Boy, there sure are a lot of ‘em out there! For this discussion, we’ll divide our fasteners into two very broad groups – mechanical and adhesive. The comments I offer in this article reflect my personal opinions; are for general information only and are based on several years of sales and service experience working for one of the largest designers and manufacturers of mechanical fasteners in North America. In this capacity, I have worked in both the construction and mass assembly industries.
As always, follow manufacturer’s recommendations and local construction and bylaw authorities whenever using fasteners of any design to install a sign or sign component.
The Mechanical Fastener
A mechanical fastener is a device made of metal, plastic, organic and/or composite materials that adheres or anchors to a base material through tension and friction. We know them as dowels, pins, nails, screws, bolts, rivets, shields, plugs and dozens of other names.
Look at the simple steel nail. It’s a mechanical fastener. When hammered into wood, the nail holds by the friction between its shank and the wood fibres. Sometimes the “grip” is improved by adding ridges, barbs or by twisting the shank into a spiral. (By the way, a little cabinetmaker’s hint – when driving a nail near the end of a board, to reduce splitting, first blunt the tip of the nail with a couple of taps from the hammer. This causes the nail to “punch” through the wood fibre rather than spreading the fibres apart, lessening the tendency to split.) The concrete nail works in just the same way but is thicker and sometimes heat-treated to withstand the pounding. So here are a few simple rules:
At least 50% of the length of a nail should be in the bottom anchor material.
The length of the nail should be as long as practical for the total thickness of materials being fastened.
Soft woods and materials require spiralled and barbed nails for best holding.
Use coated nails for exterior applications.
Next, screws and bolts, are threaded rather than driven. They can be self-tapping (cut their own threads as they go in), use a pre-tapped (threaded) hole or can be combined with a nut. Screws and bolts still hold in place because of friction of the threads. You can increase the resistance to loosen by tightening the screw more (and too much = broken screw!) and actually “stretch” the screw. This puts more “tension” into it and more tension is more friction. Here’s a little technical tidbit – a good locking washer design works because it provides tension to the screw and uses “barbs” only as a secondary locking action. Even the lowly split-ring lock-washer works on this principle. Here are some basic rules:
Use only one locking washer per screw.
Use locking washers for high vibration areas and wide temperature ranges.
Use plain flat washers to provide a bearing surface for the fastener
heads and nuts to smoothly rotate when tightening.
They also spread the load over a broader area.
For most fasteners, strength comes with size (diameter) and quality of materials and manufacturing. Its holding power comes from quality of fit and correct installation as well. Sloppy holes and damaged threads are no good!
If fastener size has to be small because of installation conditions then the number should be upped to compensate. As a general rule and with practical limits, bigger is better for safety.
Here’s some technical stuff but hang in there with me! A screw’s diameter is measured on the outside of the threads but its strength comes from its root or core diameter (that’s at the bottom or valley of the threads). So a ¼” (.250”) screw is the diameter measured across the tops of the threads. But the root diameter is around .190” or a bit more than 3/16”. What does that all mean? Here are the rules of thumb:
The minimum number of threads engaged (threaded in) should be 4
Each step up in fastener size increases strength by roughly 30%
Fasteners should be installed accurately and to the manufacturer’s specifications – don’t guess!
Choose the fastener based on the material you’re anchoring to.
Adhesive Systems
My comments here are brief. I have limited expertise in adhesives beyond working with various hide glues (Old Nelly), polyvinyl (white/yellow glues), epoxies (2-part liquid or paste), silicone (sealant/adhesive), thermal set (hot glue) and cyanoacrylates (instant glue). Most of my opinions come from several years of practical experience.
But here are a few things to keep in mind:
Use brand name or buy from a knowledgeable supplier (don’t overlook the local hobby shop – they’ve got some great stuff!)
Use acknowledged industry standards when in doubt
Use an adhesive that is best matched to the base material(s)
Check weather and temperature extremes
Don’t mix different adhesives or brands
Minimize joint gaps – thinner glue line is better
Know if the adhesive takes paint or other finishes
Clean surfaces to be joined thoroughly.
Blow dust out of holes where using pins with silicone
Mix epoxies exactly to manufacturer’s directions
Let the adhesives have their full recommended cure time before working
Use protective gear (e.g. mask, gloves) according to adhesive used
Check shelf life of stored adhesives – don’t use stale, dated materials
In general, be prepared to work with several different types of adhesives or systems. One size does not fit all. Don’t go cheap on the adhesive system – this is the wrong place to cut costs. Rather, use intelligent adhesive choices based on the materials and conditions of each application. If white glue is the right stuff then why use the more expensive epoxies?
