Have at it Hammer and Tongs by Bob MacMaster
One thing we can all agree about is that concrete, brick, mortar, rock and the like are very hard and in some ways brittle. (By the way, old concrete is harder than new.) In days past (and if you remember this, retirement can’t be far away!) you made holes in these materials with a star drill and hammer and into the hole went your anchor.
It generally took two people; one to hold the star drill with pliers or “tongs” and the other to strike the drill with a “hammer”. After each blow, the drill was turned a quarter turn and the process was repeated.
Today, using carbide bits with an incredible variety of electric hammer-drills, making the holes in concrete, etc., is quick and easy. If you get one for your tool box, buy the best you can afford – they take a lot of pounding. Look for a pistol grip design with a 3/8” or 1/2” chuck and a lever or collar to turn it into a standard drill.
The majority of holes that sign installers will make will be small in diameter, likely under 1/2” but there may be occasion for holes up to 1”. As always, clear the hole of dust before inserting your anchor. As a rule of thumb, make your hole 1/2” deeper than the length of the anchor. The hole diameter recommended by the manufacturer is critical to the anchor’s advertised holding power.
That means you need to keep an eye on the wear of your carbide bit. As the tip wears, the hole gets smaller and the effort to drill goes up as does the anchor installation. As a rule of thumb, expect to get 25-50 holes out of a carbide-tipped drill in clay brick, stone and standard concrete and perhaps 75-100 holes in mortar and cement brick.
Maybe I should pause for a moment to point out that I’ve been using the word anchor when referring to a fastener used with concrete and the rest. This has become a standard name for fasteners used in concrete and like type materials. It is generally made of more than one piece so you can think of it as a “system”. There is generally a central pin or screw driven into a sleeve or shield and the sleeve (shield) expands to grip or “anchor” the fastener to the wall of the hole.
That’s the traditional concept but there have been some new anchor designs in recent years that have taken the form of specialized screws that tap directly into the concrete. We’ll look at those in a moment.
Let’s finish reviewing the traditional anchor system with a few observations. The shield types come in a huge variety of flavours. The shield can be of one or several joined pieces made from plastic, wood fibre, soft metals, steel, epoxy resin or combinations. The center pin can be nail-like or a threaded screw, bolt or stud. In general these fastener systems are expanding or wedging type devices that apply considerable pressure to the surround material.
We said that concrete, brick, rock and the like can be brittle so be aware that over time the pressure of the anchor can crack the substrate and the effectiveness of the anchor is all but nullified. Also, these types of anchors generally require more accurate installation; are only marginally re-useable and require much larger hole sizes than the actual pins/screws holding the load. There is a tendency for this style of anchor to be weather and temperature sensitive.
So as a rule of thumb, (yep … another one!) use expansion type anchors in concrete and rock and look for less forceful types of anchors for both clay or concrete brick and mortar. Use smaller anchors to reduce anchoring forces and increase their numbers to meet the load requirements of the sign.
This brings us back to the threaded anchor I mentioned earlier – the self-tapping concrete screw! Here I will use a brand name that I know well – the Tapcon. I was involved in the market introduction of this innovative product back in 1975. It represents a class of anchors. There are competing brands now but I can’t offer an opinion on them as I don’t know them. I am sure many of them are excellent.
The Tapcon is a specially shaped, heat-treated and plated screw that is designed to self-tap (make its own threads) when screwed into a pre-drilled hole in concrete, brick or mortar. It even comes packaged with a carbide bit of the appropriate size so there’s no guess work. Since it cuts threads and holds like a regular screw it applies no stresses to the substrate (especially brick); can be removed and re-installed in the same hole and requires only a small hole for installation. No special knowledge is required. It’s very easy to work with!
You may have noticed I stayed clear of powder actuated tools (blank pistol cartridges used to fire steel pins into concrete). I still believe that these are in the realm of the pro and not for we mortals.
Let me leave you with these thoughts. For anchors, pull-out strength may be less important than shear strength as more often than not you are hanging on a wall. The shear capacity of an anchor is generally substantially more than its pull-out capacity (good!). Concrete can accelerate corrosion so look to anchors with good protection and finish.
Always clear the hole of debris before installing the anchor. Always provide extra clearance depth in the hole (approx. 1/2”). Be very cautious about anchoring close to the edge of concrete or brick – for every inch of anchor length try to stay 1/2” away. If using epoxy or silicon with pins, thoroughly blow out hole and use a minimum clearance hole to maximize adhesive strength (accurate templates are a must!). Some west coast concrete is made with garnet as an aggregate (that’s the stone mixed with the sand and cement to add strength to concrete). It can cut drill bit life in half or worse!
So much more could be said but we hope what information I have offered will be of some help in your future installs!
