding tensile pressures of 180,000
psi (180 ksi) or 1220 MPa respectively minimum before
tensile failure occurs. These fasteners have proven elastic
performance up to 78 % of its minimum breaking strength
and can provide sustained clamp loads of approximately
75% of its minimum breaking
strength.
If the geometry and
strength of the SHCS are
required for the application,
these fasteners are readily
available in a black oxide
finish.
TECHNICAL ARTICLE
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