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Fastener facts
Here are facts every
distributor salesperson should know when customers debate the use of
mechanical vs. adhesive fastening systems.
Depending on which
manufacturer you ask, you’ll get opposing points of view about
whether it’s best to use mechanical or adhesive anchoring systems.
Each type has its advantages and disadvantages. Here are a few things
that every distributor salesperson should know about mechanical vs.
adhesive fasteners.
In general,
mechanical fasteners work best on hollow-core materials such as
drywall, hollow-core concrete block and plaster. These fasteners open
up on the back side, inside the material being fastened to, then
compress against the material being fastened to when the fastener is
tightened.
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Examples
of mechanical anchors
One-step
anchors.
These anchors are designed to be installed through the fixture
because the size of the anchor is the same as the drilled
hole. This reduces drilling time and layout or hole spotting,
reducing installation time.
Bolt
anchors.
These anchors are designed to be installed flush with the
surface of the base material. They are used in conjunction
with a threaded machine bolt or, in some types, with a
threaded rod.
Hollow
wall anchors.
These are used in hollow materials such as concrete plank,
block, structural tile, wallboard and plaster. Some types can
also be used in solid materials. Adhesive anchors can also be
used for hollow wall applications using anchor rods and screen
tubes.
Screw
anchors.
These anchors are designed to be installed flush with the
surface of the base material. They are used in conjunction
with sheet metal, wood or lag screws, depending on the anchor
type.
Self-tapping
screws.
These screws drill and tap in one driving operation. The
screw’s threads interlock with the base material as it
threads into the hole.
Wedge
anchor.
A wedge anchor is a common anchor type that works by pulling a
stud up around the anchor’s clip as it tightens. Wedge
anchors exhibit the highest holding values among mechanical
anchors, but need a strong base material to prevent the
concentrated compression forces from pulverizing or cracking
the material.
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Two main things to
protect against with mechanical fasteners are the fastener pulling out
of the wall or breaking off. Pull-out relates to tension and breaking
concerns shear. Manufacturers provide a wealth of tables and data that
list the type of fastener and how it rates in tension and shear
strength.
Adhesive fasteners
generally offer advantages for applications requiring high load
capacities. Rather than concentrating stress at a single point,
adhesives distribute stress load over a broader area, resulting in
more even distribution. An
adhesive-bonded joint better resists flex and vibration stresses than,
for example, a riveted joint.
Adhesives also resist
corrosion that occurs in a mechanically fastened joint. Adhesive
systems tend to be more resilient than comparable mechanical anchors,
so they perform better against impact and vibration loads.
Typical prepackaged
adhesive systems include capsules, pump-style cartridges and
cartridges used with a special mixing nozzle.
Sometimes, mechanical
fastening methods and adhesives working together form a stronger bond
than either method alone. Threadlocking and gaskets are two examples.
This article originally appeared in the
July/August '01 issue of Progressive Distributor. Copyright 2001.
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