Here’s another woodworker’s hint. When gluing resinous (oily or sappy) woods, just before gluing, “kill” the joint surfaces by wiping with acetone, MEK or lacquer thinner. As with any solvent, take handling, ventilating and breathing precautions!
Usually, outdoor conditions demand higher performing materials than indoor applications and that includes adhesives. Weather or water resistant is not weather or water proof! Signs facing south deal with different issues to signs facing north. What works in Florida may be entirely wrong for the far north of the country. An adhesive system must tolerate many things – be sure to choose accordingly and think in terms of the sign’s destination rather than out your front door.
The Fastener Game
Boy, there sure are a lot of ‘em out there! For this discussion, we’ll divide our fasteners into two very broad groups – mechanical and adhesive. The comments I offer in this article reflect my personal opinions; are for general information only and are based on several years of sales and service experience working for one of the largest designers and manufacturers of mechanical fasteners in North America. In this capacity, I have worked in both the construction and mass assembly industries.
As always, follow manufacturer’s recommendations and local construction and bylaw authorities whenever using fasteners of any design to install a sign or sign component.
The Mechanical Fastener
A mechanical fastener is a device made of metal, plastic, organic and/or composite materials that adheres or anchors to a base material through tension and friction. We know them as dowels, pins, nails, screws, bolts, rivets, shields, plugs and dozens of other names.
Look at the simple steel nail. It’s a mechanical fastener. When hammered into wood, the nail holds by the friction between its shank and the wood fibres. Sometimes the “grip” is improved by adding ridges, barbs or by twisting the shank into a spiral. (By the way, a little cabinetmaker’s hint – when driving a nail near the end of a board, to reduce splitting, first blunt the tip of the nail with a couple of taps from the hammer. This causes the nail to “punch” through the wood fibre rather than spreading the fibres apart, lessening the tendency to split.) The concrete nail works in just the same way but is thicker and sometimes heat-treated to withstand the pounding. So here are a few simple rules:
At least 50% of the length of a nail should be in the bottom anchor material.
The length of the nail should be as long as practical for the total thickness of materials being fastened.
Soft woods and materials require spiralled and barbed nails for best holding.
Use coated nails for exterior applications.
Next, screws and bolts, are threaded rather than driven. They can be self-tapping (cut their own threads as they go in), use a pre-tapped (threaded) hole or can be combined with a nut. Screws and bolts still hold in place because of friction of the threads. You can increase the resistance to loosen by tightening the screw more (and too much = broken screw!) and actually “stretch” the screw. This puts more “tension” into it and more tension is more friction. Here’s a little technical tidbit – a good locking washer design works because it provides tension to the screw and uses “barbs” only as a secondary locking action. Even the lowly split-ring lock-washer works on this principle. Here are some basic rules:
heads and nuts to smoothly rotate when tightening.
For most fasteners, strength comes with size (diameter) and quality of materials and manufacturing. Its holding power comes from quality of fit and correct installation as well. Sloppy holes and damaged threads are no good!
If fastener size has to be small because of installation conditions then the number should be upped to compensate. As a general rule and with practical limits, bigger is better for safety.
Here’s some technical stuff but hang in there with me! A screw’s diameter is measured on the outside of the threads but its strength comes from its root or core diameter (that’s at the bottom or valley of the threads). So a ¼” (.250”) screw is the diameter measured across the tops of the threads. But the root diameter is around .190” or a bit more than 3/16”. What does that all mean? Here are the rules of thumb:
Adhesive Systems
My comments here are brief. I have limited expertise in adhesives beyond working with various hide glues (Old Nelly), polyvinyl (white/yellow glues), epoxies (2-part liquid or paste), silicone (sealant/adhesive), thermal set (hot glue) and cyanoacrylates (instant glue). Most of my opinions come from several years of practical experience.
But here are a few things to keep in mind:
In general, be prepared to work with several different types of adhesives or systems. One size does not fit all. Don’t go cheap on the adhesive system – this is the wrong place to cut costs. Rather, use intelligent adhesive choices based on the materials and conditions of each application. If white glue is the right stuff then why use the more expensive epoxies?
Here’s another woodworker’s hint. When gluing resinous (oily or sappy) woods, just before gluing, “kill” the joint surfaces by wiping with acetone, MEK or lacquer thinner. As with any solvent, take handling, ventilating and breathing precautions!
Usually, outdoor conditions demand higher performing materials than indoor applications and that includes adhesives. Weather or water resistant is not weather or water proof! Signs facing south deal with different issues to signs facing north. What works in Florida may be entirely wrong for the far north of the country. An adhesive system must tolerate many things – be sure to choose accordingly and think in terms of the sign’s destination rather than out your front door.
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