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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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