SPRING 2022

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THE DISTRIBUTOR’S LINK
Guy Avellon
Guy Avellon has been in MRO and Fastener Distribution for over 30 years, in such positions Sales
Engineer, Chief Engineer, Manager of Product Marketing, Product Engineering & Quality and
Director of Quality & Engineering. He founded GT Technical Consultants where he performs failure
analysis, lectures on fastener safety, works for law firms and designs/audits Quality systems. He is a
member of SAE, is Vice Chairman of the ASTM F16 Fastener Committee, Chairman of the F16.01 Test
Methods Committee and received the ASTM Award of Merit in 2005. Guy can be contacted at 847-
477-5057, Email: ExpertBoltGuy@gmail.com or visit www.BoltFailure.com.
WHAT FASTENER DISTRIBUTORS NEED TO KNOW
ABOUT FAST FASTENER FACTS AND ANSWERS
After presenting hundreds of Fastener Safety training
seminars, there have always been standard questions
asked from users and purchasers regarding the selection
and use of fasteners. I have compiled many points into
quick, one sentence phrases that will help answer many
of those asked and unasked questions.
Fastener Selection
[1] Always be sure the order is correct if there is a
question.
a. This seems basic but maintenance personnel
use jargon and descriptions not easily recognizable on a
Purchasing Order to non-technical personnel.
[2] If the order includes one Grade or Class of
fastener and a different Grade or Class of nut that is the
same size, ask and reconfirm.
[3] Always use a nut whose strength matches the
grade of its mating fastener.
a. This may happen at the procurement level where
incorrect product was bought, due to lack of specification
or price.
b. This may occur at the maintenance level where
many types of products are stored and may be mixed
when excess product is returned.
[4] Make sure all of the fasteners and nuts in a
multiple connection are the same grade.
a. Sometimes fasteners may become mixed and put
into the same storage container.
[5] Bolt lengths should be long enough to
CONTRIBUTOR ARTICLE
accommodate a flat washer under the head and under
the nut when applicable.
a. There only needs to be at least two bolt threads
sticking out of a tightened nut. Any more threads than
two are useless and increases the stresses on the
threads in the joint.
[6] Always use a hardened SAE flat washer under
the nut and bolt head with any fastener whose strength
is an SAE Grade 5 or ISO Class 8.8 or stronger.
[7] USS flat washers should only be used on sheet
metal, plastics or compressible materials.
a. The USS flat washer does not increase the load
bearing surface any more than an SAE washer does on
a steel joint.
b. The only fastener products that will increase the
load bearing surface area is a flanged head bolt and nut
because it is an integral part of the fastener.
[8] Fine threads (UNF) will produce 10% more clamp
load than a coarse threaded fastener.
a. This is due to the differences in stress area;
there is more metal with the UNF.
b. The shallow helix angle makes fine threads less
susceptible to loosening from vibration.
[9] Never mix nut and bolt finishes in a multiple bolt
connection.
a. That is, non-plated with plated or with different
types of coatings.
b. Especially with hot dipped galvanized products
where the nuts may be overtapped.
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