To install a window block into a concrete wall, attach a wall cabinet to it, or hang a lamp from the ceiling, you need a special fastener - a concrete screw. How to use such hardware, and which of them to choose for a particular purpose, you need to figure out in advance so that you don’t have to redo the work. To do this, you need to take into account the weight of the structure, the density of concrete, the location of attachment and some other factors.
For fastening to wood and concrete, you need to choose different hardware Source yandex.ru
Screw device
Concrete screws are made of high-strength steel, passivated with special compounds to protect against corrosion and mechanical damage when screwed in. Depending on the alloy used for passivation, self-tapping screws are available in yellow, grey, black and silver.
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A screw consists of a head and a body - a metal rod with a thread. The lower part of the body of the self-tapping screw is narrowed in the form of a cone. There are notches applied to it that prevent the screws from unscrewing and falling out of the holes, and the concrete from cracking during installation.
The thread of the self-tapping screws also has notches that enhance its adhesion to concrete. The height of the thread along the body of the screw can vary. Hardware with uneven thread heights is widespread. They are suitable for working with cellular (porous) concrete (polystyrene concrete or wood concrete), brick (ceramic, silicate or Lego brick) and similar materials.
Self-tapping screws for concrete differ from conventional screws by having a more frequent thread pitch. It allows you to use dowels without drilling holes.
Concrete dowel - technical specifications
Self-tapping screws (without drilling concrete) are made on the basis of hardened steel , which gives the product increased strength. A yellow galvanic zinc coating is applied to the surface. The treatment improves the mechanical characteristics and anti-corrosion properties of fasteners.
The greater the depth of fastening, the higher the load-bearing capacity of the screw. The product is effective in case of pulsating load
Phillips screws are ideal for use with a standard hand screwdriver or power tool. TORX slot, fasteners with loops, convex heads, heads with external threads, hexagon (wrench) are used with the corresponding type of tool.
The thread is cut unevenly. The quality of adhesion of the surface and fasteners is improved by applying special notches. The dowel adheres well to porous substrates and hollow blocks.
Varieties and sizes
Screws, self-tapping screws and anchors for concrete must comply with the interstate standard “Screws” - GOST 1147-80. They differ from each other in the following characteristics:
- material type;
- coating;
- head shape and slot type;
- thread design.
Self-tapping screws are made of carbon, corrosion-resistant steel or brass. By the color of the screw you can determine the technology that was used to apply the protective coating:
- yellow or silver color for galvanized hardware - they are galvanically coated with a layer of zinc, which protects them from corrosion;
- Oxidized screws that have been in contact with oxidizing agents are black;
- gray and dark gray color for screws that have been phosphated.
