Expansion Bolts

Published by Robert Carlisle on May 9th 2012

Purchase Anchors

Expansion bolts are fasteners used in masonry materials that expand once inserted into a predrilled hole in the masonry. The expansion of the anchor is accomplished in different ways and the anchors are designed for different applications. Expansion bolts come in a number of different configurations and types. Each type of expansion anchor has unique features and beenefits.

Configurations

Male –comes in different styles and either will protrude above the masonry surface or will insert into a predrilled hole
Female – are inserted into a predrilled hole in the concrete and has internal threads to accept a threaded bolt

Base Materials

Some expansion anchors are designed for use in solid base material only, such as concrete while others can be used in a variety of masonry materials, such as brick or block. Other anchors can be used in natural base materials, such as stone. The use of an expansion anchor in the natural base material is questionable due to the inconsistency of the material and the lack of testing.

Types of Expansion Anchors

MALE ANCHORS FOR CONCRETE

Wedge Anchors –variety of diameters ranging from 1/4” to 1-1/4”; manufactured in zinc plated carbon steel, hot-dipped galvanized carbon steel, 303/304 stainless steel and 316 stainless steel; protrudes above the surface of the concrete; utilizes a nut to expand anchor and to secure item being fastened
Sleeve Anchors – wide range of diameters from 1/4” to 3/4”; available in zinc plated carbon steel and 304 stainless steel; head styles include an acorn nut, hex nut, flat countersunk or round; not all diameters come with all head styles; turning of the nut or head expands anchor; can be flush with surface of material being fastened or can protrude dependent upon the head style
Hammer Drive Anchor – available in two diameters of 3/16” and 1/4” for light duty fastening; head is a round mushroom; nail driven with a hammer into the anchor body will expand anchor; once set, the hammer drive anchor cannot be removed and is tamperproof
Nylon Nail-It – similar to the hammer drive anchor with the difference of an anchor body made from a nylon type material; comes in the head styles of the mushroom head, flat countersunk head, and round head; nail on the nylon nail-it has a slot for easy removal
Strike Anchors – heavy-duty type anchor; available in diameters from 1/4” to 3/4”; comes in carbon steel with yellow zinc plating; utilizes a hardened steel pin to expand the anchor; allows uniform installation; the nut tightens the fixture to the concrete and does not expand the anchor
Split Drive – one-piece anchor; available in one diameter of 1/4” and in lengths up to 3”; permanent, tamper-proof anchor with two head styles of round head and flat countersunk; the split drive anchor is pre-expanded and holds firmly once driven into the predrilled hole in the concrete

FEMALE ANCHORS FOR CONCRETE

Drop In Anchor - available 1/4”, 3/8”, 1/2”, 5/8” and 3/4”; designated diameter refers to the inside or the bolt diameter; manufactured in carbon steel zinc coated, 304 stainless steel and 316 stainless steel; a setting tool is required to properly set the drop-in anchor
Lag Shield – requires the use of a lag screw which is purchased separately; embedment depth of the anchor and the thickness of the material being fastened determine the length of screw used; lag shields come in a short or long version in six diameters of 1/4”, 5/16”, 3/8”, 1/2”, 5/8” and 3/4”; short lag shield is used in denser, harder base material and the long lag shield is used in softer, more suspect base material
Machine Screw Anchor – use of specific setting tool is required to set the machine screw anchor in the concrete; eight diameters are available in #8, #10, 1/4”, 5/16”, 3/8”, 1/2”, 5/8” and 3/4”; the designated diameter refers to the inside diameter or bolt diameter used with the machine screw anchor; all bolts used with the anchor must have national coarse threads with a length determined by the thickness of the material being fastened plus the embedment depth
Double and Single Expansion Anchor – single expansion anchor is used in harder denser base material and the double expansion anchor is used in softer, more suspect type base materials; both come in six diameters of 1/4”, 5/16”, 3/8”, 1/2”, 5/8” and 3/4”; special setting tool is not required; the bolt when inserted and turned clockwise expands the anchor via the expansion nut; both anchors require bolts with national coarse threads; the length of the bolt is determined by adding the thickness of the material to be fastened to the embedment depth of the anchor

MALE ANCHORS FOR BRICK AND BLOCK

Sleeve Anchors – as described above, sleeve anchors are versatile anchors used in brick and block that provide excellent holding values; length of the sleeve anchor used in any specific application is critical because the expansion end of the anchor must be against solid material
Hammer Drive Anchor – great light duty fastener in brick and block; length of anchor chosen is critical because the working end of the anchor must not be in a hollow section of the brick or block
Nylon Nail-It – versatile as the hammer drive anchors described above

FEMALE ANCHORS FOR BRICK AND BLOCK

Lag Shield – same as the female anchors used in concrete described above; works equally well in brick or block base materials
Machine Screw Anchor – excellent holding values in brick and block with a wide range of diameters; base material must be thick enough to allow anchor to be set using the setting tool; hollow wall-setting tool is available through a company called Greenlee
Double and Single Expansion Anchor – both work well in brick or block; double expansion anchor provides the best opportunity for a successful fastening due to the expansion of the anchor along its entire length