When working with concrete fasteners and anchors, it is important to
understand the terminology used. Understanding the terms used in the
installation of these anchors will help you correctly and safely install
the concrete fasteners needed for your application. Below is a list of
terms and definitions that will help you when working with these
anchors.
Anchor spacing- the distance from centerline to centerline between two anchors
Base material- the concrete, brick or block material into which an anchor is placed
Concrete breakout- anchor failure from the deepest
embedment of the anchor to the surface of the base material at an angle
of about 35 degrees; referred to as the cone of concrete becuase the
breakout with be triangular shaped or cone shaped
Concrete screw- Tapcon® brand concrete screws that are
made from carbon steel and the threads are hardened to allow them to tap
base material such as concrete, brick or block. The threads are an
alternating high/low design with diamond cut notches. Tapcons are plated
with a Climaseal® coating for excellent rust resistance.
Critical spacing- the required distance between anchors to meet the maximum holding values
Critical edge distance- the required distance from an unsupported edge of concrete to meet the maximum holding values
Displacement controlled expansion anchor- anchors that are expanded by driving a nail into the anchor body
Drop-in anchor- created from two pieces of tubular steel
shield and a cone-shaped expander plug. The shield is threaded for
one-half of the length of the interior portion of the anchor, the other
half of the anchor is slotted. The slotted portion of the anchor is
where the case hardened cone-shaped expander plug is positioned.
Double expansion anchor- the double expansion anchor
is made up of five parts: a cone shaped expander nut, a hollow cone,
outer body and two spring bands. The spring bands hold all the anchor
parts together into one preassembled single piece and are made from
zinc-plated steel. The hollow cone and cone nut are the same except that
the cone nut has internal threads and are made from Zamak material. The
outer body is tubular and made from die-cast zinc alloy Zamak.
Edge distance- the distance from centerline to centerline of an anchor from an unsupported edge of the base material
Lag shield anchor- comes in two lengths (short and long)
and are made up of two parts that are preassembled. The interior part of
the anchor is threaded to accept lag screw threads. The outer part is
ribbed from the bottom of the anchor to three-quarters up the length of
the anchor body. Lag shields are amde from a Zamak material that is rust resistant.
Machine screw anchor- machine screw anchors
are made up two parts: the internal threaded cone and the outer sleeve.
The outer sleeve is made of rust-resistant material called Zamak. The
internal threaded cone is made from zinc plated low carbon steel.
Metal hit anchor- the metal hit anchor
or hammer drive anchor is a die-cast anchor consisting of a cylindrical
zinc alloy body and zinc plated steel pin expander. The body is split
for a major portion at the opposite end the pin expander is inserted.
The anchor body is hollow for the entire length to allow space for the
pin expander. The pin expander is made from heat treated, high carbon
steel that is zinc plated.
Minimum edge distance- the minimum distance to not spall the concrete when anchor is expanded
Minimum spacing- the minimum distance from centerline to
centerline for the anchor expansion forces not to overlap; rule of thumb
is 10 anchor diameters
Minimum embedment- the minimum distance that an anchor should be placed in the base material to achieve holding values
Nylon nail-its- the body of a nylon nailit
is made from a polyamide resin thermoplastic mold injected material,
the steel pin expander is a low carbon zinc plated steel. The body is
hollow, one end is split and the other end has either a mushroom head,
round head or flat head. The steel pin expander has threads on the
pointed end and the head is slotted to accept a screwdriver.
Single expansion anchor- this anchor is made of three
pieces that are preassembled. The anchor body is made from Zamac, a die
cast zinc alloy. The internal lugs are a cone shaped nut. A spring band
made from low carbon steel and zinc plated holds the anchor body and
internal lugs together.
Sleeve anchor- this anchor is made up of four parts: nut,
washer, threaded stud and sleeve. The threaded stuf is flared to a cone
shape at one end and the rest of the stud is threaded. The sleeve is a
tubular piece of steel that fits over the stud and expands when the stud
is pulled up through it. These anchors come fully assembled and ready
to use.
Split drive anchor- anchor that is all steel, one piece
available in two head styles- flat counter sunk and round. These anchors
are made from heat-treated carbon steel and are throughly hardened. At
the opposite end of the head, the anchor is sheared into two
pre-expanded halves.
Strike anchor- a displacement controlled expansion anchor.
The body is steel with a hole down the interior length of the anchor.
The hole is smaller in diameter at the opposite end of the threads where
the slots are. One end of the anchor is threaded for a portion of its
length and the opposite end has four equally spaced slots. A hardened
nail is inserted into the interior hole in the anchor and is used to
expand the slotted end of the anchor.
Unsupported edge- is where the concrete ends, the sides of a slab of concrete of column of concrete
Wedge anchor- made of a steel rod that is threaded on one
end and the other end has a diameter necked down for a short distance
that tapers outwardly to the full diameter of the tod. A clip is
permanently preassembled in this space.
Depending on your specific application, these terms can help you
correctly and safely use concrete anchors to fasten a fixture to a
variety of base materials including concrete, brick and block.
As with any anchoring project, it is important to keep safety in mind and follow instructions carefully. Always remember to wear safety goggles, handle all tools with extra care and follow all technical specifications. This article is meant to serve only as a basic explanation of concrete fasteners. Always refer to manufacturer's instructions or consult a contracting expert during any anchoring project.
Article Written By:
Bob Carlisle, President of Concrete Fasteners
Concrete Fasteners, Inc. has over 40 years of experience selling concrete fasteners. We can ship out one box or a whole pallet of concrete anchors. Our products are of the highest quality... "your satisfaction is guaranteed". We ship all orders the same day the order is received.