corrosion, they resist vibration. They are
free-flowing liquids or semi-solid adhesives
which completely fill the gaps between
mating threads of fasteners and joints.
Proof positive
To prove the performance of its thread
locking system against other methods,
LOCTITE submitted its products for
independent testing in a transverse shock
and vibration machine in which pneumatic
hammers force relative movement of the
stressed parts. At the same time, the existing
pre-stress force was continuously measured
for the number of load cycles. Characteristic
clamp load retention curves of the various
locking methods were then compared.
While a similarly favourable load cycle
performance was provided by the ribbed
flange bolt, it does have other disadvantages.
It’s expensive, requires a relatively large
amount of space for the flange bearing and
causes unavoidable damage to the surface of
the clamped parts around the bolt bearing.
A bolt with a saw-toothed flange also
performed well but its teeth penetrated the
bearing’s surface of the clamped material.
The head and the nut were damaged during
loosening, limiting their possible application
to parts with hardened surfaces that cannot
be reliably connected.
Above: LOCTITE 243 is used to lock bolts which must resist massive pressure.
As well as performing well, the
LOCTITE thread lockers are said to cut
costs by replacing expensive special locking
bolts or nuts, allowing less costly standard
assemblies to be used.
If it’s good enough for
Crossrail…
With such a good result for clamp load
retention and cost efficiency, it is no wonder
that when Herrenknecht AG was evaluating
the best way to secure threaded assemblies
on its tunnel boring machines for Crossrail
it chose LOCTITE. LOCTITE 243 is used to
lock bolts which must resist massive pressure
as the machines eat into the sub-soil. This is
a medium strength adhesive that is suitable
for all metals including passive substrates.
And it’s a similar story with Local
Motors’ Rally Fighter, high performance,
off-road racing car that needs to withstand
extreme conditions without constant
maintenance. Cars like the Rally Fighter are
subject to jarring bumps and vibration that
shake loose even the sturdiest of nuts and
bolts. By applying a LOCTITE thread locker
mechanics knew that once they tightened the
bolt or screw, it would stay tightened, even in
the toughest environments.
Extensive choice
LOCTITE thread locking adhesives are
available in varying viscosities and strengths
to meet the needs of a wide range of
applications. They are single-component
and semi-solid adhesives that cure at room
temperature to a hard, solid thermoset plastic
when applied between steel, aluminium,
brass and most other metal surfaces.
Low strength formulations allow
disassembly with standard hand tools and
are ideal for adjustment screws, calibration
screws, meters, gauges and for thread sizes
up to M80. Medium strength provides
a greater degree of performance and is
good for machine tools, presses, pumps,
compressors and gearboxes.
High strength products are used where
frequent dismantling is unlikely and may
require localised heat for removal, as do
wicking compounds that are widely used for
pre-assembled fasteners.
Continuous development of LOCTITE
thread lockers has greatly extended the
application scope of these products. They
are now much more effective on passive
substrates such as stainless steel and their
greater oil tolerance makes them less
sensitive to improperly cleaned parts. And
importantly, these qualities have been
achieved without compromising any of
the products’ other key properties such as
chemical resistance and shelf life.
Henkel
01442 278000
www.henkel.co.uk
0 200 400 600 800 1000
Number of load cycles
100
80
60
40
20
0
Prestress force in %
Standard bolt with Loctite
threadlocking system
Adhesive bolt (ribbed ange bolt)
Bolt with saw-toothed ange
Nut with polymide washer
Bolt with DIN 6797 A tooth lock washer
Bolt with DIN 127 A spring washer
Unsecured standard bolt
www.fastening-solutions.co.uk 19
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