Click here to return to main Learning Centre page
Have at it Hammer and Tongs
One thing we can all agree about is that concrete, brick, mortar, rock and the like are very hard and in some ways brittle. (By the way, old concrete is harder than new.) In days past (and if you remember this, retirement can’t be far away!) you made holes in these materials with a star drill and hammer and into the hole went your anchor.
It generally took two people; one to hold the star drill with pliers or “tongs” and the other to strike the drill with a “hammer”. After each blow, the drill was turned a quarter turn and the process was repeated.
Today, using carbide bits with an incredible variety of electric hammer-drills, making the holes in concrete, etc., is quick and easy. If you get one for your tool box, buy the best you can afford – they take a lot of pounding. Look for a pistol grip design with a 3/8” or 1/2” chuck and a lever or collar to turn it into a standard drill.
The majority of holes that sign installers will make will be small in diameter, likely under 1/2” but there may be occasion for holes up to 1”. As always, clear the hole of dust before inserting your anchor. As a rule of thumb, make your hole 1/2” deeper than the length of the anchor. The hole diameter recommended by the manufacturer is critical to the anchor’s advertised holding power.
That means you need to keep an eye on the wear of your carbide bit. As the tip wears, the hole gets smaller and the effort to drill goes up as does the anchor installation. As a rule of thumb, expect to get 25-50 holes out of a carbide-tipped drill in clay brick, stone and standard concrete and perhaps 75-100 holes in mortar and cement brick.
Maybe I should pause for a moment to point out that I’ve been using the word anchor when referring to a fastener used with concrete and the rest. This has become a standard name for fasteners used in concrete and like type materials. It is generally made of more than one piece so you can think of it as a “system”. There is generally a central pin or screw driven into a sleeve or shield and the sleeve (shield) expands to grip or “anchor” the fastener to the wall of the hole.
That’s the traditional concept but there have been some new anchor designs in recent years that have taken the form of specialized screws that tap directly into the concrete. We’ll look at those in a moment.
Let’s finish reviewing the traditional anchor system with a few observations. The shield types come in a huge variety of flavours. The shield can be of one or several joined pieces made from plastic, wood fibre, soft metals, steel, epoxy resin or combinations. The center pin can be nail-like or a threaded screw, bolt or stud. In general these fastener systems are expanding or wedging type devices that apply considerable pressure to the surround material.
We said that concrete, brick, rock and the like can be brittle so be aware that over time the pressure of the anchor can crack the substrate and the effectiveness of the anchor is all but nullified. Also, these types of anchors generally require more accurate installation; are only marginally re-useable and require much larger hole sizes than the actual pins/screws holding the load. There is a tendency for this style of anchor to be weather and temperature sensitive.
So as a rule of thumb, (yep … another one!) use expansion type anchors in concrete and rock and look for less forceful types of anchors for both clay or concrete brick and mortar. Use smaller anchors to reduce anchoring forces and increase their numbers to meet the load requirements of the sign.
This brings us back to the threaded anchor I mentioned earlier – the self-tapping concrete screw! Here I will use a brand name that I know well – the Tapcon. I was involved in the market introduction of this innovative product back in 1975. It represents a class of anchors. There are competing brands now but I can’t offer an opinion on them as I don’t know them. I am sure many of them are excellent.
The Tapcon is a specially shaped, heat-treated and plated screw that is designed to self-tap (make its own threads) when screwed into a pre-drilled hole in concrete, brick or mortar. It even comes packaged with a carbide bit of the appropriate size so there’s no guess work. Since it cuts threads and holds like a regular screw it applies no stresses to the substrate (especially brick); can be removed and re-installed in the same hole and requires only a small hole for installation. No special knowledge is required. It’s very easy to work with!
You may have noticed I stayed clear of powder actuated tools (blank pistol cartridges used to fire steel pins into concrete). I still believe that these are in the realm of the pro and not for we mortals.
Let me leave you with these thoughts. For anchors, pull-out strength may be less important than shear strength as more often than not you are hanging on a wall. The shear capacity of an anchor is generally substantially more than its pull-out capacity (good!). Concrete can accelerate corrosion so look to anchors with good protection and finish.
Always clear the hole of debris before installing the anchor. Always provide extra clearance depth in the hole (approx. 1/2”). Be very cautious about anchoring close to the edge of concrete or brick – for every inch of anchor length try to stay 1/2” away. If using epoxy or silicon with pins, thoroughly blow out hole and use a minimum clearance hole to maximize adhesive strength (accurate templates are a must!). Some west coast concrete is made with garnet as an aggregate (that’s the stone mixed with the sand and cement to add strength to concrete). It can cut drill bit life in half or worse!
So much more could be said but we hope what information I have offered will be of some help in your future installs!
Click here to return to main Learning Centre page