While it may seem a humble player in any given design, liquid
thread locker can have huge impacts in terms of effi ciency,
productivity and safety.
30 » MARCH 2021 » WWW.MADEIN.IE
threaded fasteners to self-loosen. The
manufacturer was swift to act on fi eld
reports and resolved the problem by
applying a wicking-grade adhesive
thread locker to the threaded bolts on
installed printers. It also adopted
adhesive thread locking as a standard
assembly method in the factory to
eliminate self-loosening at source.
In a typical assembly, there is as
little as 15% thread to thread surface
contact. The remaining space allows
movement of the bolt within the nut,
ultimately resulting in it loosening
after just a few machine cycles.
Changes in temperature have a similar
eff ect, causing micro expansion and
contraction of the metal components
leading to short-term frictionless
situations where the bolt unwinds from
the nut.
A common antidote to the problem
is the application of a mechanical
thread locking device such as a spring
washer or a double nut. Both help
delay the onset of self-loosening but
ultimately failure is still inevitable if
the assembly isn’t frequently retorqued.
By comparison, the liquid thread
locker fi lls all voids between the
mating threads and solidifi es to form a
thermoset plastic that unitises the
assembly. It eff ectively stops
the micro-movements that
lead to self-loosening and,
at the same time, seals the
assembly against corrosion
and air borne contaminants
such as dust.
When designing
a new machine
or system, it’s
not always new
technology that
wins market
share. Proven product reliability
is a powerful selling point and it
can often be signifi cantly boosted
by taking a fresh look at basic
assembly methods. Preventing the
early failure of the humble threaded
fastener is a good case in point.
Threaded bolts that self-loosen
during the machine’s operation can
cause all manner of problems from
increased maintenance and downtime
to quality issues and lost production.
So, when customers of an East
European manufacturer of screen
printers began reporting bolt
failures on its machines, the
company went back to basics.
Vibration and heat
In operation, these largescale
printers generate a lot
of vibration and heat, both
of which were causing the
These adhesives are available in a
choice of strengths in easy fl owing
liquids or semi-solid form to suit the
application; all allow disassembly with
hand tools for repair and maintenance.
The adhesive thread locker the
printer manufacturer chose for bolt
assembly is, Loctite 243 from Henkel.
It is a single component, medium
strength thread locker that has recently
been upgraded to off er good bond
strength on contaminated surfaces,
provide higher temperature resistance
and perform well on passive metals
without an activator.
Worker safety
Failure of a threaded assembly through
self-loosening not only risks lost
production but also worker safety. This
was the situation an Australian mining
operation faced when M36 anchor bolts
threatened the collapse of the jaw
crusher equipment frame.
The bolts had been locked by spring
washers which simply could not rise to
the challenge of securing bolts on a
piece of equipment subjected to
continuous vibration and high shear
forces. This resulted in the loosening
– and ultimately the breaking off – of
anchor bolts and the collapse of
concrete footings.
Spring washers – also known as lock
or helical spring washers - are one of
the most popular mechanical devices
FASTENING
B LTS
FROM THE
BLUE
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