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Lead anchors can be referred to as lead anchors because they have been manufactured from lead, although not recently due to environmental issues and the use of improved materials. All anchors that are referred to as lead anchors are manufactured by casting parts and then combined into the final product. Today most of the lead anchors are manufactured from a product called Zamac 7. This material is easily poured into molds, are rust resistant and environmentally safer.
First Lead Anchors
The first type of lead anchor utilized lead tape. Once the hole was drilled in the concrete then the lead tape was cut off a roll to be inserted tightly in the hole. A sheet metal screw was then inserted into the hole and turned clockwise, pushing the lead tape outward and holding the screw tight in the hole. This method worked well and gave excellent holding values if done properly. The problem with this method was that the holding values were inconsistent from hole to hole and from installer to installer. However, the principals applied to the lead tape have remained the same for all expansion type anchors used today.
Why Lead Was Used
Concrete fasteners were made from lead because it was easily melted and poured into molds. Once in a solid state, the lead would be pliable and soft. It could be formed to fit the contour of the base material, and be shaped and expanded.
Principles of Lead Anchors
The basic principle of the lead anchors is to drill a hole, then fill it with more material than was taken out. This creates expansion forces, friction and, ultimately, holding values. The evolution of the lead type anchor has led to fasteners that are easily manufactured and that provide an excellent, consistent holding values in a variety of base materials. Most of the modern type of anchors can be used in solid concrete, brick, block or mortar joints.
Styles of Anchor
Most of the anchors that are referred to as lead anchor are female anchors, i.e. designed to have a threaded fastener inserted into them. The principle behind the female anchors is to allow the screw to expand the anchor as the screw is inserted. One type of anchor called the machine screw anchor can utilize a setting tool to set the anchor before the screw is inserted. The machine screw anchor must only be used in solid materials because the bottom of the hole is required to allow the anchor to set properly. One type of anchor is manufactured as a male type fastener. It is expanded by striking a nail with a hammer and, as the nail goes into the anchor body, it expands against the inside walls of the hole in the masonry.
Types of Lead Anchors
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.